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.

Definition

The utilization categories category for low-voltage switchgear defines the characteristic operating conditions for switchgear such as contactors, circuit-breakers, circuit-breaker-fuse units, contactor relays, etc. These devices are dimensioned for different electrical loads and for different operating conditions.
The characteristic of the load to be switched or controlled determines the requirements for the switchgear and its correct selection for the intended application. In particular, the stress on the switching path caused by current and voltage during switching on and off is of enormous importance. For example, the switch-on and switch-off current at resistance load corresponds to the continuous operating current, while, for example, squirrel cage motors consumes multiple of the rated operating current during switch-on and in the acceleration phase.

Categorisation of Utilization category in IEC standard

Contact load in amperes for heaters and motors can be found directly on the contactor.
The "Utilization category" are mainly categorized in IEC 60947 in the following volume:
In addition, IEC/EN 61095 also defines categories for "household and similar applications".

Table

The following table provides an overview of the various abbreviations. Within a utilization category, the suitable size may be selected for the respective type. This depends on the rated current, the rated voltage and the electrical load to be switched.
Utilization CategoryTypical ApplicationApplicable IEC norm
AC-1Non-inductive or slightly inductive loads, example: resistive furnaces, heaters60947-4-1
AC-2Slip-ring motors: switching off60947-4-1
AC-3Squirrel-cage motors: starting, switches off motors during running time60947-4-1
AC-4Squirrel-cage motors: starting, plugging, inching60947-4-1
AC-5aSwitching of discharge lamps60947-4-1
AC-5bSwitching of incandescent lamps60947-4-1
AC-6aSwitching of transformers60947-4-1
AC-6bSwitching of capacitor banks60947-4-1
AC-7aSlightly inductive loads in household appliances: examples: mixers, blenders60947-4-1
61095
AC-7bMotor-loads for household appliances: examples: fans, central vacuum60947-4-1
61095
AC-8aHermetic refrigerant compressor motor control with manual resetting overloads60947-4-1
AC-8bHermetic refrigerant compressor motor control with automatic resetting overloads60947-4-1
AC-12Control of resistive loads and solid state loads with opto-coupler isolation60947-5-2
AC-13Control of solid state loads with transformer isolation60947-5-1
AC-14Control of small electromagnetic loads60947-5-1
AC-15Control of A.C. electromagnetic loads60947-5-1
AC-20Connecting and disconnecting under no-load conditions60947-3
AC-21Switching of resistive loads, including moderate overloads60947-3
AC-22Switching of mixed resistive and inductive loads, including moderate overloads60947-3
AC-23Switching of motor loads or other highly inductive loads60947-3
AC-31A
AC-31B ³)		Non-inductive or weakly inductive loads60947-6-1
AC-33A
AC33B³)		Motor loads or mixed loads including motors, resistors and up to 30 % incandescent lamp load60947-6-1
AC-35A
AC-35B ³)		Gas discharge lamp load60947-6-1
AC-36A
AC36B ³)		Incandescent lamp load60947-6-1
AC-40Distribution circuits of mixed resistive and inductive loads60947-6-2
AC-41Non-inductive or weakly inductive loads, resistance furnaces60947-6-2
AC-42Slip ring motors: Starting, switching off60947-6-2
AC-43Squirrel cage motors: Starting, switching off during operation60947-6-2
AC-44Squirrel cage motors: Starting, counter-current braking ¹) or reversing ¹), typing ²)60947-6-2
AC-45aSwitching of gas discharge lamps60947-6-2
AC-45bSwitching incandescent lamps60947-6-2
AC-51Induction-free or slightly inductive loads, resistance furnaces60947-4-3
AC-52aControl of the stator winding of a slip-ring motor: 8-hour operation with starting currents for starting processes, maneuvering, operation60947-4-2
AC-52bControl of the stator winding of a slip ring motor: Intermittent operation60947-4-2
AC-53aControl of a squirrel cage motor: 8-hour operation with starting currents for starting processes, maneuvering, operation60947-4-2
AC-53bControl of a squirrel cage motor: Intermittent operation60947-4-2
AC-55aSwitching of electrical controls of discharge lamps60947-4-3
AC-55bSwitching incandescent lamps60947-4-3
AC-56aSwitching transformers60947-4-3
AC-56bSwitching of capacitor batteries60947-4-3
AC-58aControl of a hermetically sealed refrigeration compressor motor with automatic reset of overload releases: 8-hour operation with starting currents for starting, maneuvering, operation60947-4-2
AC-58bThe control of a hermetically sealed refrigeration compressor motor with automatic reset of the overload trips: Intermittent operation60947-4-2
AC-140Control of small electromagnetic loads with holding current ≤ 0.2 A; e.g. contactor relays60947-5-2
AProtection of circuits, with no rated short-time withstand current60947-3
BProtection of circuits, with a rated short-time withstand current60947-3
DC-1Non Inductive or slightly inductive loads, resistance furnaces, heaters60947-4-1
DC-3Shunt-motors, starting, plugging, inching, dynamic braking of motors60947-4-1
DC-5Series-motors, starting, plugging, inching, dynamic braking of motors60947-4-1
DC-6Switching of incandescent lamps60947-4-1
DC-12Control of resistive loads and solid state loads with opto-coupler isolation60947-5-1
60947-5-2
DC-13Control of D.C. electromagnetics60947-5-1
60947-5-2
DC-14Control of D.C. electromagnetic loads having economy resistors in the circuit60947-5-1
DC-20Connecting and disconnecting under no-load conditions60947-5-1
DC-21Switching of resistive loads, including moderate overloads60947-5-1
DC-22Switching of mixed resistive and inductive loads, including moderate overloads 60947-5-1
DC-23Switching of highly inductive loads 60947-5-1