Utilization categories

In electrical engineering utilization categories are defined by IEC standards[1] and indicate the type of electrical load and duty cycle of the loads to ease selection of contactors and relays.

Utilization CategoryType of Application[2]
AC-1Non-inductive or slightly inductive loads, example: resistive furnaces, heaters
AC-2Slip-ring motors: switching off
AC-3Squirrel-cage motors: starting, switches off motors during running time
AC-4Squirrel-cage motors: starting, plugging, inching
AC-5aSwitching of discharge lamps
AC-5bSwitching of incandescent lamps
AC-6aSwitching of transformers
AC-6bSwitching of capacitor banks
AC-7aSlightly inductive loads in household appliances: examples: mixers, blenders
AC-7bMotor-loads for household appliances: examples: fans, central vacuum
AC-8aHermetic refrigerant compressor motor control with manual resetting overloads
AC-8bHermetic refrigerant compressor motor control with automatic resetting overloads
AC-12Control of resistive loads and solid state loads with opto-coupler isolation
AC-13Control of solid state loads with transformer isolation
AC-14Control of small electromagnetic loads
AC-15Control of A.C. electromagnetic loads
AC-20Connecting and disconnecting under no-load conditions
AC-21Switching of resistive loads, including moderate overloads
AC-22Switching of mixed resistive and inductive loads, including moderate overloads
AC-23Switching of motor loads or other highly inductive loads
AProtection of circuits, with no rated short-time withstand current
BProtection of circuits, with a rated short-time withstand current
DC-1Non Inductive or slightly inductive loads, resistance furnaces, heaters
DC-3Shunt-motors, starting, plugging(1), inching(2), dynamic braking of motors
DC-5Series-motors, starting, plugging(1), inching(2), dynamic braking of motors
DC-6Switching of incandescent lamps
DC-12Control of resistive loads and solid state loads with opto-coupler isolation
DC-13Control of D.C. electromagnetics
DC-14Control of D.C. electromagnetic loads having economy resistors in the circuit
DC-20Connecting and disconnecting under no-load conditions
DC-21Switching of resistive loads, including moderate overloads
DC-22Switching of mixed resistive and inductive loads, including moderate overloads (i.e. shunt motors)
DC-23Switching of highly inductive loads (i.e. series motors)

See also

NEMA contact ratings

References

  1. ↑ IEC 60947 Standards for low-voltage switchgear and controlgear
  2. ↑ http://www.eecontrols.com/documents/Pages21-30.pdf
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