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Help replacing IGBT's

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dawesy:
so the replacement VFD turned up ( last one lost its magic smoke :( )
got it all mounted up in the new enclosure, tested all the wires from the motor for continuity
, leakage to ground etc all ok. turned on the VFD and put the required settings in pressed go.............DL error code. checked the book and it lists 'output short' as the cause.
confused i once again checked for leakage to ground, nothing. checked my meter was working, it was.
OK we'll try again........BANG..... from the motor (no smoke though) turned off the VFD and put the power back on in the shop.
took the motor apart and found one of the supply wires had moved and been catching on the fan and had shorted (this is what killed the original VFD  :doh: )
i then replaced the  damaged wire and insulated it all up again, reconnected and very gingerly put the power back on to the VFD  :zap:
it powered up fine, phew looks like i got away with it.... press go again :zap: lights out again. this time the bang came from the VFD :(
realising that i wasnt going to get this one replaced FOC i decided to strip it down. one of the tracks to one of the IGBT had gone and one pair of IGBT's have continuity across all pins so im guessing they're toast.
now i looked on line at the part number (KDG20N120H2) and fount the spec sheet for it but not able to find a UK stockist. had a look on RS's site and found two possible replacements, the major specs are the same ,voltage,amps etc but there are a few differences.#
could some one with knowledge of these components have a look at the spec sheets and tell me if the replacements from RS will work?
ive attached the PDF spec sheets below .
many thanks

awemawson:
From a brief look they both look suitable. Both have a lower Vce(sat) value than the original, which is 'good' in that they will dissipate less heat when working.

Be aware that with a s/c ibgt the driver circuitry may also have suffered from electrons in the wrong places  :bugeye:

dawesy:
hi thanks for that andrew much appreciated. would i be best swapping all 6 to keep them all the same or will swapping 2 be ok?
if its toast then thats ok but if it is just these then its a cheaper fix than a new vfd.
really wished id checked the motor befor i put this one on, but with not getting any shorts to ground when i tested it it seemed ok. obviously as the fan rotated it caught the wire and shorted  :zap: :( :bang:

John Rudd:
My advice would be to replace all 6....but if cost is an issue then the decision is easy.....
As Andrew suggested there may be other parts damaged....especially the igbt driver chip (I assume it has one!)....
Do you have a variable bench power supply?....if so that would be a good aid to diagnosing any further issues....(especially if it has current limiting)....Failing that a variac and a 60 watt lamp in series with the supply to the vsd will limit the current.
Make sure all connections at the vsd and the motor are sound before power up else you'll end up with your own firework display....
Good luck and keep us posted  :thumbup:

awemawson:
You may well get away with just swapping the pair that are short circuit. If they are pricey that'd be my first approach but don't be too disapointed if powering on gives another pop.

I've no doubt that the 6 are arranged as pairs of totem poles across the internally generated DC from the mains, with the three common points being the generated phases. Sadly this means that if they have gone short circuit the driver stage will have had that high voltage on it. A picture  of the circuitry may give a few clues.

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