top end of motor voltage tolerance

[angryman]

Apparently, military power generators are less than accurate. I have a situation where there's a 220vac 3phase motor being run by (approx)247vac and the motors are burning up....what would be the most reasonable (cheap, simple, easy to explain)way to reduce the voltage? I'm guessing I can't just put a big resistor in series....

 

[davidbeach]

Get three buck-transformers and connect them as needed to kick the voltage down to the right range.

 

[itsmoked]

Check the technical area of this site. They have lots of diagrams that show what DB is talking about.

http://www.acmepowerdist.com/

However I would wonder why the "generator?" is putting out such a high voltage. You are probably stressing a bunch of other stuff too. Bucks for the motors may leave other stuff failing. See if the generator's voltage can be adjusted to the correct value. (Could be as simple as turning a screw)

Furthermore (still considering a generator) you should definitely check the frequency! A high voltage could be a symptom of over speed. This would mean your motors are all running faster than expected, which would mean they are being forced to do more work than designed for, and hence are burning up.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[stevenal]

220 is not a NEMA standard nameplate voltage for motors. 230 is. Should be able to withstand namplate plus 10%.

 

[electricpete]

Did you take any current readings?

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[oftenlost]

Motors can tolerate 10% voltage deviation but this amount is reduced if the frequency varies according to GE Motors Selection and Application booklet. I too would be interested in the currents encountered.

 

[machmech]

Hi Keith you might have some thing there I just got rid of a military Generator it was 400 Hz. I read it was used for aircraft electronics.

Chuck

Getting older is inevitable
Acting your age is optional

 

[waross]

what would be the most reasonable (cheap, simple, easy to explain)way to reduce the voltage?

See if the generator's voltage can be adjusted to the correct value. (Could be as simple as turning a screw)

And

Furthermore (still considering a generator) you should definitely check the frequency!

respectfully

 

[suriae]

I presume that your generator is driven by an internal combustion engine and the situation was not like this from the very beginning. To begin with a cheapest solution have a mechanic check the GOVERNOR paying attention to the adjustment of speed setting and "speed droop" while observing the "voltage droop" when the generator is taking up heavy load. If you are familiar with"Dynamic Load test" of a generator then do it first. Adjust the voltage regulator as itsmoked suggested.