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Re: The chilling truth about cold horsepower

I also began thinking about the total electrical power a 1 HP motor draws. Bill is right when he listed many types of motors. I was just going to choose one and see what the locked rotor or full load amps rating is. That will give the total energy going into the motor. As Bill said that energy is partially converted to heat and lost( the label on the motor will list the Temperature rise). Most (we hope) is converted to rotational energy. I think that even the sound it produces as it runs is a source of energy loss even though it is probably an extremely small amount. Can you think of any others?

Locked rotor current is a WORST CASE and is significantly more than the motor's running current which is a better measure of the energy going into the motor. Locked rotor current is usually used to determine circuit sizing and overcurrent device trip ratings.

Motor losses are mostly thermal, which are both from electrical (resistive) losses and frictional losses in bearings. Sounds too would be a loss, but I doubt that would be even a single watt worth of loss and I wouldn't worry about it for our purposes. ANYTHING that isn't making the shaft twirl around is a loss in a motor, since ideally ALL the input energy will come out as rotational energy in the shaft.


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