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3 phase motors

MrJack96
I’ve got two questions regarding maintenance on motors. The first one is is there any hazards lubricating a motor in service I know obviously there will be mechanical safety to be aware of but electrical is there any issues. 


my second question is with motor overloads how bad for the motor is having a 1.8amp 10a overload on a motor with 1.75FLC I know it can still be overloaded by 50ma but is it a concern. 


thanks again guys!
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    A very small overload on a motor will in practice be fine except uder otherwise adverse conditions. It is not amps as such that kills motors, but temperature rise.

    If a motor rated for 40 degrees ambient is slightly overloaded at 20 degrees it should be fine. If however it is designed for up to 40 degrees ambient, but then overloaded, even slightly at 50 degrees ambient, then it may have a reduced life.


    fluctuations in mains voltage or in mechanical load may result in the overload being a little more or a little less than expected. The actual tripping current of a thermal overload relay also varies due to manufacturing tolerances and the ambient temperature around the starter.


    For a new installation, I would consider it a poor design that permits of overloading a motor, fit a smaller overload relay, or a larger motor.

    For an existing installation that shows no signs of trouble I would be inclined to accept it.
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  • 0
    A very small overload on a motor will in practice be fine except uder otherwise adverse conditions. It is not amps as such that kills motors, but temperature rise.

    If a motor rated for 40 degrees ambient is slightly overloaded at 20 degrees it should be fine. If however it is designed for up to 40 degrees ambient, but then overloaded, even slightly at 50 degrees ambient, then it may have a reduced life.


    fluctuations in mains voltage or in mechanical load may result in the overload being a little more or a little less than expected. The actual tripping current of a thermal overload relay also varies due to manufacturing tolerances and the ambient temperature around the starter.


    For a new installation, I would consider it a poor design that permits of overloading a motor, fit a smaller overload relay, or a larger motor.

    For an existing installation that shows no signs of trouble I would be inclined to accept it.
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