Relay

Q1. What is a relay?

A relay is an electromechanical or electronic switching device that opens or closes contacts to control the flow of current in a circuit, usually operated by a low-power signal.

Q2. What are the main types of relays?

Electromechanical Relay (EMR) – works with coil and moving armature.

Solid State Relay (SSR) – electronic, no moving parts, faster switching.

Time Delay Relay – provides ON/OFF delay control.

Reed Relay – compact, sealed type using reed switch.

Q3. How does a relay work?

When current flows through the relay coil, it creates a magnetic field that attracts the armature, opening or closing the contacts to control another circuit.

Q4. Where are relays used?

Control circuits in automation and PLC systems

Motor starters and protection circuits

Lighting and HVAC systems

Automotive electronics

Q5. What is the difference between NO and NC contacts in a relay?

NC (Normally Closed): Contact is closed when relay is de-energized, opens when energized.

NO (Normally Open): Contact is open when relay is de-energized, closes when energized.

Q6. What protections can relays provide?

Overcurrent protection

Overvoltage protection

Reverse polarity protection

Phase failure protection (in 3-phase systems)