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Transcript of PPT
REUELSON THOMAS &
INTELL ENGINEERING COLLEGE
A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. Torque is generated through the phenomenon of magnetic reluctance.
There are various types of reluctance motor:
Synchronous reluctance motor
Variable reluctance motor
Switched reluctance motor
Variable reluctance stepping motor
The stator consistsof single windings called main windings but single winding cannot produce rotating magnetic field.
Hence stator consists of additionalwinding called auxiliary winding which consists of capacitor in series with it.
There exists a phase difference between the currents carried by the two windings & corresponding fluxes which reacts to produce the rotating magnetics field.
The technique is called split phase technique
The reluctance motor has basically two main parts called stator & rotor
The stator has a laminated construction made up of stampings.
The stampings are slotted on its periphery to carry the windings called stator windings.
The stator carries only one winding.
The laminated construction keeps iron losses to minimum& minimizes the hysteresis losses.
Due to the particular shape of the rotor, the air gap between stator & rotor is not uniform.
The reluctance that’s is resistance of the magnetic circuit depends on the airgap.
When rotor rotates the reluctance between stator & rotor also changes.
It starts like an induction motor but runs with a small amount of synchronous torque.
The synchronous torque is due to changes in reluctance of the magnetic path from the stator reluctance of the magnetic path from the stator through the rotor as the slots align.
An inexpensive means of developing a moderate synchronous torque.
Low power factor, low pull--out torque, and low efficiency.
The torque-speed characteristics is shown in the figure.
The starting torque is highly dependent on the position of the rotor.
Simple constructionSimple construction--no brushes, commutator, or permanentmagnets, no Cu or Al in the rotor. This simplicity of the motor compensates for the drive electronics cost.
High efficiency and reliability compared to conventional AC or DCmotors
High starting torque.
Cost effective compared to bushless DC motor in high volumes.
Adaptable to very high ambient temperature.
Current versus torque is highly nonlinear
Phase switching must be precise to minimize ripple torque.
Phase current must be controlled to minimize ripple torque
Acoustic and electrical noise
High volume applications like energyefficient vacuum cleaner motors, fanmotors, or pump motors.
This motor is used in
clocks and all kinds of timing devices
reluctance motor has got a high power density at low cost, which makes them ideal for many applications.
But when this motor is operated at low speed then it experiences a high torque ripple and due to high torque ripple noise is caused.
Until now their use has been limited due to inherent in designing them as well as controlling them. use of sophesticated computer design tools and low cost embedded systems have overcome this challenge.