Utilization categories
The use category is determined for electrical switchgear or fuses. It is defined as the " combination of specified requirements, which was selected taking into account the operating conditions of a switching device or a fuse to meet a substantial group of practical applications ." To the specified requirements may, for example, making capacity (if applicable), breaking and other parameters, the data of the associated circuits, the appropriate conditions for the operational behavior and the function include. (IEV 441-17-19 )
The Utilization of Low-voltage switchgear defines the characteristic conditions for switching devices such as contactors, circuit breakers, load switches, disconnectors, switch-disconnectors, switch-fuse units, auxiliary contactors etc. These devices are designed for different electrical loads and for different operating conditions.
The switching to the property or to be controlled load determines the requirements for the switching devices and their correct selection for the intended application. Specifically, the stress of the switching paths by current and voltage during switching on and off are of enormous importance. To comply with the making and breaking current at resistive load continuous operation power while eg When switched on and in the acceleration phase squirrel-cage motors take a multiple of the rated operating current.
The following tables provide an overview of the different abbreviations. Within a use category the appropriate size must be selects for each type. This depends on the rated current, the rated voltage and the electrical load to be switched.
Determination of application categories in the standards
The " use categories " are mainly defined in the IEC / EN 60947 EN in the following parts:
- Part 1: General requirements
- Part 2: Circuit-breaker
- Part 3: Switches, disconnectors, switch-disconnectors and fuse-combination units
- Part 4-1: Contactors and motor starters; electromechanical contactors and motor starters
- Part 4-2: Contactors and motor-starters - AC semiconductor motor controllers and starters for AC voltage
- Part 5-1: Control circuit devices and switching elements - Electromechanical control circuit devices
- Part 6-1: Multiple function equipment - Power switch ( categories AC -32A / B)
- Part 6-2: Multiple function equipment - Control and protective switching devices ( CPS)
- Part 7-1: Ancillary equipment; Terminal blocks for copper conductors
- Part 7-2: Ancillary equipment; Protective conductor terminal blocks for copper conductors
- Moreover, in the IEC / EN 61095 also defines categories for " household and similar applications ."
Utilisation categories for ac
¹) counter-current braking or reversing the motor is the rapid braking or reversing the direction of rotation by interchanging two leads with the engine running
²) sub- typing is the process once or repeatedly for short periods energizing a motor to cause small movements of machinery
³) The utilization categories with suffix A are for frequent switching, those with suffix B for occasional switching
Utilisation categories for ac and dc voltage
Utilisation categories for DC
Switching of incandescent lamps
¹) counter-current braking or reversing the motor is the rapid braking or reversing the direction of rotation by interchanging two leads with the engine running
²) sub- typing is the process once or repeatedly for short periods energizing a motor to cause small movements of machinery
³) The utilization categories with suffix A are for frequent switching, those with suffix B for occasional switching
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