Utilization Categories

 utilization categories are defined by IEC (International Electrotechnical Commission) standards and indicate the type of electrical load and duty cycle of the loads to ease selection of contactors and relays.

AC1       Non-inductive or slightly inductive loads, example: resistive furnaces, heaters
AC2       Slip-ring motors: switching off
AC3       Squirrel-cage motors: starting, switches off motors during running time
AC4       Squirrel-cage motors: starting, plugging, inching
AC5a     Switching of discharge lamps
AC5b     Switching of incandescent lamps
AC6a     Switching of transformers
AC6b     Switching of capacitor banks
AC7a     Slightly inductive loads in household appliances: examples: mixers, blenders
AC7b     Motor-loads for household appliances: examples: fans, central vacuum
AC8a     Hermetic refrigerant compressor motor control with manual resetting overloads
AC8b     Hermetic refrigerant compressor motor control with automatic resetting overloads
AC12     Control of resisitive loads and solid state loads with opto-coupler isolation
AC13     Control of solid state loads with transformer isolation
AC14     Control of small electromagnetic loads
AC15     Control of A.C. electromagnetic loads
AC20     Connecting and disconnecting under no-load conditions
AC21     Switching of resistive loads, including moderate overloads
AC22     Switching of mixed resistive and inductive loads, including moderate overloads
AC23     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
DC1       Non Inductive or slightly inductive loads, resistance furnaces, heaters
DC3       Shunt-motors, starting, plugging(1), inching(2), dynamic breaking of motors
DC5       Series-motors, starting, plugging(1), inching(2), dynamic breaking of motors
DC6       Switching of incandescent lamps
DC12     Control of resistive loads and solid state loads with opto-coupler isolation
DC13     Control of D.C. electromagnetics
DC14     Control of D.C. electromagnetic loads having economy resistors in the circuit
DC20     Connecting and disconnecting under no-load conditions
DC21     Switching of resistive loads, including moderate overloads
DC22     Switching of mixed resistive and inductive loads, including moderate overloads (i.e. shunt motors)
DC23     Switching of highly inductive loads (i.e. series motors)


The standard utilization categories defines the current making and breaking values for contactors. they depend on the following..

1. Which type of load to be controlled (squirrel cage or slip ring induction motor, resistors)
2. The operating cycle conditions - Motor running, reverse operation, stalled or starting, counter current braking.


AC-1 - Non-inductive or slightly inductive loads
Ex : resistive load, heating, distribution.

AC-2 - Starting of slip-ring motors

AC-3 - Starting of squirrel-cage motors and switching off only after the motor is up to speed. Make Locked Rotor Amps (LRA), Break Full Load Amps (FLA)
Ex : all squirrel cage motors, lifts, escalators, conveyors, bucket elevators, compressors, pumps, mixers, air conditioning units, etc.

AC-4 - Starting of squirrel-cage motors with inching and plugging duty. Rapid Start/Stop. (Make and Break LRA)

AC-11 - Auxiliary (control) circuits