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What is Relay?


Relay is an electrically operated switch that opens and closes the circuit by receiving electrical signal from the outside source 

Relay Type:

Ø  Relay technology is divided into two categories

1. Movable Contacts

2. No-Movable Contacts

 

Mechanical Relay



                

 

Solid State Relay

                    

 

Relay Types:

Mechanical Relay

Ø  This relay has contacts that are mechanically actuated to open/close by a magnetic force

Ø  This magnetic force is produced by a coil which is excited by the electric current

Ø  Due to movable part it creates noise during operation

 

Solid-State Relay

Ø  This relay does not have mechanical contacts to control outputs

Ø  There are electrical switching elements such as Triac and MOSFET

Ø  Since no movable part is there so no noise it creates

 

Mechanical Relay- Advantages

Ø  It provides physical isolation between input and output

Ø  It can withstand higher voltages

Ø  These relays can tolerate short-term overload condition

Ø  Transients do not affect output of the relay significantly

 

Mechanical Relay- Disadvantages

Ø  Due to mechanical contacts its switching speed is slow

Ø  It has limited life span due to mechanical parts

Ø  These relays create contact-bounces which cause arcing

 

Solid State Relay - Advantages

Ø  It also provides physical isolation between input and output

Ø  Switching time is less as compared to the mechanical relay

Ø  Life expectancy is higher

Ø  These Relays offer greater reliability

Ø  No contact-bounce problems

 

Solid State Relay – Disadvantages

Ø  Resistance in the output circuit is normally higher as compared to an Electromechanical relay

Ø  It is not resilient to transient spikes and other overload conditions, like a mechanical relay, unless it is protected

Ø  A transient above the limits of the output device could destroy the solid state relay



 


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