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Which of the following statements is/are true regarding the principle of operation of a switched reluctance motor? 1) The motor relies on the interaction of magnetic fields to produce rotational motion. 2) The motor uses brushes and a commutator to produce rotational motion. 3) The motor uses permanent magnets to produce rotational motion. 4) The motor uses a series of switches to control the flow of current through its coils.
Both 2 and 4
Both 1 and 3
Both 1 and 2
Only 1
Only 1
A Switched Reluctance Motor (SRM) operates on the principle of variable reluctance, where the stator and rotor are made of ferromagnetic materials and motion is produced by the magnetic attraction between the stator poles and the nearest rotor poles. It is a brushless, non-permanent magnet machine that relies exclusively on magnetic field interaction to minimize reluctance.
IEC 60034 series
A Switched Reluctance Motor (SRM) operates on the principle of variable reluctance, where the stator and rotor are made of ferromagnetic materials and motion is produced by the magnetic attraction between the stator poles and the nearest rotor poles. It is a brushless, non-permanent magnet machine that relies exclusively on magnetic field interaction to minimize reluctance.
WmтАЛ=21тАЛL(╬╕,i)i2 тАФ Co-energy in the magnetic field
T=21тАЛi2d╬╕dL(╬╕)тАЛ тАФ Torque production based on change in inductance with respect to rotor position
The motor functions by sequentially energizing the stator phase windings, creating a magnetic field that pulls the rotor poles into alignment to minimize the air-gap reluctance. As the rotor approaches alignment, the current is switched to the next stator phase, creating continuous rotational torque. Because the rotor seeks the path of least reluctance (RтЖТmin), the torque produced is independent of the direction of current flow.
SRM is a doubly salient machine with salient poles on both the stator and the rotor.
The rotor has no windings, permanent magnets, or brushes, leading to a robust mechanical construction.
Torque direction depends on the change of inductance with position, not the current direction.
The controller (electronic converter) is essential for commutating the currents at the correct rotor position.
High mechanical robustness and simple rotor construction
Excellent high-speed capability due to the absence of rotor windings/magnets
High fault tolerance and low maintenance costs
High torque ripple causing acoustic noise and vibration
Requires a sophisticated power electronic controller for operation
Non-linear magnetic characteristics make control algorithms complex
Electric vehicles and traction systems
High-speed appliances like vacuum cleaners and kitchen mixers
Statement 2 is false because SRM is a brushless machine.
Statement 3 is false because the rotor is made of simple silicon steel laminations without permanent magnets.
Statement 4 describes the control system, but Statement 1 is the fundamental physical operating principle defining the SRM classification.
D is correct тАФ The Switched Reluctance Motor relies on the principle of magnetic attraction to reach a position of minimum reluctance to produce torque, making only statement 1 true.
In competitive exams, remember that SRM is often compared to BLDC; while both are brushless, SRM has no permanent magnets, making it cheaper but often noisier due to torque ripple.
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