Service Factor

The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage



The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage.

The NEMA (National Electrical Manufacturers Association) standard service factor for totally enclosed motors is 1.0.

 A motor operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating at at its rated nameplate horsepower.



 NEMA Service Factor at Synchronous Speed (RPM) for drip proof motors: 




Example - Service Factor

 A 1 HP motor with a Service Factor - SF = 1.15 can operate at

 1 HP x 1.15 = 1.15 HP

 without overheating or otherwise damaging the motor if rated voltage and frequency are supplied to the motor.

 Insulation life and bearings life are reduced by the service factor load.

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