Magnetic VFD and Motor Overload

Have you checked the VFD parameter settings to see if anything has been accidentally (or intentially)b changed?

Also check the VFD fault history record to see if the drive captured any fault events that may shed some light on what could be causing the problem. It may be something simple.

What are you driving with this motor? You could have some sort of blockage in the system being driven that is causing an actual motor overload, rather than a problem with the VFD...

We too have a few Magnatec drives in our facility and experienced something similar a couple of times (but not as extreme) with one driving a 150 hp motor running a fan.

Case 1: An internal wiring issue with the motor (plus according to the re-winding shop, a bearing issue even though the shaft rotated with no discernable - to the hand - problem).

Case 2: Current loads were higher than normal and the motor, fan bearings (via sound analysis during operation), and general process all checked out fine. There were no other local error codes except the overload condition. A few days after a couple of "nuisance" trips, one of the control boards burned out. Still not sure if the cooling fan went out or if there was blockage in the cooling vents but the system was apparently overheating to the point of causing an intermittent failure mode. The drive that we had was obsolete and we upgraded the electronics - which took a different set of parameters for set-up, including a different nesting order in the program. Have you recently changed out the drive and if so (and to one of the earlier posting points) are you sure the setup parameters are correct?

Is this a new installation and does it occur on start-up, during steady state operation, or ramping during process changes? When we changed from a mechanical damper control to the vfd, we had to limit the rate of startup to eliminate overamping of the motor and we also limited the rate at which the mortor would speed up when adjusted from the vfd to avoid "shocking" the system.

Tucker,

Check that the supply voltages are stable and that the motor leads are not leaky. The driven load can cause the motor to lag enough to be reflected in the 25% higher motor currents indicated. If it is not an electrical problem, it is mechanical. Look into the driven mechanism what has changed?

Luther M