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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 |