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.

Contents
Definition
Utilization categories in IEC standard
Table
See also
Usually utilization category is
References mentioned in most of the switch
gear, with the above contactor
stating to be used under AC1 -
Definition resistive load & AC3 for motor
usage
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.

Utilization categories in IEC standard

Contact load in amperes for heaters (AC1) and motors (AC3) can be found directly on the contactor.
The
"Utilization category" are mainly categorized in IEC 60947 in the following volume:

Volume 1: General requirements

Volume 2: Circuit-breakers
Volume 3: Circuit-breakers, circuit-breakers, switch-disconnectors and switch-fuse units
Volume 4-1: Contactors and motor starters; electromechanical contactors and motor starters[1]
Volume 4-2: Contactors and motor starters - Semiconductor motor controllers and starters for a.c. voltage
Volume 5-1: Control apparatus and switching elements - Electromechanical control apparatus[1]
Volume 6-1: Multi-function switchgear and controlgear - Mains switches (categories AC-32A/B)
Volume 6-2: Multi-function switchgear and controlgear - Control and protective switchgear (CPS)
Volume 7-1: Auxiliary equipment; Terminal blocks for copper conductors
Volume 7-2: Ancillary equipment; protective conductor terminal blocks for copper conductors

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 Applicable
Typical application[2][3]
category IEC norm[4]
AC-1 Non-inductive or slightly inductive loads, example: resistive furnaces, heaters 60947-4-1
AC-2 Slip-ring motors: switching off 60947-4-1
AC-3 Squirrel-cage motors: starting, switches off motors during running time 60947-4-1
AC-4 Squirrel-cage motors: starting, plugging, inching 60947-4-1
AC-5a Switching of discharge lamps 60947-4-1
AC-5b Switching of incandescent lamps 60947-4-1
AC-6a Switching of transformers 60947-4-1
AC-6b Switching of capacitor banks 60947-4-1
60947-4-1

AC-7a Slightly inductive loads in household appliances: examples: mixers, blenders

61095
60947-4-1

AC-7b Motor-loads for household appliances: examples: fans, central vacuum

61095
AC-8a Hermetic refrigerant compressor motor control with manual resetting overloads 60947-4-1
AC-8b Hermetic refrigerant compressor motor control with automatic resetting overloads 60947-4-1
AC-12 Control of resistive loads and solid state loads with opto-coupler isolation 60947-5-2
AC-13 Control of solid state loads with transformer isolation 60947-5-1
AC-14 Control of small electromagnetic loads 60947-5-1
AC-15 Control of A.C. electromagnetic loads 60947-5-1
AC-20 Connecting and disconnecting under no-load conditions 60947-3
AC-21 Switching of resistive loads, including moderate overloads 60947-3
AC-22 Switching of mixed resistive and inductive loads, including moderate overloads 60947-3
AC-23 Switching of motor loads or other highly inductive loads 60947-3
AC-31A

Non-inductive or weakly inductive loads 60947-6-1

AC-31B ³)
AC-33A

Motor loads or mixed loads including motors, resistors and up to 30 % incandescent lamp load 60947-6-1
AC33B³)
AC-35A

Gas discharge lamp load 60947-6-1

AC-35B ³)
AC-36A

Incandescent lamp load 60947-6-1

AC36B ³)
AC-40 Distribution circuits of mixed resistive and inductive loads 60947-6-2
AC-41 Non-inductive or weakly inductive loads, resistance furnaces 60947-6-2
AC-42 Slip ring motors: Starting, switching off 60947-6-2
AC-43 Squirrel cage motors: Starting, switching off during operation 60947-6-2
AC-44 Squirrel cage motors: Starting, counter-current braking ¹) or reversing ¹), typing ²) 60947-6-2
AC-45a Switching of gas discharge lamps 60947-6-2
AC-45b Switching incandescent lamps 60947-6-2
AC-51 Induction-free or slightly inductive loads, resistance furnaces 60947-4-3
Control of the stator winding of a slip-ring motor: 8-hour operation with starting currents for starting
AC-52a 60947-4-2
processes, maneuvering, operation
AC-52b Control of the stator winding of a slip ring motor: Intermittent operation 60947-4-2
Control of a squirrel cage motor: 8-hour operation with starting currents for starting processes,
AC-53a 60947-4-2
maneuvering, operation
 AC-53b Control of a squirrel cage motor: Intermittent operation 60947-4-2
AC-55a Switching of electrical controls of discharge lamps 60947-4-3
AC-55b Switching incandescent lamps 60947-4-3
AC-56a Switching transformers 60947-4-3
AC-56b Switching of capacitor batteries 60947-4-3
Control of a hermetically sealed refrigeration compressor motor with automatic reset of overload
AC-58a 60947-4-2
releases: 8-hour operation with starting currents for starting, maneuvering, operation
The control of a hermetically sealed refrigeration compressor motor with automatic reset of the
AC-58b 60947-4-2
overload trips: Intermittent operation
AC-140 Control of small electromagnetic loads with holding current ≤ 0.2 A; e.g. contactor relays 60947-5-2
A Protection of circuits, with no rated short-time withstand current 60947-3
B Protection of circuits, with a rated short-time withstand current 60947-3
DC-1 Non Inductive or slightly inductive loads, resistance furnaces, heaters 60947-4-1
DC-3 Shunt-motors, starting, plugging(1), inching(2), dynamic braking of motors 60947-4-1
DC-5 Series-motors, starting, plugging(1), inching(2), dynamic braking of motors 60947-4-1
DC-6 Switching of incandescent lamps 60947-4-1
60947-5-1

DC-12 Control of resistive loads and solid state loads with opto-coupler isolation
60947-5-2
60947-5-1

DC-13 Control of D.C. electromagnetics

60947-5-2
DC-14 Control of D.C. electromagnetic loads having economy resistors in the circuit 60947-5-1
DC-20 Connecting and disconnecting under no-load conditions 60947-5-1
DC-21 Switching of resistive loads, including moderate overloads 60947-5-1
DC-22 Switching of mixed resistive and inductive loads, including moderate overloads (i.e. shunt motors) 60947-5-1
DC-23 Switching of highly inductive loads (i.e. series motors) 60947-5-1

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
3. https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/lvsam-rm001_-de-p.pdf
4. https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/lvsam-rm001_-de-p.pdf

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