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Classification of Relays
Actually, relay is type of protecting device which has the sensing ability. Relay can be stated as a device which sense any kind of abnormality in a power system and then close its contacts, which intern close the circuit breaker. In this way, the faulty part of the circuit is automatically disconnected. Now, relays can be divided in many ways depending upon operation, construction, signal adapting etc. All of these are enlisted below:
The most basic classification comes from functioning, so from this point of view relays can be classified as
Now depending on the construction, there are various types of relays, those are
- Electromagnetic Relay
- Solid State Relay
- Microprocessor Relay
- Computerized Relay
- Non – Electric Relay (which is activated not by electricity but by temperature, pressure, etc.)
Relays can be divided depending upon the type of signals which activates the relay these are
- Current relay
- Frequency relay
- Voltage relay
- Temperature relay
- Pressure relay
- Velocity relay etc.
Now depending upon the type of protection that a relay provides, relays can be divided as
- Over current relay
- Directional Over current relay
- Distance relay
- Over voltage relay
- Reverse Power relay
- Differential relay etc.
Finally depending upon the operating principles relay can be classified as
i) Electromagnetic relay
- Attraction type relay
- Relay with movable coil
- Induction type relay
ii) Shaded pole relay
iii) Cup type relay.
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