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What is a short circuit protection or overload protection?

Short circuit protection

Switches with short-circuit/ overload protection are usually used as loads together with relays or contactors. When the switch is on, compared with the switch with DC power supply, the load of the AC switching device (protective contactor/ relay) of the switch is greatly increased (6... 10 times of the rated current) in the later static operation, because the iron core of these devices is still open. 6.1After only a few milliseconds, the static value of the load (current) can be reached. The allowable rated operating current ie listed in the data sheet will flow through the switch only when the field is turned off. Therefore, the release value of these switches must be greatly increased when they are short circuited. If, for example, the contactor cannot be closed completely again due to mechanical or electrical reasons, the switch will be overloaded.

In this case, overload protection should be used. Overload protection is designed as slow execution (with delay), and its trigger threshold can only be slightly higher than the maximum allowable value.

Based on the degree of overload, only after more than 20 ms the reaction (or current closure) will occur, in which case it should be ensured that the intact relays and contactors can be switched on and off, and that the defective switch gear will not cause damage to the Balluff switch. The short-circuit protection / overload protection is usually of bi-stable design and must be reset after triggering by switching supply voltage.


Learn more about Balluff's short circuit protection / overload protection