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VFD beginner question. 1
- Thread starter fabiosm
- Start date
Just the classic measurements to test those type components. Google it/them.
If it's a VFD under a few hp - just run it. If it has a problem with the IGBTs it will probably tell you. Use a clamp-on to see if the three phases supplying the drive are pretty close together. If they're not, but the voltages are the same, you have a bad rectifier.
You can do the same test with the outputs. The actual amp numbers will be complete and utter garbage but they should be very similar.
Keith Cress
kcress -
If it's a VFD under a few hp - just run it. If it has a problem with the IGBTs it will probably tell you. Use a clamp-on to see if the three phases supplying the drive are pretty close together. If they're not, but the voltages are the same, you have a bad rectifier.
You can do the same test with the outputs. The actual amp numbers will be complete and utter garbage but they should be very similar.
Keith Cress
kcress -
- Thread starter
- #3
Thanks Keith.
I posted this thread because I came across a case this week of a VFD displaying a short circuit fault message. When I replaced the output IGBTs, the drive stopped displaying this message and started working perfectly again.
The problem is that, when I measured them, they didn't appear to have anything uncommon. The test that i made was using a multimeter in diode scale.
Thanks,
Fabio Melo
I posted this thread because I came across a case this week of a VFD displaying a short circuit fault message. When I replaced the output IGBTs, the drive stopped displaying this message and started working perfectly again.
The problem is that, when I measured them, they didn't appear to have anything uncommon. The test that i made was using a multimeter in diode scale.
Thanks,
Fabio Melo
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1
- #4
An output short circuit fault with the motor leads disconnected is usually a shorted IGBT. They will generally short when they fail but, in your case, they didn't.
Sometimes, at a test voltage of 1.5V, the short will not appear where, at operating voltage of 660VDC, it will. That's probably what happened with your drive. You did the right thing.
Sometimes, at a test voltage of 1.5V, the short will not appear where, at operating voltage of 660VDC, it will. That's probably what happened with your drive. You did the right thing.
LPS for Dick. Too often people trust that little battery in their DMM for everything.
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Completely correct Dick.
Many modern meters deliberately test resistance at less than 0.6V to avoid forward-biasing any semiconductors. It is very easy to be misled - you need to understand the capabilities of the instruments.
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If we learn from our mistakes I'm getting a great education!
Many modern meters deliberately test resistance at less than 0.6V to avoid forward-biasing any semiconductors. It is very easy to be misled - you need to understand the capabilities of the instruments.
----------------------------------
If we learn from our mistakes I'm getting a great education!
Often when set to their highest resistance scale they change to supplying substantially more voltage, like 9V or the reference voltage.
Keith Cress
kcress -
Keith Cress
kcress -
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