Air Compressor Voltage Rating

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Bobhook149

Bobhook149

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Looked at a job today where a new air compressor is to be installed. On the name plate it lists the motor as 3 phase 200v 29A. This seems to be a strange input voltage to me. The voltage in this building is 120/208, do I need to transform the voltage down?
 
Bobhook149 said:
Looked at a job today where a new air compressor is to be installed. On the name plate it lists the motor as 3 phase 200v 29A. This seems to be a strange input voltage to me. The voltage in this building is 120/208, do I need to transform the voltage down?
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No, 200 volt motors are the correct voltage for a 208 volt system, high torque motor applications such as air compressors require the voltage rating of the motor to be close to the supplied voltage, a 230 volt motor in most cases like this would be over loaded.
 
Electric-Light said:
Motors are usually rated 208-230. 200v label on motors aren't that common. Is it a Japanese motor?
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200 volt motors are very common on 208 systems, Iwire has a chart that show this, and if you call any motor manufacture you will find using a 230 volt rated motor on a 208 system will require derating of the motor, a 10 hp 230 volt motor will only be rated about 7.5 hp at 208, a big problem with air compressors that require a lot of torque to start up, I have seen a few motors on air compressors burn up trying to run a 230 volt motor at 208.

Remember less voltage will cause more pole slippage and more current in a AC motor, so while over voltage is bad, but not as bad as less voltage.
 
I'm borrowing Iwires chart that shows what I was talking about:

ANSIC841.jpg


If you look under "nominal" and find 208 follow over to "name plate/motors" you will see 200 volts.

Manufactures can list what ever acceptable voltage their motor will run on, but if you dig deeper you will find most will have either a 200 volt 208 volts only or a 220 volt rating to cover operating from 208 to 240 volts, but if a motor has a straight 230 volt rating, it has to be de-ratted to operate on 208 if it is even allowed.
 
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stevebea said:
Aren't they usually rated 208-230 volt or 230 volt?
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Yep they are, however many Japanese motors are rated 200v right on the tag, which is the nominal voltage there for a voltage a notch above standard plug-in stuff, which is 100v there.

200v just happens to work real good with our 208v.
 
Electric-Light said:
200v just happens to work real good with our 208v.
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No, a NEMA 200 volt motor is designed with the intention of connection to a 208 volt source, just like a 230 motor is intended for connection to a 240 source and a 460 motor is intended for connection to a 480 volt source.
 
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