Principle of time relay

Time relay is a kind of control electric apparatus which uses electromagnetic principle or mechanical principle to realize time delay control. It has many kinds, such as air damped, electric and electronic, and other types.

Air damped time relay was often used in AC circuit in the early days. It used the principle of air throttling through orifices to obtain the delay action. It consists of three parts: electromagnetic system, time delay mechanism and contact.

A relay whose actuator (contact) has to be delayed for a period of time after the sensing element of a relay receives the action signal is called a time relay.

At present, the most commonly used time relay is made of large-scale integrated circuits. It uses resistance-capacitance principle to realize the delay action. Transformers are often used to reduce voltage in AC circuits, and integrated circuits are used as the core devices. Small electromagnetic relays are used as the outputs. The performance and reliability of the products are much better than those of the early air-damped time relays. The timing accuracy and controllability of the products are also improved greatly.

With the popularity of single-chip microcomputer, the current manufacturers have adopted single-chip microcomputer as the core device of time relay, and product controllability and timing accuracy can be completely adjusted by software, so the future time relay will be completely replaced by single-chip microcomputer.