Reluctance Motor

Reluctance Motor 

Construction Stator  ±Single Stator ±Single phase induction motor  

Split phase reluctance motor 

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Capacitor

type reluctance motor 

Rotor  

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 Asymmetric magnetic construction By removing some rotor teeth

Operation It starts like an induction motor but runs with a small amount of synchron synchronous ous torque. The synchronous torque is due to changes in 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 pull--out -out torque, and low efficiency

Limitations Low Efficiency Low Power factor 

Comparing

one of the new synchronous reluctance motors, on the left, with the traditional type of A.C. motor on the right. Both motors deliver the same output power.

 Applications Constant

speed applications

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Recording instruments

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Timing instruments

Switched Reluctance motor 

Switched Reluctance motor 

Variable reluctance reluctance motor drive waveforms: (a) unipolar wave drive, (b) bipolar full step (c) sinewave (d) bipolar 6-step.

Variable

Reluctance Stepper Motor  and Reluctance Motor 

 A variable reluctance motor intended to move in discrete steps, steps, stop, and start is a variable reluctance stepper motor  high ripple torque desired in stepper motors. If smooth rotation is the goal, electronic driven version of the switched reluctance motor is to be used. a variable reluctance motor is optimized for  continuous high speed rotation with minimum ripple torque

Switched Reluctance motor  Construction The stator poles have concentrated winding rather than sinusoidal winding. Switched--reluctance Switched -reluctance motor operates like a variablevariable-reluctance -reluctance step motor  However, the operation differs mainly in the complicated control mechanism of the motor. In order to develop torque in the motor, m otor, the rotor position should be determined by sensors so that the excitation timing of the phase windings is precise. Each statorstator -pole -pole pair winding wi winding nding is excited by a converter  phase, until the corresponding rotor polepole-pair -pair is aligned and is then dede-energized. -energized. The stator  stator--pole -pole pairs are sequentially excited using a rotor  position encoder for timing.

Construction«

Electronic driven variable reluctance motor 

SR MOTOR CONTROL Measured Currents Speed Reference

Speed Regulator 

Torque to Current

Current Regulator 

PWM Generation & Synchro

Commutation Angles Advanced Angle Calc Speed Estimator 

Power Hardware

SRM

Bus Voltage Position Measure

 Advantages Simple constructionconstruction- no brushes, brushes, commutator, commutator, or permanent permanent magnets, no Cu or Al in the rotor. This simplicity si mplicity of the motor  compensates for the drive electronics cost. High efficiency and reliability compared to conventional A C or DC motors. High starting torque. Cost

effective compared to bushless DC motor in high volumes.

 Adaptable to very high ambient temperature. Low cost accurate speed control possible if volume is high enough.

Disadvantages 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 Not

applicable to low volumes due to complex control issues

 Applications High volume applications like energy efficient vacuum cleaner motors, fan motors, or pump motors.

SRM driven compressor