Utilization categories
In electrical engineering utilization categories are defined by IEC standards and indicate the type of electrical load and duty cycle of the loads to ease selection of contactors and relays.[1]
| Utilization Category | Type of Application[2] |
|---|---|
| AC-1 | Non-inductive or slightly inductive loads, example: resistive furnaces, heaters |
| AC-2 | Slip-ring motors: switching off |
| AC-3 | Squirrel-cage motors: starting, switches off motors during running time |
| AC-4 | Squirrel-cage motors: starting, plugging (1), inching (2) |
| AC-5a | Switching of discharge lamps |
| AC-5b | Switching of incandescent lamps |
| AC-6a | Switching of transfomers |
| AC-6b | Switching of capacitor banks |
| AC-7a | Slightly inductive loads in household appliances: examples: mixers, blenders |
| AC-7b | Motor-loads for household appliances: examples: fans, central vacuum |
| AC-8a | Hermetic refrigerant compressor motor control with manual resetting overloads |
| AC-8b | Hermetic refrigerant compressor motor control with automatic resetting overloads |
| AC-12 | Control of resisitive loads and solid state loads with opto-coupler isolation |
| AC-13 | Control of solid state loads with transformer isolation |
| AC-14 | Control of small electromagnetic loads |
| AC-15 | Control of A.C. electromagnetic loads |
| AC-20 | Connecting and disconnecting under no-load conditions |
| AC-21 | Switching of resistive loads, including moderate loads |
| AC-22 | Switching of mixed resistive and inductive loads, including moderate overloads |
| AC-23 | Switching of motor loads or other highly inductive loads |
| A | Protection of circuits, with no rated short-time withstand current |
| B | Protection of circuits, with a rated short-time withstand current |
| DC-1 | Non Inductive or slightly inductive loads, resistance furnaces, heaters |
| DC-3 | Shunt-motors, starting, plugging(1), inching(2), dynamic breaking of motors |
| DC-5 | Series-motors, starting, plugging(1), inching(2), dynamic breaking of motors |
| DC-6 | Switching of incandescent lamps |
| DC-12 | Control of resistive loads and solid state loads with opto-coupler isolation |
| DC-13 | Control of D.C. electromagnetics |
| DC-14 | Control of D.C. electromagnetic loads having economy resistors in the circuit |
| DC-20 | Connecting and disconnecting under no-load conditions |
| DC-21 | Switching of resistive loads, including moderate overloads |
| DC-22 | Switching of mixed resistive and inductive loads, including moderate overloads (i.e. shunt motors) |
| DC-23 | Switching of highly inductive loads (i.e. series motors) |