Basic Information about Relay

Relay is an electric switch that opens or closes the other circuits under certain conditions. So, this device is essentially a switch that opens and closes with electric power through the coil contained. When the coils wrapped around the metal bar which is given input current, the electrical coil will generate an electromagnetic field that turns metal bar into a temporary magnet.

A magnetic force occurs in the metal rod. It pulls the other metal plates connected via a lever to a switch. Usually, this device triggers the switch open and close. Moreover, it depends on the type and needs. 

That is the main purpose of relay, to cut or to connect a circuit. However, there are some other usages in electrical and electronic circuits, such as to control circuit, as a control system for high voltage system but with low voltage circuit and as a control system of high-current system with low current circuit.

It is like the brain that command to disconnect and reconnect the circuit, making decisions based on the settings, sending a signal to the circuit breaker. Based on the signal transmission, circuit breaker will open or close. Unlike fuse which has different settings and can be adjusted based on the needs of security, it can be reset as well. 

To meet the needs, some manufacturers produce various types of relay. They are electromagnetic relays (EMRs), solid-state relays (SSRS), and microprocessor based relays (microprocessor based). EMRs are the traditional electro-mechanic relay, made mainly of coils and armature/lever.

Furthermore, SSRS uses semiconductor optical output device coupled to light source LED. Relay turned on by this LED, usually with a low-voltage DC power. Meanwhile, Microprocessor based relays use a microprocessor for switching mechanism. 

Each type of relay has benefits. EMRs are simple and easy to understand, not expensive, and easy to maintain. Moreover, SSRS has no mechanical movement, faster than EMRs, and does not trigger between contacts because it is the independent contact.

Microprocessor-based relay has much higher precision, more reliable, durable, has ability to work well with digital and analog I/O, but offered in more expensive prices. The advantage of using it as protective relay circuit is that it can detect the failure of the system. When it happens, the device will isolate the part of all system errors. It is also able to reduce the impact of failure after it happened to minimize the risk of fire, the danger of high-voltage systems and others.

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