Reluctance Motor
Before explaining about the motor let me clear you what is reluctance.
Reluctance:
It is the opposition offer to the magnetic force analogy to resistance in electrical circuit. It is the opposition to the flow of magnetic flux.
Reluctance is the ratio of the Magnetomotive Force to the Magnetic Flux .
The SI unit of reluctance is ampere turns per weber (At/Weber)
Construction:
Stator:
It consist of two Winding:
- Main Winding
- Auxiliary Winding
Rotor:
The rotor looks like single phase squirrel cage motor which have a symmetrical cutouts and have no winding on the rotor side, and have slots on the outer side
Working :
On giving supply to the winding the motor starts running at a speed lower than the synchronous speed (Ns=120f/P) and speed of 4 pole synchronous motor is 1500 rpm.
when we supply the motor, the motor runs at speed less than synchronous speed Nr which is less than 1500rpm.
When the motor attain a speed ,as there is air gap on the rotor side which opposes the flux, and there is development of the reluctance torque on the poles and do the magnetic locking with poles. Afterwards the motor gets lock with poles and starts moving at a synchronous speed.
Torque angle :
The angle between the stator pole and rotor pole of opposite polarity as the angle between then increases the reluctance also increases. The maximum reluctance toque attain at 45degree.
Note:
When we add mechanical load magnetic angle between the stator and rotor changes but the motor always try to run at synchronous speed but when we add more load then it will be out of synchronism and motor will be stop.
The reluctance motor is a self starting motor which runs at a synchronous speed without any external excitation.
Reluctance Motor has a constant speed characterstics.
