Relay cycles

Due to the self induction of the coil and the inertia of the parts to be moved, on activating a relay the operations do not take place suddenly. The function diagram below shows the different cycles for the most important relay configurations of undelayed power relays.

Unless otherwise stated the indicated times are maximum values, the cycles specified apply to DC-coils energized with rated voltage (without any components in series or parallel to the coil) and at the reference temperature.

  • operate time
  • release time/reset time
  • bounce time
  • minimum energization duration

Relay Technology Categories

The ‘Relay Technology Categories’ describe the degree of sealing of the relay case or its contact unit. See ‘Category of environmental protection’.

Relays with forcibly guided contacts

The compliance with regulations for the safety of persons and material is imperative in our technical world. National and international regulations take various risks into account. These safety standards also make demands on components which share with their function the safety level of a plant, machine or the equipment. For safety relays the demand for forcibly guided contact system according ZH1/457, issued by the professional association applies; the contacts have to be linked mechanically in a way, that NO and NC contacts may not be closed at the same time.

It has to be ensured that over the entire life and even in case of malfunction (e.g. contact welding) the open contact gap will be at least 0.5 mm. If specified they also comply with the wider requirements according to EN 50205 “relays with forcibly guided contacts”


Process in which a monostable relay shifts from the operate state
back to the rest state.

Title:Relay definitions
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