Excellent videos and you're a talented young engineer. I have been looking for intuitive and practical explanation for a lot of things as I have been working on a SMPS DIY Welder.
Actually I am working on 40kva ups..we developed the charger section by using igbt..in igbt block I connect snubber between +ve and -ve of igbt..where I should connect oscilloscope for measuring spike during turn off the igbt
@@lorenzo42p thats easy , you need to connect it across the resistor , but you need to make a resistor divider network to lower the voltage so you could hook it up to your scope ! ,resistance should be divided such that if your sensing 200v ,output resistive network should be 2v ,and if 400v then 4v etc .
the voltage spike is from the collapse of the magnetic field aroumd the inductor. the magnetic field energy is transformed into a voltage spike. this is useful energy. it can be stored in a capacitor, and used again.
Hi , This C R values have any dependency on switching frequency , mine is 25 Khz Ice is about 60 amps max and Vce is 20 volts and i found overshoot is about 75 volts @ 5 amps Ice.
Switching frequency doesn't usually affect turn off voltage to much extent. It can affect the turn off voltage indirectly however, for example, using a lower switching frequency on an inductive load will in theory increase the peak current, and therefore the turn off voltage. Mainly, the peak current and switching speed affect the turn off voltage. You can slow down the switching speed but of course, this leads to heating. What's the rating of your device? 70 volts at turn off with 20 Vce seems high, but not unreasonable depending on what you're using
I remember somebody doing or some product. They had a diode in series with the capacitor and a resistor across/in parallel with the diode. I thought it was a clever way of reducing ringing. Never got around to actually trying it. Maybe you could for all of us. Yea your just going to have to make up the resistor value bc I haven't the slightest.
Great video!!! i think u ve solved my problem on how to use the dv/dt protection scheme for IGBT i was thinking to use MOV but i didn't get the rated one 600+Vs and i ve to use snubber ciruit (the spike actually is suppressed by snubber)so i would be thankful if u could help on how to select R and C?
I am a bit confused. I originally watched your video (ua-cam.com/video/IdKhifMQUBI/v-deo.html) and it seems you recommend putting the snubber on C1/E2. I can't tell for sure on this video since you did not call out the terminals, but it appears you are recommending C2E1/E2 for the connection now. I am new to all of this and have damaged one IGBT module thus far. I thought the diodes were supposed to handle all of this. I am getting in some snubbers and would like to make sure I hook them up correctly. Thanks.
Matthew Kelton In most cases you would indeed connect a small metal film capacitor across C1 and E2. In extreme cases, such as presented in this video, you may need to connect a metal film capacitor across C2E1 and E2. What IGBT did you damage and how did you do it? there are plenty of ways to damage one, and it may or may not be related to the bus or snubber capacitor
subcooledheatpump I have a Powerex CM100DU-24NFH. Using their prototype driver board for it and have it wired up as in your chopper video. When I damaged it, I had no caps, as I was mistaken in thinking the built in diodes were all thr portection I needed. The IGBT is now permanently allowing current to flow. I tried to turn on a 12V motor at 4khz 25% duty. The motor jumped and appeared to sieze. The power supply went into protection mode as something was sucking all the available current. I increased current thinnking it was a spike and it kept doing it until it finally failed. With my second IGBT, i could start near 0% duty cycle and slowly move up, but i could not take a big step, nor start at any arbitrary duty. I will have my snubbers in tomorrow, so can try with them. The "sieze" problem occured with the second IGBT as well, but it has not failed, as I have not increased current now that I know that is not the source of my problem.
subcooledheatpump I should have said in the IGBT I damaged, that I was only using half the IGBT as a straight switch with no capacitors. As far as my problems are concerned, the 2nd IGBT is wired as you recommend (minus the caps) and behaves in the same manor with the motor "siezing".
Matthew Kelton Okay. If you didn't have any bus capacitors at all then it likely did destroy the IGBT due to an over voltage at turn off. In this case, I would get a replacement IGBT and start with a capacitor across the DC bus, that is, C1 and E2. I'd also try using a higher value gate resistor as a precaution, The IGBT in question is pretty small, and it can get quite jumpy using one of those powerex gate drive boards.
subcooledheatpump Thanks. I have a 22 ohm in there right now. Could this explain the siezing motor, too? I didn't think to look at the powerex fault line to see if it had done something at the gate board. I know power was still going to the motor, as I could hear the whine, but I think something else was pulling the current. What size would you have recommended? I thought a 10th would have been sufficient for the 40A motor. I killed the IGBT with an unloaded one that only is drawing a few amps.
Thank you for another excellent primer! And I still think you are the best natural teacher I have ever heard.
Mark Bunds I have to agree with that.
Excellent videos and you're a talented young engineer. I have been looking for intuitive and practical explanation for a lot of things as I have been working on a SMPS DIY Welder.
Thank you. This is exactly what I was looking for.
Actually I am working on 40kva ups..we developed the charger section by using igbt..in igbt block I connect snubber between +ve and -ve of igbt..where I should connect oscilloscope for measuring spike during turn off the igbt
have any info or pics online? sounds interesting
@@lorenzo42p thats easy , you need to connect it across the resistor , but you need to make a resistor divider network to lower the voltage so you could hook it up to your scope ! ,resistance should be divided such that if your sensing 200v ,output resistive network should be 2v ,and if 400v then 4v etc .
Always a treat to watch your videos :) Thanks
the voltage spike is from the collapse of the magnetic field aroumd the inductor. the magnetic field energy is transformed into a voltage spike. this is useful energy. it can be stored in a capacitor, and used again.
But how to do it, in such circuits when dealing with 350V DC 10A etc? Direct it to recharge the bulk capacitors, for instance?
@@tr_2sc1970 yes that's possible. Personally I direct those spikes into a series resonant primary coil to set up a displacement current
@@MasterIvo Thanks a lot for the quick reply I appreciate that.
@@tr_2sc1970 my pleasure
so the sunbber connects across the IGBT output and the negative bus rail ? is that correct ?
Hi , This C R values have any dependency on switching frequency , mine is 25 Khz Ice is about 60 amps max and Vce is 20 volts and i found overshoot is about 75 volts @ 5 amps Ice.
Switching frequency doesn't usually affect turn off voltage to much extent. It can affect the turn off voltage indirectly however, for example, using a lower switching frequency on an inductive load will in theory increase the peak current, and therefore the turn off voltage. Mainly, the peak current and switching speed affect the turn off voltage. You can slow down the switching speed but of course, this leads to heating. What's the rating of your device? 70 volts at turn off with 20 Vce seems high, but not unreasonable depending on what you're using
I remember somebody doing or some product. They had a diode in series with the capacitor and a resistor across/in parallel with the diode. I thought it was a clever way of reducing ringing. Never got around to actually trying it. Maybe you could for all of us. Yea your just going to have to make up the resistor value bc I haven't the slightest.
Great video!!!
i think u ve solved my problem on how to use the dv/dt protection scheme for IGBT
i was thinking to use MOV but i didn't get the rated one 600+Vs and i ve to use snubber ciruit (the spike actually is suppressed by snubber)so i would be thankful if u could help on how to select R and C?
Can u solve my problem..actu
nice demonstration, thank you.
You have not explain the how we can calculate the value of snubber
Is there any reason you couldn't use a zener diode to handle the transient spikes?
Muito bom!
Awesome :) Thumbs up :D
Alex
I am a bit confused. I originally watched your video (ua-cam.com/video/IdKhifMQUBI/v-deo.html) and it seems you recommend putting the snubber on C1/E2. I can't tell for sure on this video since you did not call out the terminals, but it appears you are recommending C2E1/E2 for the connection now.
I am new to all of this and have damaged one IGBT module thus far. I thought the diodes were supposed to handle all of this. I am getting in some snubbers and would like to make sure I hook them up correctly. Thanks.
Matthew Kelton In most cases you would indeed connect a small metal film capacitor across C1 and E2. In extreme cases, such as presented in this video, you may need to connect a metal film capacitor across C2E1 and E2. What IGBT did you damage and how did you do it? there are plenty of ways to damage one, and it may or may not be related to the bus or snubber capacitor
subcooledheatpump I have a Powerex CM100DU-24NFH. Using their prototype driver board for it and have it wired up as in your chopper video.
When I damaged it, I had no caps, as I was mistaken in thinking the built in diodes were all thr portection I needed. The IGBT is now permanently allowing current to flow.
I tried to turn on a 12V motor at 4khz 25% duty. The motor jumped and appeared to sieze. The power supply went into protection mode as something was sucking all the available current. I increased current thinnking it was a spike and it kept doing it until it finally failed.
With my second IGBT, i could start near 0% duty cycle and slowly move up, but i could not take a big step, nor start at any arbitrary duty. I will have my snubbers in tomorrow, so can try with them. The "sieze" problem occured with the second IGBT as well, but it has not failed, as I have not increased current now that I know that is not the source of my problem.
subcooledheatpump I should have said in the IGBT I damaged, that I was only using half the IGBT as a straight switch with no capacitors. As far as my problems are concerned, the 2nd IGBT is wired as you recommend (minus the caps) and behaves in the same manor with the motor "siezing".
Matthew Kelton Okay. If you didn't have any bus capacitors at all then it likely did destroy the IGBT due to an over voltage at turn off. In this case, I would get a replacement IGBT and start with a capacitor across the DC bus, that is, C1 and E2. I'd also try using a higher value gate resistor as a precaution, The IGBT in question is pretty small, and it can get quite jumpy using one of those powerex gate drive boards.
subcooledheatpump Thanks. I have a 22 ohm in there right now. Could this explain the siezing motor, too? I didn't think to look at the powerex fault line to see if it had done something at the gate board. I know power was still going to the motor, as I could hear the whine, but I think something else was pulling the current.
What size would you have recommended? I thought a 10th would have been sufficient for the 40A motor. I killed the IGBT with an unloaded one that only is drawing a few amps.
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