A relay is a component that is often used as a switch in a circuit. According to the type of control voltage required by its coil, it can be divided into AC relays and DC relays. The specifications of the relay are expressed by the coil control voltage and the contact current. Usually, when the load current is less than 10A, the contact of the relay can be used to directly connect or cut off the circuit. When the load current is too large, it can be used as an indirect control part.
Relays are generally composed of iron cores, coils, armatures, contact springs, etc. As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil, and an electromagnetic effect will be generated. contacts (normally open contacts) attract. After the coil is powered off, the electromagnetic attraction also disappears, and the weighing iron returns to its original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This absorption and release achieve the purpose of conducting and cutting off in the circuit. Regarding the normally open and normally closed contacts of the relay, it is possible to distinguish the static contacts that are in the disconnected state when the relay coil is not energized, and the energized static contacts called the normally open contacts are called the normally closed contacts.
In central air conditioning control systems, relays are often used as switches for power circuits such as compressors, blower motors, pumps, and four-way valves. When in use, one end of the relay control coil is connected to the power supply, and the other end is connected to the output end of the control component. Through the output control signal of the control component, the two ends of the relay control coil generate a potential difference, forming a current loop to generate electromagnetic force. Under the action of the electromagnetic force and the inherent elastic force of the relay reed, the contacts of the relay are pulled in or released, the circuit of the electrical load power supply is opened or closed, and the operation or stop of the related equipment is controlled.
The working principle of the relay is that when a certain input quantity (such as voltage, current, temperature, speed, pressure, etc.) reaches a predetermined value, it will work, change the working state of the control circuit, and achieve a given control or protection purpose. In this process, the relay mainly plays the role of transmitting the signal.
The role of the relay:
1. Expand the control range: For example, when the control signal of the multi-contact relay reaches a certain value, multiple circuits can be replaced, cut off and connected according to the different forms of the contact group.
2. Expansion: For example, sensitive relays, intermediate relays, etc., can control high-power circuits with a small amount of control.
3. Integrated signal: For example, when multiple control signals are input to the multi-winding relay in a specified form, they are more integrated to achieve a predetermined control effect.
4. Automatic, remote control, monitoring: For example, the relay of the automatic device can form a program control circuit together with other electrical appliances to realize automatic operation.
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