The service factor is an index that, applied to the normal rated power, indicates the permissible load that can be applied to the electric motor. This factor refers to the capacity under continuous overload condition. It can be considered like one reserve of power that gives to the motor a better capacity to support the functioning in unfavorable conditions.
Amongst some existing types, the electric motors are the most used because they combine the advantages of the electric energy with a relatively simple construction, reduced cost and great adaptability to most diverse loads.
In principle, any motor must be installed to supply higher power than the nominal one. However, under determined conditions, this can come to occur, causing a temperature and current increase, that depending on the duration and the intensity of the overload, can leave to the reduction of the useful life of the motor or its burning.
Therefore, a service factor defined fora motor is the factor that applied to the normal rated power, indicates the permissible overload that can continuously be used. Thus, for example, an engine of 50 HP with a factor of service 1.1 can supply to a load continuously the power of 55 HP.