500v to motors

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FORK

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I have worked several times at a small factory in a small town that is having motor issues. It is a 480v service that is metering at 500v on all three legs from the POCO. Can this be an issue for motors rated 460v-480v?
 
FORK said:
I have worked several times at a small factory in a small town that is having motor issues. It is a 480v service that is metering at 500v on all three legs from the POCO. Can this be an issue for motors rated 460v-480v?
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20 volts over 480 is no big deal, 460 volt motors are designed to run on 480 systems.
 
I'm really curious to hear about this 500V service. :confused:

I'm wondering if it's actually a 480 volt service that's running on the high end.
 
Motors have a +/- 10% tolerance. A motor for a 480v system is rated 460 to allow for a bit of voltage drop. 10% of 460 is 46 volts so at 500 V you are OK. But as the voltage increase past 10% the current goes up as the magnetic field saturates.

What are the motor issues? Far more important is the voltage unbalance.
 
peter d said:
I'm really curious to hear about this 500V service. :confused:

I'm wondering if it's actually a 480 volt service that's running on the high end.
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It must be.

500V is not a recognized standard (UL, IEEE, ANSI, NEC to name a few)voltage in the US.

The NEC requires us to refer to systems by their nominal voltage of 120, 208, 240, 480, and 600V.
 
If the 500 volt reading is new, check with the POCO, I recently had a Liebert UPS repeatedly going into alarm for high voltage. The POCO had accidentally left there automatic tap changers on boost and I wad getting 507-511 volts phase to phase.

If the 500 volt reading has been around a while, you may need to change the taps on the incoming transformer.

Jim
 
500v to motors

Thanks for the posts. Yes it is a 480v service, and yes it has been reading 500v for quite some time. (since day 1) The problems are 1. The owner is attempting to produce wood pellets instead of staying home and taking care of his farm animals. (Motors are possibly being pushed to hard.) 2. The POCO is a small town who has their own electric utility.(Under qualified and lacking experience.)
 
FORK said:
Thanks for the posts. Yes it is a 480v service, and yes it has been reading 500v for quite some time. (since day 1)
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I suggest checking with another meter, just in case.
 
It's not uncommon to see +/- 5% on a system voltage.

Roger
 
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