Experimental Evaluation of Characteristic of
Switched Reluctance Motor Made by Blanking
Amorphous Alloy Foil
Takahiro Kumagai 1, Hirotaka Sakurai 1*, Jun-ichi Itoh 1, Keisuke Kusaka 1, Takashi Yamaguchi 2,
Masayuki Nakagawa 3, and Daisuke Sato 4
1

Department of Electrical, Electronics and Information Engineering, Nagaoka University of Technology, Japan
2
Yamaguchi Manufacturing Co., Ltd., Japan, 3 Industrial Research Institute of Niigata Prefecture, Japan,
4
Nagaoka Motor Development Co., Ltd., Japan

Abstract—This paper provides the characteristics ofswitched reluctance motors (SRMs) made by blanking (a)20H1300 of high grade low-iron-loss silicon steel (0.20mm
thickness) and (b) 2605SA1 of amorphous alloy (0.025mm
thickness). As first prototype, 70W-SRM (40mm thickness) is
manufactured by blanking 1600 sheets of amorphous alloy
and adhesively laminating them. In experiment, the motor
efficiency of amorphous-alloy-SRM is improved by 6.4p.t.
compared with that of silicon-steel-SRM. In addition, theiron loss of amorphous-alloy-SRM is reduced by 61.9%
compared with that of silicon-steel-SRM.
Index Terms—Switched reluctanceamorphous alloy foil, blanking, iron loss

motor(SRM),

I. INTRODUCTION
Due to an increasing awareness of environmental issues,high-efficiency motor and high-power density motor forhome appliances, industrial application, and electricvehicles have been actively studied and developed [1-5].
In order to achieve the higher power density, the electricmotor is operated at higher speed. High speed operation
has become easier with the practical use of wide bandgap
semiconductor such as silicon carbide (SiC) and gallium
nitride (GaN). However, high speed operation deteriorates
the motor efficiency due to the iron loss which is increased
depending on the electrical frequency.
Amorphous alloy has attracted much attentions thanks
to its low iron loss properties. In the amorphous alloy, theeddy current loss is small because it is thin and highelectrical resistivity. In addition, the hysteresis loss is also
small because it has no crystal structure [6]. So far, there
are many researches to apply the amorphous alloy into thecore of classic motors such as permanent magnetic
synchronous motor (PMSM) [7-11], induction motor (IM)[12], and switched reluctance motor (SRM) [13-15]. In
particular, Ref.[15] has reported that the iron loss of motor
core was reduced by about 80% compared with 35A300 of
a general low-iron-loss silicon steel with the employmentof amorphous alloy. In addition, the efficiency of thisamorphous alloy motor achieved more than 95% at an
output of about 2kW thanks to its low iron loss properties.
However, due to the difficulty in machining amorphousalloy, wire electrical discharge machining (WEDM), laser

cutting, or chemical etching is adopted as a cutting methodof amorphous alloy foil. These cutting processes lead toincreasing of manufacturing cost and become an obstacleof mass production of an amorphous alloy motor. As theresearches for the mass production of the amorphous alloy
motor, there are two different approaches; (ⅰ) improvementof motor structure in order to avoid the complicated cutting
process or (ⅱ) improvement of blanking technology.
In approach of (ⅰ), the simplification of motor structure
have been studied for avoidance of complicated cutting
process. Ref.[16-23] have focused on an axial-gap motor
whose stator core is a cylinder with a uniform cross-section
shape in the axial direction, where it is comparatively easy
to manufacture with the amorphous alloy. In particular,
Ref.[22] has already commercialized the amorphous alloy
axial-gap motor which satisfies the IE4 efficiency class. In
addition, IE5 efficiency class is achieved with improved
amorphous alloy axial-gap motor in Ref.[23]. However,these approaches still limits the applicability of anamorphous alloy.
In approach of (ⅱ), the cutting of amorphous alloy foil
has been attempted with the development of moldprocessing machines and technologies [24-30]. Ref.[28]has been reported that amorphous alloy foil was
successfully blanked into a motor stator shape. In Ref.[29],high-speed blanking of amorphous alloy foil has been
conducted and evaluated. Ref.[30] has presented theblanking results of the amorphous alloy stacks laminatedby 20 layers. However, as far as the author knows, there isno instance to manufacture the entire motor by blanking
amorphous alloy foil. The establishment of blanking
technologies of amorphous alloy is expected in order toexpand the application of the amorphous alloy more
widelyIn this paper, as one attempt in approach of (ⅱ), a
switched reluctance motor (SRM) is manufactured byblanking the amorphous alloy and evaluated in theexperiment. As first prototype, 70W-SRM (40mm
thickness) is manufactured by blanking 1600 sheets of theamorphous alloy and adhesively laminating them. In
addition, the same designed SRM is manufactured byblanking silicon steel for comparative verification. In thispaper, the iron loss characteristic and motor efficiency

characteristic of theexperimentally evaluated.

manufactured

SRMs

are

TABLE ISPECIFICATION OF RING-CORES
Name of Ring core

II. PRE-EXPERIMENTAL EVALUATION OF RING CORES

Iron core

As a preliminary step of the experimental evaluation
with motor, the iron loss characteristics of the cores madeby different material and processing method are evaluatedwith ring core. Generally, the evaluation of the iron loss
with ring core is more basic and more accurate.
Table.1 shows the specifications of the ring cores,
whereas Fig.1 shows the photograph of the manufactured
ring cores. Four ring cores are manufactured in order toevaluate the iron loss characteristics of the cores made by
the different material and the processing method. Two ringcores are made by the laser cutting after laminating (a)20H1300 of the high grade low-iron-loss silicon steel(0.20mm thickness) and (b) 2605SA1 of the amorphousalloy (0.025mm thickness), which are referred as “SS-C”
and “AA-C” in this paper. The others are made bylaminating after blanking (a) 20H1300 and (b) 2605SA1,
which are referred as “SS-B and “AA-B in this paper.
Fig.2 depicts the diagrams of the measurement setup forthe ring core. The primary and secondary windings withthe same number of turns are wound around the
manufactured ring core. The iron loss Wi and the amplitudeof magnetic flux density B are expressed as (1) and (2).
1 T
Wi   i1 (t )v2 (t )dt ........................................... (1)T 0
2V2 _ rms...................................................... (2)B2 fN 2 Sc
where i1(t) is the current in the primary winding, v2(t) is thevoltage of the secondary winding, f is the frequency of theapplied sinusoidal voltage, N2 is the number of turns in thesecondary winding, Sc is the effective cross-sectional areaof the ring core, V2_rms is the root mean square value of v2(t)at no-load test. The active power measured by the power
meter in Fig.2, i.e. the time average value of instantaneous
power expressed by (1), is equal to the magnetic energy
consumed by the iron core.
Fig.3 shows the comparison results of the iron losses ofthe four ring cores. The sinusoidal voltage with thefrequency of 1kHz is applied into the primary winding
with the bipolar power supply. In regard to the differencein the characteristics depending on the material, the ironloss of the silicon steel are around 500W as shown in
Fig.3(a), whereas the iron loss of the amorphous alloy are
under 100W at 1.2T. Therefore, the iron loss of theamorphous alloy is over 80% lower that of the silicon steel.
In regard to the difference in the characteristics dependingon the processing process, the iron loss of the SS-B and the
AA-B are increased by 10.9% and 10.7% respectively
compared with that of the SS-C and the AA-C. This
increases of the iron loss will be due to the properties
degradation during the blanking processes. Note that theproperties degradation is the almost same for both thesilicon steel and the amorphous alloy, and neither is so

Steel Thickness
Processing Method
Lamination factor

SS-B
AA-B
SS-C
AA-C
silicon steel
amorphous alloy(20HX1300)(2605SA1)
0.025mm
0.20mmWire cut Laminated Wire cut Laminated
After
After
After
After
Laminated Blanking Laminated Blanking
97.9%
95.6%
97.5%
94.5%

Fig. 1. Photograph of ring-cores made with the processing method
as shown in Table 1.

BipolarPower
Supply(BP4610)

v2

v1
Ring
core
i1
Power meter(PW3390/
HIOKI)

Fig. 2. Diagrams of measurement setup for ring-core

Iron loss density [kW/m3]

700
600

Increased by
10.9% at 1.2T

500
400

SS-B

300
200

SS-C

100

0
0

0.2

0.4
0.6
0.8
1
Magnetic flux density B[T]

1.2

1.4

1.2

1.4

(b) Silicon steel
Iron loss density [kW/m3]

120

100

Increased by
10.7% at 1.2T

80

AA-B

60
40

AA-C

20
0
0

0.2

0.4
0.6
0.8
1
Magnetic flux density B[T](b) Amorphous alloy
Fig. 3. Comparison results of iron losses at a frequency of 1kHz.

large. Therefore, the properties degradation due toblanking the amorphous alloy is not a serious problem inpractical use.
III. DESIGN AND MANUFACTURE OF SRMS
Table.2 shows the specifications of the designed SRMs,
whereas Fig.4 shows the photograph of the manufactured
amorphous-allow-SRM. 70W SRMs (40mm thickness) aredesigned as first prototype. Two motor cores are made byblanking (a) 20H1300 and (b) 2605SA1, which arereferred as “SS-SRM” and “AA-SRM” in this paper. The
number of layers of the SS-SRM is 200, whereas that of
the AA-SRM is 1600. These motors are manufactured byadhesively laminating the blanked steel sheets. In order toincrease the effect of the iron loss reduction, a relatively
high-speed motor is designed. In addition, the coil space isbigger than a general design [31] in order to increase thewinding diameter. This results in low winding resistanceand copper loss reduction. Furthermore, the airgap isdesigned to a very small value of 0.1mm in order to obtainlarge torque per current value.

TABLE IISPECIFICATION OF DESIGN SRM
Name of motor

SS-SRM

AA-SRM

Iron core

20H1300(high grade silicon steel)

2605SA1(amorphous alloy)

Number of layers
Processing method
Output power
Rated speed
Rated torque
Input voltage
Number of phases
Number of poles
Motor size
AirgapPole arc
Number of turns
Space factor of coil

200 (cal.)
1600 (cal.)
Laminated after Blanking
70W
7200r/min
0.093Nm48V3
6 (stator) / 4 (rotor)
40mm×40mm
0.1mm
21deg. (stator) / 31deg. (rotor)
73turns
34%

IV. EXPERIMENTAL EVALUATION OF SRMS
A. Test System Configuration
Fig.5 (a) depicts the diagrams of the measurement setup
for test motor, whereas Fig.5 (b) shows the photograph ofthe measurement bench. In particular, the motor efficiency
characteristics and the iron loss characteristics of the SSSRM and the AA-SRM are experimentally evaluated withthe measurement bench. The input electric power ismeasured
with
the
power
meter
(PW3390,
accuracy±0.04%, bandwidth200kHz, HIOKI), whereas thetorque is measured with the torque meter (UTMⅡ-1Nm,
accuracy±0.01%, bandwidth1kHz, UNIPULSE). The
motor efficiency motor is expressed as (3).
P
motor  out .......................................................... (3)Pinwhere Pout is the shaft output which is calculated as productof the measured torque and the shaft angular velocity,whereas Pin is the input electric power which is measured
by the power meter. On the other hand, the iron loss Wi arecalculated by subtracting Pout, the mechanical loss Wm, andthe copper loss Wc from Pin. Therefore, Wi is expressed as(4).
Wi  Pin  Pout  Wc  Wm ....................................... (4)wwhere Wc   Rx I RMS _ x 2 ................................ (5)Fig. 4. Photograph of 70W-SRM made of blanked amorphous alloy
foil.

DC
SupplyVdc

inverterPower meter(WT1800/YO
KOGAWA)Electronic
load

SRM

Torquemeter(UTM Ⅱ
1Nm/UNIPULSE)DC
Motor(a) Diagrams of measurement setup for test motor
DC motor(load motor)

Torque meter

SRM(test motor)xuwhere Wm is the product of the measured torque and therotational angular velocity when the DC motor drives thesystem with no SRM excitation. Rx and IRMS_x are thewinding resistance and the root-mean-square (RMS) valueof the winding current of x-phase respectively [15]. All
measurements are conducted to keep the winding
temperature within the range of 30 to 35 degrees. This isbecause Wm and Wc have temperature dependability.

(b) Photograph of measurement bench
Fig. 5. Measurement system for test motor

75

6

Improved by
6.4p.t.

70

70.2%

65

7

76.6% of max. motor

AA-SRM

Iron loss [W]Motor efficiency motor[%]80

SS-SRM

60
0.1

0.2

0.3 0.4 0.5 0.6 0.7 0.8 0.9
Shaft output Pout [p.u.](1p.u.=70W)

1

1.1

FEM

5.7W

Iron loss is
reduced by 61.9%
2.2W

15
13.9W

10.3W

Iron loss Wi
Copper loss Wc

5
4.2W

4.9W

SS-SRM

AA-SRM

Mech. loss Wm

Fig. 7. Separation results of motor losses of SS-SRM and AASRM at 56W (0.8p.u.) of maximum efficiency point in Fig.2.

B. Measured characteristics of SS-SRM and AA-SRM
Fig.6 shows the motor efficiency characteristics of the
SS-SRM and the AA-SRM. The shaft output is from 0.2p.u.
to 1.0p.u. The rotation speed is rated speed. As shown in
Fig.6, the motor efficiency of the AA-SRM is higher thanthat of the SS-SRM in all output range. In additon, the AASRM achieved the maximum motor efficiency of 76.6% at
56W (0.8 p.u.). At this operating point, the motor
efficiency of the AA-SRM is improved by 6.4p.t.
compared with that of the SS-SRM. Note that the motor
efficiency of the AA-SRM is getting worse at rated output.
This is because the amorphous alloy has lower maximum
flux density as a sacrifice of low iron loss propeties,
resulting in deterioration of the motor efficiency at
relatively high torque range. However, the efficiency of
the AA-SRM is still higher than that of the SS-SRM at
rated output thanks to the iron loss reduction.
Fig.7 shows the separation results of the motor losses of
the SS-SRM and the AA-SRM at 56W (0.8p.u.) of the
maximum efficiency point as shown in Fig.6. As shown in
Fig.7, the iron loss of the AA-SRM is reduced by 61.9%
compared with that of the SS-SRM. Therefore, the ironloss reduction effect of the motor core is confirmed evenin the blanked amorphous alloy. Note that this reduction
rate of the iron loss will be lower than that reported in
Ref.[15]. One of the reasons is that the silicon steel of our
SS-SRM is 20H1300 of a high grade low-iron-loss siliconsteel (0.20mm thickness), whereas that of the SS-SRM in
Ref.[15] is 35A300 of a general low-iron-loss silicon steel(0.35mm thickness); the iron loss of the AA-SRM is
compared with that of the SS-SRM whose iron loss isrelatively low.

Measure(a) SS-SRM
7

Iron loss [W]Loss [W]

2

6

25

0

3

0

Fig. 6. Efficiency characteristics of SS-SRM and AA-SRM at rated
speed.

10

4

5.7W

1

55

20

5

Eddy current (stator)
Eddy current(rotor) Increased toHysteresis(stator)
135%
Hysteresis(rotor)
4.2W

5Eddy current (stator)
Eddy current(rotor)
Hysteresis(stator)
Hysteresis(rotor)

43

Increased to
256%

2
1

2.2W

0.8W

0
FEM

Measure(b) AA-SRM
Fig. 8. Comparison results between FEA and measurement of ironlosses at 56W (0.8p.u.) of maximum efficiency point in Fig.2.

C. Comparison results between FEA and Measurement
Fig.8 shows the comparison between the FEA results
and the measurement results of the iron losses of (a) the
SS-SRM and (b) the AA-SRM. The iron losses of the SSSRM and the AA-SRM are calculated based on themeasured iron loss curves of the ring cores of SS-B and
AA-B respectively with 2D-FEM package (JMAG). As
shown in Fig.8, the measured iron losses of the SS-SRM
and the AA-SRM are increased to 135% and 256%
respectively compared with those of the FEA results. It is
confirmed that there is a great different characteristic
between the FEA analysis and the measurement. One
possibility of the cause of this difference is the low
accuracy of iron loss analysis of FEA. It is mentioned thatthe simple iron loss calculation algorithm based on the ironloss curves is less accurate in case of the complicatedmagnetic flux waveforms of the SRM.
V. CONCLUSIONSThis paper provided the characteristics of the SRMs
made by blanking (a) 20H1300 of the high grade low-ironloss silicon steel (0.20mm thickness) and (b) 2605SA1 ofthe amorphous alloy (0.025mm thickness). As first
prototype,
70W-SRM(40mm
thickness)wasmanufactured by blanking 1600 sheets of the amorphousalloy and adhesively laminating them. In experiment, themotor efficiency of the amorphous-alloy-SRM was
improved by 6.4p.t. compared with that of the siliconsteel-SRM. In addition, the iron loss of the amorphousalloy-SRM was reduced by 61.9% compared with that of
the silicon-steel-SRM. In the future, the characteristic of
the motor made by blanking the amorphous alloy foil isevaluated more detailed in experiment and improved FEA.

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