Just What Is A Service Factor? Boat Hoist Motors

2-19-2016
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Just What Is A Service Factor? Boat Hoist Motors





This is a question we regularly receive on the Hotline. Understanding how the service factor af-fects an electric motor can be confusing, but it is not as complicated as it may seem. This guide should help explain the term service factor and its relationship to Boat Hoist and Lift motors.


The National Electrical Manufacturers Association (NEMA) defines service factor in section MG1 - 1.43 of their manual as: "The service factor of an alternating current (AC) motor is a multiplier which, when applied to the rated horsepower, indicates a permissible horsepower loading which may be carried under the conditions specified for the service factor." The conditions under which service factor may be applied are described in NEMA MG1 - 14.36 as: "When the voltage and frequency are maintained at the value specified on the motor's nameplate, the motor may be overloaded up to the horsepower obtained by multiplying the rated horsepower by the service factor shown on the nameplate."











How does Service Factor (S.F.) Apply To A Motor?


To determine the service factor horsepower of a motor, multiply the nameplate horsepower (not amperage) by the service factor. For example, if a 1 Hp motor has a service factor of 1.25, the motor's service factor maximum horsepower is:


(1 HP) x (1.25 S.F.) = 1.25 Hp

How Does Service Factor Relate to Motor Amps? Boat Hoist motors typically show two amperage values on the nameplate and in the specification sections of the equipment guide. The first value labeled "amps" is the expected running amps when the motor is operated at rated voltage and name-plate horsepower loads. The second value labeled "SF Amps" is the expected running amps when the motor is operated at rated voltage and service factor horsepower loads.