Utilization categories

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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 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, inching
AC-5a Switching of discharge lamps
AC-5b Switching of incandescent lamps
AC-6a Switching of transformers
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 resistive 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 overloads
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 braking of motors
DC-5 Series-motors, starting, plugging(1), inching(2), dynamic braking 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)

See also[edit]

NEMA contact ratings

References[edit]

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