Service factor of electric motors

Overload factor

If a “service factor” is specified on a Fabrika or Siemens motor rating plate, this means that the motor can be continuously operated with an overload.

The maximum continuous power is calculated as follows:
Pperm = service factor x PN

PN is the rated power specified on the rating plate.

When operating the motor with the max. permissible continuous power, the standard operating conditions are used as a basis – including the specified tolerances. The temperature rise limit may be exceeded by 10 K.

Some international regulations specify a service factor; for NEMA and EEMAC, this is, for example:

• IP44 motors, a service factor of 1.0
• IP23 motors, a service factor of 1.15

 

In practice, customers can specify other service factors, and special measures are required in these cases. Contact Fabrika for more information.