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IGBT DAMAGED


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#1 Guest__*

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Posted 19 December 2004 - 08:36 AM

we used in our factory VSD which controlled induction motor and that motor operated most of time as induction generator ,suddenly we found (IGBT) two from four are damaged ,so we changed the four IGBT instead of twowhich only damaged
question :can we changed only the damaged ones instead of all of IGBT?
why IGBT are damaged?
is the samething happened for cells of battery if any cells damaged we have to change all battery instead of only damaged cells?
plz can u help me/?
thanks on advance
gemi

#2 marke

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Posted 19 December 2004 - 05:50 PM

Hello Gemi

If you are operating most of the time as an induction generator, there will be energy passing from the motor into the drive. This needs to be dissipated somewhere.
The energy passed into the drive from the motor, will result in the DC Bus voltage being at a higher level than normal. Surplus energy would normally be shunted away and dissipated in a braking resistor, but if there is continuous braking, the resistor will get very hot.

The increased Bus voltage will increase the stress on the IGBTs and this may be the reason for failure. If you are continually operating in induction generator mode, then you should use an active front end drive to return that energy back to the mains supply. The additional cost may be recovered by the reduced energy usage.

It is normal to replace the two IGBTs in one phase (often in one module) and it should not be necessary to replace all IGBTs.

Best regards,

#3 Guest__*

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Posted 23 December 2004 - 10:34 AM

thanks mark
(then you should use an active front end drive to return that energy back to the mains supply.)
iam already have thyrestors (scr)which act as inverters to return power back to supply SO THAT IS MAY BE NOT THE REASON
second in one module thereis 8 (IGBT)THE DAMAGED ONLY FOUR IGBT REPLACE FOUR DAMAGED ONLY OR ALL OF THEM ,IAM AFRAID IT MAY BE CARRY MORE CURRENT WHEN THE OTHER DAMAGED
THE SAME FOR BATTERY CELLS (WE HAVE 40 CELLS )TO GIVE 80 v dc 2 volts each cell.some of battery cells damaged replace all battery or damaged cells only.that meane r the other cells affected by this damaged or not?

thanks on advance
gemi

#4 Guest__*

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Posted 23 December 2004 - 10:37 AM

we used battery cells at electrical forklift
and why r the battery damaged what could be the reason please help
thanks
gemi




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