Design and Performance of 8Slot-12Pole Permanent Magnet Flux Switching Machines for Electric Bicycle Application

International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 8, No. 1, March 2017, pp. 248~254
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v8i1.pp248-254  248
Journal homepage: http://iaesjournal.com/online/index.php/IJPEDS
Design and Performance of 8Slot-12Pole Permanent Magnet
Flux Switching Machines for Electric Bicycle Application
Laili Iwani Jusoh1
, Erwan Sulaiman2
, Rajesh Kumar3
, Fatihah Shafiqah Bahrim4
1,2,3,4
Research Center for Appied Electromagnetics, University of Tun Hussein Onn Malaysia (UTHM)
Locked Bag 101, Parit Raja 86400, Batu Pahat, Johor, Malaysia
Article Info ABSTRACT
Article history:
Received Oct 12, 2016
Revised Dec 18, 2016
Accepted Dec 28, 2016
This paper presents a new design and performance of single phase permanent
magnet flux-switching machine (PMFSM) for electric bicycle application.
8Slot-12Pole design machine were choose by analyzing the highest power
density value. All active parts such as permanent magnet and armature coil
are located on the stator, while the rotor part consists of only single piece
iron. PMFSM have a great advantage with robust rotor structure that make it
much higher power and applicable for EV application compared to SRM and
IPMSM. The design, operating principles, characteristics of torque, and
power of this new topology are investigated by JMAG-Designer via a 2D-
FEA. Size of motor and volume of PM is designed at 75mm and 80g,
respectively. Based on the investigation, it can be concluded that the
proposed topology of single phase 8Slot 12Pole PMFSM achieved the target
of highest performance of power density, approximately at 0.113W/mm3
with reduced permanent magnet and size of design motor. Due to the low
torque performance of this initial design, further works is ongoing to improve
the torque performance. In future work, outer rotor PMFSM structure design
will be presented and compared with the “Deterministic Optimization
Method” to improve the initial design.
Keyword:
Permanent magnet flux
Single phase
Switching machine
Copyright © 2017 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Erwan Sulaiman,
Research Center for Appied Electromagnetics,
University of Tun Hussein Onn Malaysia (UTHM),
Locked Bag 101, Parit Raja 86400, Batu Pahat, Johor, Malaysia.
Email: erwan@uthm.edu.my
1. INTRODUCTION
Conventional vehicles for personal mobility have over the years been operating by means of internal
combustion engine (i.e., ICE) which is based on fossil fuels. In addition, an over whelming increase in
demand for private vehicles has recently been observed in line with an equal increase in populations on a
global scale. In such a scenario, ICE automobile is seen as a potential solution for many urban dwellers, by
and large. Notwithstanding, three problems are associated with ICE namely environmental, economic and
political problems. With regards to the environmental issues, one of the major ones is the emissions.
Specifically, the problem of air pollution at an increased level due to the harmful emissions released by
hydrocarbon fuelled power sources has been a long-standing issue [1],[2].
In addition, the perceived lower efficiency of the use of fossil fuel is another setback of the ICE
automobile. In recent years, some concerted efforts have been undertaken by various parties within the
automotive industry to address the dependency on fossil fuels and to reduce the greenhouse gases emitted per
km of travel [3]. In their attempts to address these issues, auto-manufacturers have now shifted towards new
technologies such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). Notably, the idea of
operating EV as an alternative can be traced back to the early stages of the automotive industry. Since the
year of 1910, a steady increase has been observed in the number of EVs compared to the vehicles with ICE.

IJPEDS ISSN: 2088-8694 
Design and Performance of 8Slot-12Pole Permanent Magnet FLux Switching .... (Laili Iwani Jusoh)
249
Some scholars have asserted that the concerns raised by various parties in relation to the amount of pollutants
released into the atmosphere each day by ICE have made the Evs to come to the fore. They are now said to
be the future of transportation. Upon comprehensively reviewing the literature, it was found that electric
vehicles mostly refer to cars which operate electronically.
Notably, another type of electric which sometimes go unnoticed is the electric bicycle. It is
noteworthy that the electric bicycles have over the years been gaining an increaseddue to their lower energy
cost and environmental friendliness [4]. One of the reasons cited for the popularity of the electric bicycle is
thatit has the edge ofrelatively higher energy efficiency overthe other energy forms. Hence, a significant
number of individuals these days opt foran electric bicycle rather than an electric car or an electric
motorcycle [5]. It is worth highlighting that studies which have looked into the electronically operating
vehicles are scarce.
The motor which operates the bicycle is the most important component which requires meticulous
attention in the course of designing the bicycle. The type and the performance characteristics of the electric
motor equipped in the bicycles may have significant consequences on the overall performance of the Electric
Bicycle [6]. Among the types of electric motors equipped with bicycles are inter alia, Multi-Flux Permanent
Magnet (MFPM), Switch Reluctance Motor (SRM) and a Permanent Magnet Synchronous Machines
(PMSMs) [7]-[9]. Even though many of its features are appealing, it is not exempt from some limitations
such as lower power, lower torque, higher volume of permanent magnet (PM), and the level of noise which is
not desirable in this application. Considering the significance of these vehicles in societies around the world,
more studies need to be carried out to address the issues of electric machines with reduced amount of PM,
reasonable price range, easy to design, higher power and torque performance and higher efficiency. It should
be noted that PMFSM has notably been an interesting research topic because of its higher power density and
robust rotor structure [12]-[13].
2. OPERATING PRINCIPLE ON INITIAL DESIGN OF 8S-12P PMFSM
Permanent Magnet Flux Switching Motors can be potentially applied in electric bicycle which are
design to reduce the size of design motor structure and volume of permanent magnet. As one alternative to
overcome this problem, a new structure of single phase 8Slot-12Pole permanent magnet flux switching
machine is proposed as shown in Figure 1. From the design in Figure 1, it is clear that the machine consists
of only permanent magnet and armature coil allocated on the stator part. The rotor consists of only a single
piece iron, becoming more robust and suitable for electric vehicle application.
Figure 1. Initial design of 8Slot-12Pole PMFSM
2.1. Finite Element Analysis
Initially, the rotor, stator, permanent magnet and armature coil of the proposed design are drawn by
using Geometry Editor by JMAG-Designer ver. 14.0, released by the Japan Research Institute (JRI) in order
to carry out the analytical study which is completed by 2D-Finite Element Analysis (FEA). The design
specifications and limitations of the proposed machine are listed in Table 1.
Armature Coil
Shaft
Permanent
Magnet
Rotor

 ISSN: 2088-8694
IJPEDS Vol. 8, No. 1, March 2017 : 248 – 254
250
Table 1. Design Restriction and Specification
Parameter 8S-10P PMFSM
No. of phase 1
Number of stator pole 8
Number of rotor pole 12
Stator inner radius(mm) 22.25
Stator outer radius(mm) 37.5
Rotor outer radius(mm) 22
Rotor inner radius(mm) 7.5
Rotor tooth width(mm) 4
Stator tooth width(mm) 4
Stator pole height(mm) 15.25
Rotor pole height(mm) 9
Motor stack length(mm) 20.3
Air gap length (mm) 0.25
PM Volume (g) 80
Necessary steps involved in the process, the expected end time and division were set in the step
control components where as the stack length was spelt outinthe full model conversion. In this regard, the
steps, division and the stack length wereset to 37, 36 and 20.3mm, respectively.In this proposed motor, the
motor rotation is through 1/Nr of a revolution, the flux linkage of armature containsone periodic cycle and
therefore, the frequency of back-emf induced in the armature coil is Nr times of the mechanical rotational
frequency. In general, the mechanical rotation frequency, fm and the electrical frequency, fe for the proposed
machine can be spelt outby means of Equation 1 and for the expected end time, T is calculated by means of
Equation 2.
m
r
e f
N
f  (1)
e
f
T
1

(2)
The where fe, Nr and fm refer to the electrical frequency, number of rotor poles and mechanical
rotation frequency, respectively. The value with in the armature coil and number of turns are recorded
correctly by means of Equation 4 and 5, respectively
a
a
a
a
I
S
J
N


(3)
copper
a
a
A
S
N


(4)
Where N, J, α, S and I refer to thenumber of turns, current density, filling factor, slot area and input current,
respectively. For the subscript arepresents armature coil. Referring to Table 1, the comparative performance
of the electric bicycle application it can be clearly seen.
3. PERFORMANCE ANALYSIS OF NUMBER OF TURN AND FILLET ROTOR DESIGN
It has to be highlighted that the investigation of flux profiles were carried out under the open circuit
conditions as can be seen in Figure 2 (a) and (b) respectively, in which the machine topology was analyzed at
zero degree rotor position. As it can be observed, the machine which surfaced almost identically excited the
PM flux lines and distributions in a uniform manner as the flux surged from the stator to rotor and returned
passing through the rotor teeth in completing the full flux cycle of the PM. The observations also indicated
that the rotor structure showed higher flux concentration at 8 out of its 12 poles, hence causing the rotor
toeasily rotate even at a relatively lower supply of excited armature flux. In addition, the flux distribution was
investigated with the aim of monitoring the field saturation effect on the machine it can be seen in Figure 2
(b). Not withstanding, the maximum flux density at this point was read at 2.3T.

251
Figure 2. Flux lines and Flux Distribution of 8S-12P PMFSM
3.1. Back emf and Cogging Torque Analysis
The cogging torque analyses for PMFSM machine types were diagnosed by setting armature current
density, Ja=0 Arms/mm2
. Figure 3 shows the cogging torque investigation of the examined 8Slot-12Pole
PMFSM design machines, with having the highest peak-to-peak cogging torque at approximately 0.11Nm.
Based on the previous study, cogging torque can be relatively reduced by varying the air gap distance
between stator and rotor [14]. In fact, cogging torque could be further decrease by rotor pole-notching, rotor
pole-pairing and rotor skewing. Back EMF iscommonly used to refer to the voltage that occurs in electric
motors where there is relative motion between the armature of the motor and the magnetic field from the
motor's field magnets, or windings. Figure 3 shown that waveform exhibits a more favorable sinusoidal
feature with amplitude of approximately 9.4V. Main factors influencing the back EMF is magnetic-pole
eccentricity, the slot opening, the thickness of PM and the equivalent length of air gap.
Figure 3. Cogging torque performance for 10S-15P, 8S-12P, 4S-8P and 2S-8P
3.2. Initial Torque and Power Performance
Under this load analysis discussion, the current density of armature coil, Ja is being supplied into the
system varied from Ja of 5 Arms/mm2
up to JA of 30 Arms/mm2
. In order to accomplish this procedure, the
number of turn of armature coil are calculated and set by using Equation 6.
(5)
It is note worthy that the calculation of output power can be performedby means of manipulating the
data of both torque and speed. Since all the required data were obtained in the previous analysis, equation (8)
was therefore used to substitute them. Subsequently, as for the rotation on a fixed axis, the calculated power
was observed to be equal to the multiplication between torque and angular velocity of the rotating piece,
which was defined by equations (6), (7), and (8) respectively.
(6)
-1
-0.5
0
0.5
1
-15
-10
-5
0
5
10
15
0 60 120 180 240 300 360
Emf[V] T[Nm]
Electrical Cycle [º]
Back EMF Cogging Torque

 ISSN: 2088-8694
252
(7)
( ) (8)
Where P is power in kilowatt (kW), τ is torque in Newton metre (Nm), and S is speed in revolution per
minute (r/min). Therefore, the resulting data of initial torque and power performances single phase 8S-12P
PMFSM design machine are plotted in Figure 4.
Figure 4. Ouput power versus armature current densities, Ja
Figure 4 illustrates the output torque and power waveforms obtained based on FEA at maximum
current density approximately at 1.04Nm and 674W respectively. This is a great advantage of PMFSM with
robust rotor structure that make it much higher power and applicable for EV application compare to IPMSM
and SRM.
3.3. Torque and Power versus Speed Characteristics
Consequently, the torque and power versus speed characteristics of the designed motor is plotted in
Figure 5. From the graph, the highest output torque is measured at 1.04Nm at the base speed of 6182 r/min
equivalent to 14.1Km/h. On the other hand, the power curve of the proposed machine shown approximately
at 542W at the same based speed of 6182 r/min. Table 2 clearly showed the comparison performance of the
electric bicycle application.
Figure 5. Torque and power vesus speed characteristic
Table 2. The Performance Comparison
Output Performance Unit IPMSM SRM PMFSM
Maximum Torque Nm 1.6 7.05 1.04
Maximum speed rpm N/A 500 6812
Power Density W/mm3
0.009 N/A 0.113
Motor weight Kg 6.804 6.7 921g
0
0.5
1
1.5
0
200
400
600
800
0 5 10 15 20 25 30
P[W] T[Nm]
Ja[Arms/mm²]
power torque
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
0 10 20 30 40 50 60
T[Nm]
Speed[Km/h]
P[W]
Power

253
4. CONCLUSION
Based on the investigation carried out in the earlier section, it can be concluded that the proposed
topology of single phase 8Slot 12Pole PMFSM achieved the target of high power density performance with
reduced permanent magnet and size of design motor. At the same time, this design already achieved the
target to reducing cost as the main objective of many electric bicycle manufactures. Due to the low torque
performance of this initial design, further works is ongoing to improve the torque performance. In future
work, accurate investigation for iron loss distribution should be employed and outer rotor structure design
will be presented and compared with the “deterministic optimization method”.
ACKNOWLEDGEMENTS
This research was partly sponsored by the Centre for Graduate Studies UTHM and Ministry of
Higher Education Malaysia (MOHE).
REFERENCES
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[3] H. S. Mohamed, et al., “Motion Control for a PMSM in HEV Application”, International Journal of Emerging
Technology and Advanced Engineering, vol/issue: 2(10), pp. 435-439, 2012.
[4] W. Du, et al., “Research on battery to ride comfort of electric bicycle based on multi-body dynamics theory,” 2009
IEEE International Conference on Automation and Logistics, Shenyang, pp. 1722-1726, 2009.
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in laboratory at “1 decembrie 1918” university of alba iulia,” Semiconductor Conference (CAS), 2015
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[8] J. Lin, et al., “External-Rotor 6-10 Switched Reluctance Motor for an Electric Bicycle,” IEEE Transactions on
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BIOGRAPHIES OF AUTHORS
Laili Iwani binti Jusoh was born in Besut, Terengganu on August 2, 1987. She received her
B.E (2007-2010) and M.E (2010-2014) degrees in Electrical Engineering from University of
Tun Hussein Onn, Malaysia. Since September 2015, she has been a researcher in Research
Center for Applied Electromagnetics (EMC) at Universiti Tun Hussein Onn, Johor, Malaysia.
Her research interest are mainly focused on Design and Investigation of Single Phase
Permanent Magnet Flux Switching Machines (PMFSM) for Electric Bicycle Application.

 ISSN: 2088-8694
254
Erwan Sulaiman was born in Johor, Malaysia, on August 31, 1978. He received his B.E and
M.E degrees in Electrical Engineering from University of Malaya in 2001 and University Tun
Hussein Onn Malaysia (UTHM) in 2004. He got Doctor Degree in Electrical Engineering from
Nagoya Institute of Technology (NIT), Japan in 2012. Currently, he is serving as an associatate
professor at Department of Electrical Power Engineering, University Tun Hussein Onn
Malaysia. His research interests incorporate design optimizations of HEFSM, WFFSM, in
particular, for HEV drive applications.
Rajesh Kumar was born on 3rd
September 1992 at Umerkot, Pakistan. He obtained his
intermediate education from his hometown while he obtained B.E in industrial electronics from
Institute of Industrial Electronics Engineering, Karachi, Pakistan in 2013.. He is currently
enrolled in M.E at Department of Electrical Power Engineering, University Tun
Hussein Onn Malaysia. His research intentions are mainly focused on design and
modeling of permanent magnet flux switching machine (PMFSM).
Fatihah Shafiqah Bahrim was born in Johor, Malaysia on November 1992. She received the
B.S. degree in electrical engineering from Universiti Teknologi Mara (UiTM), Selangor,
Malaysia in 2015. Since September 2015, she has been a researcher in Research Center for
Applied Electromagnetics (EMC) at Universiti Tun Hussein Onn, Johor, Malaysia. Her present
research interests include design and modelling of electrical machine, special electrical
machine and embedded power electronics.

Design and Performance of 8Slot-12Pole Permanent Magnet Flux Switching Machines for Electric Bicycle Application

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Design and Performance of 8Slot-12Pole Permanent Magnet Flux Switching Machines for Electric Bicycle Application