Department of information technology

1. Department of information technology

2. Electromagnetic Relay • Prepared by: • Urvil 130410116116 • Aarsh 130410116055 • Nirman 130410116124 • Under the guidance of: • Mr. Sagar Ahire

3. Outline • Why Electromagnetic Relays? • Common Applications of Electromagnetic Relays • The Principle Behind Electromagnetic Relays • What’s Inside an Electromagnetic Relay • Typical Sample Application • Electromagnetic Relay Advantages and Limitations • Important Specifications of Electromagnetic Relays • Conclusion

4. Why Electromagnetic Relays? • Separation of AC and DC circuits • Interface between electronic control circuits and power circuits

5. Common Applications of Electromagnetic Relays • Solenoid Activation Control • Many Automotive Applications (Electric Fuel Pump) • Motor Control

6. Electromagnetic Relays: What’s Inside This diagram shows the basic parts of an electromagnetic relay: a spring, moveable armature, electromagnet, moveable contact, and stationary contact. The spring keeps the two contacts separated until the electromagnet is energized, pulling the two contacts together. Moveable Contact Moveable Armature Stationary Contact Spring Electromagnet

7. Wiring Up an Electromagnetic Relay This diagram shows how to wire an electromagnetic relay. When the control circuit turns the electromagnet on, the moveable armature is drawn towards the electromagnet and connects the moveable contact and the stationary contact. This completes the circuit and delivers power to the load. Power Supply Load Moveable Contact Moveable Armature Stationary Contact Spring Electromagnet To Control Circuit

8. Typical Sample Application Suppose, there is a need to control a solenoid valve for a water drain application. Control is to be accomplished with a microcontroller. The solenoid valve requires 120 VAC to open. Assuming that a 120 VAC power supply is available, how can control of the solenoid valve be accomplished using a microcontroller that can only supply 5 VDC? This problem is easily solved using a relay. There are many relays that are turned on and off with a 5 VDC coil. The relay provides the interface between the microcontroller and the 120 VAC power supply that is needed to open and close the valve.

9. Typical Sample Application Ground To Microcontroller Coil Relay 120 VAC Solenoid Valve Circuit for Control of a 120 VAC Solenoid Valve

10. Electromagnetic Relay: Advantages • Contacts can switch AC or DC • Low initial cost • Very low contact voltage drop, thus no heat sink is required • High resistance to voltage transients • No Off-State leakage current through open contacts

11. Electromagnetic Relay :Limitations • The contacts wear and thus have limited life depending on loads • Short contact life when used for rapid switching applications or high loads • Poor performance when switching high currents

12. Important Specifications of Electromagnetic Relays • Coil Voltage – Voltage required for switching • Contact Rating – How much current the relay can handle • Normally Open (NO) or Normally Closed (NC)

13. Conclusion Electromagnetic relays are an excellent solution to separate electronic control circuitry and power circuitry. Electromagnetic relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. When used in the a proper application, the electromagnetic relay provides safe and reliable integration between power circuits and control circuits.

14. Thank you for watching….