Vol.3, No.1, 36-41 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.31004
Investigation on the performance of DI-BSCCO
superconducting electric motor
Chin Kat Meng, Nasri A. Hamid*, Mohd. Yusri Abd. Rahman
Department of Engineering Sciences & Mathematics, College of Engineering, Universiti Tenaga Nasional, Kajang, Selangor, Malay-
sia; *Corresponding author：
Received 3 November 2010; revised 5 December 2010; accepted 8 December 2010.
ABSTRACT
Superconducting electrical devices have been
developed in various fields especially in indus-
trial energy over a decade. Superconducting
motor is one of the electrical devices that at-
tracted the attention of engineers and re-
searchers from the universities and industries
due to its distinctive energy efficiency. This
paper describes the performance of supercon-
ducting electric motor and its performance was
compared with conventional copper electric
motor. Direct current (DC) synchronous single-
phase series motor has been chosen as the
base for development of both motors. Two pro-
totypes of electric motor fabricated using con-
ventional copper coil and superconducting coil
were developed with similar motor type, design,
dimension, and features. The superconducting
motor coil was wound using Bi-2223 (DI-BSCCO)
Type H wires developed by Sumitomo Electric
Industries Limited, Japan. A finite element
analysis was performed to get a clear view on
flux plots of the magnetic induction. Features of
the superconducting motor and the special coil
frame designed to protect the superconducting
wire was also presented in this paper. In addi-
tion, the torque performances for both types of
motor were measured. The superconducting
electric motor was found to consume lower
power to produce the same output compared
with the conventional copper-wound motor.
Keywords: Superconductor; Magnetic flux; Finite
Element Analysis; Electric Motor
1. INTRODUCTION
Since the discovery of superconductivity in 1911 by
Kamerlingh Onnes, the dream of creating highly effi-
cient electric machine is getting closer to a reality. Su-
perconducting materials are able to carry current with
zero resistance and reduce power loss during the process
of transmitting electricity [1]. This distinctive property
of superconductor has seized the attention of many re-
searches and a lot of studies have been carried out to
produce superconducting wire with high stability. Fi-
nally, long length superconducting wire has been suc-
cessfully produced with a very reliable performance
[2,3]. Superconducting devices such as magnetic reso-
nance imaging (MRI) and superconducting quantum
interference devices (SQUID) have been used in medi-
cine and industry extensively. Several others electrical
power devices such as motor, generator, fault current
limiter and magnetic storage system have been devel-
oped [4-6]. Superconductor required cooling process
below the critical temperature, Tc which is also called as
transition temperature to become zero resistance. The
conventional low temperature superconductor operates
at below 20 K, where cooling by liquid helium is re-
quired. In 1986, researchers discovered high temperature
superconductor where the critical temperature is higher
than 77 K. Therefore, the use of cheaper refrigerant such
as liquid nitrogen is sufficient to cool the superconduct-
ing material and become superconductivity [7].
The distinctive properties of superconductor enable
the development of high efficiency energy devices. It is
believed that superconducting motor is able to reduce in
size and minimize energy loss compared to the conven-
tional copper-base motor [7,8]. In this work, a low
power superconducting electric motor is fabricated and
its performance was compared with a conventional elec-
tric motor. All the specifications for both types of motor
are similar except for the coils. The intended applica-
tions of the motor are for driving industry devices such
as pump and fan that can operate continuously at a con-
stant speed. The features and performance of both types
of motor were investigated. The simulation of the flux
plot was also presented.

K. M. Chin et al. / Natural Science 3 (2011) 36-41
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2. EXPERIMENTAL
2.1. Motor Design Description
The new architecture for designing of electric motors
was first introduced about a decade ago [9]. In our work,
similar approach was adopted at the designing stage of
the motor. Figure 1 shows the model of motor prototype
that was designed. It has three main structures, namely,
coil, stator and rotor. Two different coils were fabricated;
the first type was wound with high-temperature super-
conductor (HTS) DI-BSCCO wire and the second type
was wound with normal cooper wire. The design of the
motor was made flexible where the coils can be inter-
changed easily. The stator was laminated by a metal
sheet with 5 mm thick. In addition, to reduce the effect
of eddy current loss during the motor operation, each
layer of lamination was insulated with varnish. The fab-
ricated coil was directly mounted to the two-leg of the
stator and cooled by liquid nitrogen. In addition, the ro-
tor was installed to the stator with the support of the ro-
tor housing. The stator is designed with a deep “U”
shape; where the rotor will be mounted at the opening of
the “U” with rotor housing and coils will be directly
assembled to one of the stator legs. With this design,
various tests can be conducted, each with different
number of coil [10]. Table 1 shows the summary of the
design of the motor.
2.2. Coil Structure
For the superconducting wire, its critical current is
strongly influenced by the bending diameter of the wire
at 77 K [2]. A frame was designed to protect the super-
conducting wire from any external impact or damage.
Figure 2 shows the dimensional sketch of the coil layout,
where the coil was wound around the frame with a dou-
ble pancake style. Each coil structure has a total of 100
turns. Figure 3 shows the final product of the supercon-
ducting coil. Similar design was used to fabricate the
Figure 1. Model of the prototype.
Table 1. Summary of the design of the conventional and su-
perconducting motors.
Motor Type: DC Synchronous Machine
Details of Field Winding
Field winding wire type: Copper
Operating current: < 2 A
Details of Superconducting Coils Winding Stator
Stator winding wire type: HTS
Cooling type: Immersion
Coolant: Liquid Nitrogen (LN
2)
Operating Temperature: 77 K
Operating current: < 65 A
Details of Copper Coils Winding Stator
Stator winding wire type: Copper
Operating current: < 16 A
Stator Lamination Sheet
Metal sheet type: Cooled-roll metal sheet
Thickness: 0.5 mm
Figure 2. Dimensional sketch of the coil.
Figure 3. Superconducting coil structure.

K. M. Chin et al. / Natural Science 3 (2011) 36-41 38
conventional copper coil as shown in Figure 4. The
conventional coil structure has exactly the same design
and dimensions with the superconducting coil.
Table 2 shows the materials and specifications for the
superconducting coil and its components. Selection of
the materials for the coil unit is important to ensure the
effective distribution of magnetic flux. Ferromagnetic
material must be avoided in the coil components to
eliminate the suppression of magnetic flux [11]. In this
design, brass which is a non-magnetic material was used
in the construction of the frame and edge plate.
3. THEORY
3.1. Electromagnetic Theory
Rotating machinery working principles are based on
electromagnetic laws. One of the main laws is Ampere’s
law which is defined as “the line integral of the magnetic
field strength taken around any closed path is propor-
tional to the total current flowing across any area,
bounded by the path” [12]. Mathematically, the law is
expressed by:
H
dlJ ds
 (1)
where J is conduction current density, H is magnetic
field intensity, dl is the differential length, ds is differen-
tial surface enclosed by the closed path of length, and
 is integral over a closed loop or closed path.
3.2. Field Strength of Magnetic Circuit
A magnetic field system comprises of N-turns coil
wound on the ferromagnetic core. The coil carries a con-
stant current, i through a uniform cross-sectional area, Ac
of the core. When the current flows inside the conductor,
magnetic field is generated inside the core and a mag-
netic flux is confined to the ferromagnetic core. In the
actual practice, a small portion of the flux will leak to
the environment but this can be neglected due to its
small percentage compared to the total flux. Therefore,
the current through the enclosed path is expressed by:
J
ds Ni
 (2)
where N is number of turn wound on the core and i is
current inside conductor. From (1) and (2), the following
relationship is obtained and is expressed by:
H
dl Ni
 (3)
Figure 5 shows the equivalent magnetic circuit of the
motor. Subscripts r, a, y, and c indicate “rotor”, “air-
gap”, “york” and “cor e”, respectively.

represents
magnetic flux. Symbols c

and r

denote magnetic
fluxes that are generated by the coil and the rotor, re-
spectively. “R” indicates the reluctance inside the circuit.
In this case, circuital law can be applied to this flux path,
and thus from (3), the total current in the circuit shown
in Figure 5 is expressed as:
Figure 4. Conventional copper coil structure.
Table 2. Specification of the superconducting coil and compo-
nents.
No.Item Material Specification
1 HTS coil Type H Double Pancake 100 turns
2 Frame Brass -
3 Edge Plate Brass -
4 Terminal Copper -
5 Separator GFRP Thickness 0.2 mm
6 Edge SeparatorGFRP Thickness 0.2 mm
7 Insulation PlateGFRP Thickness 0.2 mm
8 Screw Blot - M3
9 Screw - M3
*GFRP = Glass Fiber Reinforced Polymer
r

r

c

a
R
r
R
a
R
y
R
Figure 5. Equivalent magnetic circuit of the system.

K. M. Chin et al. / Natural Science 3 (2011) 36-41
3939
Ni HL
 (4)
or
22
ccrryya ar r
NiNiHLHLH L (5)
4. RESULTS AND DISCUSSIONS
4.1. Finite Element Analysis
A finite element analysis was applied to investigate
the behavior of the magnetic flux inside the motor. The
analysis is very useful to verify an ideal magnetic circuit
and to detect any error in the electrical connection, espe-
cially for the DC machine. Another advantage of apply-
ing finite element analysis before the actual testing is to
avoid any short-circuit current between the motor com-
ponents. Figure 6 shows the model of the motor which
was constructed from the finite element analysis. The
model was built with a full scale dimension.
Figure 7 shows the magnetic flux path in the circuit.
From the flux plot, it indicates that the flux loss was in
the form of flux leakage and fringe effect. The simulated
result shown in Figure 8 indicates that the flux density
was inside the body of the motor. In the figure, it is ob-
vious that a high flux density is in the area around the
air-gap and the rotor. In contrast, the other parts of the
motor do not show high flux density, indicating a low
distribution of flux. The high flux density in the rotor
and air-gap area is needed to establish a high force that
enables the rotor to rotate.
4.2. Motor Assembly and Testing
The lamination of metal sheet on the motor formed
the stator. The superconducting coil was mounted on one
leg of a stator. A rotor was then mounted on the rotor
housing and the housing was attached to the stator. Thus,
a complete superconducting electric motor was assem-
bled. The procedure was repeated to assemble a copper
electric motor. Photograph of the completed assembly of
Figure 6. Model generated from the finite element analysis.
superconducting coil motor and copper coil motor are
shown in Figure 9 and Figure 10, respectively.
Flux lossFringe
X
Figure 7. Simulation of the magnetic flux path.
Figure 8. Simulation of the magnetic field density.
Figure 9. Superconducting coil motor assembly.

K. M. Chin et al. / Natural Science 3 (2011) 36-41 40
Figure 10. Conventional copper coil motor assembly.
Figure 11. The performance of motor with superconducting
coil.
Figure 12. The performance of motor with copper coil.
Motor torque measurement is used to gauge the per-
formance of the fabricated motor. Motor torque is one of
the motor ratings that is normally used to rate the motor
rotary force produced on its output shaft [13]. In the
measurement of motor torque, lever length is referred to
the radius of the shaft, and the force applied to the lever
is generated by the weight attached to the motor shaft.
DC current is used to provide the input current to both
the field coil and the rotor. In testing both types of mo-
tors, a constant current was supplied to the rotor, while
the current applied to the coil was varied at a fixed in-
terval with a load mounted on a shaft.
The data was taken once the rotor started to rotate. In
testing the motor with the superconducting coil, a rapid
cooling of the coil affected its performance. As such, the
coil was cooled gradually by pumping a small amount of
liquid nitrogen into the reservoir at a time until equilib-
rium temperature was reached. Testing conventional
copper coil was repeated with the same conditions but
without any cooling process. From the testing results, the
input power against the horizontal torque generated by
the shaft for each type of motor were plotted and are
shown in Figure 11 and Figure 12. The figures show
that the input power to establish a certain level of torque
for the superconducting coil motor is much lower than
the conventional copper coils motor. This shows that for
the same volume of conductor used in the construction
of the motor, the motor with superconducting coil per-
formed better performance in term of higher efficiency
than the motor with copper coil. One of the possible
factors in the enhancement of the efficiency of the motor
system is due to lower hysteresis loss inside the super-
conductor coils [14].
5. CONCLUSIONS
The design and feature of the motor components have
been presented in this paper. The results of finite ele-
ment analysis on the motors design have also been pre-
sented. Successful preliminary testing of the prototypes
of the bench-top motor proved that the performance and
energy efficiency of motor with superconductor coils is
superior. In addition, the superconducting motor is
lighter and compact with almost zero flux and noise
leakages. The encouraging results indicate the potential
of superconductor applications in machine devices and
the possibility of commercialization in the near future.
6. ACKNOWLEDGEMENTS
This project is supported by the Ministry of Science, Technology
and Innovation (MOSTI), Malaysia under the eScience Grant project
no. 03-02-03-SF0132.

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