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
AC1
     A load with a power factor exceeding 0.95
i.e. Predominately resistive		 Heating and Distribution
AC2
 2.5 x Full load current Starting current   Starting, plugging and inching of slip ring motors
AC3
 5 - 7 x Full load Full load current
NOT the starting current		   Compressors, pumps, standard squirrel cage motors

 

  
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