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Can the frequency of a power supply affect motors?

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  • 26-06-2008 2:30pm
    #1
    Mr Magnolia
    Moderators, Recreation & Hobbies Moderators Posts: 10,435 Mod ✭✭✭✭


    Can a change in the frequency of a supply affect the performance/life of a 110V motor?

    I've seen it discussed here before but I'm still interested in discussing it further.

    If an electric motor is rated for 120V 60Hz can it function properly on a 110V 50Hz supply?

    Assume the rotating drum isn't controlled via an electronic circuit. Does the drop in frequency affect the performance and/or lifetime expectancy of the motor? Can we expect modern equipment/motors to be able to function correctly on either frequency?

    Any/all opinions welcome :)


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    #2
    Andrea B.
    Registered Users Posts: 1,926 ✭✭✭Andrea B.


    If you are talking about the direct supply to the motor, yes, the frequency determines the speed, so expect a proportional increase/decrease in speed. On a performance front, that's specific to the task?

    If the motor is running on a frequency not rated, then it's cooling (speed/airflow etc.) and mechanical functions have most likely not been stress tested in design at those speeds (unless validation parameters reached them EG. a 60Hz motor was tested between 50Hz and 70Hz).

    All in all, I'm not giving back my DeWalt 12" US chopsaw, just because it's running 16% less than rated.


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    #3
    Hoagy
    Registered Users Posts: 708 ✭✭✭Hoagy


    If you're talking about power tools, then it's generally not a problem. Most power tools have universal motors with brushes which are more or less indifferent to the supply frequency and will even operate on DC.
    Large appliances like washing machines etc are more likely to have induction motors where the frequency controls the speed and hence the cooling as Andrea B has mentioned.


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    #4
    Tom Donnavan
    Registered Users Posts: 49 ✭Tom Donnavan


    universal motors which use brushes should not be affected by the 10 hz drop but some induction motors (solid steel looking rotar as opposed to wire wound armature) have a centrafugal sw on the rotar to knock out of circuit the start capacitor at approx 85% of full load speed.If the sw does not open it may burn out the motor. if it is a dear motor it is possible to get an electronic relay fitted which opens after 1.5 to 4 seconds.

    R.P.M. = FREQUENCY * 60 (seconds in minute) / no. pairs of poles.


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    #5
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    the frequency only affects the speed of induction motors. power tools with universal motors wont be affected by frequency


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