Quite a few electronic components. particularly active ones. cannot withstand too high voltages. Preventing costly circuits dying a premature death because the supply voltage has risen too high makes overvoltage protector no luxury. Such a protector must, of course, act swiftly, otherwise, the deed has been done before it had a chance to act. Therefore. (slow-acting) relays are not suitable for this purpose. The circuit is shown here, a so-called crow-bar. contains several fast-acting components. It is intended to be connected to the mains and the appliance to be protected. -The circuit depends, as it were, on brute force: when the supply voltage rises too high. a thyristor short-circuits the output. This means that the too high voltage is immediately removed from the connected appliance and also that fuse F, blows. Brute force, indeed!
The voltage at which the crowbar carry-s into action is set between 5 V and 25 V with P.
