Main switch

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Three oil switches for high voltage in a substation; The switches are remote controlled and operated with compressed air

The main switch is part of an electrical system. It disconnects the equipment from the electrical supply at all poles. Main switches can be operated manually or externally. They can also take over system protection by equipping them with overcurrent and overvoltage or undervoltage releases.

In building installation , main switch often refers to a circuit breaker that is installed between the house connection and the measuring device ( electricity meter ) and is accessible to the user of the system in order to switch it off completely. This function can also be taken over by an SLS switch .

Main switches for use in industry are defined in the European standard EN 60204-1 or VDE 0113 Part 1. The main switch must then correspond to one of three types:

A main switch is not required for devices and machines with a maximum power of 3680 W or 16 A. Its function can be fulfilled by a plug-in device .

The main switch must meet the following requirements:

  • It may only have one off and one on position, which are labeled with O and I.
  • In the off position he must z. B. be lockable with padlocks to prevent accidental switching on while working on the electrical equipment.
  • If the main switch takes over the emergency stop or emergency stop function, the control panel must be red and the background yellow. If not intended for use in an emergency, the actuator should be black or gray.

In interlinked systems, the main switches of the individual machines are often equipped with a black control panel. This does not perform an emergency stop or emergency stop function for the individual machine. There is a main switch for the entire line with a red control panel and a yellow background, which, when pressed, carries out the emergency stop function for the entire line. It should be noted, however, that an emergency stop function in the sense of all-pole galvanic isolation - in contrast to the emergency stop function for stopping all dangerous movements - is not generally prescribed for machines. In some cases, there is no provision for an emergency stop to be triggered via the main switch, as the immediate power cut, for example, causes the control to fail or active braking of a movement by a converter can no longer take place.

Individual evidence

  1. EN 60204-1: 2006, section 5.3.3).


  • Theodor Schmelcher: Handbook of Low Voltage, project planning information for switchgear, switchgear and distribution boards. 1st edition, Siemens Aktiengesellschaft (Abt. Verlag), Berlin and Munich, 1982, ISBN 3-8009-1358-5 .
  • Günter Springer: Expertise in electrical engineering. 18th edition, Verlag - Europa - Lehrmittel, Wuppertal, 1989, ISBN 3-8085-3018-9 .