The perfect choice of one-stop service for diversification of architecture.

Introduce Commonly Used Control Appliances

The use of relays and contactors to realize the control and protection of motors and production equipment is called relay contact control. A relay control system is composed of control appliances that undertake different functions, such as buttons, switches, relays, and contactors.

1. Combination switch

Combination switch structure

The combination switch is also called a transfer switch.

1. Purpose

It is generally used as a switch for the power supply of electrical equipment, and also used for start/stop control of small-capacity motors.

2. Structure

For a commonly used three-pole switch, each pole has a pair of static contact pieces connected to the outer terminal of the box, and the movable contact piece can be rotated under the control of the handle to achieve the on/off control of the circuit.

3. Type

There are single pole, double pole, three pole and four pole, etc., and the rated current is 10A, 25A, 60A and 100A.

As shown in the figure below, when rotating the shaft with the handle, three electric shocks can be connected or disconnected at the same time.

Combination Switch

The following picture shows the application of the combination switch: controlling the start and stop of a small-capacity motor.

Use the combination switch to directly control the start and stop of the motor.

Second, the button

Buttons are often used to connect and disconnect control circuits.

The outline drawing, structure and symbols of the button are shown in the figure. Usually the red button represents stop and the green button represents start.

Three, AC contactor

It is used to switch on and off high-current circuits frequently.

1. Structure and principle

When the coil is energized, the static iron core generates electromagnetic attraction and pulls in the moving iron core. Since the contact system is linked with the moving iron core, the moving iron core drives the three moving contact pieces to run at the same time, and the contacts are closed to connect power supply. When the coil is de-energized, the suction force disappears, and the moving iron core linkage part is separated by the reaction force of the spring, so that the main contact is disconnected and the power supply is cut off.

Principle of AC Contactor

2. Symbols

Coils and contacts belonging to the same device are indicated by the same text.

Commonly used AC contactors include CJ10, CJ12, CJ20 and 3TB series.

Technical indicators of the contactor: rated working voltage, current, number of contacts, etc.

Four, intermediate relay

It is usually used to transmit signals and control multiple circuits at the same time. It can also be used directly to control small-capacity motors or other electrical actuators.

The intermediate relay has a small capacity and a large number of contacts, and is used to control the circuit.

Several commonly used intermediate relays:

Five, thermal relay

Used for motor overload protection.

1. Working principle

The heating element is connected to the main circuit of the motor. If it is overloaded for a long time, the bimetal will be heated. Due to the large expansion coefficient of the lower layer of the bimetallic sheet, it bends upwards, the lever is pulled back by the spring, and the movable break contact is disconnected.

2. Symbols

Commonly used thermal relays:

Six, fuse

Used for short-circuit protection in low-voltage lines.

1. Classification

Commonly used fuses are: plug-in fuse, screw fuse, tube fuse and filled fuse.

2. Symbols

3. Selection of the rated current IF of the fuse

(1) Resistive loads such as electric lamps and electric furnaces


(2) Single motor

Fuse rated current ≥ motor starting current/2.5

(3) Motors that start frequently

Fuse rated current ≥ motor starting current/1.6-2

Seven, circuit breaker

Circuit breaker refers to a switching device that can close, carry and break current under normal circuit conditions and can close, carry and break current under abnormal circuit conditions within a specified time.

Circuit breakers are generally composed of contact system, arc extinguishing system, operating mechanism, trip unit, shell and so on.

Circuit breaker symbol:

Introduce Commonly Used Control Appliances 1

recommended articles
Related Blogs blog
There might be better ways to do this but we need more details on the topic.However one possible way around this is Voltage sensor high current Mosfet switch. Feel f...
Although GPR has been widely used in hydrology, engineering, environment and other fields, many basic theoretical and technical problems have not been fundamentally ...
So I am thinking of a possible answer to my own question:Build my own journal note entry app linked to a wiki.Zim Wiki uses a file based system for wiki. Maybe I cou...
About 8 I think1. where can i get ncaa football 10 rosters with names?For the last two years I got mine from "Pastapadre". From what i can tell they are really prett...
The Haunting I vaguely remember some kind of eye injury in the movie.• Other Related Knowledge ofa cocktail glass— â€&...
rsync can be somewhat painful if you have a very large number of files - especially if your rsync version is lower than 3. On the other hand: if you use tar, you wou...
Blockchain Technology Explained: Powering BitcoinMicrosoft recently became the latest big name to officially associate with Bitcoin, the decentralized virtual curren...
PLEASE HELP ME CHOOSE A VIDEO CAMERA!?the Flip ultra HD is a really good HD portable camcorder, and it's fairly cheap. A lot of famous youtubers use it, such as timo...
In order to implement the tasks proposed in the outline of the national medium and long term science and technology development plan (2006-2020), the national key R ...
Alibaba group and Royal Philips of the Netherlands announced that they have officially signed an IT infrastructure service framework agreement to jointly promote the...
no data
Customer service