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Thread: Question on a 460V, 3 phase 50hertz pump motor

  1. #1
    Join Date
    Sep 2005
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    Question on a 460V, 3 phase 50hertz pump motor

    This is a pump motor in a Heidleberg printing press. Made in Germany. I was fixing a refrigeration problem on the chiller portion of the machine. I couldn't help notice a pump & motor assembly the maintenance man just installed didn't sound quite right. I put my hand on it to find it very hot. The tag on the motor shows it's rated at 7amps @ 50 hz. I took a reading and saw it drawing 7.5 amps. I later found out the press manager ordered the motor but when confronted with the decision of choosing a 60hz. motor or a 50hz. motor, he basically flipped a coin and ordered the 50 hz. motor out of ignorance. I feel obligated to point this out to him before the motor cooks. I realize I've given very little information about the pump or the motor, that's because I don't have anymore info. Just looking for smarter people than I to give their opinion. I feel running a 50hz. motor at 60 hz. will increase the RPM's slightly and increase the load which explains why it's so hot and drawing .5amps over it's nameplate rating. Do you agree with my assessment? FYI, the motor he removed had a 60hz. and a 5.5 amp rating.
    Again the motor in question doesn't have a dual 50/60hz. rating, nameplate says 50 hz. 7.0 amps.

  2. #2
    Join Date
    Apr 2009
    Mobile, AL.
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    It is hot because the pump and motor needs to turn a specific speed against a specified head pressure.
    The 50 Hz motor would turn 1500 rpm on 50Hz and it will turn 1800 rpm on 60Hz.
    If the pump is sized for the 50 Hz speed (1500 rpm) then it will be turning faster and absorbing or putting out more horsepower.
    A 50 Hz motor on 60 HZ will produce 20% more hp than nameplate.
    A 50 hz motor would be 1500 rpm ant it's proper voltage would be about 380.
    The same motor woild run 1800 rpm on 60 Hz and 460 v and produce 20 % more power.
    If the motor has beem replace because it burned out it is possible that the load on the pump turning faster is requireing more power than would be proper. Sometimes the impeller is trimmed to reduce the output to the proper amount.
    The germans would be able to tell you.
    A given pump absorbs power at least on the square with speed. 20% faster would mean at LEAST 40% more power and probably more like twice as much.

  3. #3
    Join Date
    Nov 2004
    Anchorage Alaska / Seattle WA
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    Jbarron4 is exactly correct... tell the customer and sell him a new motor... 50hz motors that are not dual voltage rated don't work in this country very long... and the one your looking at will be no different. He probably called the manufacture of the machine which happens to be in Germany... a 50hz nation and they sent the one they usually manufacture it with. Simple fix..

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