PF755 - Inverter Overtemperature Factory Limit

We have a Powerflex 755 set up for motion control that is giving us a overtemperature alarm.

We swapped out the drive for one of our new spares and we get the same issue. Is there any kind of troubleshooting I can do ?

The cabinet is pretty cool that this drive is located in, and this alarm/fault happens pretty regularly.

Fault Information:
Inverter Overtemperature Factory Limit
Subcode 2.
Trnsistr OvrTemp

Have you checked that the heatsink isn't full of dust/dirt? In my experience, the PF750 series does not like dirt, especially when compared to the older 700 and 1336 drives. Also note some of the large drives stick the heatsink out of the back of the cabinet and will get full of dirt, even though the drive itself is in a clean cabinet.

Is this motion with an induction motor or motion with a PM servomotor? If servomotor, does this occur when the axis is standing still under load? Is this a new application or has it been running for a while?

With an induction motor sitting at zero speed under load the electrical supply to the motor is still rotating around the motor at slip frequency. This distributes the current load through all the transistors in the power section. With a PM servomotor at zero speed there is no magnetic field motion so there is no change in the current demanded from any given power section transistor. Depending on where the motor is stopped this could have one transistor operating at a high current continuously. I'm not sure the PF755 was ever really intended to do that.

Keith

Helliana,
The drive we installed was fresh from Rockwell, and we still get this fault. I suppose it still has the possibility for debris to get inside of the drive. Ill see what I can find out.

kamenges,
This is a servo motor. Its a AB MPL series. This has been in operation for about 6 months, then all of a sudden we started getting these faults. We swapped the drive for a new one and still get this issue. It only happens during movement.

We actually have another machine identical to this one, and it doesnt have this issue. Its been in service for almost 3 years.

Have you swapped the motors between the two machines?

Also, trend the axis torque feedback between the two machines as the machine runs through a cycle. It the machines are the same the torque profiles should be the same.

Keith