Developed by Sir James Dyson, Switched reluctance motor also called as variable reluctance motor market is an electric motor operates by producing reluctance torque between iron laminated rotor and energized stator pole. It does not require any permanent magnets. Stator is similar to brushless dc motor. So in switched reluctance motors, mechanical construction design is simplified but electrical designing becomes complicated. Number of phase in the motor determine the number of pole in stator. A 3-phase motor has 6 stator poles as 2 opposite ended stator pole forms one phase of the motor. Count of rotor poles is always different from stator poles. Phase winding in case of switched reluctance motor resides on stator only. Windings used switched reluctance motor are concentrated windings. To form the phase of the motor, connection of windings in series on the stator poles is done. As both stator and rotor are simple in construction and design, faults are less and hence more fault tolerant.
One of the major advantages of switched reluctance motor are they continue to run with disabled or shorted poles but with the reduced smoothness or torque. Disadvantages of the switched reluctance motor are that difficulty to control, noisy, have torque ripple effect, need shaft sensor for operation. Torque in switched reluctance motor has limitation of maximum allowed current and bus voltage speed. Some of the applications of switched reluctance motor are air conditioning system which are environment friendly for passenger trains, advanced weaving machine technology, motor blower for vacuum cleaning, and food processor compact drives. Switched reluctance motor also find applications in high volume appliances and appliances which have very high starting torque. Considerable efforts are made to improve on the noise characteristics of switched reluctance motor but this can still be a limitation for applications where operating speed range required is very broad.
Mechanical design same as switched reluctance motor is used in generator. Such generators run with much higher speed than the conventional ones. Single phase switched reluctance motors are mostly used because of their low cost of manufacturing. Maximum duty cycle of a single phase witched reluctance motors is 0.5 and due to this there is high torque discontinuity and hence high noise and torque ripple. Home appliances and hand tools which are insensitive to the high noise and torque ripple use this single phase switched reluctance motor.
Major drivers for the market include high torque density property of switched reluctance motors as compared to induction motors. Improved efficiency has also increased the demand for switched reluctance motors. Construction of switched reluctance motors is more rugged as compared with the induction motors which has also augmented the demand for the switch reluctance motor. Another driver for the market is the switch reluctance motor’s application in cost efficiency and energy. Application in high power electronic switches is another reason for growth in the market. The switch reluctance motor’s suitability to be used in very high temperature ambience is also the factor increasing the use of the switch reluctance motor in the market. Major advantage of being least expensive of all the motor types is the key reason for the growth of the switch reluctance motor market. One of the key challenges posed to the switch reluctance motor market is its disadvantage of acoustic noise and torque ripple.
The market can be segmented based on the application (Fuel Pump, Throttle Control, Oil Pump, Vacuum Cleaner, Lawnmower, Washing Machine, Fans, Automatic doors in buildings and vehicles), type (4/2 2-Phase switched reluctance motor, 6/3 3-Phase switched reluctance motor), and geography (North America, Europe, Asia Pacific, Middle East & Africa, Latin America).
The key players in the market include U.S. Motors, Nidec SR drives, Maccon, Emotron, Control Engineering etc.