Home Blog High Efficiency Switched Reluctance Motors

High Efficiency Switched Reluctance Motors

Dr. Manoj Kumar Nigam

Professor & Head

Department of Electrical Engineering

Kalinga University, Nava Raipur Chhattisgarh



One of the earliest electric motor designs still in use today is the switched reluctance motor (SRM). The “switched reluctance” (SR) machine is a modified version of the traditional reluctance machine that has been developed. This development is partially attributable to the growth of power electronic drives and partially to the recent demand for variable speed drives. “Switched reluctance” refers to the two characteristics of the machine configuration when good power semiconductors became available.

A magnetically conspicuous rotor can freely rotate to a location where it encounters the least amount of flux in a magnetic circuit, which is how the reluctance motor works. The SR motor has entered the adjustable speed drive market thanks to advancements in machine design and improved magnetic materials. The motor is inexpensive to construct and extremely dependable due to its straightforward brushless design. A straightforward and incredibly dependable power converter circuit is produced by the phase windings’ unipolar current requirements. The researchers are currently concentrating on SR motors and drives that have just one or two phase windings in order to develop applications for the technology in high volume, low cost markets like HVAC, automotive auxiliaries, and home appliances. Power MOSFETs, GTOs, IGBTs, and power transistors have all been developed recently in the power ranges needed for SRM control. Permanent magnets (PMs), brushes, and commutators are eliminated by SRMs. Steel laminations that form salient poles comprise the stator. The stator poles are surrounded by a sequence of coil windings that are separately connected in phase pairs. The rotor is essentially a piece of steel (and laminations) shaped to form salient poles in the absence of rotor winding. It is the only kind of motor with double salient, or salient poles in both the stator and the rotor. The SR machine promises a dependable and affordable variable-speed drive as a result, and it will surely replace many drives that use cage induction and DC commutator machines in the near future due to its inherent simplicity. In home appliance applications, the switched reluctance motor is a recent addition. Numerous researchers in electrical machines are studying the dynamic behaviour of switched reluctance motors (SRMs) by keeping an eye on the dynamic response (speed and torque), keeping an eye on and minimising torque ripple, and developing various controller types to lower costs while enhancing the SRM’s overall performance, which includes high practicability and reliability. applications


Because of its sturdy design, the SRM can withstand extreme temperatures and vibrations. When compared to adjustable-speed drive bridge-type inverters, SRM controllers offer the added benefit of reducing the number of power-switching devices by 50% because they do not require bipolar (reversed) currents. Unlike standard motor drives, an SRM drive has inherent reliability and fault tolerance. It can operate in a “limp-home” mode with reduced performance if one of its transistors fails in a phase.


  • SR motors come with many advantages, including: Enhanced performance over a wider speed range with higher torque output and the same (or slightly higher) efficiencies as “premium efficiency” induction motors.
  • Small unit sizes use less material and have less inertia.
  • Minimal expenses, including minimal manufacturing, material, and maintenance costs. It doesn’t make use of pricey magnets.
  • With the right drive, it can accelerate and reach speeds of up to 100,000 revolutions per minute.
  • The stationary stator generates the majority of the heat and can be cooled relatively easily.


A good machine drive must be able to smoothly transition between the four quadrants and meet the general requirements of forward/reverse and positive or negative torque. Additional requirements for true “servo quality” control include very low torque ripple, quick dynamic response, good stability, zero speed operation, and smooth reversing. Optimal performance for basic variable-speed drives necessitates constant management of the firing angles, or the angles at which power semiconductors switch on and off, even in the absence of these servo-quality requirements. Because their torque is proportional to current, DC commutator motors and brushless DC motors are well suited to these sophisticated requirements. Vector control, also known as field-oriented control, enables PM synchronous motors and AC induction motors to efficiently acquire this feature.

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