Service Factor of Electrical Motor

Service factor is the built-in reserve capacity of the motor.

If the nameplate FLA(full load amp) capacity of your motor is 2.6 amps, and the service factor (SF) of the motor is 1.12, the motor can be safely run at 2.9 amps.

I've done it before with constant load pumps with no problems.

Good luck.

Service factor 1.12 means the motor can run safely with 12% over load. As per IEEE standard, the motors shall be designed to 1.15 service factor. However you should investigate the reason for the over current and run the motor within the FLA.

Supposing your motor is rated at 1.1kW, it will be so rated to operate at a particular maximum ambient temperature, which will be mentioned by the manufacturer. For operation at any higher ambient temperature one will have to de-rate the motor. Similarly, if the ambient temperature is lesser, one can afford to overload the motor. Such permissible overloading under reduced ambient temperature conditions is specified as Service Factor.

It should be noted that the term "Service Factor" is only defined by NEMA, the North American Manufacturers Association. There is no stated equivalency in IEC motor design specifications. So in essence, all IEC motors have a "1.0 Service Factor". Being that your motor is apparently rated in kW and designed for 415V 50Hz, it's unlikely there is ANY SF rating for it. The only possibility is that someone used a NEMA motor rated for 1.5HP 460V and in applying 415V 50Hz to it, they are de-rating it to 1.1kW. If that 1.5HP 460V motor had a 1.15 SF on it, then that would make sense.

But the idea of SF use is intended for occasional overloads. This time frame is unfortunately not specifically defined, so many OEMs drive through that gaping loophole rather than use the next available size motor. What NEMA MG-1 used to say was that performance and motor life expectancy may suffer when motors are run into the SF. It was amended to remove that statement, but the fact remains...

Slight correction of myself.

If it is a NEMA designed motor, it would have to be larger than 1.5HP because 1.1kW would be straight across (1.5 x .746 = 1.19). But because of the difference in speed, the mechanical power rating will drop by 20%. A 2HP 460V 60Hz motor, when supplied with 415V 50Hz, will yield 1.6HP at the shaft, which when converted to kW comes out to be 1.38kW. So maybe they are saying that even though they nameplated the motor as 1.1kW, it does have some overhead, which they are calling "Service Factor".

Dear all

Thanks everybody for your informations

with regards

jcg154

The motor service factor is the cushion the motor manufacturer builds into the motor to prevent damage from occasional surges, spikes and short-term heavy loading. The motor service factor is not some sort of secret code for certain chosen people.

The maximum amperage is plainly stated on the motor nameplate and the installer should make certain that the motor does not draw more than the nameplate maximum amperage.