We were called out to a farm that has a single phase, 7.5hp, 230v Baldor motor that trips the breaker as soon as the motor gets up to speed. It has 3 start capacitors and 3 run-capacitors (I couldn't tell you at this time if they are in series or parallel). The start capacitors tested okay, one of the run capacitors tested okay, the other two showed 0 mfd's (failed).
Could it just be that the two run-caps happen to be bad, or is something else causing them to go bad? And how might this cause the brkr to trip? The OL's aren't tripping. Current goes up to around 110 or so during start-up, then drops down to 40 (during the times that it didn't trip the brkr), which is nameplate for this motor. Voltage is around 240 before start-up, then dips to around 217 during start-up (the transformer is close, so this doesn't seem right?)
I don't know a ton about motor troubleshooting. Talking to a co-worker, he mentioned that if the start-caps were bad it would trip the OL's, but if the brkr is tripping, it's most likely the run-caps. If this is true can someone explain how this works and why?
Thanks for any input,
Sky
Could it just be that the two run-caps happen to be bad, or is something else causing them to go bad? And how might this cause the brkr to trip? The OL's aren't tripping. Current goes up to around 110 or so during start-up, then drops down to 40 (during the times that it didn't trip the brkr), which is nameplate for this motor. Voltage is around 240 before start-up, then dips to around 217 during start-up (the transformer is close, so this doesn't seem right?)
I don't know a ton about motor troubleshooting. Talking to a co-worker, he mentioned that if the start-caps were bad it would trip the OL's, but if the brkr is tripping, it's most likely the run-caps. If this is true can someone explain how this works and why?
Thanks for any input,
Sky