PowerFLex700 tripping issue

We have a Power Flex 700 VFD installed which in turn gives power supply to 55 kw motor. Once the VFD tripped due to over heating of vfd. We inspected and found there was vfd was actually overheated. We arranged for proper air circulation and cooling of VFD. But even after that the fault came again. This time the temperature of exhaust air from VFD was not that hot. It was only 36 degree centigrade. We checked the thermister. It was OK.

When we start the VFD, the temperature starts with 36 degree, but soon rises quickly to about 85 degree centigrade even if the actual temperature of exhaust air is not so hot and VFD trips due to VFD temerature fault.

Can anyone give a solution to the problem?

There is no "VFD Temperature Fault" by itself, there is a Heat Sink Over Temperature fault (code 8), a Control Board Over Temperature fault (code 55) and there is a Transistor Over Temperature fault (code 9). Which one was it specifically? It makes a difference when trying to troubleshoot.

Then, was it working fine for a long time and recently began exhibiting these symptoms, or is this new and it is happening right away?

Possible causes if it is old and this just started happening:

• An internal circulating (stirring) fan has failed
• Failing power device
• Faulty thermal switch on the heat sink.

If this is a new installation and this is happening right away, it's possible that someone has the PWM Frequency (parameter 151, carrier frequency, not motor frequency) set too high for the connected load. In other words if you increase the carrier frequency to reduce audible noise, you must also de-rate the drive to account for the added switching losses in the power devices. Any setting above 4kHz requires de-rating of the drive output current capacity.

It is actually Powerflex400 VFD.

The fault is Heat sink over Temperature fault( fault 08). We checked the thermister by taking out the thermister and checked the resistance. It was OK.

It is not a new VFD. It had run for almost 180 hours.

The motor is run for 15 mins duration after each 2 hrs.

check your motor and cable condition.

refer the previous amp during running with load.

We have replaced with a new VFD( spare one), put the same settings as the damaged one. The VFD is running OK.

The VFD was becoming faulty even before starting the motor. Fault was coming 2 minutes after VFD was power ON without giving any load ( motor load)

i have a similar problem with our relatively new powerflex 753 indicating error code 9(transistor overtemp) kindly guide.

according to the manual:
The output transistors have exceeded the maximum operating temperature.
See P941 [IGBT Temp Pct] and/or P942 [IGBT Temp C].
If using the drive on a chiller plate, P38 [PWM Frequency] must be set to 2 kHz.