the drive is F13(GROUND FAULT) Its a intermittent issue when the motor is starting. we have checked everything i can think of. insulation on the cable good.no wire same to be grounded. we meggered the motor and all was looking good. Has anyone ever seen this issue.
powerflex 700 issue
- Thread starter ivia1983
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Krusscher
Senior Member
- Location
- Washington State
- Occupation
- Electrician
I've had it with a few Toshiba's that would do that and we would replace them and it would go away. Never really got down to why they did it but it was at a scrap yard and metal dust would find its way into the panels.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
Drives occasionally have oddball faults that pop up from time to time. Could be a lot of things. Have you checked the drive power section for any possible faults that might be visible? Maybe a crack? Maybe a black line where there was a fault at one time?
Could also be that the algorithm that the drive is using to determine a ground fault has occurred is being fooled by something else.
Could also be that the algorithm that the drive is using to determine a ground fault has occurred is being fooled by something else.
Saturn_Europa
Senior Member
- Location
- Fishing Industry
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- Electrician Limited License NC
I had the same thing on a small horsepower Power Flex 525. I ended up replacing the drive.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
GF in a VFD is what’s called “residual current detection”, it is summing the 3 output phase currents to make sure they come out to something close. That said, for a PF700 drive the difference must be 25%! Note that the current doesn't actually NEED to be going to ground, just that there is a current IMBALANCE of at least 25%. That's a significant amount of current depending on the size of the drive.
There are numerous things that can cause this, but the most common that are associated with it happening only when the motor is STARTING are a loose connection somewhere, water in a conduit or j-box, or capacitive charging current in the motor lead conductors. Capacitive charging current in the wires happens when the conductors are randomly laid in the raceway and because they are conductors separated by an insulating gap, they can act like a capacitor. When you first start the drive, that "capacitor" pulls all available current to charge it up, but because it is random, it is not pulling it the same on each phase and the drive trips. If the wires are not "VFD cable", this is easier to happen (the individual conductors inside of VFD cable are twisted, which helps prevent this issue). If you have loose wires inside of steel conduit, you can twist them before pulling them, but people rarely do this. So first eliminate the simpler ones, such as a loose connection somewhere or water intrusion. Then to test then capacitive charging current issue, pull the conductors out and "triplex" them (twist them together) and pull them back in.
There are numerous things that can cause this, but the most common that are associated with it happening only when the motor is STARTING are a loose connection somewhere, water in a conduit or j-box, or capacitive charging current in the motor lead conductors. Capacitive charging current in the wires happens when the conductors are randomly laid in the raceway and because they are conductors separated by an insulating gap, they can act like a capacitor. When you first start the drive, that "capacitor" pulls all available current to charge it up, but because it is random, it is not pulling it the same on each phase and the drive trips. If the wires are not "VFD cable", this is easier to happen (the individual conductors inside of VFD cable are twisted, which helps prevent this issue). If you have loose wires inside of steel conduit, you can twist them before pulling them, but people rarely do this. So first eliminate the simpler ones, such as a loose connection somewhere or water intrusion. Then to test then capacitive charging current issue, pull the conductors out and "triplex" them (twist them together) and pull them back in.
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