Before we use the high-voltage switchgear, we need to understand the structure of the product, such as circuit breakers, contactors, intermediate relays, thermal relays, buttons, indicators, universal transfer switches and travel switches can be said to be the more common components of high-voltage switchgear, the next to introduce you to the following principles and applications of these common electrical components, to understand their role in the electrical circuit to master the usual operating conditions of the components.

(1) circuit breaker

Low-voltage circuit breakers, also known as automatic air switches, can be manually switched, and can be used to distribute electrical energy, infrequent start asynchronous motors, power lines, motors and other protection, when they are seriously overloaded, short-circuit or undervoltage and other faults can automatically cut off the circuit.

Circuit breaker

(2) Contactor

The contactor is composed of two parts: electromagnetic mechanism and contact system. The electromagnetic mechanism is composed of coil, moving iron core and static iron core; the contactor contact system is composed of two parts: main contact and auxiliary contact; the main contact is used to open and close the main circuit, and the auxiliary contact is used to control the circuit.


(3) Thermal Relay

A thermal relay is a relay that operates in reverse time by using the principle of thermal effect generated by the current passing through the component.

Thermal relay

(4) Intermediate Relay

The principle of intermediate relay is to turn an input signal into multiple output signals or amplify the signal relay. In essence, it is a voltage relay, but it has more contacts and sensitive action. When the number of contact pairs of other appliances is not enough, they can be extended with the help of intermediate relays, and there is also the expansion of contact energizing capacity through intermediate relays.

Intermediate relay

(5) Indicator light

The function of the indicator light is to indicate the operation or stopping status of the equipment, to monitor whether the power supply of the control appliance is normal, to use the red light to monitor whether the tripping circuit is normal, and to use the green light to monitor whether the closing circuit is normal.

Indicator light

(6) Transfer switch

The universal change-over switch consists of an operating mechanism, a panel, a handle and several contact holders and other components. The on/off status of each contact is indicated by a black dot when the handle is turned to different gears. A black dot indicates that the contact is closed, while one without a black dot indicates that the contact is broken.

Changeover switch

(7) Schematic diagram of the control mode in the motor contactor.

Use of high and low voltage switchgear need to understand the knowledge