VFD Help

[vinnygalbo]

I have had 2 VFDs on the same piece of equipment go bad by an apparent
line to line short circuit. It destroyed the line contactor, tripped the motor circuit breaker, the feed circuit breaker, and the main circuit breaker feeding the panel. Motor was meggered line to line, and line to ground with no bad readings. It is now running fine in bypass mode.

Any help would greatly be appreciated.

 

[wyliesdiesels]

Sounds like an intermittent short when the motor is running.

Any burnt smells in the motor?

Need more info:

Line voltage?

Motor HP rating?

VFD brand model and size

Breaker sizes, brands & models.

Panel brands & models.

 

[American Locomotive]

Size of motor, voltage of equipment?

 

[lukebarber]

It sure sounds like you need a line reactor on that setup.

Does this load cycle frequently?
Do you stop the load by sending the stop command to the VFD, or opening the line side contactor?

Here's a good read on line and load reactor basics.

 

[MattT]

line contactor,

Where is this? And how often is it switched?

Sounds like an intermittent short when the motor is running.

Any burnt smells in the motor?

It'd be unusual for a motor, or motor wiring, problem to do anything besides faulting the drive.

It sure sounds like you need a line reactor on that setup.

 

[walta]

Do you have any of the machines original controls still in the circuit between the VFD and the motor?

If you do operating them while the VFD is powered up can damage the VFD in the way you describe.

The motor should not have a circuit breaker. If you do leave it, be certain to set the overload settings in the VFD lower than the one in the motor.

Try a different brand of VFD one that does not require a contactor. The only reason for a VFDs manufacture to require an external contactor is they do not trust there stop function to work.


Walt

 

[wyliesdiesels]

yeah the contactor and all the breakers is a bit odd.

should not have anything between motor and drive.

Drive should have protection for motor.

We need some more info

OP can you post some photos of your setup

 

[MattT]

Do you have any of the machines original controls still in the circuit between the VFD and the motor?

If you do operating them while the VFD is powered up can damage the VFD in the way you describe.

Switching between the drive and motor can damage the drive output. Never seen it damage the input.

yeah the contactor and all the breakers is a bit odd.

Contactor is the big red flag based on what little info the OP has given us. The breakers may be overkill but shouldn't be hurting anything unless they're tripping regularly.

One other thing is the OP mentions a bypass. If that kicked in when it shouldn't things could get real interesting

 

[JackRich]

Do you have any of the machines original controls still in the circuit between the VFD and the motor?

If you do operating them while the VFD is powered up can damage the VFD in the way you describe.

The motor should not have a circuit breaker. If you do leave it, be certain to set the overload settings in the VFD lower than the one in the motor.

Try a different brand of VFD one that does not require a contactor. The only reason for a VFDs manufacture to require an external contactor is they do not trust there stop function to work.


Walt

+1

 

[Muzzy]

Were the replacement VFD's programmed with the correct motor nameplate information?

Also +1 on adding a line reactor.

 

[laser3kw]

what happen to the OP?

We need to have questions answered