Page 8 - IJOCTA-15-4

M. A. Aman et al. / IJOCTA, Vol.15, No.4, pp.549-577 (2025)
electrification of transportation systems. It is pre- rotor. Figure 2 illustrates common arrangements
dicted that over 500 megatons of CO 2 equivalent of a 4-phase 8/6 SRM.
will be reduced by 2034. 2
Electric vehicles employ a diverse range of
electric motors, including the switched reluc-
tance motor (SRM), squirrel cage induction mo-
tor (SCIM), brushless direct current (DC) motor,
synchronous reluctance motor, and permanent
magnet synchronous motor (PMSM). 3

Figure 2. Cross-sectional view of a typical 4-phase
8/6 switched reluctance motor. Adapted from Petrus
et al. 11

Figure 1. Anticipated reduction in greenhouse Robert Davidson constructed the world’s first
gases. Adapted from Haidar et al. 2 electric locomotive for the Edinburgh–Glasgow
railway line in 1842, a locomotive that was then
The PMSM is commonly utilized in trac- used to power a motor he created in 1839. 12
tion motors due to its high efficiency, wide Davidson’s motor worked and went on to become
torque–speed range, and high power density. 4 one of history’s most notable inventions. Figure
However, new alternatives were sought after due 3 illustrates the structure of Davidson’s motor.
to the increasing prices and limited availability
of rare earth materials used in PMSMs. Fer-
rite permanent magnets are unsuitable alterna-
tives due to their low residual flux, susceptibility
to demagnetization, and lower torque density in
5
comparison to rare-earth PMSMs. Therefore, re-
searchers are moving toward the development of
magnet-free motors. While SCIMs are employed
6
in specific commercial EVs, their performance is
reduced in comparison to other traction motors.
Synchronous reluctance motors represent a fea-
sible option for key drivetrains due to their ab-
7
sence of permanent magnets. However, these mo- Figure 3. Davidson’s motor. Adapted from Ahn
tors exhibit a lowered power factor, increased core and Lukman. 12
losses, notable torque ripple, reduced efficiency,
and lower torque density. 8 Recent developments in high-power SRMs
On the other hand, SRMs provide various ad- for EVs highlight the competitive advantages of
vantages over other electric motor technologies, PMSMs in terms of torque-speed range, power
13,14
including a simple design, adaptability in control density, and efficiency. Figure 4 illustrates a
methods, enhanced efficiency, cost-effectiveness, brief performance comparison among the DC mo-
and resilience in operating under fault conditions. tors, SCIM, PMSM, and SRMs.
Due to the lack of windings and permanent mag- These figures illustrate that DC motors are
nets, the machine rotor is suitable for applica- large, expensive, and heavy, with less rugged-
tions requiring extremely high-speed drives. 9,10 ness and fault tolerance, but they provide con-
The operating principle of SRM is to produce sistent torque and possess a simple cooling mech-
torque by varying magnetic reluctance. SRM has anism. Meanwhile, SCIMs are medium in size and
dual saliency—saliency in both the stator and the weight, inexpensive, and rugged, with a medium
550