HVAC - 1 s.board supply for 1 AHU, autoran and inverter burn! Investigated is AHU's motor short circuit! Why?

I have did the Mega-test for the wiring is ok but the motoris showing short-circuit. When it occured the main imcoming power was triped also! I suspect is the motor cause the autoran and ABB inverter are burn! But this motor is for the AHU air supply, is that high changes of the water cause the motor short circuit although the motor should be suitable under the environment. Cuase any expert or electrical expert answer me? Thank you very much.

Answer:
Could be a short in the motor (insulation failure), or if it is a variable speed drive, bad Coast settings could cause the motor to generate power back into the inverters and burn the inverters (i.e. if coast time is too short, VSD voltage will drop but spinning motor will backfeed into VSD!)

I guess the AHU has manuals. It is better to consult the manuals as we have different type of AHU and brands and models.

Your English is difficult to understand. What I presumed is that there is short circuit and Inverter burnt. Naturally. If the motor is short then the inverter which supplies power to the motor will burn since the short circuited motor will draw large current.

But normally the inverter will have short circuit protection along with fuses and trip circuit(MCCB).

If water falls on the motor short circuit is possible. So please check all the circuit and systems.

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HVAC - 1 s.board supply for 1 AHU, autoran and inverter burn! Investigated is AHU's motor short circuit! Why?

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