Old RELAY elevator controller - complete run-through (beginners welcome!)
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- Опубліковано 4 чер 2024
- This video explains the circuits of an old J&E Hall relay elevator controller, still in operation today!
All explained with my 'attention to detail' and hopefully in such a way that anyone can understand.
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NV likely is a very low value, typically 1R, very high power resistor, so that it will take 400A to ensure the fuses or breakers do clear the power, but such that the current is not going to cause the power transformer in the factory to saturate, and blow open the incoming primary fuses, or blow open the primary winding of the transformer. NV stands for Nominal Value, a resistor that is massive, capable of handling 400A short term ( 1 second) while the fuse or breaker has time to clear the fault, before the lift overtravels to the point of hitting past the bump stops on either car or counterweight. Needs to be robust because it gets tested every certification cycle for trip ability, and those little microswitch contacts get massively over current, so are likely to fuse closed in any case every so often.
I'm wondering if there has been accidents reported where the lift would go past the last floor and also what happened (did motor got stuck or did it damaged building)
I was going to comment "NV - I'll put my thinking cap on". However, this is very interesting information and something I would never have thought of! Many thanks for the answer!
I don't think it works that way. The path to NV will be opened in a failure state not closed.
It is possible that the NV "relay" may be a no voltage trip circuit breaker or disconnect (think opposite of a shunt trip setup) upstream of the elevator cabinet. That way if the elevator over traveled, the over travel switch would break the circuit to the coil and the upstream disconnect or breaker would kill all mains power to the cabinet, which would be an important failsafe in the event that a set of motor contactor contacts welded themselves in place and the motor would keep running even after control power was removed.
I grew up around my grandpa, and great grandpa fixing 95% of all of their stuff. They started explaining wiring diagrams to me when I was really, really young. They would show me the diagram, and then help me find the components on the whatever it was, dryer, washing machine, refrigerator, etc. I take it for granted that I know how to read wiring diagrams until I am around someone who doesn't. Then I will try and teach them at least the basics.
We still have several of these in service in Wellington, NV was an option to drop the main feed due to lack of power supply, in this country they all had a phase failure unit connected in this point in case someone reversed the mains on the street or that one phase was down causing the motor to run the wrong direction, the overloads are timed solenoids as mentioned above. The Chokes purpose is not to smooth the mains but to reduce the voltage to the slow speed motor essentially giving you another speed step and to protect the slow speed motor from overload, generally the motors are 16 pole vs 4 pole so levelling speed is 1/4 running speed, when running through chokes (or resistors on cheaper units) this allows more of a ramp down to the levelling speed. Chokes also didn’t need to be changed for large or smaller motors as would resistors. The contact on the brake was always called a cooling contact but it also reduced the back emf when the brake was disconnected reducing the flash on the contacts, less voltage on the coil also makes it drop faster giving a more accurate stop.
Excellent video, loved how you used highlighting over the original schematic to show the operation.
Thank you very much! Yes took ages to prepare all the layers, I also had to 'draw over' the original schematic to put as a top layer to enhance it further. Excellent result though.
Electromechanical relay ladder logic is just beautiful, and you did a good job with it :)
Engineers: let's spend a lot of time designing a complex choke discharge circuit. Capacitors: I'm going to make your life miserable
The choke is for limiting the current to the slow speed winding to reduce its torque and smooth out the downshift.
FINE job, Mr. Matt! Quality as usual! CHEERS!
Magnificent work and super detailed as always!
Thank you so much 😀
Good old times where schematics were provided on the device itself...
Fantastic video to help beginners to understand relay logic.
DASHPOTS 02:20 The oil in the dashpot is there to damp a sudden surge in the coil during motor (circuit) inrush, it is the strength of the magnetic field that determines the travel of the solenoid armature acting against the delay the oil viscosity imparts. The Solenoid then travels up to disconnect the contactor actuating coil circuit. The delay is adjusted by turning the dashpot oil reservoir and the index pointer shows the current adjustment. Great detailed presentation and graphics Thanks
When I first looked at the schematic diagram, it appeared that "NV" and the contacts in series with it formed a "crowbar" circuit that essentially throws a dead short between L1 and L2 (two of the main 3-phase power rails). In modern electronics (and especially power supply design) a "crowbar" circuit is used to short out a power rail if the voltage regulator fails and puts an over-voltage on the rail. The "crowbar" will short the over-voltage to ground, protecting the rest of the circuit, and will typically "blow" the fuse or circuit-breaker, requiring manual intervention to restore normal operation. Of course, the term "crowbar" likely refers to the large steel bar which can be used to physically short-circuit high-power circuits. (Don't try this at home!). Also see the comment from @SeanBZA.
Thank you for the channel. Always interesting topics and first-class production value.
Great episode, fantastic attention to detail as always, Nv- my thoughts as others have said would be that it cuts mais power to the cabinet, that would then require an engineer to attend, because if its over travelled something has gone fairly majorly wrong, ie contractor jammed in so cutting the control circuit wouldn't make any difference.
We have over travel switches on filters at work, that run up and down on railway track, if they miss the turn around limit and hit the over travel then they stop dead and need maintenance to attend. Each filter weighs about 6 T so it can make a big mess if they over travel.
awesome video
Great explanation, but one thing you cannot convey to us is what that equipment smells like! It's something that has to be experienced first hand. Old electrical stuff just has a smell and combined with old grease and oil, it's a real unique smell. Some of it is probably burning ozone would be my guess.
Another masterpiece. You are the Stephen Hawking of elevators. I'm going to have to watch this a few more times just to absorb all the info. Any tips on maintaining audience retention in your videos? I seem to lose everyone after about a minute. Thanks for the video.
Hiya. Thanks! Ok some advice then...
You have to put yourself in the place of the person watching the video. For me, most people that watch my videos are NOT subscribers - only about 6% are subscribers. So the average viewer, is perhaps not someone that's interested in lifts at all! Your challenge is to make them click then watch your video.
The video title and thumbnail are the first step to attract people to click on your video - this is the first challenge. If your video has captured the attention of someone and they've chosen to click your video, now you need something almost immediately to prevent them clicking out of the video, so you need something to keep them watching.
In the first 5 seconds (certainly within 10 seconds) you need a 'wow' factor. For me, it's something really exciting that comes later on in the video. So it'll be like, relays activating, the lift moving in the shaft, then something that people think 'what the heck is that'? Then I'll say "all this, coming up!!!". Then comes the intro.
Your videos are really good and you spend a lot of time on them, I can see that. But when I click on your videos, the first thing I see is your channel name scrolling up the screen very slowly. Remember what I said about captivating the viewer, probably most people won't want to see your intro through. It gives people too long to reconsider and click something else. So when the logo splits apart, I think you need it the other way around - go straight into what people are going to see in your video, show case a few exciting bits, but at this stage don't do your intro or show yourself doing a voiceover. Exciting bits first, then the intro.
Your intro, in my opinion, needs to be much faster, because nothing much is happening on your intro and it gives people too long to think 'CBA' and click away. Make it much faster, even if the text just zooms out of the middle of the screen, then parts in the middle (I know you want it to look like a lift, but for most people (especially the majority of your audience who probably are not interested in lifts), they wont see the connection between text rising and it being a lift - in which case trying to portray your logo as a lift is wasted anyway.
So - 1) Interesting title and thumbnail, 2) Within the first 5-10 seconds show case the interesting bits in your video that are coming up, 3) Cut to your intro but make it much quicker - if it's a bit boring then even more reason to make it quick and snappy (sorry to be so brutal, but just trying to help), 4) then cut to you telling people about the video, and so on.
5) Within the video (within the first 3 mins if possible), place a 'carrot on a stick' to keep people watching - for example "Now we come to this device, it's really interesting, and I'll tell you about it later". Never say "now we come to this device, BUT I'll show you later" - never suggest a negative (the word 'but') that may p*ss people off! :)
I hope this has helped you a bit, let me know if I can help further. Let me know if anything works for you above, i'm always interested.
Well, I have a theory about the N.V. device. But first of all: there is one important part of the circuit which you completely left out: the overload (O/L) relay. That's a three-bobbin current sensing relay, and it was very well visible in the first video. Now let's see how it is working:
1. First of all, the motor is always magnetized through the slow speed windings - as it takes time for R1 relay to actually change position, and by that, activating the fast relay; so the motor is started on the slow speed (which also means higher torque!), and that (and only that!) winding is receiving current through the O/L windings.
2. Now, as we can see, there is a series circuit, consisting of the NC contact of the O/L relay; the N/C contact of the overrun limit switch, and the NO contact of the N.V. device.
3. My theory is that the N.V. device is the self-latching bobbin of the main circuit breaker. This means, that device must be always energized to keep the main breaker closed. If for any reason this control circuit opens: by tripping the overcurrent relay; or by overrun, or even for blackout, the N.V. device got de-energized, which in turn causes the main breaker get tripped, and that means, a technician must intervene and check if the conditions are safe to energize the lift again.
I am not an elevator technician, but actually an electrical engineer, and for me that's the only way that circuit there makes sense.
It seems I might be wrong with the start sequence. I revisited the first video, and at 7:56 it is very well visible that the current sensing relay is actually labeled as SS O/L - which I can interpret as Slow Speed Over Load - and by checking the diagram it is exactly what it does: monitors the current to the low speed windings. The only thing I don't understand: why we are checking the overload condition _at the end_ of the travel? I mean, if the lift is overloaded, it should be deactivated immediately, shouldn't be? Why is it good to cut power a few meters before arriving to the station, after that we did all the travel carrying that overload, I have no idea...
Just brilliant. Gonna have to watch that again.
The "SS O/L" thing is only the power sensing part of the circuit. It detects the overload and opens the contact to the "NV" part. I think the NV is one of the two boxes hanging at the wall behind the controller box 1:04. It has to be something that also stops the lift if the up or down relay is failing in open the contacts. So only interrupting the power to the rectifier would not be enough in that rare case.
Thank you for another awesome video!
11:18 So, if there is a power outage, then the brake would be applied automatically due to loss of energy of the brake relay?
Great video as always!
Yes, it is a fail safe so the brake will apply if no power is present.
Makes total sense! Thanks for confirmation!
new video !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
LOL "The choke is CURRENTLY turned off." - A little electrical humo(u)r there.
There is only one resistor visible at 4:32 - there are 2 places below that resistor where the resistors are missing ...
I would say that's the resistor in parallel with the brake coil on the drawing.
I'm guessing that the NV trips the brakes on the car, in case of gearbox failure or hoist ropes slip on sheeve
Hey! do you still record sirens now i love secomak/klaxon CS8's
I wonder what the original rectifier was. I was expecting to see a vacuum tube, not diodes. Was the original selenium or something?
probably germanium diodes.
It would have been a Selenium rectifier as they were tested technology and a very common componet. It would be about six inches long looking like a finned heat-sink. They fail with age and give off an unmistakable pungent smell that is unforgettable.
When this was built, the original rectifier was probably selenium. They made a horrible smell if overheated.
@@Damien.DWell, germanium transistors can handle a few amps. But I've never seen a germanium diode able to handle more than few mA and possibly also the voltage (there isn't any transformer in the schematic so it could be rectifying mains). The contactors and relays together do draw some current and small germanium signal diodes definitely wouldn't be able to handle it.
@@xxexplosivexxxxexplosivexx8512 AFAIK the Philco Predicta TVs of the late 1950s used germanium power diodes, they definitely existed. If the voltage rating of a single diode was not enough they would just use several in series. This is exactly what they did with selenium rectifiers. The reason they were stacks of fins is because several low-voltage devices were put in series. In lower voltage applications like battery chargers there would only be a single fin because the reverse voltage rating of a single element was enough.
Having said that, they would've used selenium here. 1955 is a bit too early for germanium power diodes and the elevator controller was probably designed years prior.