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Igbt Damaged In Ab Inverter


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Dear Friends,


I had been working for re-programming an Allen Bradley 5.5kw inverter for running a 2.2kw motor. The inverter had been working with 5.5kw motor perfectly before re-programming. When I set all parameters and enabled the inverter, “Enabled” displayed on its HMI but motor did not start while I set 3.5HZ in “Minimum freq” parameter. After almost 5 sec, when inverter was enabled, its IGBT blasted like a bomb and ……..

My inverter is now dead. I was amazed how it could be possible. I have many times programmed the inverters but it happened first time in my 13years field life.

Any body has any idea for that problem?


"Don't assume any thing, always check/ask and clear yourself".

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Is the 2,2kW motor good at all (had it been checked, started on line and checked running before the connection to the VFD) ?

And maybe the circuit breaker intended for the previous 5,5kW motor was mistakenly used with the faulty 2,2kW one?

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Hello AB2005


Have you checked the 2.2KW inverter?

I would suggest that there may be a problem with it.

At 3.5 Hz, if the shaft was not rotating, the motor could draw excessive current, especially if it has a fault and this coupled with poor inverter protection could be why the smoke came out.

I would check to see if you have the motor wired up correctly. A common fault here is to connect a 230/400 volt motor in delta for 400V operation when it should be connected in star.


Best regards,


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This is my general practice that I always check the motor, cable and other accessories before powering up. I installed that inverter separately with new MCB 16A. Motor current was set 3A and motor resistance was ok and tested.


Normally when we enable the AB inverter “Enable” and frequency command display on its HMI. But in my case “Enable” displayed but no frequency command appeared and after 5sec, IGBT blasted and MCB tripped. Really first time I had seen that.

After that I rechecked the motor and all circuit and found every thing OK. I checked that motor with another inverter and found OK. This is possible that I made a mistake but what? If high current passed in inverter, why it did not trip?


"Don't assume any thing, always check/ask and clear yourself".

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