Utilization category

The utilization category is for electrical switching devices or fuses fixed. It is defined as the "combination of specified requirements that has been selected taking into account the operating conditions of a switchgear or fuse in order to meet an essential group of practical applications". The specified requirements may include, for example, making capacity (if applicable), breaking capacity and other parameters such as the short-circuit power , the data of the associated circuits , the corresponding conditions for the operating behavior and the function. ( International Electrotechnical Dictionary - IEV 441-17-19 )

General

The utilization category for low-voltage switchgear defines the characteristic operating conditions for switching devices such as contactors , circuit breakers , load switches , disconnectors , switch-disconnectors, switch-fuse units, control relays, etc. These devices are for different electrical loads sized and for different operating conditions.

The properties of the load to be switched or controlled determines the requirements for the switching devices and their correct selection for the planned application. In particular, the stress on the switching paths caused by current and voltage when switching on and off are of enormous importance. For example, the switch-on and switch-off currents correspond to the continuous operating current at resistive loads. B. Squirrel cage motors absorb a multiple of the rated operating current when switched on and in the acceleration phase.

When switching, a switching arc occurs , which depends on the strength and type of the connected load. The DC- ... categories must break the arc through a sufficient isolating distance and the contacts must withstand the higher thermal load. With AC-… the zero crossing helps to make it go out more quickly and easily. The AC-… are designed for a tendency towards higher inrush and switch-off currents than the DC-… categories. The differences in the inductive load of the switching contacts and the switching capacity can be found within the category.

The following tables provide an overview of the various abbreviations. The suitable size must be selected for the respective type within a utilization category. This depends on the nominal current , the nominal voltage and the electrical load to be switched .

Definition of utilization categories in the standards

Contact load in amperes for heaters (AC1) and motors (AC3) can be found directly on the contactor

The " utilization categories " are mainly defined in IEC / EN 60947 in the following parts:

• Part 1: General specifications
• Part 2: Circuit Breakers
• Part 3: Load switches, disconnectors, switch disconnectors and switch fuse units
• Part 4-1: Contactors and motor starters; electromechanical contactors and motor starters
• Part 4-2: Contactors and motor starters - Semiconductor motor control devices and starters for AC voltage
• Part 5-1: Control devices and switching elements - Electromechanical control devices
• Part 6-1: Multi-function switching devices - Transfer switching equipment (Categories AC-32A / B)
• Part 6-2: Multi-function switchgear - Control and protection switchgear (CPS)
• Part 7-1: Auxiliary equipment; Terminal blocks for copper conductors
• Part 7-2: Auxiliary equipment; Protective conductor terminal blocks for copper conductors
• In addition, categories for “household and similar applications” are also defined in IEC / EN 61095 .

Utilization categories for alternating voltage

Utilization category	typical application	IEC device standard
AC-1	non-inductive or weakly inductive load. Resistance furnaces	60947-4-1
AC-2	Slip ring motors: starting , switching off	60947-4-1
AC-3	Squirrel cage motors : starting. Switch off during the run	60947-4-1
AC-4	Squirrel cage motors: starting, countercurrent braking ¹) or reversing ¹), jogging ²)	60947-4-1
AC-5a	Switching of gas discharge lamps	60947-4-1
AC-5b	Switching of incandescent lamps	60947-4-1
AC-6a	Switching transformers	60947-4-1
AC-6b	Switching of capacitor banks	60947-4-1
AC-7a	weak inductive load for household and similar applications	60947-4-1 61095
AC-7b	Motor loads for household applications	60947-4-1 61095
AC-7c	Switching the controls of compensated discharge lamps	61095
AC-8a	Control of hermetically sealed cooling compressor motors with manual reset of the overload release	60947-4-1
AC-8b	Control of hermetically sealed refrigerant compressor motors with automatic reset of the overload release	60947-4-1
AC-11	replaced by AC 15	earlier 60947-4-1
AC-12	Control of ohmic load and semiconductor load with separation by optocouplers	60947-5-1 60947-5-2
AC-13	Controlling semiconductor load with isolation transformers	60947-5-1
AC-14	Controlling small electromagnetic load	60947-5-1
AC-15	Controlling electromagnetic load with AC voltage	60947-5-1
AC-20A AC-20B ³)	Switching on and off at no load	60947-3
AC-21A AC-21B ³)	Switching ohmic load including moderate overload	60947-3
AC-22A AC-22B ³)	Switching mixed ohmic and inductive loads including moderate overload	60947-3
AC-23A AC-23B ³)	Switching of motor loads or other strongly inductive loads	60947-3
AC-31A AC-31B ³)	non-inductive or weakly inductive loads	60947-6-1
AC-33A AC33B³)	Motor loads or mixed loads including motors, resistors and up to 30% incandescent lamp load	60947-6-1
AC-35A AC-35B ³)	Gas discharge lamp load	60947-6-1
AC-36A AC36B ³)	Light bulb load	60947-6-1
AC-40	Distribution circuits from mixed ohmic 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 while running	60947-6-2
AC-44	Squirrel cage motors: starting, countercurrent braking ¹) or reversing ¹), jogging ²)	60947-6-2
AC-45a	Switching of gas discharge lamps	60947-6-2
AC-45b	Switching of incandescent lamps	60947-6-2
AC-51	induction-free or slightly inductive loads, resistance furnaces	60947-4-3
AC-52a	Controlling the stator winding of a slip ring motor: 8-hour operation with starting currents for starting processes, maneuvering, operation	60947-4-2
AC-52b	Controlling the stator winding of a slip ring motor: intermittent operation	60947-4-2
AC-53a	Controlling a squirrel cage motor: 8-hour operation with starting currents for starting processes, maneuvering, operation	60947-4-2
AC-53b	Controlling a squirrel cage motor: intermittent operation	60947-4-2
AC-55a	Switching of electrical controls for discharge lamps	60947-4-3
AC-55b	Switching of incandescent lamps	60947-4-3
AC-56a	Switching transformers	60947-4-3
AC-56b	Switching of capacitor banks	60947-4-3
AC-58a	Control of a hermetically sealed cooling compressor motor with automatic reset of the overload releases: 8-hour operation with starting currents for starting processes, maneuvering, operation	60947-4-2
AC-58b	Control of a hermetically sealed cooling compressor motor with automatic reset of the overload releases: intermittent operation	60947-4-2
AC-140	Control of small electromagnetic loads with holding current ≤ 0.2 A; z. B. auxiliary contactors	60947-5-2

¹) Countercurrent braking or reversing the motor is the rapid braking or reversal of the direction of rotation by swapping two supply lines ( outer conductor ) while the motor is running

²) Jogging is the one-time or repeated short-term switching on of a motor in order to cause small movements of machines

³) The utilization categories with the ending A apply to frequent switching, those with the ending B to occasional switching

Utilization categories for AC and DC voltage

Utilization category	typical application	IEC device standard
A.	Protection of circuits without rated short-time withstand current	60947-2
B.	Protection of circuits with rated short-time withstand current	60947-2

Utilization categories for DC voltage

Utilization category	typical application	IEC device standard
DC-1	non-inductive or weakly inductive load, resistance furnaces	60947-4-1
DC-3	Shunt motors: starting, countercurrent braking ¹) or reversing ¹), jogging ²), resistance braking of motors	60947-4-1
DC-5	Series motors : starting, countercurrent braking ¹) or reversing ¹), jogging ²), resistance braking of motors	60947-4-1
DC-6	Switching of incandescent lamps	60947-4-1
DC-12	Control of ohmic load and semiconductor load with separation by optocouplers	60947-5-1 60947-5-2
DC-13	Controlling electromagnets with direct voltage	60947-5-1 60947-5-2
DC-14	Control of electromagnetic load with direct voltage with economy resistors in the circuit	60947-5-1
DC-31	Drag loads	60947-6-1
DC-33	Motor loads or mixed loads including motors	60947-6-1
DC-36	Light bulb load	60947-6-1
DC-40	Distribution circuits from mixed ohmic and inductive loads	60947-6-2
DC-41	non-inductive or weakly inductive loads, resistance furnaces	60947-6-2
DC-43	Shunt motors: starting, countercurrent braking ¹), jogging ²)	60947-6-2
DC-45	Resistor braking of DC motors Series motors: starting, countercurrent braking ¹), jogging ²)	60947-6-2
DC-46	Resistor braking of DC motors Switching of incandescent lamps	60947-6-2

¹) Countercurrent braking or reversing the motor is the rapid braking or reversal of the direction of rotation by swapping two supply lines while the motor is running

²) Jogging is the one-time or repeated short-term switching on of a motor in order to cause small movements of machines

³) The utilization categories with the ending A apply to frequent switching, those with the ending B to occasional switching

Source:

Proof of service life and switching capacity (extract)

Birth cat.	lifespan							Switching capacity
	turn on				Turn off			turn on				Turn off
	${\displaystyle I_{n}}$	${\displaystyle {\frac {I}{I_{n}}}}$	${\displaystyle {\frac {U}{U_{n}}}}$	cos ${\displaystyle \varphi }$	${\displaystyle {\frac {I_{c}}{I_{n}}}}$	${\displaystyle {\frac {U_{r}}{U_{n}}}}$	cos ${\displaystyle \varphi }$	${\displaystyle I_{n}}$	${\displaystyle {\frac {I}{I_{n}}}}$	${\displaystyle {\frac {U}{U_{n}}}}$	cos ${\displaystyle \varphi }$	${\displaystyle {\frac {I_{c}}{I_{n}}}}$	${\displaystyle {\frac {U_{r}}{U_{n}}}}$	cos ${\displaystyle \varphi }$
AC-1	x	1	1	0.95	1	1	0.95	x	1.5	1.05	0.8	1.5	1.05	0.8
AC-2	x	2.5	1	0.65	2.5	1	0.65	x	4th	1.05	0.65	4th	1.05	0.8
AC-3	≤17	6th	1	0.65	1	0.17	0.65	≤100	8th	1.05	0.45	8th	1.05	0.45
	> 17	6th	1	0.35	1	0.17	0.35	> 100	8th	1.05	0.35	8th	1.05	0.35
AC-4	≤17	6th	1	0.65	6th	1	0.65	≤100	10	1.05	0.45	10	1.05	0.45
	> 17	6th	1	0.35	1	1	0.35	> 100	10	1.05	0.35	10	1.05	0.35
	${\displaystyle I_{n}}$	${\displaystyle {\frac {I}{I_{n}}}}$	${\displaystyle {\frac {U}{U_{n}}}}$	${\displaystyle {\frac {L}{R}}}$[ms]	${\displaystyle {\frac {I_{c}}{I_{n}}}}$	${\displaystyle {\frac {U_{r}}{U_{n}}}}$	${\displaystyle {\frac {L}{R}}}$[ms]	${\displaystyle I_{n}}$	${\displaystyle {\frac {I}{I_{n}}}}$	${\displaystyle {\frac {U}{U_{n}}}}$	${\displaystyle {\frac {L}{R}}}$[ms]	${\displaystyle {\frac {I_{c}}{I_{n}}}}$	${\displaystyle {\frac {U_{r}}{U_{n}}}}$	${\displaystyle {\frac {L}{R}}}$[ms]
DC-1	x	1	1	1	1	1	1	x	1.5	1.05	1	1.5	1.05	1
DC-2	x	2.5	1	2	2.5	1	2	x	4th	1.05	2.5	4th	1.05	2.5
DC-5	x	2.5	1	7.5	2.5	1	7.5	x	4th	1.05	15th	4th	1.05	15th

x all values : Rated  current: Inrush current: Inrush current  :  Voltage  : Rated voltage  : Recurring voltage  [ms]: Time constant ${\displaystyle I_{n}}$ ${\displaystyle I}$ ${\displaystyle I_{c}}$ ${\displaystyle U}$ ${\displaystyle U_{n}}$ ${\displaystyle U_{r}}$ ${\displaystyle {\frac {L}{R}}}$ ${\displaystyle \tau }$

See also: Eaton wiring manual and Siemens system manual

literature

• Wilfried Knies, Klaus Schierack: Electrical systems engineering; Power plants, networks, switchgear, protective devices . 5th edition. Hanser Fachbuchverlag, Leipzig 2006, ISBN 978-3-446-40574-5 .

• Georg Schöllhorn: Switching, protecting, distributing in low-voltage networks . 3. Edition. Siemens Aktiengesellschaft, Berlin and Munich 1992, ISBN 3-8009-4122-8 , p. 116 ff .

Footnotes

1. ↑ ^{a b c} wiring book. Norms. Eaton Industries GmbH (Moeller), p. 606 , accessed on April 11, 2012 . 
2. ↑ Low-voltage switchgear. (PDF; 6.4 MB) A guide for use. Rockwell Automation, 2009, pp. 12ff , accessed September 5, 2012 . 
3. ↑ Siemens system manual. (PDF; 21.5 MB) 3.1.1 Utilization categories. Siemens, May 2017, pp. 117–120 , accessed January 27, 2019 .