The choice of electromagnetic relay, its working principle and wiring method are explained in detail

Electromagnetic relay is a common electrical appliance in industrial circuits. Many people do not understand the choice of electromagnetic relay very well. There are many questions about how to choose a good electromagnetic relay. So how to choose electromagnetic relay?

1. Select the rated working current of the coil of the electromagnetic relay: For a DC electromagnetic relay driven by a transistor or integrated circuit, the rated working current of the coil (usually twice the pull-in current) should be within the output current range of the drive circuit.

2. Select the contact type and contact load of the electromagnetic relay: the same type of relay usually has a variety of contact methods to choose from (electromagnetic relays include: single contact, double contact, multiple contact and normally open contact, normal Closed contact, etc.), the contact type suitable for the application circuit should be selected.

3. Choose electromagnetic relay coil power supply voltage: When choosing electromagnetic relay, first choose whether the relay coil power supply voltage is AC or DC. The rated working voltage of the relay should generally be less than or equal to the working voltage of its control circuit.

4.Choose the appropriate volume of the electromagnetic relay: the size of the relay is usually related to the size of the relay contact load. The choice of the relay is based on the request of the application circuit.

Relay is an automatic switching element with isolation function, which is widely used in remote control, telemetry, communication, automatic control, mechatronics and power electronic equipment, and is one of the most important control elements.

Electromagnetic relay is an electronic control device. It has a control system (also called an input loop) and a controlled system (also called an output loop). It is usually used in automatic control circuits. In fact, it uses a smaller current. Lower voltage to control larger current. A kind of "automatic switch" for higher voltage. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

The general principle of electromagnetic relay is to use electricity to generate magnetism and make the output end pull in or open. The static contact that is in the off state when there is no power is called "normally open contact"; the static contact that is in the on state is called "Normally closed contact".

Working principle of electromagnetic relay: Electromagnetic relay is generally composed of electromagnet, armature, spring sheet, contact, etc. Its working circuit is composed of two parts: low voltage control circuit and high voltage working circuit. The electromagnetic relay can also realize remote control and automatic control. As long as a certain voltage is applied to the two ends of the coil, a certain current will flow in the coil, which will produce electromagnetic effects. Under the action of electromagnetic force, the armature will overcome the pull force of the return spring and attract to the core, thereby driving the armature. The moving contact and the static contact (normally open contact) are pulled together.

When the coil is de-energized, the electromagnetic attraction will disappear, and the armature will return to its original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This pulls in and releases, so as to achieve the purpose of conducting and cutting off in the circuit. The "normally open and normally closed" contacts of the relay can be distinguished as follows: the static contact that is in the off state when the relay coil is not energized is called "normally open contact"; the static contact that is in the on state is called It is "normally closed contact". The wiring method of electromagnetic relay is shown in the figure below.