1. Equivalent Circuit of a Single Phase Induction Motor
The double revolving field theory can be effectively used to obtain the equivalent circuit of a single phase induction motor.
Imagine the single phase induction motor is made up of one stator winding and two imaginary rotor windings. One rotor is rotating in forward direction i.e. in the direction of rotating magnetic field with slip s while other is rotating in backward direction i.e. in direction of oppositely directed rotating magnetic field with slip 2 - s.
1. Without core loss

2. 2. With core loss

3. Hysteresis motor
A hysteresis motor is a synchronous motor without salient (or projected) poles and without dc excitation which starts by virtue of the hysteresis losses induced in its hardened steel secondary member by the revolving filed of the primary and operates normally at synchronous speed and runs on hysteresis torque
It is a single-phase motor whose operation depends upon the hysteresis effect i.e., magnetization produced in a ferromagnetic material lags behind the magnetizing force.

4. Hysteresis Motors Stator Rotor same as for induction motor
Smooth cylinder

5. Principle of Operation
Stator Flux establishes these magnetic poles
Rotor poles “induced” by Stator Flux

6. Rotor poles follow the rotating flux, but lag behind by angle δh
Stator poles moving CCW

8. Ts α φsφrsinα Where, φs = stator flux φr = rotor flux

9. Hysteresis Power Loss, Ph
where
fr = frequency of flux reversal in the rotor (Hz)
Bmax = maximum value of flux density in the air gap (T)
Ph = heat-power loss due to hysteresis (W)
kh = constant

10. Hysteresis Motor at Synchronous Speed
No load and negligible rotational losses
Induced rotor magnets remain locked with the rotating poles produced by the stator

11. Hysteresis Motor at Synchronous Speed
The rotor slows down and the induced rotor magnets lag the rotating poles of the stator by an angle δmag .
The rotor returns to synchronous speed at the new torque angle.
Apply a step increase in shaft load.

12. Hysteresis Motor at Synchronous Speed
If shaft load causes δmag>90°, the rotor pulls out if synchronism, the magnet torque drops to zero, and the machine develops hysteresis torque. This torque is not sufficient to carry the load.

13. Torque-Speed Characteristic
Constant Hysteresis Torque allows the motor to synchronize any load it can accelerate
“Normal” Operating Range

14. Advantages
Rotor as no teeth and no windings
No mechanical vibration
Quiet and Noiseless operation
Suitability to accelerate High inertia load
Possibility of multispeed operation
Application
Sound recoding Instrument
Sound producing equipment
Tape recorder
Electric Clock
Tele-printers
Timing Devices
High quality recorder player

15. Reluctance motor
Stator
Rotor

16. Operating principle
When power is applied to the stator windings, the rotor's magnetic reluctance creates a force that attempts to align the rotor pole with the nearest stator pole.

17. Reluctance Motor There are various types of reluctance motors:-
Synchronous reluctance
Variable reluctance
Switched reluctance
Variable reluctance stepping.

18. SWITCHED RELUCTANCE MOTOR
The stator and rotor of a Switched Reluctance motor have salient poles
This doubly-salient arrangement is very effective for electromagnetic energy conversion.
The stator part carries coils on each pole, the coils on opposite poles being connected in series.
The rotor does not have magnets or coils attached with the rotor slots. It is a solid salient-pole rotor made of soft magnetic material with a laminated-steel.

19. The Switched Reluctance Motor
The Stator contains
3 electro-magnets
powered by DC
Current.

20. The Rotor is a Plain Piece of Steel capable of carrying a magnetic flux
The rotor is connected
To a shaft that is it
hoped will turn to
make something
happen.

21. Magnetic Reluctance Magnetic flux likes to find an easy flow path
A nice piece of steel is a much better flow path than air
The magnetic flux will try to get the steel path to line up (considered magnetic reluctance)

22. Making the Motor Work If I keep turning magnetic fields off
And on around the stator I can
Have the rotor continuous chasing
The magnetic field and thus
Turning the shaft –
I now have a DC motor with no
Rings or brushes. (But one wholly
Heck of a lot of switches)

23. A bunch of extra poles and then let a project logic controller program do the field
Switching to smooth out the torque.

24. Advantages of Switched Reluctance Motor
Reluctance motor offers following advantages. These are:
Construction of the motor is simple.
Brushes, commutators , permanent magnets are absent
Starting torque is quite good
Accurate speed control is possible
Cost effective and easy maintenance.
Higher efficiency
More power per unit weight and volume
Has no windings or slip rings in the rotor
Can run at very high speed (upto 30,000 rpm) in hazardous atmospheres.
Four-quadrant operation is possible with appropriate drive circuitry.

25. Disadvantage of Switched Reluctance Motor
Noisy in the operation
This type of motor not well-suited for smooth torque production.
Flux linkage and Non-linear function of stator currents as well as rotor position control of the motors a tough challenge.
Applications
Washing Machines, Weaving Machinery.
Centrifugal Pumps, Compressors, Door Openers
Analog Electronic Meters.
Control Rod Drive Mechanisms of Nuclear Reactors.
Microcontroller Based Operation Control Circuits.