1. Electromagnetic Relays
Attracted Armature Type
Induction Disc Type
Induction Cup Type
Moving Coil Type

2. Hinged Attracted Armature Type relay

3. Shaded Pole Induction Disc Relay
Robust & reliable Construction
Fluxes displaced in space & time
Used for over current protection
Eddy currents in disc
Used for slow speed relays
Disc rotation α driving toque
Reset/pick up ratio > 95%
Brake magnet to avoid over run

4. Wattmetric type Induction Disc Relay
Two electromagnets
Upper and lower produce two different flux
Energised by two different sources
If energised by same source then R and X would be made different to get phased difference between fluxes

5. Induction Cup Relay

6. Induction Cup Relay Stationary core inside rotating cup
Spindle carries arm - closes relay contacts
Spring for resetting torque
No brake magnet
Principle of Induction motor

7. Induction Cup Relay Rotor is hollow cylinder (inverted cup)
Two pairs of coils produce rotating field
Cup has less inertia than disc
Interaction of rotating flux with current
Less magnetic leakage
Torque per VA is 3 times than disc type
Operating time 0.01 s
High torque/inertia ratio
Suitable for higher speeds of operation
Used for distance & directional relays
Stationary core inside rotating cup
Spindle carries arm - closes relay contacts
Spring for resetting torque
No brake magnet
Principle of Induction motor

8. Moving Coil Relay

9. Torque Production in Induction Relay

10. Torque Production in Induction Relay

11. Force Produced in Induction Relay

12. Force Produced in Induction Relay

13. Force Produced in Induction Relay

14. Force Produced in Induction Relay

15. Force Produced in Induction Relay

16. Force Produced in Induction Relay

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18. Force Produced in Induction Relay

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20. Force Produced in Induction Relay

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22. Force Produced in Induction Relay

23. Force Produced in Induction Relay

24. Force Produced in Induction Relay

25. Force Produced in Induction Relay

26. Force Produced in Induction Relay