Utilisation Categories for Contactors

IEC 947-4 specifies the following usage categories for contactors. These definitions may also be used for switches and relays.

Category Closing current
(Switch on surge)
Breaking capacity
(Contact opening current)
Notes Typical Use
    A load with a power factor exceeding 0.95
i.e. Predominately resistive
Heating and Distribution
2.5 x Full load current Starting current   Starting, plugging and inching of slip ring motors
5 - 7 x Full load Full load current
NOT the starting current
  Compressors, pumps, standard squirrel cage motors


Creative  Design  Innovation