Working principle and function of relay: Symptoms and manifestations of relay failure

A relay is an electrical control device mainly composed of coils, contacts, and springs. It is a device that uses small current to control large current, commonly used in power systems, automation equipment, and household appliances. The following will provide a detailed introduction to the working principle, function, symptoms, and manifestations of a faulty relay.

1、 The working principle and function of relays

working principle:
The working principle of a relay is based on the phenomenon of electromagnetic induction, which changes the on/off state of a large current by controlling the on/off state of a small current. When the current flowing into the coil generates a magnetic field through electromagnetic induction, this magnetic field will attract or release the contacts, thereby achieving the on/off of the control circuit.
effect:
The main function of a relay is to control large currents with small currents, achieving the switching and protection functions of the circuit. It is often used in the following areas:
Automation control: Relays can be used to control the switches of various devices, achieving automation control.
Power system: Relays are widely used in power generation, transmission, distribution, and consumption, for the protection, segmented control, and fault detection of power transmission lines.
Household appliances: Relays serve as switching components for electrical appliances, used to control the on/off of lights, fans, televisions, and other household appliances.
Electronic devices: Relays are used in electronic devices to switch and control various functions, such as power control, signal amplification, AC to DC conversion, etc.
2、 Symptoms and manifestations of relay failure
A relay is a mechanical electrical device that may be damaged or malfunctioning due to prolonged use and environmental factors. Here are several common symptoms and manifestations of a broken relay:

Contact sticking or detachment:
The contacts of the relay may stick or fall off during the process of long-term current interruption. This will cause the relay to fail to switch on and off properly, resulting in the equipment not working or unable to complete the corresponding control tasks.
Coil or contact burnout:
When a relay is subjected to high current for a long time, the coil or contact may experience overload or short circuit faults, leading to burnout. At this point, the relay will not be able to generate a normal magnetic field, making it impossible to control large currents with small currents.
Coil open or short circuit:
An open or short circuit in the coil may occur in the coil part of the relay, causing the relay to be unable to be excited or disconnected normally. When the circuit is open, the coil cannot generate sufficient magnetic field, and the relay cannot work; When short circuited, the relay will continue to be energized, affecting its normal switching operation.
Magnetic field failure or weakening:
The coil of the relay provides a magnetic field, and the strength of the magnetic field directly affects the working effect of the relay. Long term use or environmental factors can cause the magnetic field in the coil to weaken or fail, resulting in the relay being unable to turn on, off, or control normally.
Abnormal noise or vibration:
When the relay is working normally, it will generate certain noise and vibration. But when the relay is damaged or malfunctioning, these noises or vibrations may increase abnormally or produce irregular changes.
Relay cannot be excited:
Relays typically require external current drive to function, but when a relay malfunctions, it may not be able to be energized properly. This will cause the relay to malfunction or fail to complete the corresponding control function.
In summary, the working principle and function of relays are devices that use small currents to control large currents, commonly used in power systems, automation equipment, and household appliances. However, prolonged use and environmental factors may lead to relay damage or failure, manifested as contact sticking or detachment, coil or contact burnout, coil open circuit or short circuit, magnetic field failure or weakening, abnormal noise or vibration, and relay inability to be excited.