Auto transformer help?
Auto transformer help?
(OP)
Hello all, I am an electrical contractor that does alot of control wiring and troubleshooting. I recently had to have a motor rebuilt due to power co. single phase problems during a storm. Upon reinstalling the new rebuilt we turned power off to the other motor. These are 60 hp 230v motors and are using auto transformer reduced voltage start. When we tried to restart the motor that had previously been running it sounded as though it was single phasing. All incoming voltages were good and during start up only experienced about 2 volt drop. My question is, is there any real good way to check voltage output on transformer? Or is there a proper way to troubleshoot the autotransformer?





RE: Auto transformer help?
If it is single phasing, (and assuming you already checked fuses etc.) most likely you burned up a set of contacts on one of the contactors when you lost a phase from the utility.
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RE: Auto transformer help?
respectfully
RE: Auto transformer help?
RE: Auto transformer help?
In a properly designed system the starter should be capable of as many starts per hour as the motor.
The time delay is usually as short as possible. Ideally the acceleration should be as smooth as possible. If the motor stops accelerating on the autotransformer and noticably "hangs" at an intermediate speed the time delay should be shortened.
respectfully
RE: Auto transformer help?
Timing is going to vary by load. Officially, you want to transition at the moment the motor stops accelerating because to not do so is stressing the motor and unduly wasting thermal time on the OL relay. Typically though, any longer than 15 seconds and you are risking the transformer as well. If it is a pump, I rarely see the transition time setting be over 5 seconds.
Just out of curiosity, what makes you think it is single phasing?
RE: Auto transformer help?
RE: Auto transformer help?
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