Several years ago I had an industrial plant that had a 50 HP motor burn up the first night after it was rewound. The plant opened only two months before and everything was new. After checking everything I discovered that the heater block had a different colored reset button going over the paperwork there was a 25% differences depending on the color of the reset button. We went through every motor control room and had to drop two sizes in the heaters to get the right protection of the motors. The best part was my company had a 25 year working relationship. My son still does all their electrical and machinal work. Like a lot of things in life sometimes, you have to dig deep to find the problem. Cheep isn't always the best way to go.
Great! I've been asking about this for a while and have not gotten a confident answer. Finally. Now I know the answer,without having to put together the setup myself. Thanks a million guys.
I've run two of them for about a year and a half now. Not a problem as of yet. A VFD will do the same thing but allow different parameters such as frequency control and soft starts on electrical motors, as well as many other things. For me it was a very inexpensive way for me to get 3 phase rather than buy a traditional phase converter. Great Video guys!!
Great Video!! Industrial Electrician and Machinist here. This is spot on. A static phase converter starts the motor by creating the third phase but runs the motor on single phase. For small HP motors, single phase VFDs work great. Set the VFD to 60HZ, and use the machine controls to control speed. Most older motors do not have the proper winding insulation to handle VFD speed control.
I have used a similar Tripp-Lite 5hp device for 25 years. They are effectively a starter. The motor is really running on just one leg. Power from the motor is reduced to less than 2/3 of nameplate rating. Never had any overheating problems. For low duty applications without frequent starts/stops/reversing, it can be cost effective over a rotary converter. Real 3phase is still the best followed by a rotary generated power.
I have a plan B, after I purchased my used equipment, I replaced a three phase motor with a single phase motor. It does take some engineering to adapt to a different motor, but now I do not need any phase converter whatsoever. I know I would get some negative comments about what I've done, but for me it was the simplest thing to do. I don't use a VFD, I use the belt and gear box for speed control.
Thanks for the video, Keith. You can make a crude but workable rotary phase converter yourself using a spare three-phase motor (needs to be rated at higher HP than the motor you are starting) as an idler motor. Use a cap to start the idler motor, then tap off the three legs of the idler motor to the machine you want to start. Not as elegant as the American Rotary products, but much cheaper, and works fine.
yea that is better than the box 'o' caps solution for sure. I have one and that is how every commercial rotary phase converter starts life, the question is how much further did the manufacturer take it.
The idler motor trick is basically what rotary power does with some capacitors to even things out. Additionally, another trick that you can use for three phase power and assuming that you have multiple three phase machines is to simply turn on additional machines and let the idle. They won't really create much of a load if they're idle, and the back-emf they create simply because they're running will result in the three-phase power being smoother and capable of handling a larger motor under load.
Twenty years ago, I followed someone else's instructions, and somehow built a 5 hp rotary converter that works great. The 5 hp 3-phase motor was salvaged for free from a trash heap, and it was manufactured in 1946. I replaced the bearings, and cut most of the output shaft off. I added a small fan blade to the shaft and added a shroud. I start the rotary motor thru a static converter, and then shut off the static unit. Total cost was about $175, mostly for the static converter from a company that doesn't exist any longer (Tools Unlimited).
I think something that was missed was that in the DPS manual states that under 50% motor load the voltages will be irregular, but above that the voltages balance out. I think that should have been noted and tested before discrediting the device, especially since the channel is being sponsored by a company that would be threatened by this device. I have machines on VFD's and rotaries, and will be running my dust collector off of a DPS, which the motor will be under load all the time.
Thread drift: I've used a spike maul and have participated in a triple spiking when spiking up rail. It starts off even, but after the second or third round, the hammer blows go from being even to one hammer following closely by the first followed by the fast incoming third hammer. Luckily, it doesn't take more than 3 rounds to drive a spike home, and the spikers will get used to the close together swings on the next spike to be driven. Instead of hit-pause- hit-pause-hit, the hammers sound like hit-hit-hit in rapid succession.. It makes no difference who is spiking, as they will fall into the same spiking pattern after the first round. It's pretty cool to listen and watch 3 spikers working together and hearing those hammers ring.
I wonder why? Doing the same thing swinging hammers on iron out of a forge, blacksmiths get nice even timing as the usual thing. If someone speeds up or slows down they're a beginner that hasn't gotten it yet.
A better analogy for three phase is to think of a single piston internal combustion engine compared with a three cylinder engine - the three cylinder is smoother running as the power is delivered more evenly through each revolution.
Agreed. Even better, the instantaneous power sum of the three phases is exactly the same at any time in the cycles - there can be ZERO ripple in the torque provided by a *well-designed* three-phase induction motor, i.e. no need for a flywheel other than the rotating mass of the rotor itself. Nicola Tesla invented & patented [in 1888] a two-phase early version of the modern three-phase induction motor [and ~simultaneously by Italy's Galileo Ferraris], but the final step to the beautiful result was left to Mikhail Dolivo-Dobrovolsky in 1889. Only three wires needed to transport mechanical [rotary] energy for hundreds of miles at high efficiency. The world would never be the same...
One other advantage of three phase is that you can run motors on it that don't need brushes like single-phase and dc motors do. Ok, there are motors with capacitors to create an auxillary phase, but those don't run as smooth and aren't as efficient as true three phase motors.
Very interesting topic. I saw another you tube machinist that had one of these and ended up changing it to a VFD to get rid of his problems. Your test showed why he was having a problem.
I'm a retired plant electrician and you are right on the money. These are a slow death to the motor and just because they work in the short term you will pay the piper when motor blows up and if you are real unlucky the fire will burn your shop down. You might comment if these have are UL listed. That in itself would speak volume's. I use a 10 HP American Rotary and on a 3 HP Acer 3VKH mill and the voltage and current is right on the spec. If money tight a properly installed VFD is a much better solution.
Just installed a electronic phase converter, the motor start is poor. I ordered my American Rotary phase converter today. I have waited long enough to get this lathe, I will wait a little longer until I get the rotary phase converter. Thanks for the video.
Interesting video - thank you. As someone with an electronics background, it would have been nice to see oscilloscope traces, comparing the rotary phase converter (RPC) with the digital phase shifter (DPS). It would also have shown your '3 guys hammering a tent peg' analogy very clearly. However, from the voltage and current readings you gave, the DPS is no substitute for the RPC.
They also didn't show a RPC worst feature, startup. They sag horribly on inrush on the third leg. That's the reason they have such large capacitor banks inside the RPC. The generated leg is limited to the locked rotor amps of the motor inside of it, but at that current voltage approaches zero. So you will see 10% or less of the inrush current on the generated leg vs the pass though legs, with a drop in voltage too. Due to the delta configuration of the 3 phase, this means your motors basically single phase on startup if there is a large load on the motor, as L1-L2 will have all the current, and L1-L3 and L2-L3 will have little current. The voltage sag will also effect the motors if you get close to the capacity of the RPC. The try to compensate for this with large banks of run caps wired in. A VFD/DFS will produce even voltage and current per phase up to the limit of the device. It will provide less peak inrush current to a motor, but all 3 phases will have the same inrush. Thus will have much much higher starting torque.
This is not to say it is impossible to have an entirely solid state three phase converter. It will have more to the electronics than half a dozen little caps.
The guy failed to take into account power factor, THD, (total harmonic distortion), inrush current and many other factors. Bottom line, there is no great substitute for commercial three phase power other than an appropriately sized generator capable of three phase power. The old rotary phase converters were literally a single phase motor with a belt driven three phase generator next to it.
weeeeeeeeeeeelllll also, at least assuming the current clamp was true RMS, you need to get the true reactive power. Obviously since the DPS can't create a good 120 degree phase shift you will have an imbalance but not sure it's the dire end of the world situation advertised here - but of course this channel will always give the edge to a RPC. I think an inverter with a nice big shunt reactor on it is the best option, but that's serious cash so I get it - RPS is probably the best balance of power, cost and reliability for a home shop.
I had a machine shop when I was younger and I paid PG&E $5000.00 to have 3 phase Delta power brought in from the switching yard about 5 miles away. It worked great and I never had any problems. It was 208 volts 60 cycles and ran my machines well.
@@carlthor91 It seems to me that within the last ten years a friend paid Pacific Graft and Extortion a whole bunch more than that. I believe that he had to "buy: three transformers, plus the poles and wire. The "engineering" was over $3-5k.
@@DavidSellars-b8l I am in Northern Canada right dead between two hydro plants, three phase is only 300 feet North of me on a pole. My split phase pole is ~60 feet from my power mast. So no poles, just new wire, mast, and meter.
In my area, they just look at you and say No! If I owned a building that has three phase, it is my understanding that the monthly cost would be out of my budget.
More like a commercial for your sponsor Keith. Use a decent VFD for your 3-phase power requirements...no moving parts, stable outputs, motor overload protection, adjustable speed, braking, and very reliable. IMHO
when i got my bridgeport mill , i looked in to vfd and static phase converters . i was told not to use them on motors built before 1980 because the varnish that was used in the older motors melts at a lower temp and you will more then likely burn it out. Two you don't have any whare nere full power. good videos keith. can't wait to see your next one!!!
its not the melting of the varnish that is the problem its the withstand. the output from a vfd is very noisy, those spikes can stress the winding insulation and induce lots of static charge on the rotor which can pit the bearings. I have seen these things in action so pick your poison.
NO. I was there to ensure that. american rotary supplied the 40hp unit keith is using and the two little boxes of caps and asked him to make this video and i live relatively close to them so no they exerted absolutely no external factors influenced the making of this video in any way.
A Variable Frequency Drive (VFD) sounds a whole lot better to me. It is way more versatile with variable ramp up times, motor braking, variable speed and about a hundred other things it can do. I have been running motors on VFD's for extended run times, unlimited starts per hour with no issues for over 10 years and with the latest vector drives there is very little loss of power at slow speeds.
Several examples I've seen on these videos always had a real high pitch whine that I find very uncomfortable to be around. I am very reluctant to try them for that reason.
@@katelights but also 1 vfd with a hanging hook with twistlock plugs can get you running in a one man shop if similar size motors. Did that til I got my rotary
With internal components coming from the same place, you're wasting your money buying expensive VFDs that work no better or last any longer than Chinese imports.
I've converted many machines to run on single phase using HuanYang VFDs and they are very good and very reliable. At around $100 for a 3HP version I think they are excellent value too. As comparison SPCs suck. I have no experience of RPCs but the noise of the motor would drive me nuts.
This was a FANTASTIC video. Really makes me want to rip out all of my static converters and VFDs and replace them with a rotary and dedicated 3 phase panel. Unfortunately, I don't have a few grand laying around lol... But this video did give me a lot of knowledge and perspective on what's potentially happening on my machines, I'll be taking a look at some amperages...
@@hersch_tool I put my RPC on a steel dolly with large casters. Then I can rearrange my shop at will and have easy access for any mods. That also made it easy to assemble on the bench, pick off with my lift (patients lifts are light and fit through a standard doorway making them epic back savers) and roll into place. I connect most of my equipment like a job site using SOOW cable for easy reconfig and though I never expect to move if I expand my shop it will be a breeze.
15 years ago I needed a phase converter. Since I was using cnc press brakes I chose an American rotary phase converter as it had a real sine wave output and well balanced legs. I then tried a vfd on my mill. It worked great until I let the magic smoke out. And couldn’t put it back again
G'day Keith, I run all my machines with VFD's. Easy to program with acceleration/deceleration, variable speed, braking etc. Got one of the newer generation units on my Victor Lathe, single phase direct to 415v, no need to rewire the motor to delta. They are cheap and for me with a small shop compared to a rotary which burns up power when the machines aren't running generates heat and noise, its the way to go. Cam
no the voltage would only shift a little and the current on the direct lines would increase proportionally to the current demand. remember its I 1ph X (square root)3= I 3phase.
The volume of a capacitor is an indicator of its energy storage capacity. At higher loads, when more energy needs to be stored, the fairly small energy storage capability of those capacitors may have led to worse unbalance. As you suggest, the best way to tell is to do a full-load test.
i have a American rotary 20ad rotary phase convertor L1 is 120 volts, L2 is 275 volts, L3 is 120 volts. I was told that was normal when I bought it in 2015 now I am not so sure. perhaps I should check amps also.
Thanks Guys that clears up why they're not for at older motors . Which is all I have but was going to try one to run a planer IVE had and wanting to get p and working like it should be. Federal planer isnt large but I have a one horse three phase to put on the super structure. Like you did on yours.
The technical details of AC power and especially 3 phase power are beyond what most electricians and many engineers understand. AC power is not the simple product of voltage and current like DC is because of phase differences. Three phase power is even more complex. To draw any real conclusions you need a true AC power meter. Fluke has them about $12K. Almost every AC motor uses a capacitor to shift the phase. The rotary phase convertor uses them too. The capacitor phase shifter produces a third phase shifted signal that is not perfect. But it doesn't need to be to get the motor to spin. The cap values are chosen for a typical motor which means performance will differ from one motor to the next using a shifter way outside it rating may work very poorly or not at all. A shifter will always delver less than full HP which in many cases is acceptable considering we never use it all anyway. There no reason to believe that the motor will suffer in any way by operation on a shifter. You can't just measure voltage and current in a AC circuit and jump to that conclusion. In your case the current on two legs was higher but the other lower so maybe the power was the same or even less. A better test would be to run the motor on the two power sources under identical loads and measure the temperature. No doubt the temperature would differ by a few degrees but who cares you're not going to run that tool all day long at max power. The capacitor phase shifter is a simple reliable and safe means of driving a 3 phase motor from single phase power. When properly done it will not harm your motor. While it is a compromise in many cases the value for money wins out over the rotary convertor especially for the hobbyist. it is more efficient than the rotary convertor which uses substantial power even when idling. Those that turn on their rotary convertor on and leave it on waste a lot of power. The VFD is a great way of driving a motor but doesn't share between machines but has many other advantages. The shifter and the VFD are perfectly valid low cost ways of driving a motor. In many applications the VFD us probably the best, American Rotary would like to demonize these and make them disappear.
Best explanation, I was confused whether I use a VFD or a rotary converter and after reading your comment I'm going with the VFD as I didn't think of the constant running of the 3ph converter . In my case the extra saving is better in the long run. thanks from Australia 🇦🇺
So does this box rectify the incoming AC to DC and then drive a three phase inverter creating three phases, each 120 degrees out of phase? I would have liked to see the waveforms of the three phases displayed on a scope.
Great video. I just bought a laguna 18-36 wood lathe that uses a dps to convert 110 to three phase and adds a vfd for speed control and reverse. Are they basically using this same setup?
I have a 5hp lathe, 3hp knee mill, and 3hp baldor 12inch grinder exactly like the one you have behind the sander. they are on a 5hp ronk rotary PC it works great and been in service for over 10 years now.
I first came across these static phase converters about 20 years ago. I had to install them in a neighborhood development for a water pump in a pond for a fountain and some other things. The ones I installed had a start-up procedure where you had to change the capacitance of the start/run circuitry based on the voltages you see when trying to start and run your load. Once I had the start-up done, I found the voltage and amperage was fairly well balanced. From what I can see, these converters you have are a much cheaper version of what I installed. I do not mean to contradict you in your final statements about static converters, but it comes down to the old saying, "you get what you pay for". The ones I installed worked for about 12 years before the development took out the pumps and re-did the whole pond thing in that neighborhood.
A friend’s dad ran his three phase Bridgeport mill in a suburban basement on single phase and a couple of capacitors. He used it 5 days a week for 50 years. When an electrician saw the setup, he confidently told me it would burn the motor out in an hour.
Mine had the simple converter but I prefer the power boost and speed control of the VFD I replaced it with. The primitive converter will now run a buffer.
We call that Appalachian Engineering. It's amazing how sophomoric 90% of the electricians can get (or those that do electrical work, anyway) . The first thing I'd consider is the actual load on the mill. Personally, as an industrial electrical/millwright contractor with over 50 years in the trade, I have never seen anybody continuously run a Bridgeport at 100% of the rated horsepower in my life, but I have seen dozens of guys cap starting lathes and mills in home shops with zero headaches. I have even done it myself when I was first starting out. Where you usually get into problems is with compressors. A sheave reduction of 15 or 20 % and converting it to continuous run (Unload to control cutin/ cutout) usually solves that problem and guys get to use their sandblaster with a 3 ph 5 horse industrial compressor in their home shop . An air conditioner starting cap and current relay makes a good starter if you are on a tight budget. (Just remember you cannot run the cap more then 2 or 3 seconds just to get the motor running.) Would I try it on a 96" tandem roll at the Steel Mill,,,,,,Hell no!!!! But if you got a little Clausing 5400 in the basement there is nothing to worry about. BTW, The thing nobody mentioned on that belt sander is the heaters in the Motor starter. - You have to change them with the cap box.....and Kieth, there is no way in hell you would barf that motor by grinding a radius in the end of a piece of 1/2x4 Hot rolled. Belt sanders are pretty crude machines and the effect of the imbalance is pretty much irrelevant. It takes a little screwing around with the values but you can easily make a phase converter out of a 3-pole disconnect, cheap starting cap and a common 15 Amp light switch. ---- I even saw a guy make one out of a disco a motor and a recoil starter off a model N Briggs gas motor. (Yep, you can pull start a 3ph motor).... It's not alchemy at all.
Great video Keith! There is quite a lot of information out there about these but some of the finer details are missing. I’ve long wondered about the EMF. I haven’t confirmed this with my scope but as I understand it a VFD effectively turns AC into DC. The issues you experienced make sense as an AC signal rises and falls DC can overlap as you described. I also wonder if the higher amperage and voltages you are seeing is the motor fighting itself due to the EMF or overlapping voltages (lead?). Lots of good food for thought. Will definitely have to reconsider my setup.
yea that is how vfds work, all of them. convert to DC, filter caps, then high current high voltage transistors to create an output of the desired voltage and frequency.
Hi Keith good video you have got me worried so i hope I'm right this converter is a static type and not the same as a VFD that come in single phase and three phase . I also hope you guys do a video on the VFD type converters . Thanks JM
I can screw in a light bulb, install a new plug on a lamp and even comfortable adding a new circuit and breaker in my panel. Until this video I never had a clue what three phase power was or how it worked. I have a much clearer understanding now. Thanks.
There’s no substitute for a real generated third leg. Give the motor what it was designed to run on and it will do so for a long time. Really appreciate you addressing this issue as I feel that many - understandably - are tempted to go a route other than a rotary phase converter to save money and for ease of installation. As I think your video makes perfectly clear… do so at your own risk.
Thanks for your contend. There are - luckily - not many situations in central europe where you do not have easy access to three phase power, so until now I did not even have known about those boxes. Buuuut the gamer in me had to have the last word by realizing that „DPS“ is an acronym refering to „damage per second“ or in this instance „damage per start“.
I made my own Rotary Phase converter, I have Start capacitors that get the Idler motor spinning then drop out of the circuit and Run capacitors that balance the voltage / current between the 3 legs. 2 of the legs are standard 240V out of my panel the idler motor generates the 3rd leg using Run capacitors to balance it. I know you never hear of 2 phase but when you pull 240 V from your fuse panel you have 2 of the legs already, the idler motor produces the 3rd leg and the run capacitors are use to balance it as close as possible. Keep in mind that from each leg to ground the voltages are 120, 120, and 240. Keep the L3 hot leg off of any transformers ECT... that are looking for 120V
There is another option, solid state phase conversion (Phase Technologies). I have two, one of which is in my machine shop powering CNC equipment. They are expensive but very precise 3 phase generation. If you hook an oscilloscope to the output you can not tell which phase is generated and which is original.
I have installed those things too. they are more or less a vfd that has a static out put at 60hz. a vfd is likely cheaper. depends on how many machines you are going to have hooked to it. they make the same whine that vfds do as well.
Hey Keith! I wanted to point out that the DPS manual states there are voltage imbalances up to 50% that will balance under load. Is there any way you can test this?
It would be interesting to see the power factor on the 240 side (e.g. the ratio of the input current to the input voltage). That might explain why different output legs have different voltages and current.
I've been running a three phase motor in delta configuration with a capacitor between two legs on 230 V single phase. This is called Steinmetz circuit over here and only recommended to a max 1 - 1.5 kw motor. I would never use that for a bigger or expensive motor since the phase shift is less than 90° instead of 120° and you get ripple curents and the different amperages. You also don't magically get the full power of real three phase. It's a simple solution for small tools, and should be treated as that. I am just running a small buffer this way and it's ok.
I was reading up on these and it says that there will be voltage and amp imbalance when the motor is under 50% load. It says they will balance once the motor is over 50% load. I would like to see that tested as a follow-up if you have time.
I would like to see the difference on a power analyzer. I don't think the phase shift is 120deg and that will cause the unbalance on the current. What worries me is that one phase was in an over current state. Power analyzer is basically a 6 channel oscilloscope, nice to compare voltage and current curves on one screen. We have compared the wave forms on a FVD before and after the line inductors. Even after the inductor the wave form was not a sinewave.
I've heard these described as two phase with a starting circuit which your demo proved out. For an in depth, but easy to follow review of motors controllers and VFD's go to Pump Ed 101 by Dr. Joe Evans. I have had the pleasure of sitting in on his presentations at workshops in the past. His online material appears to be transcriptions of his presentations. really good stuff. Thanks again for providing another very informative video.
On the DPS you stated one phase passes through so its the other phase that is altered to create the 3rd phase. I wonder what the current was on each phase coming into the DPS.
Ok I am an electrical engineer , worked in heavy power motors etc , question for your guy did you check the power factor in both cases ? the larger caps were there to provide a lag PF while the motor ( inductor ) will give a lag PF , I would be very interested if how much watt less current is present which would skew the reading as taken with the amp clamp simply analogy for single phase v three phase single phase is like a single cylinder engine and three phase is a three cylinder engine , all will know which is the smoother of the two ,but if the circuit is unbalanced the three phase will cause the motor to run rough . as a last request can you show us the wave form for a rotary and a the Little box of tricks ( I very much doubt that the motor winding will suffer with such a crude device VFD re synesize the three phase from DC in the unit and before the smoothing cap it is a square wave due to the circuity
sure, if we had those tools but as with any video there needs to be a limit on how much stuff you put into it. idealy the capacitive reactance should cancel the motors inductive reactance to give you a PF of 1.0. the point of the box 'o' caps is to generate enough phase shift to create a rotating magnetic field in the motor. the degree of that shift will dictate the amount of torque the motor puts out. rest assured the PF is very poor, if the thing works like its supposed to i would expect something like 0.6 - 0.7. the only one who cares abute that is the power company and we have limited tools to make those measurements so its not in the video.
Well in reality, since the PF is the phase shift between voltage and current and the motor ideally has a maximum efficiency to reach it horsepower is at unity or PF = 1, it's more than the utility that cares. To get to the required needed HP the motor needs to do its job when the PF is shifted to 0.6 to 0.7 requires much greater current since the voltage, under normal conditions, would be fixed. This greater current will generate more heat, which will affect the lifespan of the windings/motor. So it doesn't just affect the utility, it will affect the life of the motor too.
The old saying you get what you pay for rings true here I don't have a shop full of three phase equipment but I use to work in a place that has tons of conveyor belts and other three phase stuff and know how much it matters having good power over the three phases
Could you put high res pictures of both sides of the board up? I'd like to analyze the circuit myself (for fun, no commercial purpose). Curious to see what other nastiness this will generate. They are playing tricks for sure to make the motor turn.
I run my lathe off single phase with a homemade rotary converter. I used a potential relay and a pile of capacitors from the scrap yard. I set it up with a digital amp and voltage gauge for each leg from Amazon. It's a 10hp and has been in use for 10 years. The slave motor was also brought from the scrap yard just needing bearings, 25hp motor. With the digital gauges I can live data monitor each leg while using the lathe or any other machine plugged into that outlet. Study up on it and use common sense to get it done.
Just curious if anyone watching uses or has seen a Phase Perfect DPC? They are pricey for the home shop guy, but are supposed to provide service-grade 3 phase power that can be used for machines with sensitive electronics.
as a 'marine electrician' i got lots of stories.... amazing what can be done with old scrap... and salvage.... I was shown a jointer with 1' blades and 7' table w/ a7.5hp 3ph drive. powered from a 50amp 1ph breaker (??)....that fed 240vac into two legs of a 3ph switch to run a 240v 1ph 1.5hp motor and another switch tied to a 10hp 3ph motor paralleled with the jointer motor. These 2 motors were also joined with a lovejoy coupling ya, man! weird... so turn on the power, turn on the 1ph motor to spin up the 10hp... turn on the 3ph switch, then turn off the 1ph switch and the planer gets the 3rd phase to run well. I moved the 'converter' to in side the shop from it's dog house; and later an old planer (7.5?hp) was added that could be used if the jointer was off.
Key VFD advantage is speed adjustment on lathes DURING the cut (slower on the outside of a large diameter, faster towards the center) and of course variable speed on lathe and mill. RPCs are better for heavy steady loads not needing speed control. Bonus, more motors also act as more idlers. I start my compressors one at a time (two industrial 5HP are easier to power than a single 10HP and when not blasting I only use one) off my RPC. OTOH my lathe and mill have VFDs. See the Practical Machinist forum for the best detailed info on using both in a machine shop context. Note some power companies bill all three phase at commercial rates so a large RPC may be a much better deal. Check before spending money. Also many areas do not have three phase at the pole.
We are a DPS manufacturer and seller. Thank you for making DPS video. However, it seems like the video was made without much knowledge of the characteristics of DPS. It appears that there was no load on the motor when testing the DPS. However, the motor is never used without load. When the motor load is less than 50%, there may be an imbalance from the voltages and currents output from the DPS. Normally, when the motor load is 50% more, voltages and currents will be balanced. The current in the middle phase of the DPS output changes depending on the motor load. Most of our customers are using DPS very well on their 3 phase motors. We are concerned that customers may have misunderstandings about DPS due to this video. We think that if the person who made this video had read the DPS user manual carefully, he would not have made a video like this. Thank you.
Can you do the same comparison using a VFD? Yes, I know a Rotary Inverter is the best option but when you have just two machines to run and one is on a VFD, is it practical/ more economic to change over to a rotary system even if you use only one machine at a time and only once every other month?
I lucked out. I found a residential property that had three phase already set up in a 4500 sqft shop building that the previous owner was using for his business. It was the deciding factor for buying the property. Otherwise I would have gone with the rotary option to power my machines.
Im using a DPS on my Clausing Colchester 12X40 and mine goes out on reset after about 20 minutes of use because the motor is getting to hot. Can anybody tell me which VFD I should get for it? It’s a 3/4HP 3 phase. It’s against the wall right now and I forgot how many amps it draws. Thanks
Rotary converters are the best, will outlast electronics in my opinion, and the sine wave is clean. The old capacitor-type “converters” aren't really converters, as they're designed only for starting a 3 phase motor, where one leg kicks out after they start, and you lose 1/3 of the power. That is why rotary has always been the best, if a well-made motor is used. I used a 20 HP, 3 Phase, Lincoln Electric Co. motor on the converter I had, with a small 1/2 HP blower motor (also known as a pony motor) to start the larger turning at the push of a button. Really, they're easily made. When there's no 3 phase on the pole, it's your only hope, as I called the power company for an estimate to run 3 phase to my shop, and the price was staggering years ago.
![[CC] DPS Digital Phase Shifter in a Demo Board & Testing with a Hioki CM3286-01](/img/n.gif)
Several years ago I had an industrial plant that had a 50 HP motor burn up the first night after it was rewound. The plant opened only two months before and everything was new. After checking everything I discovered that the heater block had a different colored reset button going over the paperwork there was a 25% differences depending on the color of the reset button. We went through every motor control room and had to drop two sizes in the heaters to get the right protection of the motors. The best part was my company had a 25 year working relationship. My son still does all their electrical and machinal work. Like a lot of things in life sometimes, you have to dig deep to find the problem. Cheep isn't always the best way to go.
Great! I've been asking about this for a while and have not gotten a confident answer. Finally. Now I know the answer,without having to put together the setup myself. Thanks a million guys.
I've run two of them for about a year and a half now. Not a problem as of yet. A VFD will do the same thing but allow different parameters such as frequency control and soft starts on electrical motors, as well as many other things. For me it was a very inexpensive way for me to get 3 phase rather than buy a traditional phase converter. Great Video guys!!
Great Video!! Industrial Electrician and Machinist here. This is spot on. A static phase converter starts the motor by creating the third phase but runs the motor on single phase. For small HP motors, single phase VFDs work great. Set the VFD to 60HZ, and use the machine controls to control speed. Most older motors do not have the proper winding insulation to handle VFD speed control.
I have used a similar Tripp-Lite 5hp device for 25 years. They are effectively a starter. The motor is really running on just one leg. Power from the motor is reduced to less than 2/3 of nameplate rating. Never had any overheating problems. For low duty applications without frequent starts/stops/reversing, it can be cost effective over a rotary converter. Real 3phase is still the best followed by a rotary generated power.
I have had an American Rotory phase converter in my shop for 10 years and it has worked flawlessly.
I have a plan B, after I purchased my used equipment, I replaced a three phase motor with a single phase motor. It does take some engineering to adapt to a different motor, but now I do not need any phase converter whatsoever. I know I would get some negative comments about what I've done, but for me it was the simplest thing to do. I don't use a VFD, I use the belt and gear box for speed control.
“We’re not Fireball…” Nice shout out to Jason and his belt sander test. Great video, very informative!
as AvE said sometimes its what you cut out that makes the video.
Thanks for the video, Keith. You can make a crude but workable rotary phase converter yourself using a spare three-phase motor (needs to be rated at higher HP than the motor you are starting) as an idler motor. Use a cap to start the idler motor, then tap off the three legs of the idler motor to the machine you want to start. Not as elegant as the American Rotary products, but much cheaper, and works fine.
yea that is better than the box 'o' caps solution for sure. I have one and that is how every commercial rotary phase converter starts life, the question is how much further did the manufacturer take it.
I’ve been running this configuration for years with zero problems
The idler motor trick is basically what rotary power does with some capacitors to even things out.
Additionally, another trick that you can use for three phase power and assuming that you have multiple three phase machines is to simply turn on additional machines and let the idle. They won't really create much of a load if they're idle, and the back-emf they create simply because they're running will result in the three-phase power being smoother and capable of handling a larger motor under load.
Thanks Keith. One dead giveaway is when you have a very heavy machine running on a little plastic box.
just wait until the very heavy machine is "supported" by little plastic boxes!
Twenty years ago, I followed someone else's instructions, and somehow built a 5 hp rotary converter that works great. The 5 hp 3-phase motor was salvaged for free from a trash heap, and it was manufactured in 1946. I replaced the bearings, and cut most of the output shaft off. I added a small fan blade to the shaft and added a shroud. I start the rotary motor thru a static converter, and then shut off the static unit.
Total cost was about $175, mostly for the static converter from a company that doesn't exist any longer (Tools Unlimited).
was.... ? well man dont keep us waiting!
I think something that was missed was that in the DPS manual states that under 50% motor load the voltages will be irregular, but above that the voltages balance out. I think that should have been noted and tested before discrediting the device, especially since the channel is being sponsored by a company that would be threatened by this device. I have machines on VFD's and rotaries, and will be running my dust collector off of a DPS, which the motor will be under load all the time.
I noticed that too! I want to see what this thing can/will do with load
Very informative and instructive. I have been considering 3-phase power in my shop and this has convinced me about the way I need to go. Thanks!!
Thread drift:
I've used a spike maul and have participated in a triple spiking when spiking up rail. It starts off even, but after the second or third round, the hammer blows go from being even to one hammer following closely by the first followed by the fast incoming third hammer. Luckily, it doesn't take more than 3 rounds to drive a spike home, and the spikers will get used to the close together swings on the next spike to be driven. Instead of hit-pause- hit-pause-hit, the hammers sound like hit-hit-hit in rapid succession..
It makes no difference who is spiking, as they will fall into the same spiking pattern after the first round. It's pretty cool to listen and watch 3 spikers working together and hearing those hammers ring.
dose it count of you are not singing?
Nice response! Thanks. "If the hammer isn't singing, you ain't a-swingin"
I wonder why? Doing the same thing swinging hammers on iron out of a forge, blacksmiths get nice even timing as the usual thing. If someone speeds up or slows down they're a beginner that hasn't gotten it yet.
Great video Keith, well explained for those of us that don't use 3 phase. Thanks for sharing.
A better analogy for three phase is to think of a single piston internal combustion engine compared with a three cylinder engine - the three cylinder is smoother running as the power is delivered more evenly through each revolution.
Agreed. Even better, the instantaneous power sum of the three phases is exactly the same at any time in the cycles - there can be ZERO ripple in the torque provided by a *well-designed* three-phase induction motor, i.e. no need for a flywheel other than the rotating mass of the rotor itself.
Nicola Tesla invented & patented [in 1888] a two-phase early version of the modern three-phase induction motor [and ~simultaneously by Italy's Galileo Ferraris], but the final step to the beautiful result was left to Mikhail Dolivo-Dobrovolsky in 1889. Only three wires needed to transport mechanical [rotary] energy for hundreds of miles at high efficiency. The world would never be the same...
@@jrb_sland Yes, excellent explanation.
One other advantage of three phase is that you can run motors on it that don't need brushes like single-phase and dc motors do. Ok, there are motors with capacitors to create an auxillary phase, but those don't run as smooth and aren't as efficient as true three phase motors.
That is a very good analogy!
@CatNolara it's a minor point, but not all single phase AC motors require brushes. AC Induction motors do not.
Very interesting topic. I saw another you tube machinist that had one of these and ended up changing it to a VFD to get rid of his problems. Your test showed why he was having a problem.
I'm a retired plant electrician and you are right on the money. These are a slow death to the motor and just because they work in the short term you will pay the piper when motor blows up and if you are real unlucky the fire will burn your shop down. You might comment if these have are UL listed. That in itself would speak volume's. I use a 10 HP American Rotary and on a 3 HP Acer 3VKH mill and the voltage and current is right on the spec. If money tight a properly installed VFD is a much better solution.
Just installed a electronic phase converter, the motor start is poor. I ordered my American Rotary phase converter today. I have waited long enough to get this lathe, I will wait a little longer until I get the rotary phase converter. Thanks for the video.
Pure honesty backed with knowledge and reality.
Interesting video - thank you. As someone with an electronics background, it would have been nice to see oscilloscope traces, comparing the rotary phase converter (RPC) with the digital phase shifter (DPS). It would also have shown your '3 guys hammering a tent peg' analogy very clearly. However, from the voltage and current readings you gave, the DPS is no substitute for the RPC.
Yes I like to geek out too on visual
They also didn't show a RPC worst feature, startup. They sag horribly on inrush on the third leg. That's the reason they have such large capacitor banks inside the RPC. The generated leg is limited to the locked rotor amps of the motor inside of it, but at that current voltage approaches zero. So you will see 10% or less of the inrush current on the generated leg vs the pass though legs, with a drop in voltage too. Due to the delta configuration of the 3 phase, this means your motors basically single phase on startup if there is a large load on the motor, as L1-L2 will have all the current, and L1-L3 and L2-L3 will have little current. The voltage sag will also effect the motors if you get close to the capacity of the RPC. The try to compensate for this with large banks of run caps wired in.
A VFD/DFS will produce even voltage and current per phase up to the limit of the device. It will provide less peak inrush current to a motor, but all 3 phases will have the same inrush. Thus will have much much higher starting torque.
This is not to say it is impossible to have an entirely solid state three phase converter. It will have more to the electronics than half a dozen little caps.
The guy failed to take into account power factor, THD, (total harmonic distortion), inrush current and many other factors. Bottom line, there is no great substitute for commercial three phase power other than an appropriately sized generator capable of three phase power. The old rotary phase converters were literally a single phase motor with a belt driven three phase generator next to it.
weeeeeeeeeeeelllll also, at least assuming the current clamp was true RMS, you need to get the true reactive power. Obviously since the DPS can't create a good 120 degree phase shift you will have an imbalance but not sure it's the dire end of the world situation advertised here - but of course this channel will always give the edge to a RPC. I think an inverter with a nice big shunt reactor on it is the best option, but that's serious cash so I get it - RPS is probably the best balance of power, cost and reliability for a home shop.
I had a machine shop when I was younger and I paid PG&E $5000.00 to have 3 phase Delta power brought in from the switching yard about 5 miles away. It worked great and I never had any problems. It was 208 volts 60 cycles and ran my machines well.
For me if I would want 3 ph now. I would have to pay $3k-$5k to go ~ 300 feet. I am just 300 feet from the transformer triplet up the pole.
@@carlthor91 It seems to me that within the last ten years a friend paid Pacific Graft and Extortion a whole bunch more than that. I believe that he had to "buy: three transformers, plus the poles and wire. The "engineering" was over $3-5k.
@@DavidSellars-b8l I am in Northern Canada right dead between two hydro plants, three phase is only 300 feet North of me on a pole. My split phase pole is ~60 feet from my power mast. So no poles, just new wire, mast, and meter.
oah how times have changed. there is 3ph not 150 yards from my house and xcell quoted me $11,000 for a connection to the garage only.
In my area, they just look at you and say No!
If I owned a building that has three phase, it is my understanding that the monthly cost would be out of my budget.
Great information in this splendid video, thanks!
Have you seen the phase inverted Leo, from Tally Ho, uses on his big ‘ol ship saw?
More like a commercial for your sponsor Keith. Use a decent VFD for your 3-phase power requirements...no moving parts, stable outputs, motor overload protection, adjustable speed, braking, and very reliable. IMHO
he has 20 motors all of various size so the rotophase was the best and most cost effective solution by far.
Thanks for the video. Would like to see the same comparison using a VFD.
Every VFD I have checked showed essentially equal voltages and currents on each phase, which is what you want to see on all 3 phase motors.
@@carrollprice1213- thanks.
Thanks! Been looking at digital phase converter and did not understand the pitfalls. Great info.
when i got my bridgeport mill , i looked in to vfd and static phase converters . i was told not to use them on motors built before 1980 because the varnish that was used in the older motors melts at a lower temp and you will more then likely burn it out. Two you don't have any whare nere full power. good videos keith. can't wait to see your next one!!!
its not the melting of the varnish that is the problem its the withstand. the output from a vfd is very noisy, those spikes can stress the winding insulation and induce lots of static charge on the rotor which can pit the bearings. I have seen these things in action so pick your poison.
You think Rotary Phase Convertors being your sponsor had any influence on this test?
NO. I was there to ensure that. american rotary supplied the 40hp unit keith is using and the two little boxes of caps and asked him to make this video and i live relatively close to them so no they exerted absolutely no external factors influenced the making of this video in any way.
When are you going to finish the steam stoker engine repair
A Variable Frequency Drive (VFD) sounds a whole lot better to me. It is way more versatile with variable ramp up times, motor braking, variable speed and about a hundred other things it can do. I have been running motors on VFD's for extended run times, unlimited starts per hour with no issues for over 10 years and with the latest vector drives there is very little loss of power at slow speeds.
VFD are great, but their main disadvantage is cost. if you have a lot of machines they can add up real fast.
Several examples I've seen on these videos always had a real high pitch whine that I find very uncomfortable to be around. I am very reluctant to try them for that reason.
@@katelights but also 1 vfd with a hanging hook with twistlock plugs can get you running in a one man shop if similar size motors. Did that til I got my rotary
With internal components coming from the same place, you're wasting your money buying expensive VFDs that work no better or last any longer than Chinese imports.
I've converted many machines to run on single phase using HuanYang VFDs and they are very good and very reliable. At around $100 for a 3HP version I think they are excellent value too. As comparison SPCs suck. I have no experience of RPCs but the noise of the motor would drive me nuts.
Great advise and great demo! Thank you.
This was a FANTASTIC video. Really makes me want to rip out all of my static converters and VFDs and replace them with a rotary and dedicated 3 phase panel. Unfortunately, I don't have a few grand laying around lol... But this video did give me a lot of knowledge and perspective on what's potentially happening on my machines, I'll be taking a look at some amperages...
keep the vfds and use the static converters and a big motor to build your own roto phase! you have most of the parts already, go for it!
@@nilzlima3027 Haha, solid plan is solid. Might even make a great video... 🤔🤣
@@hersch_tool I put my RPC on a steel dolly with large casters. Then I can rearrange my shop at will and have easy access for any mods. That also made it easy to assemble on the bench, pick off with my lift (patients lifts are light and fit through a standard doorway making them epic back savers) and roll into place. I connect most of my equipment like a job site using SOOW cable for easy reconfig and though I never expect to move if I expand my shop it will be a breeze.
@@Comm0utUnless you just love irritating noise park it outside or in another building to muffle the constant drone.
15 years ago I needed a phase converter. Since I was using cnc press brakes I chose an American rotary phase converter as it had a real sine wave output and well balanced legs. I then tried a vfd on my mill. It worked great until I let the magic smoke out. And couldn’t put it back again
stoopid magic smoke! i tried the liquid smoke, no dice.
Excellent info, with real life numbers to back it up.
G'day Keith, I run all my machines with VFD's. Easy to program with acceleration/deceleration, variable speed, braking etc. Got one of the newer generation units on my Victor Lathe, single phase direct to 415v, no need to rewire the motor to delta. They are cheap and for me with a small shop compared to a rotary which burns up power when the machines aren't running generates heat and noise, its the way to go.
Cam
Would have been interesting to have tested the leg voltages and currents at the rated load. I suspect they would have stabilized quite a bit.
no the voltage would only shift a little and the current on the direct lines would increase proportionally to the current demand. remember its I 1ph X (square root)3= I 3phase.
The volume of a capacitor is an indicator of its energy storage capacity. At higher loads, when more energy needs to be stored, the fairly small energy storage capability of those capacitors may have led to worse unbalance. As you suggest, the best way to tell is to do a full-load test.
i have a American rotary 20ad rotary phase convertor L1 is 120 volts, L2 is 275 volts, L3 is 120 volts. I was told that was normal when I bought it in 2015 now I am not so sure. perhaps I should check amps also.
I totally agree with you Keith, the rotary phase converter is my preference also. Nice and informative video Sir. Good day and peace too. vf
Thanks Guys that clears up why they're not for at older motors . Which is all I have but was going to try one to run a planer IVE had and wanting to get p and working like it should be. Federal planer isnt large but I have a one horse three phase to put on the super structure. Like you did on yours.
The technical details of AC power and especially 3 phase power are beyond what most electricians and many engineers understand. AC power is not the simple product of voltage and current like DC is because of phase differences. Three phase power is even more complex. To draw any real conclusions you need a true AC power meter. Fluke has them about $12K. Almost every AC motor uses a capacitor to shift the phase. The rotary phase convertor uses them too. The capacitor phase shifter produces a third phase shifted signal that is not perfect. But it doesn't need to be to get the motor to spin. The cap values are chosen for a typical motor which means performance will differ from one motor to the next using a shifter way outside it rating may work very poorly or not at all. A shifter will always delver less than full HP which in many cases is acceptable considering we never use it all anyway. There no reason to believe that the motor will suffer in any way by operation on a shifter. You can't just measure voltage and current in a AC circuit and jump to that conclusion. In your case the current on two legs was higher but the other lower so maybe the power was the same or even less. A better test would be to run the motor on the two power sources under identical loads and measure the temperature. No doubt the temperature would differ by a few degrees but who cares you're not going to run that tool all day long at max power.
The capacitor phase shifter is a simple reliable and safe means of driving a 3 phase motor from single phase power. When properly done it will not harm your motor. While it is a compromise in many cases the value for money wins out over the rotary convertor especially for the hobbyist. it is more efficient than the rotary convertor which uses substantial power even when idling. Those that turn on their rotary convertor on and leave it on waste a lot of power.
The VFD is a great way of driving a motor but doesn't share between machines but has many other advantages.
The shifter and the VFD are perfectly valid low cost ways of driving a motor. In many applications the VFD us probably the best, American Rotary would like to demonize these and make them disappear.
Best explanation, I was confused whether I use a VFD or a rotary converter and after reading your comment I'm going with the VFD as I didn't think of the constant running of the 3ph converter .
In my case the extra saving is better in the long run.
thanks from Australia 🇦🇺
So does this box rectify the incoming AC to DC and then drive a three phase inverter creating three phases, each 120 degrees out of phase? I would have liked to see the waveforms of the three phases displayed on a scope.
Great video. I just bought a laguna 18-36 wood lathe that uses a dps to convert 110 to three phase and adds a vfd for speed control and reverse. Are they basically using this same setup?
Very interesting. I wondered how advisable those solid state phase converters were.
I have a 5hp lathe, 3hp knee mill, and 3hp baldor 12inch grinder exactly like the one you have behind the sander. they are on a 5hp ronk rotary PC it works great and been in service for over 10 years now.
Nice job brother
Thanks for the information
I first came across these static phase converters about 20 years ago. I had to install them in a neighborhood development for a water pump in a pond for a fountain and some other things. The ones I installed had a start-up procedure where you had to change the capacitance of the start/run circuitry based on the voltages you see when trying to start and run your load. Once I had the start-up done, I found the voltage and amperage was fairly well balanced. From what I can see, these converters you have are a much cheaper version of what I installed. I do not mean to contradict you in your final statements about static converters, but it comes down to the old saying, "you get what you pay for". The ones I installed worked for about 12 years before the development took out the pumps and re-did the whole pond thing in that neighborhood.
A friend’s dad ran his three phase Bridgeport mill in a suburban basement on single phase and a couple of capacitors. He used it 5 days a week for 50 years.
When an electrician saw the setup, he confidently told me it would burn the motor out in an hour.
if the thing is well tuned and the motor is kept cool it can work, the question is how good are you and what are you willing to wager.
Mine had the simple converter but I prefer the power boost and speed control of the VFD I replaced it with. The primitive converter will now run a buffer.
We call that Appalachian Engineering. It's amazing how sophomoric 90% of the electricians can get (or those that do electrical work, anyway) .
The first thing I'd consider is the actual load on the mill. Personally, as an industrial electrical/millwright contractor with over 50 years in the trade, I have never seen anybody continuously run a Bridgeport at 100% of the rated horsepower in my life, but I have seen dozens of guys cap starting lathes and mills in home shops with zero headaches. I have even done it myself when I was first starting out.
Where you usually get into problems is with compressors. A sheave reduction of 15 or 20 % and converting it to continuous run (Unload to control cutin/ cutout) usually solves that problem and guys get to use their sandblaster with a 3 ph 5 horse industrial compressor in their home shop . An air conditioner starting cap and current relay makes a good starter if you are on a tight budget. (Just remember you cannot run the cap more then 2 or 3 seconds just to get the motor running.)
Would I try it on a 96" tandem roll at the Steel Mill,,,,,,Hell no!!!! But if you got a little Clausing 5400 in the basement there is nothing to worry about.
BTW, The thing nobody mentioned on that belt sander is the heaters in the Motor starter. - You have to change them with the cap box.....and Kieth, there is no way in hell you would barf that motor by grinding a radius in the end of a piece of 1/2x4 Hot rolled. Belt sanders are pretty crude machines and the effect of the imbalance is pretty much irrelevant.
It takes a little screwing around with the values but you can easily make a phase converter out of a 3-pole disconnect, cheap starting cap and a common 15 Amp light switch. ---- I even saw a guy make one out of a disco a motor and a recoil starter off a model N Briggs gas motor. (Yep, you can pull start a 3ph motor).... It's not alchemy at all.
Thanks for sharing Keith
Hello from San Antonio, TEXAS!
Great video Keith! There is quite a lot of information out there about these but some of the finer details are missing. I’ve long wondered about the EMF. I haven’t confirmed this with my scope but as I understand it a VFD effectively turns AC into DC. The issues you experienced make sense as an AC signal rises and falls DC can overlap as you described. I also wonder if the higher amperage and voltages you are seeing is the motor fighting itself due to the EMF or overlapping voltages (lead?). Lots of good food for thought. Will definitely have to reconsider my setup.
This isn’t a VFD, it’s a static phase converter.
@@MrSleepProductionsIncAh. I misunderstood I thought he was referring to a VFD with just a different wording.
yea that is how vfds work, all of them. convert to DC, filter caps, then high current high voltage transistors to create an output of the desired voltage and frequency.
Hi Keith good video you have got me worried so i hope I'm right this converter is a static type and not the same as a VFD that come in
single phase and three phase . I also hope you guys do a video on the VFD type converters . Thanks JM
I can screw in a light bulb, install a new plug on a lamp and even comfortable adding a new circuit and breaker in my panel. Until this video I never had a clue what three phase power was or how it worked. I have a much clearer understanding now. Thanks.
Thank you for the honest video,no hipe just good honest info.
keith cut out most of the hype.
There’s no substitute for a real generated third leg. Give the motor what it was designed to run on and it will do so for a long time. Really appreciate you addressing this issue as I feel that many - understandably - are tempted to go a route other than a rotary phase converter to save money and for ease of installation. As I think your video makes perfectly clear… do so at your own risk.
Great info Keith...
Great info, thanks for putting this out there!
One of the best comb overs/fronts I've seen lol
Your looking good keith.
I wondered about those. Thanks for testing in real life.
I had AC and DC circuit analysis in Engineering College but that was a LONG time ago (now retired)! Made my brain hurt...
I put a VFD on my 10hp screw compressor. Loaded it runs at 50hz and unloaded idles at 30hz. I enjoy the speed control for most of my machines.
Excellent Info!
Thanks for your contend. There are - luckily - not many situations in central europe where you do not have easy access to three phase power, so until now I did not even have known about those boxes. Buuuut the gamer in me had to have the last word by realizing that „DPS“ is an acronym refering to „damage per second“ or in this instance „damage per start“.
same thing, different time standard!
I made my own Rotary Phase converter, I have Start capacitors that get the Idler motor spinning then drop out of the circuit and Run capacitors that balance the voltage / current between the 3 legs. 2 of the legs are standard 240V out of my panel the idler motor generates the 3rd leg using Run capacitors to balance it.
I know you never hear of 2 phase but when you pull 240 V from your fuse panel you have 2 of the legs already, the idler motor produces the 3rd leg and the run capacitors are use to balance it as close as possible. Keep in mind that from each leg to ground the voltages are 120, 120, and 240. Keep the L3 hot leg off of any transformers ECT... that are looking for 120V
This was very helpful. Thanks for showing
Can we forward and reverse the motor using DPS?
There is another option, solid state phase conversion (Phase Technologies). I have two, one of which is in my machine shop powering CNC equipment. They are expensive but very precise 3 phase generation. If you hook an oscilloscope to the output you can not tell which phase is generated and which is original.
That is the path I am headed down, more for the reasons of compact space and less noise that RPC.
I have installed those things too. they are more or less a vfd that has a static out put at 60hz. a vfd is likely cheaper. depends on how many machines you are going to have hooked to it. they make the same whine that vfds do as well.
Great educational video
Nils seems to be Small Engine Mechanic Mike's long lost brother. 😊
i will neither confirm nor deny...
@@nilzlima3027 😂🤣😂
Thanks for the explanation
Hey Keith! I wanted to point out that the DPS manual states there are voltage imbalances up to 50% that will balance under load. Is there any way you can test this?
Glad you did this video
It would be interesting to see the power factor on the 240 side (e.g. the ratio of the input current to the input voltage). That might explain why different output legs have different voltages and current.
That there is a good video. Thanks Keith
I've been running a three phase motor in delta configuration with a capacitor between two legs on 230 V single phase. This is called Steinmetz circuit over here and only recommended to a max 1 - 1.5 kw motor. I would never use that for a bigger or expensive motor since the phase shift is less than 90° instead of 120° and you get ripple curents and the different amperages. You also don't magically get the full power of real three phase. It's a simple solution for small tools, and should be treated as that. I am just running a small buffer this way and it's ok.
I was reading up on these and it says that there will be voltage and amp imbalance when the motor is under 50% load. It says they will balance once the motor is over 50% load. I would like to see that tested as a follow-up if you have time.
I would like to see the difference on a power analyzer. I don't think the phase shift is 120deg and that will cause the unbalance on the current. What worries me is that one phase was in an over current state. Power analyzer is basically a 6 channel oscilloscope, nice to compare voltage and current curves on one screen. We have compared the wave forms on a FVD before and after the line inductors. Even after the inductor the wave form was not a sinewave.
I've heard these described as two phase with a starting circuit which your demo proved out. For an in depth, but easy to follow review of motors controllers and VFD's go to Pump Ed 101 by Dr. Joe Evans. I have had the pleasure of sitting in on his presentations at workshops in the past. His online material appears to be transcriptions of his presentations. really good stuff.
Thanks again for providing another very informative video.
On the DPS you stated one phase passes through so its the other phase that is altered to create the 3rd phase. I wonder what the current was on each phase coming into the DPS.
The input to the DPS is 240v single phase.
Great review. Curious to see the differences compared to an Automation Direct or similar VFD.
As an engineer, I love the geekery!
at some point i may have a 'scope, one or more of those and some time so we might do that.
Ok I am an electrical engineer , worked in heavy power motors etc , question for your guy did you check the power factor in both cases ? the larger caps were there to provide a lag PF while the motor ( inductor ) will give a lag PF ,
I would be very interested if how much watt less current is present which would skew the reading as taken with the amp clamp
simply analogy for single phase v three phase single phase is like a single cylinder engine and three phase is a three cylinder engine , all will know which is the smoother of the two ,but if the circuit is unbalanced the three phase will cause the motor to run rough .
as a last request can you show us the wave form for a rotary and a the Little box of tricks ( I very much doubt that the motor winding will suffer with such a crude device
VFD re synesize the three phase from DC in the unit and before the smoothing cap it is a square wave due to the circuity
sure, if we had those tools but as with any video there needs to be a limit on how much stuff you put into it. idealy the capacitive reactance should cancel the motors inductive reactance to give you a PF of 1.0. the point of the box 'o' caps is to generate enough phase shift to create a rotating magnetic field in the motor. the degree of that shift will dictate the amount of torque the motor puts out. rest assured the PF is very poor, if the thing works like its supposed to i would expect something like 0.6 - 0.7. the only one who cares abute that is the power company and we have limited tools to make those measurements so its not in the video.
Well in reality, since the PF is the phase shift between voltage and current and the motor ideally has a maximum efficiency to reach it horsepower is at unity or PF = 1, it's more than the utility that cares. To get to the required needed HP the motor needs to do its job when the PF is shifted to 0.6 to 0.7 requires much greater current since the voltage, under normal conditions, would be fixed. This greater current will generate more heat, which will affect the lifespan of the windings/motor. So it doesn't just affect the utility, it will affect the life of the motor too.
Great information, Thanks
The old saying you get what you pay for rings true here I don't have a shop full of three phase equipment but I use to work in a place that has tons of conveyor belts and other three phase stuff and know how much it matters having good power over the three phases
Could you put high res pictures of both sides of the board up? I'd like to analyze the circuit myself (for fun, no commercial purpose). Curious to see what other nastiness this will generate. They are playing tricks for sure to make the motor turn.
I run my lathe off single phase with a homemade rotary converter. I used a potential relay and a pile of capacitors from the scrap yard. I set it up with a digital amp and voltage gauge for each leg from Amazon. It's a 10hp and has been in use for 10 years. The slave motor was also brought from the scrap yard just needing bearings, 25hp motor. With the digital gauges I can live data monitor each leg while using the lathe or any other machine plugged into that outlet. Study up on it and use common sense to get it done.
Just curious if anyone watching uses or has seen a Phase Perfect DPC? They are pricey for the home shop guy, but are supposed to provide service-grade 3 phase power that can be used for machines with sensitive electronics.
as a 'marine electrician' i got lots of stories.... amazing what can be done with old scrap... and salvage....
I was shown a jointer with 1' blades and 7' table w/ a7.5hp 3ph drive. powered from a 50amp 1ph breaker (??)....that fed 240vac into two legs of a 3ph switch to run a 240v 1ph 1.5hp motor and another switch tied to a 10hp 3ph motor paralleled with the jointer motor. These 2 motors were also joined with a lovejoy coupling ya, man! weird...
so turn on the power, turn on the 1ph motor to spin up the 10hp... turn on the 3ph switch, then turn off the 1ph switch and the planer gets the 3rd phase to run well.
I moved the 'converter' to in side the shop from it's dog house; and later an old planer (7.5?hp) was added that could be used if the jointer was off.
Very informative!! THANK YOU!!
Nils Lima with roots in Rogaland?
rogaland? a land of rogues?
Key VFD advantage is speed adjustment on lathes DURING the cut (slower on the outside of a large diameter, faster towards the center) and of course variable speed on lathe and mill.
RPCs are better for heavy steady loads not needing speed control. Bonus, more motors also act as more idlers. I start my compressors one at a time (two industrial 5HP are easier to power than a single 10HP and when not blasting I only use one) off my RPC. OTOH my lathe and mill have VFDs. See the Practical Machinist forum for the best detailed info on using both in a machine shop context.
Note some power companies bill all three phase at commercial rates so a large RPC may be a much better deal. Check before spending money. Also many areas do not have three phase at the pole.
We are a DPS manufacturer and seller. Thank you for making DPS video.
However, it seems like the video was made without much knowledge of the characteristics of DPS.
It appears that there was no load on the motor when testing the DPS.
However, the motor is never used without load.
When the motor load is less than 50%, there may be an imbalance from the voltages and currents output from the DPS. Normally, when the motor load is 50% more, voltages and currents will be balanced. The current in the middle phase of the DPS output changes depending on the motor load.
Most of our customers are using DPS very well on their 3 phase motors. We are concerned that customers may have misunderstandings about DPS due to this video.
We think that if the person who made this video had read the DPS user manual carefully, he would not have made a video like this. Thank you.
I almost bought one of those vfd,s. Glad I didn’t. Thank you.
Very interesting. Thanks!
Can you do the same comparison using a VFD? Yes, I know a Rotary Inverter is the best option but when you have just two machines to run and one is on a VFD, is it practical/ more economic to change over to a rotary system even if you use only one machine at a time and only once every other month?
I lucked out. I found a residential property that had three phase already set up in a 4500 sqft shop building that the previous owner was using for his business. It was the deciding factor for buying the property. Otherwise I would have gone with the rotary option to power my machines.
Thank you for sharing. 👍
Single phase...1 guy pushing the merry-go-round. 3 phase...3 guys spinning it.
Im using a DPS on my Clausing Colchester 12X40 and mine goes out on reset after about 20 minutes of use because the motor is getting to hot. Can anybody tell me which VFD I should get for it? It’s a 3/4HP 3 phase. It’s against the wall right now and I forgot how many amps it draws. Thanks
Actually my question is if I get like a 5HP model is that ok?
Rotary converters are the best, will outlast electronics in my opinion, and the sine wave is clean. The old capacitor-type “converters” aren't really converters, as they're designed only for starting a 3 phase motor, where one leg kicks out after they start, and you lose 1/3 of the power. That is why rotary has always been the best, if a well-made motor is used. I used a 20 HP, 3 Phase, Lincoln Electric Co. motor on the converter I had, with a small 1/2 HP blower motor (also known as a pony motor) to start the larger turning at the push of a button. Really, they're easily made.
When there's no 3 phase on the pole, it's your only hope, as I called the power company for an estimate to run 3 phase to my shop, and the price was staggering years ago.