Electronics in and around Power Relays

Electronics control of relays

In addition to standard transistor control circuits. (see chapter 5) other electronic circuits are widely used to extend a relays function such as in timer relays or to reduce the power consumption of the relay’s coil.

Timer relays

Customized integrated circuits are used in the control circuits of timer relays. The power relay is the interface between these circuits and the load. Some control circuits are packaged in the form of plug in modules, which can be inserted into a relay socket to extend the relays functions.

Standard functions can include delay on, delay off, cyclic and interval timers. Using this method. a standard industrial power relay may be converted into a multi- pole timer.

Energy saving circuits

The combination of electronics and monostable or bistable relays. can reduce the power needed to switch or to keep the relay pulled in. This can be achieved by using a custom integrated circuit which operates in the following way: when energization voltage is applied. the duration of the energization current is only very short, and when switched off, a capacitor supplies the necessary energy to resetthe relay. Depending on the duty cycle and “on” time, energy savings can be considerable.