Principles and Applications of Common Electrical Components for Cranes

Circuit breakers, contactors, intermediate relays, thermal relays, pushbuttons, indicator lights, universal transfer switches and limit switches are the eight most common components in electrical control circuits. The principles and applications of commonly used electrical components are described here. The role of the electrical circuit to grasp the normal operation of these components.

1, circuit breaker

Low-voltage circuit breakers, also known as automatic air switches, can be manually switched, and can also be used to distribute electrical energy, infrequently start asynchronous motors, and protect power lines, motors, etc. when they are severely overloaded, short-circuited, or undervoltage faulted. Automatically cut off the circuit.

Breaker text symbol: QF

2, contactor

The contactor consists of two parts: the electromagnetic mechanism and the contact system. The most common contactor coil voltages are AC220V, AC380V and DC220V.

The contactor electromagnetic mechanism consists of a coil, a moving iron core (armature) and a static iron core; the contactor contact system consists of a main contact and an auxiliary contact. The main contact is used to switch off the main circuit, and the auxiliary contact is used to control the contactor. Circuit.

The contactor text symbol is: KM

3, thermal relay

A thermal relay is a relay that operates in reverse time using the principle of thermal effects produced by current passing through the element.

Thermal relay text symbol: FR

4, the middle relay

The principle of the intermediate relay is a relay that turns one input signal into multiple output signals or amplifies the signal (ie, increases the capacity of the relay contacts). Its essence is voltage relay, but it has more contacts (up to 8 pairs), contact capacity up to 5-10A, and sensitive movement.

When the number of contactors of other electrical appliances is not enough, their number of contacts can be expanded by means of an intermediate relay, and there is also an expansion of electric shock energization capacity by means of an intermediate relay.

Middle relay text symbol: KA