A NEW IPMSM DESIGN FOR TWO-WHEELER

EV APPLICATIONS
A Report submitted in Partial Fulfilment of the Requirements
for the
6th Semester B.Tech. Summer Internship
(Mode of Internship is ONLINE)

By

Anoubam Delin Sharma(2101EE0219)

Kilangleima Chingsubam(2101EE0228)

Under the guidance of

Dr. Sreenu Sreekumar

Assistant Professor
Department of Electrical Engineering, NIT Silchar

DEPARTMENT OF ELECTRICAL ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY, SILCHAR

July 2024
 DECLARATION
We hereby declared that the project entitled “A NEW IPMSM DESIGN FOR TWO-
WHEELER EV APPLICATIONS” submitted to the NIT, Silchar, is a record of an original
work done by us under the guidance of Ms. Lourembam Ranjita Devi, Head of Department
of Electrical Engineering. Where others’ ideas or words have been included, we have
adequately cited and listed in the reference materials. We have adhered to all principles of
academic honesty and integrity.

Anoubam Delin Sharma(2101EE0219)

Kilangleima Chingsubam(2101EE0228)

i
 ACKNOWLEDGEMENTS
First of all, it is a great pleasure to express our gratitude and regards to our project guide,
Ms. Lourembam Ranjita Devi, for her encouragement, whole-hearted cooperation, and
constructive advice, criticism, and advice throughout the duration of our project. Her useful
suggestions for this whole work in cooperative behaviour are sincerely acknowledged.
We also deeply express our sincere thanks to our respected Registrar, Mr. Ng. Bhogendra
Meitei, Manipur Technical University, for encouraging and allowing us to work on the
project “A New IPMSM Design for Two-wheeler EV Applications.”
Also, we would like to take this opportunity to thank those who have directly and indirectly
helped in our project. We respect and love our parents, family members, and friends for their
love, support, and encouragement throughout the project.
Last but not least, we thank all the teachers for providing us with the technical skills and
knowledge that will always remain our asset and to all non-teaching staff for their gracious
hospitality.

Anoubam Delin Sharma(2101EE0219)

Kilangleima Chingsubam(2101EE0228)

ii
 ABSTRACT
The increasing number of vehicles in the transportation industry has made air
pollution and global warming a primary worldwide concern. Electric vehicles (EVs) are the
best option to reduce this issue. One of the most crucial parts of EVs is the electric motor. It
must be designed for high torque, a broad speed range, and high efficiency at all speeds.
Several electric motors are available for use in EV applications. Interior Permanent Magnet
Synchronous Motors (IPMSM) in two-wheelers provide high torque, which is crucial for
quick acceleration and high efficiency and is essential for optimizing battery life in electric
two-wheelers. The performance of the IPMSM differs based on the type of rotor design
used. The shape and arrangement of the magnets in the rotor significantly impact the motor's
output torque, torque ripple, and efficiency. This study aims to enhance the efficiency, power
density, and output torque characteristics of IPMSM by analyzing different rotor shapes. It
also focuses on optimizing the rotor shape. This helps to minimize eddy current loss and
improves the efficiency. Specific rotor designs can cause cogging torque, which is
undesirable. Improper rotor design may result in cogging. It can be reduced with careful
design selections. This study investigates the impact of skewing of the motor on various
parameters of an IPMSM V-type motor, focusing on back EMF, phase flux linkage, cogging
torque, and steady-state torque. The analysis reveals that a skew angle of 12° with 11 slices
offers a balanced performance, significantly reducing cogging torque to 0.12 Nm and
providing smoother static torque at 0.0113 Nm, thereby enhancing overall motor
performance.

iii
 LIST OF FIGURES

Figure Page No.

Figure 1.1: CO2 Equivalent Emission 2

Figure 3.1: Model of IPMSM 4

Figure 4.1: IPMSM V-type motor 6

Figure 4.2: Stator core 7

Figure 4.3: Stator slot 8

Figure 4.4: Rotor 9

Figure 5.1: Electromagnetic torque 11

Figure 5.2: Mechanical Speed 11

Figure 5.3: Flux Linkage Before Skewing 12

Figure 5.4: Flux Linkage After Skewing 12

Figure 5.5: Phase Back Emf Before Skewing 12

Figure 5.6: Phase Back Emf After Skewing 12

Figure 5.7: Cogging Torque Before Skewing 13

Figure 5.8: Cogging Torque After Skewing 13

Figure 5.9: Steady State Torque Before Skewing 13

Figure 5.10: Steady State Torque After Skewing 13

Figure 5.11: Static torque 14

iv
 LIST OF TABLES

Table Page No.

Figure 3.1: Specification of IPMSM 7

Figure 3.2: Stator slot dimensions 9

Figure 3.3: Rotor dimensions 10

Figure 4.1: Skewing specification 14

v
 TABLE OF CONTENTS (TOC)
Serial No. Title Page No.
Declaration i
Acknowledgements ii
Abstract iii
List of figures iv
List of Tables v
1. Introduction 1-2
1.1 Problem formation and statement 2
1.2 Objective 2
2. Literature Review 3
3. Mathematical Modelling of IPMSM 4-5
4. Design of IPMSM 6-10
4.1 Motor design 6
4.2 Stator core 7-8
4.2.1 Selection of number of poles 8
4.2.2 Selection of number of stator slots 8
4.3 Stator slot 9
4.4 Rotor 9
4.5 Skewing of electric motor 10
5. Result and Discussion 11-14
5.1 Simulink Result 11
5.2 Ansys Result 11
5.2.1 Phase flux linkage 11
5.2.2 Phase back EMFs 12
5.2.3 Cogging torque 12
5.2.4 Steady state torque 13
5.2.5 Static torque 13
5.3 Motor skewing 14
6. Conclusion and future scope 15
7. References 16

vi
 CHAPTER I

INTRODUCTION
With increasing concerns about energy security and environmental impacts such as
global warming, internal combustion engine (ICE) based vehicles that consume fuel derived
from fossil fuels will have a limited role in future transportation. Fig. 1.1 illustrates the rising
trend of carbon dioxide emissions through time [1]

Electric vehicles, on the other hand, have the potential to reduce greenhouse gas
(GHG) emissions [2]. One of the most crucial components of EVs is the electric motor.
Given this, various types of electric motors have been proposed. The interior permanent
magnet synchronous motor (IPMSM) is popular in various applications [3]. IPMSM provides
high torque for two-wheeler EV applications, which is crucial for quick acceleration and high
efficiency and is essential for optimizing battery life [4] [5]. They also have low vibration
and noise levels compared to other electric motors [9]

IPMSM faces several challenges like high cost, thermal management, and
demagnetization risk due to the rise of temperature, causing loss of magnetism and reducing
efficiency [5]. The most influential factor affecting the performance of IPMSM is the rotor
shape. Therefore, determining an appropriate IPMSM rotor shape is essential for designing a
highly functional driving motor for EV applications [9]

The study aims to enhance the efficiency, power density, and output torque
characteristics of IPMSM by analyzing different rotor shapes. It also focuses on optimizing
the rotor shape, minimizing eddy current losses in the magnets, leading to improved motor
efficiency. Specific rotor designs can cause cogging torque, which is undesirable. It can be
reduced with careful design selections. This paper focuses on designing, analyzing, and
optimizing IPMSM motors for two-wheelers based on various performances in EV
applications.

1
 CO2 equivalent emission
equivalent
3000
2500
2000
1500
2 1000
CO
500
0
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021

Year

Figure 1.1: CO2 equivalent emission

1.1 Problem formation and statement

This study focuses on designing and analysing IPMSM motors for two-wheelers to improve
their efficiency, power density, and output torque characteristics while addressing challenges
like cogging and ripple torque. The following problem statements are identified and solved:

1. Cogging torque can cause noise and vibration, affecting the overall performance. The
skewing technique reduces the peak value, leading to a smoother distribution of magnetic
forces.

2. the permanent magnets are adjusted to enhance magnetic flux linkage to achieve higher
steady-state torque.

3. The skewing technique is also used to reduce ripple torque, leading to smoother torque
output.

4. To obtain the optimal design of IPM, which has high torque, power, and efficiency.

1.2 Objective

1. To create a mathematical model and simulation of a two-wheeler IPMSM motor.

2. To compare different IPMSM rotor shapes and analyse their impact on two-wheeler
performance.

3. Optimal design of an IPMSM motor for two-wheeler application.

2
 CHAPTER 2

LITERATURE REVIEW
The growing use of traveling vehicles has increased the problem of air pollution,
global warming issues, and increased use of petroleum. Human awareness of energetic and
environmental concerns encourages research in alternative solutions for the automotive field,
such as multiple fuelling, hybridization, and electrification. Electric bikes can be considered
a good alternative for both personal and good transportation, especially for small and
medium distances. An electric bike is usually powered by a rechargeable battery, and its
practical performance is influenced by motor power, battery capacity, road type, operation
weight, control, etc [1] [2]

Interior permanent magnet synchronous motors (IPMSM) are integral to the

advancement of electric bike technology due to their high efficiency, power density, and
torque-to-weight ratio, which are essential for the dynamic requirements of electric bikes [3].
These motors are favored over surfaced-mounted permanent magnet motors (SPM) for their
superior electromagnetic performance and cost-effectiveness in high-speed operations [4].
However, the design of IPMSM motors must address challenges such as cogging and torque
ripple, which can affect the smoothness of the ride. Techniques like skewing have been
analysed and shown to reduce cogging torque, enhancing motor performance significantly
[6].

Recent developments in IPMSM motor design have focused on topological variations,

such as multi-layer and multi-segmented rotor structures, which aim to reduce cogging
torque, ripple torque, and iron loss, further improving efficiency and performance [3].

In summary, IPMSM motors represent a significant advancement in motor technology, with

their design and optimization being areas of active research and development. The
integration of these motors into various applications continues to evolve, driven by the need
for high efficiency and performance in a world with increasing energy demands. The ongoing
research and development in this field suggest that IPMSM motors will remain critical in
transitioning towards more energy-efficient technologies [3] [4].

3
 CHAPTER 3

MATHEMATICAL MODELLING OF IPMSM

3.1 Mathematical model

Figure 3.1: Model of IPMSM

The mathematical model of IPMSM is implemented in MATLAB SIMULINK, as shown in

Figure 3.1. Direct axis current rate of change,

𝑑𝑖
𝑑𝑡
𝑑
= 𝐿1𝑞(𝑣𝑑 + 𝐿𝑞𝜔𝑒𝑖𝑞 − 𝑅𝑠𝑖𝑑) (1)

Quadrature axis current rate of change,

𝑑𝑖
𝑑𝑡
𝑞
= 𝐿1𝑞(𝑣𝑞 − 𝑅𝑠𝑖𝑞 − 𝐿𝑑𝜔𝑒𝑖𝑑 − ф𝑚𝜔𝑒) (2)

Electromagnetic torque equation,

𝑃 3
𝑇𝑒 = ( )(ф𝑑𝑖𝑞 − ф𝑞𝑖𝑑)
2 3

ф𝑑 = 𝐿𝑑𝑖𝑑 + ф𝑚

ф𝑞 = 𝐿𝑞𝑖𝑞

𝑇𝑒 = 𝑃
2 ( 3
2 ) ((𝐿𝑑𝑖𝑑 + 𝜔𝑚)𝑖𝑞 − 𝐿𝑞𝑖𝑞𝑖𝑑)

4
 𝑇𝑒 = 𝑃
2 ( 32 )(𝐿𝑑𝑖𝑑𝑖𝑞 + ф𝑚𝑖𝑞 − 𝐿𝑞𝑖𝑞𝑖𝑑)

𝑇𝑒 = 𝑃
2 ( 3
2 )((𝐿𝑑−𝐿𝑞)𝑖𝑑𝑖𝑞 + ф𝑚𝑖𝑞) (3)

Mechanical torque,

Tm = TL + bωm + j dω m
dt

j dω
dt
m
= Tm − TL − bωm

j dω
dt
m
= 1j (Tm − TL − bωm)

(4)

where id and qi are the direct axis and quadrature axis current, respectively. L d and Lq are the
direct axis and quadrature axis inductance respectively. V q and Vd are the direct axis and
quadrature axis voltage. ꞷe and ꞷm are the electrical and mechanical angular speed. ф m, фd
and фq are the permanent magnet flux linkage, direct axis flux linkage and quadrature axis
flux linkage respectively. Te and Tm is the electromagnetic and mechanical torque
respectively. TL and P are the load torque and number of poles, respectively. B and j are the
damping coefficient and moment of inertia, respectively. Rs is the stator resistance.

5
 CHAPTER 4
DESIGN OF IPMSM

4.1 Motor Design

In the IPMSM motor, slots are the grooves in the stator core where copper windings
are placed, providing space for the stator windings to generate magnetic fields. Poles are
the magnetic regions on the rotor that alternate between north and south and determine the
number of magnetic field cycles in the motor. Permanent magnets are embedded within
the rotor, creating a constant magnetic field. The rotor is the rotating part of the motor that
houses the permanent magnets. The shaft is the central rod attached to the rotor and
transmits mechanical power [4].

Figure 4.1 and Table 4.1 show the structure and specifications of an IPMSM for an
electric vehicle. The IPMSM has 6 poles, 36 slots, and distributed winding. V-shaped
permanent magnets are applied to concentrate the magnetic flux.

6
 Figure 4.1: IPMSM V-type motor

Table 4.1: Specifications of IPMSM

Description Value Unit
Output power 4.84 kW
Speed 1980 rpm
Connection Star

Number of poles 6
Number of stator slots 36
Steel type of stator M22_4G

4.2 Stator core

The stator core comprises thin punched laminations of electrical grade steel
stampings that carry the alternating magnetic field. The steel type used is M22_4G. The
analytic model of the stator core is shown in Figure 4.2. The stampings are fixed to the
stator frame. Each stamping is insulated from the other with a thin varnish layer. The
thickness of the stamping usually varies from 0.3 to 0.5 mm.

Figure 4.2: Stator core

7
4.2.1 Selection of number of poles

The selection of a number of poles ensures a balance between performance and size
constraints. It directly affects the torque and speed characteristics of the motor. Fewer
poles result in higher synchronous speeds, as speed is inversely proportional to the

number of poles.

It is given by,

Ns = 120𝑓
𝑃

where, Ns = Synchronous speed f =

frequency, P = number of poles

4.2.2 Selection of the number of stator slots

The selection of a number of stator slots is crucial because it affects the distribution
of the magnetic field and influences harmonics. Proper selection leads to quieter motor
operation. More slots result in a better winding factor and reduce copper loss.

It is given by,

𝑁𝑠
q=
𝑚×𝑃

where m= number of phases

P = number of poles

8
 4.3 Stator slot

Figure 4.3: Stator slot

Stator slots are designed to hold the stator windings, typically made of insulated
copper or aluminium conductors. The dimensions of the stator slot are shown in Figure 4.3,
and its values are given in Table 4.2. The number and shape of stator slots are crucial in
determining the motor’s performance characteristics, such as efficiency, torque, and speed.

Table 4.2: Stator slot dimensions

Parameter Value Unit Description
Wst 4.10 mm Width of the stator tooth
Wsy 9.3 mm Width of the stator yoke

Bs0 1.5 mm Slot opening width

Bs1 3.76 mm Slot opening width
Hs0 1.5 mm Slot opening height
Hs1 1 mm Slot depth

Hs2 20 mm Slot width

D0 90 mm Stator outer diameter

4.4 Rotor

The rotor design of IPMSM V-type motors is a crucial factor influencing the motor’s
performance. It transmits mechanical power from one part to another. The magnets are
embedded in the rotor. The V-type IPM motors are widely used in EVs because of their
high torque density and efficiency. The analytic model of the rotor is shown in Figure 4.4
and Table 4.3 show the structure and specifications of an IPM rotor for an electric vehicle.

9
 Figure 4.4: Rotor
Table 4.3: Rotor dimensions
Parameter Value Unit Description
D 90 mm Bore diameter
G 0.7 mm Air gap
Dsh 25 mm Shaft radius

Dm 2.69 mm Depth of magnet

Wm 16 mm Width of magnet

⍺𝒗 170 degree Angle of the magnet

4.5 Skewing of electric motor

Skewing is a technique used in electric motors for angular displacement of the stator
slots or rotor segments, which are relative to the axis of rotation. This technique reduces
undesirable effects such as torque ripple and cogging torque, which can affect the motor’s
performance. Skewing helps in smoothing the torque output and improves the overall
efficiency of the motor [7] [10].

10
 CHAPTER 5
RESULT AND DISCUSSION

5.1 Simulink Result

Figure 5.1: Electromagnetic torque Figure 5.2: Mechanical speed

The electromagnetic torque and mechanical speed of the IPMSM are shown in
Figures 5.1 and 5.2. In figure 5.1, the torque is produced by the motor's interaction between
the stator and rotor magnetic fields. The magnitude of the electromagnetic torque depends on
the current in the stator windings, the angle between the rotor and stator magnetic fields, and
the design of the motor. On the other hand, figure 5.2 refers to the rotational speed of the
motor shaft. This speed is related to the frequency of the stator current and the number of
pole pairs in the motor.

11
5.2 Ansys Result
The back EMF induced in the IPMSM is directly proportional to the rotor's speed and
the motor's field strength. The produced back EMF behaves like a resistance, so if the speed
of the electric motor or field strength is increased, the back EMF increases, which
consequently increases the resistance to the current flow in windings. Therefore, the current
delivered to the armature is reduced. It is easier to control a waveform that has been
improved to a sinusoidal wave. The magnetic flux can flow smoothly within the magnetic

circuit by applying an unequal air gap.

5.2.1 Phase flux linkage

Flux linkage is the magnetic flux that links with a phase winding and is determined by
the rotor position, which changes sinusoidally and stator winding arrangements.

The waveform of flux linkage before and after skewing the motor is shown in Figures 5.3
and 5.4, respectively. Before skewing, the waveform produces harmonic, whereas, after
skewing, the stator slots or rotor magnets are tilted, reducing harmonics and providing a
smoother variation of flux linkage.

Figure 5.3: Flux linkage before skewing. Figure 5.4: Flux linkage after skewing

5.2.2 Phase back EMFs

Phase-back EMFs are the electromagnetic force induced in the stator windings due to
rotor motion and determined by the voltage induced in the windings. Its amplitude is directly
proportional to rotor speed and flux linkage. The waveform of induced voltage before and
after skewing is shown in Figures 5.5 and 5.6, respectively. Before skewing, the waveform
has many harmonics; after skewing, the waveform is smoothened and reduces harmonics,
which provides less torque ripple and improves the sinusoidal nature.

12
 Figure 5.5: Phase back EMFs before skewing. Figure 5.6: Phase back EMFs after skewing

5.2.3 Cogging torque

Cogging torque is caused by the interaction between rotor magnets and stator teeth
and occurs even without current in the windings. It depends on the number of slots and poles.
The waveform of cogging torque before and after skewing is shown in Figures 5.7 and 5.8,
respectively. Before skewing, it can be seen that the stator teeth are less smooth. After
skewing, the alignments of the rotor magnets and stator teeth are disrupted, leading to a
smoother distribution of magnetic forces.

Figure 5.7: Cogging torque before skewing. Figure 5.8: Cogging torque after skewing

5.2.4 Steady state torque

Steady-state torque is the constant torque produced when the motor operates at a
stable speed and load. The torque maintains the motor's speed under normal operating
conditions. The torque before and after skewing is shown in Figures 5.9 and 5.10,
respectively. Before skewing, torque ripple can be significant due to cogging torque and slot
harmonics, and after skewing, torque ripple is significantly reduced, leading to smoother

torque output.

13
Figure 5.9: Steady-state torque before skewing Figure 5.10: Steady-state torque after skewing

5.2.5 Static torque

In Figure 5.11, the static torque reaches its maximum value of 14.5 Nm at a rotor
position of 120 degrees. This maximum torque occurs because of the optimal alignment of
the permanent magnets within the rotor and the stator windings. At a 120º rotor angle, the
magnetic field generated by the permanent magnets interacts most effectively with the
magnetic field produced by the stator windings, resulting in maximum torque output.

Figure 5.11: Static torque

5.3. Motor skewing

Table 3.4 illustrates how skewing in an electric motor can effectively reduce cogging
torque, improve operational smoothness, and slightly impact flux linkage and back EMF.
Table 5.4: Skewing specifications
Skew Number Flux Back EMF Cogging torque Electromagnetic Ripple
Angle of slices linkage (V) (N-m) torque (N-m) torque
(Wb) (N-m)

14
 0° 1 0.6572 216.95 0.76 5.5377 0.2729

4° 5 0.6499 215.12 0.61 5.5502 0.0125

8° 7 0.6400 215.00 0.23 5.5553 0.0118

12° 11 0.6573 212.54 0.12 5.5627 0.0113

As the skew angle increases, the number of slices also increases, where each slice
corresponds to a skewed rotor segment. The back EMF decreases due to distortion in a
magnetic field while reducing its peak value. Cogging torque experiences a reduction in its
peak value, which minimizes the alignment of stator slots and rotor magnets, leading to low
noise and vibration. Static torque and back EMF also decrease with increased skew, resulting
in a smoother curve with less harmonic. With a 12° skew angle and 11 slices, it provides a
balanced performance with a back EMF of 212.54 V, significantly reduced cogging torque at
0.12 Nm, and a lower but smoother static torque of 0.0113 Nm. This combination reduces
ripple and harmonic and improves overall waveform [7] [10]

CHAPTER 6

CONCLUSION AND FUTURE SCOPE

The mathematical modelling of IPMSM provided analysis of its performance

characteristics. Through the derivation and implementation of mathematical equations in
MATLAB SIMULINK, the dynamic behaviour of the motor was examined. The direct and
quadrature axis current rate of change equations, as well as the electromagnetic and
mechanical torque equations, is crucial for understanding how the motor responds to various
electrical input and mechanical loads.

This report analyses the design of the IPMSM for two-wheeler electric vehicles have
shown several results. The skewing technique has significantly enhanced the motor’s
performance by reducing cogging torque and ripple torque, resulting in smoother operation
with low noise and vibration. By adjusting the position and shape of the magnets has led to
improve in magnetic flux linkage, thereby increasing the steady-state torque which is
essential for acceleration and overall performance in two-wheelers [8]. The detailed analysis
of phase flux linkage, back EMFs and steady-state torque before and after skewing has
provided valuable insights in improving the motor performance.

15
For the future scope,

• To analyse motor performance for different shape of magnet.

• To obtain the optimal design of IPM rotor which provides high efficiency, power and
torque.
• Thermal analysis of IPM motor to prevent demagnetization and extend the lifespan of
the motor.

References
[1] Warming, G. (2009). 101: Costs. William Yeatman.

[2] Davis Stacy C, Diegel Susan W, Boundy Robert G. Transportation energy data book, 28 th
ed. Oak Ridge; 2009

[3] Shukla, A., & Basak, S. (2022, December). A new topology of multilayer interior
permanent magnet synchronous motor with reduced rare earth magnets. In 2022 IEEE 1st
Industrial Electronics Society Annual On-Line Conference (ONCON) (pp. 1-6). IEEE.

[4] Dong, J., Huang, Y., Jin, L., & Lin, H. (2016). Comparative study of surface-mounted and
interior permanent-magnet motors for high-speed applications. IEEE Transactions on
Applied Superconductivity, 26(4), 1-4.

[5] Y. Wang, H. Li, X. Zhao. Design and optimization of an IPMSM with high efficiency and
low torque ripple for EV applications. IEEE Transactions on Industry Applications, 2023

[6] M. Kim, J. Lee, Y. Cho. Analysis of cogging torque reduction techniques in interior
permanent magnet synchronous motors. Journal of magnetism and magnetic materials,
2020

[7] L. Chen, M. Wang, R. Wang. Skewing effects on performance enhancement of IPMSM

for electric vehicle applications. IEEE Transactions on Magnetics, 2021

16
[8] S.RajaSekhar; D.Prudhvi Raju; K.Jagadeesh Babu; K.Paulson and K.Ganamanikanta.
Development of Electric Two-wheeler Vehicle. International Journal for Modern Trends
in Science and Technology 2021, 7, pp. 7-11

[9] Wang, W., Shang, M., Li, Y., Yao, Z., Niu, J., & Juan, Z. (2023). Thermal performance
analysis of jet cooling method in a high-power permanent magnet synchronous motor.
Journal of Thermal Science and Engineering Applications, 15(1), 011006.

[10] Cawkwell, T., Haris, A., Gonzalez, J. M., Rodrigues, L. K., & Shirokov, V. (2023). A
Methodology for Applying Skew in an Automotive Interior Permanent Magnet Rotor for
Robust Electromagnetic and Noise, Vibration and Harshness Performance. World Electric

Vehicle Journal, 14(12), 350.

17