I am replacing an IGBT for the current controller in an eddy current dyno. There is an IGBT that takes the rectified 220Vac and turns it into about 311V dc and stores it in some monster caps. The problem is that lightning or for some other reason the IGBT has failed. Anytime there is current applied to the circuit it passes straight through the igbt, and therefore makes the dyno run at full load. Luckly the breaker is sized small enough that it blows the breaker before the coils burn up in the dyno's absorber.
The part is obsolete now, and my question is if I can put the newer part in it. It is the same package, same ratings, but has dual IGBTs in it. I will have to cut off the gate and ground pins of the 2nd IGBT pins 11 and 12 for it to fit into the circuit board. Can I leave the gate floating for the 2nd IGBT? Do I need to use a resistor to pull down the gate between pins 11 and 12?
Hi mike ! You can leave it floating or another option is to parallel both, using a 2nd gate resistor with the same value as the original one. The output current will be shared so each will handle roughly half the load.
Thanks for the info. Would it be safer to just add a resistor between pins 11 and 12, the gate and drain, or does it truly not matter and floating is alright?
I am replacing an IGBT for the current controller in an eddy current dyno. There is an IGBT that takes the rectified 220Vac and turns it into about 311V dc and stores it in some monster caps. The problem is that lightning or for some other reason the IGBT has failed. Anytime there is current applied to the circuit it passes straight through the igbt, and therefore makes the dyno run at full load. Luckly the breaker is sized small enough that it blows the breaker before the coils burn up in the dyno's absorber.
Sounds like back-EMF toasted it - a large MOV to prevent over-voltage on the DC bus is perhaps needed?
The part is obsolete now, and my question is if I can put the newer part in it. It is the same package, same ratings, but has dual IGBTs in it. I will have to cut off the gate and ground pins of the 2nd IGBT pins 11 and 12 for it to fit into the circuit board. Can I leave the gate floating for the 2nd IGBT? Do I need to use a resistor to pull down the gate between pins 11 and 12?
You should use a hard short between 11 and 12, no point bothering with a resistor - a floating gate
in a high power high voltage MOSFET or IGBT will mean immediate "BANG!"
joseluis_collado:
Hi mike ! You can leave it floating or another option is to parallel both, using a 2nd gate resistor with the same value as the original one. The output current will be shared so each will handle roughly half the load.
Cheers, JL.
Please don't give blatantly wrong advice - you clearly know little about high power modules.
I was a little hesitant to leave it floating, I know from experience that it's a bad idea with mosfets, and definitely bad with regular transistors, but i'm not very experienced with IGBTs. I'll go ahead and short pins 11 and 12. The IGBT failed when it was not in use, that's what making me think it's lightning.
I have a new module enroute and am looking forward to a 50$ fix instead of a 800$ fix for an entire new board.
From a users point of view there is little difference between a MOSFET and an IGBT - certainly
the gate structure works exactly the same way.
However IGBT's do not have the body diode that MOSFETs have (some come with a separate
diode in the same package, but by not means all).
In general below 100V MOSFETs are the normal choice, from 100V to 1800V IGBT's rule
In higher voltage power electronics more robust devices like thyristors are more likely to
be seen, despite their inability to turn off. If you have a multi-megawatt electric motor, its
controller will probably be using dirty big thyristors.
electric bike - MOSFETs, 36V
electric car - IGBTs, 400V
electric train - thrystors, 11,000V