Pump Motor Reversed at Generator Set Power

3 replies [Last post]
aldrin277's picture
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Joined: 2015-08-11

Hi! I'm Aldrin and I'm new in this forum. I am an electrical service technician in a power generating set sales and services firm. I have a situation which might need your expertise or could relate to your previous experiences.

We have supplied a 350kW generating set to a condominium. This building has a 380V, 3-phase system and a 220V, 3-phase system. The 220V system is being distributed through a 3-phase step-down transformer. The power switching between the building's two main sources (Utility and Genset) is done with an automatic transfer switch (ATS). The problem is when the power is switched to the generator set during utility failure. When this occurs, all of the 3-phase 220V pump motors are running in reverse. We don't think the generator set is out of phase because the 3-phase, 380V motors (including the elevators and blowers) are running normally.

Is there anyone that has experienced this before and have pinpointed the main cause of trouble? Your thoughts would be much appreciated.

testor's picture
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Joined: 2016-02-03

Are the motors that stay running the correct direction being run off VFDs? If they are they will run properly even with a phase reversal.

aldrin277's picture
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Joined: 2015-08-11

Thank so much for the reply, Sir. That's one thing I have to find out cause that really makes sense in terms of phasing conflict. I'm still wondering because the utility and gen-set are in-phase, but this information was only given to me by those who performed the test and I didn't actually observe the testing. I'm not really sure they actually did the test, either.

aldrin277's picture
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Joined: 2015-08-11

I see. I never thought VFDs had phase reversal protections. I'll have to find out if these 380V motors are running on VFDs. If so, I could rearrange the gen-set phase for the 220V motors. Thank you so much for the idea. This helps me a lot.

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