YILDIZ TEKNİK ÜNİVERSİTESİ
MAKİNE MÜHENDİSLİĞİ FAKÜLTESİ
SWITCHED RELUCTANCE MOTOR
20067917 Abdoulaye S Sissoko
MECHATRONICS ENGINEERING
POJECT REPORT
Project consultant: Prof. Dr. Muhammet Garip
İSTANBUL, 2025
1
TABLE OF CONTENTS
Pages
1.Structure and basic working principle................................................................................. 3
2.Different motor types and their comparisons...................................................................... 4
3.Manually derived mathematical model............................................................................... 8
4.Motor driver circuits and control methods......................................................................... 8
5.Application areas of the motor............................................................................................ 9
6.Market analysis................................................................................................................... 10
7.References.......................................................................................................................... 12
2
1. STRUCTURE AND BASIC WORKING PRINCIPLE OF THE MOTOR
1.1.
Structure of a switched reluctance motor(SRM)
An SRM consists of the following main components: stator, rotor and power
electronics.
Fig1.Structure of an SRM
The stator contains laminated steel core with salient poles. Each pole has a
concentrated wind. Windings are grouped into phases (generally 3 or 4 phases).
The rotor also contains salient poles, but no windings or permanent magnets. It
is unexcited so no current flows through it.
The electronic powers serve as switchers of the current in the stator windings at
the right time.
1.2.
Basic working principle
The SRM operates based on the principle of variable reluctance. The controller
energizes a pair of stator poles. This will create a magnetic field that attracts the
nearest rotor toward alignment with the stator poles. As the poles are aligned,
they move, producing torque. Just before alignment is complete, the stator poles
are de-energized. And finally, the controller switches current to the next stator
phase, repeating the process. This sequence is repeated in such a way that a
3
continuous torque is generated and the rotor keeps rotating.
2. DIFFERENT MOTOR TYPES AND THEIR COMPARISONS
2.1.
Conventional SRM
This is the most common type and in that, the magnetic flux flows radially from
the stator to the rotor. Both the stator and the rotor have salient poles. It needs
position sensors and sensorless control techniques.
Fig2. Structure of a conventional SRM
2.2.
Axial-Flux SRM
The flux flows axially. The rotor and stator are disc shaped. Sometimes, it has
multiple stator-rotor layers.
4
Fig3.Axial-flux SRM
2.3.
Segmented SRM
It’s easier to cool and manufacture and its stator is composed of separate
magnetic segments, each with its own coil.
Fig4. Segmented SRM
2.4.
Doubly salient SRM
Conventional SRMs are a subset of doubly salient SRMs.
5
Fig5. Doubly salient SRM
2.5.
Linear SRM
In this motor, the rotor moves in a linear direction.
Fig6. Linear SRM
6
2.6.
Multi-phase SRM
It can have 3,4,5,6 or more phases.
Fig7. Multi-phase SRM
2.7.
Comparisons
Let’s dress at a table that will show the comparisons between them.
Type
Structure
Key feature
Pros
Cons
Conventional
Cylindrical,
Most common
Simple, robust
High torque
salient poles
Axial-flux
Disc-type
ripple
Compact
Lightweight
Harder to
manufacture
Segmented
Modular stator
Easy
Efficient
Hard
coils
manufacturing
thermal
control
management
Linear
Multi-phase
Linear
Linear
No need for
Lower force
stator/rotor
movement
gear machines
density
>3 phases
Enhanced
Low torque
Expensive
control
ripple
Tab1. Comparisons table of SRM types
7
3. MANUALLY DERIVED MATHEMATICAL MODEL
First of all, the electrical equation can be found by using the Kirchhofs’s Voltage Law:
𝑣 = 𝑅𝑖 +
𝑑𝜆
𝑑
𝑑𝑖
𝑑𝐿
= 𝑅𝑖 + (𝐿𝑖) = 𝑅𝑖 + 𝐿 + 𝑖
𝑑𝑡
𝑑𝑡
𝑑𝑡
𝑑𝑡
By applying chain rule, we obtain: 𝑣 = 𝑅𝑖 +
+ 𝑖𝜔
3.1.Electrical dynamics.
The torque in SRMs is generated due to change in inductance with rotor position and is:
𝑇= 𝑖
3.2.Electromagnetic torque equation.
And finally by applying Newton’s second law for dynamics, we obtain:
𝐽
+ 𝐵𝜔 = 𝑇 − 𝑇 3.3Mechanical dynamics.
4. MOTOR DRIVER CIRCUIT AND CONTROL METHODS
4.1.
Motor driver circuits for SRM
The most common drivers of SRM are: asymmetric half bridge converter, cdump converter and resonant converter(less common than the previous two).
Asymmetric half bridge converter allows bidirectional current control and
freewheeling. It’s simple and reliable.
Fig8. Schematic of an asymmetric half bridge converter
C-dump converter is designed for energy recovery during phase turn-off and
uses a dump capacitor to absorb the demagnetization energy
Fig9. Schematic of C-dump converter
8
Resonant converter uses LC circuits for soft switching and reduced EMI. It has high
efficiency and lower switching loss.
Fig10. Schematic of aresonant converter
4.2.
Control methods for SRM
Controlling SRMs is non trivial due to the high torque ripple and non linear
inductance/rotor position. The different methods are:
-Open loop control: used in simple application like fan and pumps;
-Current control: provides torque control by regulating phase current;
-Torque control: control current to achieve desired torque;
-Angle-based control: optimizes torque and minimizes noise;
-Sensorless control: estimates rotor position using back-EMF, inductance
profiling or machine learning;
-Advanced controls: MPC,Fuzzy logic control, Neural networks SMC.
5. APPLICATION AREAS OF SRM
5.1. Industrial applications
SRMs is excellent in harsh environments, where robustness and minimal maintenance are
key. It is used in: pumps, compressors, conveyor systems, CNC machines, textile
machines and vacuum cleaners.
5.2. Automotive applications
They are an alternative to PMSMsespecially to avoid the use of rare earth magnets. We can
9
cite: electric propulsion, Hybrid vehicles, electric power steering, cooling fans and inwheel motors as applications.
5.3. Home appliances
SRMs are attractive for cost-sensitive and energy efficient home products. It is used in:
washing machines, dishwashers, blenders andixers.
5.4. Transportation systems
They offer efficiency and long term durability in heavy-duty transportations. They are used
in: electric trains, elevators, trams and escalators.
5.5. Medical devices
SRMs are preferred where clean, noise controlled operation is required. It is used in: surgical
tools, lab centrifuges and imaging systems.
6. MARKET ANALYSIS
6.1.Companies from Turkey
In Turkey, academias like ITU collaborates with industry to develop SRM technology
for defense and industrial system.
Company
Focus area
Arçelik
Home appliances, motor R&D
Tofaş
Automotive manufacturing
Aselsan
Defense electronics and systems
Tab2.SRM companies in Turkey
6.2.Companies from USA
Company
Focus area
Turntide Technologies
Clean-tech motors
H2W Technologies
Custom linear and rotary motors
General Motors
Automotive
Tab3.USA leading companies in SRMs
10
Turntide Technologies is world leader in commercializing SRMs fot HVAC and
building energy systems.
6.3.Companies from Europe
Company
Country
Focus area
AEM
UK
Automotive, areospace SRMs
Lafert Group
Italy
Industrial motors
Siemens AG
Germany
Industrial and traction motors
Tab4.SRMs producers in Europe
6.4.Companies from the Far East
Asian countries leads in high volume integration of SRMs into mass-market
applications like scooters, trains and robotics.
Company
Country
Focus area
CRRC
China
Rail traction systems
Nidec Corporation
Japan
Precision motors, EV motors
Hyundai Mobis
South
Automotive electrification
Korea
Tab5.Powerhouses of SRMs in Asia
11
7. REFERENCES
[1] https://www.monolithicpower.com/en/learning/mpscholar/isolation-solutions/llcconverters/introduction-to-resonant-converters
[2] https://www.motioncontroltips.com/how-do-switched-reluctance-motors-differ-fromstepper-motors/
[3] https://www.elec28.com/how-a-switched-reluctance-motor-works-and-what-it-is/
[4] https://www.researchgate.net/figure/Axial-flux-SRM-structure_fig10_317868847
[5] https://www.electrical4u.net/induction-motor/switched-reluctance-motor-srmconstruction-working-types-advantages/attachment/linear-srm/
[6] https://www.mdpi.com/1996-1073/15/23/9212
[7] https://www.researchgate.net/figure/C-dump-converter-of-SRM_fig5_317868508
12