Electric Vehicle Motors – III | Inverter-Fed PMSM, SRM Construction & Operating Principle | Lecture 25

The Permanent Magnet Synchronous Motor (PMSM) and Switched Reluctance Motor (SRM) are among the most promising traction motors for modern electric vehicles due to their high efficiency, reliability, and power density. In this lecture, we begin by understanding why a PMSM must always be driven by an inverter (Variable Frequency Drive – VFD). You will learn how the inverter converts the battery's DC power into variable-voltage, variable-frequency three-phase AC using Pulse Width Modulation (PWM), enabling smooth starting, speed control, and high-performance operation. The lecture also discusses the practical applications of PMSMs in electric vehicles, including traction drives, field-weakening operation for high-speed driving, compact packaging, thermal management, and the major advantages and limitations of PMSMs.

The lecture then introduces the Switched Reluctance Motor (SRM), explaining its construction, operating principle, and torque production mechanism. You will learn why the SRM rotor contains neither permanent magnets nor windings, how torque is produced by the rotor's tendency to move toward a minimum magnetic reluctance position, and why SRMs are considered simple, robust, and cost-effective. The lecture further explains the construction of SRMs, different stator–rotor pole combinations (6/4, 8/6, 12/8, etc.), the process of magnetic domain alignment during operation, and the concept of electrical angle and pole pitch in switched reluctance machines.

Topics Covered

Inverter-Fed PMSM
Variable Frequency Drive (VFD) for PMSM
Pulse Width Modulation (PWM)
Applications of PMSM in Electric Vehicles
Field-Weakening Operation
Advantages and Limitations of PMSM
Introduction to Switched Reluctance Motor (SRM)
SRM Construction and Rotor Design
Minimum Magnetic Reluctance Principle
Torque Production in SRM
Stator and Rotor Pole Configurations (6/4, 8/6, 12/8)
SRM Operating Principle
Pole Pitch and Electrical Angle in SRM

Who Should Watch?

B.Tech. and M.Tech. students
Power Electronics learners
Electric Vehicle enthusiasts
GATE and ESE aspirants
Researchers working on electric drives and traction motors
Engineers designing EV motor drive systems

Recommended References

D. P. Kothari and I. J. Nagrath, Electric Machines, 5th Edition, McGraw Hill.
J.-W. Ahn and G. F. Lukman, Switched Reluctance Motor: Research Trends and Overview, CES Transactions on Electrical Machines and Systems, 2018.
B. Bilgin, J. W. Jiang, and A. Emadi, Switched Reluctance Motor Drives: Fundamentals to Applications, CRC Press, 2019.

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