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What is the working principle of the relay? Aug 20, 2018

What is the working principle of the relay?


3 Phase Relay Switches.jpgA relay, also called an electric cymbal, is an electronic control device that has a control system and a controlled system. It is usually used in an automatic control circuit. It is actually an automatic switch that uses a small current to control a large current. . Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit. The relay coil is indicated by a long square symbol in the circuit. If the relay has two coils, draw two long square boxes. At the same time, the relay's text symbol "J" is marked in the long box or next to the long box. There are two ways to represent the contacts of a relay: one is to draw them directly on the long square side, which is more intuitive.

A thermal relay operates by generating heat when a current passes through a heating element. Thermal relays are mainly used for thermal protection of electrical equipment, such as motor overload protection. The thermal relay consists of a heating wire, a bimetal, a guide, a test rod, a push rod, a moving contact piece, a static contact piece, a spring, a screw, a reset button, and a setting knob. Only when the current flowing through the heating element exceeds a certain value, the internal mechanism will act, causing the normally closed contact to open, the larger the current, the shorter the operating time. The rated current of the heating element of the thermal relay can be adjusted by setting the knob.