電気学会論文誌●（●●●●●●●部門誌）
IEEJ Transactions on ●●●●●●●●●●●●●●●
Vol.●● No.● pp.●-●●
DOI: ●.●●/ieejeiss.●●.●

Paper

Experimental Evaluation of Switched Reluctance Motor Made by
Blanking Amorphous Alloy Foil
Takahiro Kumagai＊a) Student Member, Hirotaka Sakurai＊ Student Member,
Taisuke Shioi＊ Student Member, Hirotaka Kato＊ Student Member,
Jun-ichi Itoh＊ Senior Member, Keisuke Kusaka＊ Member,
Takashi Yamaguchi＊＊ Non-Member, Masayuki Nakagawa＊＊＊ Non-Member,
Daisuke Sato＊＊＊＊ Member(Manuscript received Jan. 00, 20XX, revised May 00, 20XX)
This study reveals the characteristics of switched reluctance motors (SRMs) made by blanking (a) 20HX1300 of high grade lowiron-loss silicon steel (0.20mm thickness) and (b) 2605SA1 of amorphous alloy (0.025mm thickness). The blanking of theamorphous alloy is an innovative technology for the mass production of the high efficiency amorphous-alloy-motor. The impact ofthe processing methods on the magnetic properties are evaluated using the ring cores processed by the following methods: the wire
cutting and the blanking. On the other hand, the experiment with the SRMs processed by the blanking evaluates the characteristics
depending on the material. As first prototype, 70W-SRM (40mm thickness) is manufactured by blanking 1600 sheets of theamorphous alloy and adhesively laminating them. In the experiment, the motor efficiency of the amorphous-alloy-SRM is improvedby 6.9 p.t. compared with that of silicon-steel-SRM. In addition, the iron loss of amorphous-alloy-SRM is reduced by 78.7%
compared with that of silicon-steel-SRM.
Keywords : Switched reluctance motor (SRM), ring core, finite element analysis (FEA), amorphous alloy foil, blanking, iron loss

1.

synchronous motor (PMSM) [7-11], an induction motor (IM) [12],and a 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 employment of amorphous alloy. In addition,
the efficiency of this amorphous alloy motor achieved more than
95% at an output of about 2kW thanks to its low iron loss properties.
However, wire electrical discharge machining (WEDM), laser
cutting, or chemical etching is adopted as a cutting method of theamorphous alloy foil due to the difficulty in machining amorphousalloy. These cutting processes lead to increasing of manufacturing
cost and become an obstacle of mass production of an amorphousalloy motor. As the researches for the mass production of theamorphous alloy motor, there are two different approaches; (ⅰ)
improvement of motor structure in order to avoid the complicatedcutting process or (ⅱ) improvement of blanking technology.
In approach (ⅰ), the simplification of the motor structure has beenstudied 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 amorphousalloy axial-gap motor which satisfies the IE4 efficiency class. In
addition, IE5 efficiency class is achieved with the improved
amorphous alloy axial-gap motor in Ref.[23]. However, theseapproaches still limit the applicability of the amorphous alloy.
In approach (ⅱ), the cutting of the amorphous alloy foil has been
attempted with the development of mold processing machines andtechnologies [24-30]. Ref.[28] has been reported that amorphous

Introduction

High-efficiency motor and high-power density motor for home
appliances, industrial application, and electric vehicles have been
actively studied and developed due to an increasing awareness ofenvironmental issues [1-5]. The electric motor is operated at higher
speed in order to achieve the higher power density. High speed
operation has become easier with the practical use of wide bandgap
semiconductors such as a silicon carbide (SiC) and a gallium nitride(GaN). However, high speed operation deteriorates the motor
efficiency due to the iron loss which is increased depending on theelectrical frequency.
Amorphous alloy has drawn much attentions thanks to its low
iron loss properties. In the amorphous alloy, the eddy current loss issmall because it is thin and high electrical 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 the core of classic motors such as a permanent magnetica) Correspondence to: Takahiro Kumagai. E-mail:kumagai_t1125@stn.nagaokaut.ac.jp＊
Nagaoka University of Technology,1603-1, Kamitomioka-machi, Nagaoka-shi, Niigata 940-2188,
Japan＊＊
Yamaguchi Manufacturing Co., Ltd.,10245-1, Katakai-machi, Ojiya-shi, Niigata 947-0101, Japan＊＊＊
Industrial Research Institute of Niigata Prefecture,
1-11-1, Abuminishi, Niigata-shi Chuo-ku, Niigata 950-0915,
Japan
＊＊＊＊
Nagaoka Motor Development Co., Ltd.,
16-2085, Nagaoka Business Incubation Center, Fukasawamachi, Nagaoka-shi, Niigata, 940-2135, Japan© 200● The Institute of Electrical Engineers of Japan.

1Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)Table 1.

alloy foil was successfully blanked into a motor stator shape. In
Ref.[29], the high-speed blanking of the amorphous alloy foil has
been conducted and evaluated. Ref.[30] has presented the blanking
results of the amorphous alloy stacks laminated by 20 layers.
However, as far as the author knows, there is no instance tomanufacture the entire motor by blanking amorphous alloy foil. In
other words, the characteristics of the entire motor by blanking theamorphous alloy have not been revealed. The establishment of theblanking technologies of the amorphous alloy and the quantitativeevaluation for the impact of the blanking process are expected inorder to expand the application of the amorphous alloy more widely.
In this paper, an entire switched reluctance motor (SRM) is
manufactured by blanking the amorphous alloy. The newcontribution of this paper is experimental evaluation of the iron loss
characteristic and motor efficiency characteristic of the
manufactured SRM by blanking the amorphous alloy.
This paper is organized as follows; first, the impacts of theprocessing methods on the magnetic properties are evaluated withthe ring cores processed by two methods: the wire cutting and theblanking; Next, the experiment with the SRMs processed by theblanking evaluates the characteristics depending on the material. As
first prototype, 70WSRM (40mm thickness) is manufactured byblanking 1600 sheets of the amorphous alloy and adhesively
laminating them. In addition, the same designed SRM is
manufactured by blanking silicon steel for comparative verification.
Note that this paper is the updated version of the conference paper[31]. The manuscript additionally evaluates the B-H characteristics
and iron loss characteristics with ring cores, improves the accuracyof finite element analysis (FEA), and replaces all the oldexperimental results of 7200r/min with the new experimental
results of 10000r/min.

2.

Name of Ring core
Iron core
Steel Thickness
Processing Method
Lamination factor

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

BipolarPower
Supply(BP4610)

v2

v1
Ring
core
i1
Power meter(PW3390/
HIOKI)

Pre-experimental iron loss evaluation of ringcores

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

The B-H characteristics and the iron loss characteristics of thecores made by different material and different processing method
are evaluated with ring cores as a preliminary step of theexperimental evaluation with motor. Generally, the evaluation of
the iron loss characteristic with ring core is more basic and moreaccurate.
2.1 Experimental preparation
Table.1 shows the specifications of the ring cores, whereas Fig.1
shows the photograph of the manufactured ring cores. Four ringcores are manufactured in order to evaluate the iron loss
characteristics of the cores made by the different material and thedifferent processing method. Two ring cores are made by the laser
cutting after laminating (a) 20HX1300 of the high grade low-ironloss silicon steel (0.20mm thickness) and (b) 2605SA1 of theamorphous alloy (0.025mm thickness), which are referred as “SSC” and “AA-C” in this paper. The others are made by laminating
after blanking (a) 20HX1300 and (b) 2605SA1, which are referred
as “SS-B and “AA-B in this paper. The conductive elements of thelaser cut surface of the manufactured SS-C and AA-C are removed
with etching process in order to prevent the increase of the eddy
current loss due to the short circuit between laminated steel sheets.
Note that the lamination factor kl is calculated fromkl Specifications of ring-cores

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
96.9%
90.8%
95.9%
93.1%
* The conductive elements of wire cut surface
are removed with etching process

and Vvol is the volume of the ring core. As shown in Table 1, thelamination factors of AA-C and AA-B are a little worse than that of
SS-C and SS-B. This deterioration of the lamination factor will be
due to the thinner and the higher number of layers of the amorphousalloy than these of the silicon steel.
Fig.2 depicts the diagrams of the measurement setup for the ringcore. The primary and secondary windings are wound around the
manufactured ring core. The magnetic flux density B(t) and themagnetizing force H(t) are expressed as

B (t ) 1 t
v2 (t )dt .......................................................... (2)N 2 Sc 0

H (t ) N1i(t )....................................................................... (3),lwhere v2(t) is the voltage of the secondary winding, N2 is thenumber of turns in the secondary winding, Sc is the effective crosssectional area of the ring core, i1(t) is the current in the primarywinding, N1 is the number of turns in the primary winding, and l isthe effective magnetic path length of the ring core. On the other
hand, the iron loss Wi and the amplitude of magnetic flux density
Bm are expressed asm.......................................................................... (1),
 mVvol

where m is the mass of the ring core, m is the density of the material,
2

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)1.738T

SS-C

1.715T

1.5
SS-B

1
0.5
0
-10000

-5000

-0.5

0

5000

300

Iron loss density/freq. [W/m3/Hz]

Magnetic flux density B [T]

2

10000

-1
-1.5

SS-B

250
Keddy=0.287

200

Khys=144.7

SS-C
Keddy=0.238

150
Khys=122.7

100
0

-2
Magnetizing force H [A/m]

100

200
300
Frequency f [Hz](a) Silicon steel

AA-C

1.551T

1.5

1.546T

1

AA-B

0.5
0
-10000

-5000

-0.5

0

5000

10000

-1
-1.5

75
Keddy=0.0233

70

AA-B

Khys=60.9

65
60

AA-C

55

Keddy=0.0307

50

Khys=49.545
0-2Magnetizing force H [A/m]

100

200
300
Frequency f [Hz]400(b) Amorphous alloy(b) Amorphous alloy

Fig. 3. Measured B-H characteristics at a frequency of 50Hz.

Fig. 4. Measured iron loss characteristics at 1.0T.

Table 2.

SS-C
SS-B
AA-C
AA-B

Wi 

Bm 

Magnetic flux density at 7500A/m andpermeability around 0A/m

B75 (=B at 7500A/m)
1.738T
1.715T
1.551T
1.546T

Table 3.

i (=dB/dH around 0A/m)
0.0195H/m
0.0117H/m
0.0241H/m
0.0195H/m

2 fN 2 Sc

500

Coefficients of the Steinmetz equation
Khys.
122.7
144.7
49.5
60.9

SS-C
SS-B
AA-C
AA-B

Keddy.
0.238
0.287
0.03070.0233

Therefore, the amorphous alloy has slightly lower magnetic flux
density and higher permeability compared with the silicon steel. B75
of SS-B and AA-B are decreased by only 1.3% and 0.3%
respectively compared with that of SS-C and AA-C in regard to thedifference in the characteristics depending on the processing
process. In addition, i of SS-B and AA-B are decreased by 40.0%
and 19.1% respectively compared with that of SS-C and AA-C.
Therefore, the blanking process has little effect on the magnetic flux
density, but it decreases the permeability. This decrease of thepermeability will be due to the properties degradation with plasticstrain and elastic strain generated at the end of the steel sheet during
the blanking processes. However, i of AA-B is still same level asthat of SS-C in spite of the properties degradation.
2.3 Experimental results of iron loss characteristic
Fig.4 shows the measured iron loss characteristic at 1.0T,
whereas Table 3 shows the coefficients of the Steinmetz equation.
The frequency of the applied sinusoidal voltage is low frequency offrom 50Hz to 500Hz in order to evaluate the eddy current loss notincluding the skin effect which occurs in the high frequency region.
The Steinmetz equation is expressed as

1 T
i1 (t )v2 (t )dt ...........................................................(4)T 0

2V2 _ rms

500(a) Silicon steel

Iron loss density/freq. [W/m3/Hz]

Magnetic flux density B [T]2400................................................................... (5),where f is the frequency of the applied sinusoidal voltage, V2_rms is
the root mean square value of v2(t) at no-load test. Note that v2(t) is
not the value converted to the voltage of the primary winding, but
the measured value of the voltage of the secondary winding. The
active power measured by the power meter in Fig.2, i.e. the time
average value of instantaneous power expressed by (4), is equal tothe magnetic energy consumed by the iron core.
2.2 Measurement results of B-H characteristic
Fig.3 shows the measured B-H characteristics, whereas Table 2
shows the magnetic flux density at 7500A/m (which is defined asB75) and the permeability around 0A/m (which is defined as i). The
frequency of the applied sinusoidal voltage is low frequency of
50Hz in order to avoid the effects of the eddy current loss. B75 of
AA-C and AA-B are 10.8% and 9.9% lower than that of SS-C and
SS-B respectively in regard to the difference in the characteristics
depending on the material. In addition, i of AA-C and AA-B are
23.6% and 66.7% higher than that of SS-C and SS-B respectively.

Wi  K hys f Bm hys  K eddy f 2 Bm 2 ....................................... (6),where hys, Khys and Keddy represents the coefficients of thehysteresis loss and the eddy current loss. Khys and Keddy are
3

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)calculated as the intercept and slope of Wi / f at Bm = 1T as shownin Fig.4. Keddy of AA-C and AA-B are 87.1% and 91.9% lower thanthat of SS-C and SS-B respectively in regard to the difference in thecharacteristics depending on the material. Therefore, the eddy
current loss of the amorphous alloy is expected to be 1/10 of thesilicon steel at the same f and the same Bm. In addition, Khys of AAC and AA-B are 59.7% and 57.9% lower than that of SS-C and SSB respectively. Therefore, the hysteresis loss of the amorphous alloy
is expected to be less than 1/2 of the silicon steel at the same f andthe same Bm = 1[T] (because of Bmhys=1). Keddy of SS-B is increased
by 20.6% compared with that of SS-C, whereas Keddy of AA-B isdecreased by 24.1% compared with that of AA-C in regard to thedifference in the characteristics depending on the processing
process. This will be due to the following two factor; (ⅰ) the increaseof the eddy current loss due to the remaining conductive elementsof the wire cut surface which could not be removed even by etchingprocess in SS-C and AA-C and (ⅱ) the properties degradation withthe plastic strain and elastic strain generated at the end of the steel
sheet during the blanking processes in SS-B and AA-B. In thesilicon steel, the impact of (ⅰ) is greater than that of (ⅱ). On the other
hand the amorphous alloy, the impact of (ⅰ) is smaller than that of(ⅱ). On the other hand, Khys of SS-B and AA-B are increased by
17.9% and 23.0% compared with that of SS-C and AA-C. This will
be due to the factor (ⅱ). Therefore, the blanking process has little
effect on the eddy current loss, but it increases the hysteresis loss.
This increase of the hysteresis loss is a problem in the electricalproperties of the blanked material. Note that the eddy current loss
dominates the iron loss of the high-speed motor. Therefore, theproperties degradation due to blanking the amorphous alloy is not aserious problem in practical use.

3.

Magnetic flux density B [T]

2
1.5

1
0.5

Enlarge0-15000-10000

-5000

-0.5

0

5000

10000

15000

-1
-1.5
-2
Magnetizing force H [A/m](a) Entire (±15000A/m, ±2T)

Magnetic flux density B [T]

0.5

0.4
0.3

-50

-40

1.55T

0.2

0.05T

0.1

-30

-20

0
-10
-0.1 0

10

20

30

40

50

-0.2

-0.3
Every 0.05T

-0.4
-0.5
Magnetizing force H [A/m](b) Enlarge (±50A/m, ±0.5T)

Fig. 5. Measured hysteresis loops of AA-B
Table 4.

Improvement of accuracy of iron loss analysis in
FEA

Characteristic of 20HX1300 and 2605SA1

20HX1300(SS-B)
2605SA1(AA-B)

d [mm]
0.2
0.025

p [10-6Ωm]
0.55
1.3

Keddy
0.287
0.0233


2.40
29.5

[38-39] in this paper. This method is performed considering the skineffect of the eddy current loss. Note that the classical eddy current
loss calculated by the homogenization method does not include theexcess loss such as anomalous eddy current loss. Therefore, themodified coefficient  of the classical eddy current loss is definedas

It was confirmed that the accuracy of FEA is low in the simple
iron loss calculation algorithm based on the iron loss curve [31].
This is because the analysis based on the iron loss curve is notapplicable into the complicated magnetic flux waveforms of theSRM. In this paper, the hysteresis loss is analyzed based on Play
Model [32-33], whereas the eddy current loss is analyzed by
Homogenization method [34-35]. These methods are higher
accuracy than that based on the iron loss curve thanks to theconsideration of the DC bias characteristics of the hysteresis loss
and the skin effect of the eddy current loss [36-37].
3.1
Preparation of Play model based method
Fig.5 shows the measured hysteresis curves of AA-B. The playmodel is the magnetization model which reproduces any minor loop.
The hysteresis loss is calculated from the history of magnetization,i.e. the area of the B-H loop. This method is performed considering
the DC bias characteristics of hysteresis loop. It is necessary forPlay model to prepare a group of major B-H loops with different
amplitude as shown in Fig.5. These B-H loops are measured by themethod as explained in Subsection 2.2. The measurement range isfrom 0.05T to 1.90T for 20HX1300, and from 0.05T to 1.55T for
2605SA1. These measured data were implemented in JMAG
Designer.
3.2
Preparation of Homogenization method
Table 4 shows the characteristic of 20HX1300 and 2605SA1. The
classical eddy current loss Weddy_cla is calculated from the thickness
d and electrical resistivity  of the electrical sheet in thehomogenization method. The values of d and  are the catalog valueKeddy f 2 Bm 2
( fdBm )2
6p



Keddy
( d )2 .................................................. (7),6pwhere Keddy represents the coefficients of the eddy current loss
which does not include the skin effect as explained in Subsection
2.3. The eddy current loss Weddy including the excess loss Weddy_ex isexpressed as

Weddy  Weddy _ cla  Weddy _ ex   Weddy _ cla .............................(8).
Therefore, the eddy current loss is calculated by multiplying theanalysis value of the classical eddy current loss by the modified
coefficient . As shown in Table.4, the  of the blanked silicon steel
is 2.40, whereas the  of the blanked amorphous alloy is 29.5. Thereis a pretty difference between the actual eddy current loss and theeddy current loss calculated by the physical property such as the
thickness and electrical resistivity in the blanked amorphous alloy.

4. Design and Manufacture of SRMs
Table.5 shows the specifications of the designed SRMs, whereas
Fig.6 shows the photograph of the manufactured amorphous-allow4

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)Specifications of test SRMs
AA-SRM

Iron core

20HX1300(high grade silicon steel)

2605SA1(amorphous alloy)

Number of layers
Processing method
Output power
Maximum speed
Number of phases
Number of poles
Motor size
AirgapPole arc
Number of turns
Space factor of coil25

20

Motor loss [W]

SS-SRM200 (cal.)
1600 (cal.)
Laminated after Blanking
70W
10000r/min
3
6 (stator) / 4 (rotor)
40mm×40mm
0.1mm
21deg. (stator) / 31deg. (rotor)
73turns
34%

Not selectable due tomechanical constraints

AA-SRM

15

Copper loss

SS-SRM

10

SS-SRM
5

Iron loss

0
0.05

0.1

AA-SRM

0.15
0.2
0.25
Airgap length lg [mm]0.3(a) Motor loss

0.92

AA-SRM
Expected efficiency he [-]Table 5.
Name of motor

0.88

Selected

Smaller air gap length
leads to higher efficiency
for both SRMs

0.84
0.8

SS-SRM

0.76

Not selectable due tomechanical constraints

0.72
0.05

0.1

0.15
0.2
0.25
Airgap length lg [mm]0.3(b) Expected efficiency

Fig. 7. Effect of airgap length
Table 6. Cost comparison in different processing
methods excluding the cost of molds and equipment

Fig. 6. Photograph of 70W-SRM made of blanked amorphousalloy foil.

Silicon steel
Amorphous alloy

SRM. 70W SRMs (40mm thickness) are designed as first prototype.
Two motor cores are made by blanking (a) 20HX1300 and (b)2605SA1, which are referred as “SS-SRM” and “AA-SRM” in thispaper. The detail of the employed innovative technology inblanking of the amorphous alloys is found in Ref.[40]. The
comparative evaluation of the electrical characteristics of thedifferent blanking technologies will be discussed in a future work.
Note that the stator outer diameters of the blanked motor core are
40mm. There are problems of the material availability and the moldprecision in order to blank larger motor core. The number of layersof SS-SRM is 200, whereas that of AA-SRM is 1600. These motors
are manufactured by adhesively laminating the blanked steel sheets.
Since it is difficult to laminate very thin steel sheets of theamorphous alloy with a caulking or a welding, an impregnation
lamination is employed. There is a problem of the lower
productivity due to the requirement of the manufacturing time forthe adhesion process. In order to increase the effect of the iron loss
reduction, a relatively high-speed motor is designed. In addition,
the coil space is bigger than that of a general design [41] in order toincrease the winding diameter. This results in low winding
resistance and copper loss reduction. Furthermore, the airgap lengthis selected in order to achieve the highest efficiency within themechanical constraint of 0.1 mm.
Fig.7(a) depicts the relationship between the airgap length andthe motor loss, whereas Fig.7(b) shows the relationship between theairgap length and the motor efficiency. As shown in Fig.7(a), thelarge airgap extremely increases the copper loss. This is because thereluctance torque becomes small due to small change of themagnetic resistance with the change of the airgap length. The

Table 7.

Wire cure After
Laminated
KSS-B
KAA-B

Laminated After
Blanking
KSS-B×1/30~1/50
KAA-B×1/10

Cost comparison of blanking processing indifferent materials

Material priceJig tool costs
Re-polishing cost
Assembly cost

Silicon steel
Amorphous alloy
Laminated After Blanking
KSS-M
KSS-M×2
KSS-J
KSS-J×3~5
KSS-R
KSS-R×30~50
KSS-A
KSS-A×30~50

copper loss of AA-SRM remains almost the same to that of SSSRM. Therefore, the high efficiency is not expected due to small
effect of reducing the motor loss with the low iron loss
characteristics of the amorphous alloy. In this paper, the airgap
length in both SS-SRM and AA-SRM are selected to be 0.1mm inorder to achieve the highest efficiency within the mechanicalconstraint.
The information about the cost, structural strength, and heatresistant are described. Note that the main subject of this paper isthe evaluation of the electrical characteristics of the motors madeby blanking the amorphous alloy. Therefore, the information about
the cost and other are described as reference values.
Table.6 shows the cost comparison in the different processing
methods excluding the cost of the molds and the manufacturing
equipment. The cost reduction by the blanking of the silicon steel
in the mass production is expected to be 1/30~1/50 compared withthat of the wire cutting. On the other hand, that of the amorphousalloy is expected to be 1/10 due to the larger number of required
5

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)sheets and the difficulty of processing of amorphous alloy.
Table.7 shows the cost comparison of blanking processing in the
different materials. The material cost of the amorphous alloy is
expected to be increased by 2 times compared with that of thesilicon steel [42]. In addition, the jig tool cost is expected to be
increased by from 3 times to 5 times. This is because the clearanceof the jig tool is very small, and the required accuracy of the jig
tools is very high. In addition, the re-polishing cost is expected to
be increased by from 30 times to 50 times. This is because not only
the number of required sheets is larger but also the tensile strengthis high in the amorphous alloy. In addition, the assembly cost is
expected to be increased by from 30 times to 50 times because of
the large number of required sheets, more frequently re-polishing,
and the manufacturing time for the adhesion process in theimpregnation lamination.
The structural strength of the motor made by blanking theamorphous alloy is higher than that of the silicon steel. This isbecause the structural strength depends on the hardness of the core.
The hardness of the amorphous is approximately 5 times higher
than that of the silicon steel. On the other hand, the heat-resistant is
expected to be same.

5.

DC
SupplySRM

inverter

Vdc

Torquemeter(UTM Ⅱ
1Nm/UNIPULSE)

Power meter(WT1800/YO
KOGAWA)

DC
Supply(Regenerative)

DC/DC
converter

DC
Motor

(a) Diagrams of measurement setup for test SRM

SRM(test motor)

Torque meter

DC motor(load motor)

Experimental evaluation of SRMs

5.1 Test system configuration
Fig.8 (a) depicts the diagrams of the measurement setup for test
motor, whereas Fig.8 (b) shows the photograph of the measurement
bench. In particular, the motor efficiency characteristics and theiron loss characteristics of SS-SRM and AA-SRM areexperimentally evaluated with the measurement bench. The input
electric power and the root-mean-square (RMS) value of thewinding current are measured with the power meter (PW3390,
accuracy ±0.04%, bandwidth 200kHz, HIOKI), whereas the torqueis measured with the torque meter (UTMⅡ-1Nm, accuracy±0.01%,
bandwidth1kHz, UNIPULSE). The winding temperature ismeasured by thermocouple built into the winding.
The motor efficiency hm is expressed ashm (b) Photograph of measurement bench

Fig. 8. Measurement system for test SRM
step1

Pout _ m
Pin



step3

step4 step5 step6

Speed

m

Torque meter
output*Pout Toutm............................................................... (9),
Pin
Pin

600s

30s

Mech. loss becomesstable thanks towarm-up of bearing

Tout

30s

30s

Tmech

T=0

* The torque meter output is positive when the load side
is twisted CCW viewed from the drive side.

Fig. 9. The speed and the torque meter output during theexperiment (Step1~Step6)

where Pout is the shaft output which is calculated as product of themeasured torque Tout and the shaft angular velocity m, whereas Pinis the input electric power which is measured by the power meter.
According to the preliminary verification in Ref.[31], themechanical loss has large dispersion. In addition, there areindividual differences of mechanical loss in SS-SRM and AA-SRM.
Therefore, it is impossible for the evaluation with Eq.(9) to make afair comparison. In order to resolve the above problems, theefficiency he regarding the mechanical loss as a part of the shaft
output is defined as

he 

step2

Table 8.

Step1
Step2
Step3
Step4
Step5
Step6

Pout  Wm Toutm  Tmechm................... (10),Pin
Pin

The operation of load motor and test motor ateach step

Load motor
Acceleration
ASR
ASR
ASR
Deceleration
No excitation

Test motor
PurposeNo excitation
No excitation
Warm-up of bearing
ACR
Output measurement
No excitation Mech. loss measurement
No excitation
No excitation Zero point confirmation

Wi  Pin  Pout  Wc  Wmw

 Pin  Toutm   Rx (ttemp ) I RMS _ x 2  Tmechmwhere Pout_m is the shaft output when the mechanical loss Wm isregarded as shaft output. Note that Wm is the product of themeasured torque Tmech and the rotational angular velocity m when
the DC motor drives the system with no SRM excitation. On theother hand, the iron loss Wi is calculated by subtracting Pout, Wm,
and the copper loss Wc from Pin. Therefore, Wi is expressed as.............(11),x uwhere Rx(ttemp) is the winding resistance of x-phase respectively at
winding temperature ttemp, whereas IRMS_x is the root-mean-square(RMS) value of the winding current of x-phase respectively.
5.2
Test procedure
The copper loss (winding resistance) depends on the winding

6

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)

0.9

Efficiency hm [-]10

86.0% at 1.05p.u.

0.8

Copper loss Wc [W]

AA-SRM
77.8% at 1.01p.u.

0.7
SS-SRM

0.6

Efficiency is pretty bad
1p.u.=70W
due to the mechanical loss (rated output)

0.5
0.4

Reduced byapproximately 20%

1p.u.=70W(rated output)

8

SS-SRM

6
4

AA-SRM

2

0

0

0.2

0.4
0.6
Output Pout [p.u.]

0.8

1

0

0.2

0.4
0.6
0.8
Output Pout_m [p.u.](a) Copper loss(a) Not regarding the mechanical loss as a part of the shaft output (Eq.(9))

10

90.9%
AA-SRM Improved by 6.9p.t.

0.88

Iron loss Wi [W]

0.92

Efficiency he [-]

1

90.4%

0.84
83.5%

0.8

SS-SRM

0.76

1p.u.=70W(rated output)

6
Wi / Pout_m→large

0.2

0.4
0.6
0.8
Output Pout_m [p.u.]

Reduced byapproximately 75%
SS-SRM
Wi / Pout_m→small4
AA-SRM

2

0
0

0.72
0

1p.u.=70W(rated output)

8

0.2

0.4
0.6
0.8
Output Pout_m [p.u.]

11(b) Iron loss

Fig. 11. Motor loss comparison between SS-SRM and AA-SRM
in all output range at 10000r/min.

(b) Regarding the mechanical loss as a part of the shaft output (Eq.(10))

Fig. 10. Efficiency characteristics of SS-SRM and AA-SRM
in all output range at 10000r/min.

14

temperature, whereas the mechanical loss depends on the bearing
temperature. In particular, the bearing temperature cannot bemeasured in this system. Therefore, a warm-up operation is requiredin order to sufficiently warm the bearing.
Fig.9 shows the speed and the torque during the experiment(Step1~Step6), whereas Table8 shows the operation of load motor
and test motor at each step. At first, the motor is accelerated by load
motor (Step1). Next, the load motor drives the system with no SRM
excitation for a long time (Step2). In Step2, the mechanical loss
becomes stable thanks to warm-up of bearing. Next, the test motor
output the torque by controlling the current to the pulse current withthe command amplitude (Step3). In Step3, the efficiency and ironloss are calculated from the average value of the measured value inthis section. Next, the load motor drives the system with no SRM
excitation again (Step4). In Step4, the mechanical loss is calculated
from the average value of the measured value in this section. Finally,
the motor is decelerated (Step5) and stop (Step6). The zero point of
the torque meter is confirmed in the stopped state (Step6).
5.3 Measured characteristics of SS-SRM and AA-SRM
Fig.10 shows the motor efficiency characteristics of SS-SRM and
AA-SRM at 10000r/min. The mechanical loss is not regarded as aapart of the shaft output (i.e. use of Eq.(9)) in Fig.10(a), whereas
the mechanical loss is regarded as a apart of the shaft output (i.e.
use of Eq.(10)) in Fig.10(b). As shown in Fig.10(a), the motor
efficiency of AA-SRM is higher than that of SS-SRM in all output
range. In addition, AA-SRM achieved the maximum motor
efficiency of 86.0% at 1.05p.u. of rated power (70W). In the low
torque region, the efficiency is pretty bad due to the mechanical loss.
As shown in Fig.10(b), the motor efficiency of AA-SRM isapproximately 90% in all output range. In addition, AA-SRM
achieved the motor efficiency of 90.4% at rated power (70W). At
this operating point, the motor efficiency of AA-SRM is improvedby 6.9 p.t. compared with that of SS-SRM.

12
Loss [W]10

Reduced by 78.7%

5.8

Reduced by 21.9%

8
6
4

8.0

2

1.2

Iron loss

6.2

Copper loss

0
SS-SRM

AA-SRM

Fig. 12. Motor loss comparison between SS-SRM and AA-SRM
of rated power (70W) at 10000r/min.
Fig.11 shows the comparison results of (a) the copper loss and(b) the iron loss of SS-SRM and AA-SRM. As shown in Fig.11(a),the copper loss of AA-SRM is reduced by approximately 20%
compared with that of SS-SRM. In addition, as shown in Fig.11(b),the iron loss of AA-SRM is reduced by approximately 75%
compared with that of SS-SRM. Note that the increase in the ironloss of AA-SRM decreases at high output, i.e. Wi / Pout_m becomeslow. This is because the increase of the magnetic density decreases
at high output due to the magnetic saturation of the amorphous alloy.
In addition, the increase in the iron loss increases at low output, i.e.
Wi / Pout_m becomes high. In the current hysteresis control with aconstant hysteresis width, the iron loss due to the switching of theinverter is almost same, i.e. the influence becomes relatively large
in the low output.
Fig.12 shows the comparison result of motor loss at rated power(70W). As shown in Fig.12, the copper loss of AA-SRM is reducedby 21.9% compared with that of SS-SRM. On the other hand, theiron loss of AA-SRM is reduced by 78.7% compared with that of
SS-SRM. Therefore, it is confirmed that the iron loss reduction
effect of the motor core with the amorphous alloy is high even in
the blanked amorphous alloy.

7

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)

0.95

8
7

AA-SRM
Iron loss Wi [W]Efficiency hm [-]

0.9
0.85
0.8
0.75

SS-SRM

0.7
0.65

Efficiency is leveling off
due to the mechanical loss

0.6
2000

4000
6000
Rotation speed [r/min]

8000

5Error isExperiment approximately 15%

43
2

1p.u.=70W(rated output)

1

0.55
0

FEA

6

0

10000

0

0.2

(a) Not regarding the mechanical loss as a part of the shaft output (Eq.(9))

0.95

Efficiency he [-](a) SS-SRM

SS-SRM

0.7

65.6%

0.65

Iron loss Wi [W]

0.75

83.5%

Improved by 8.3%
Improved by 6.0%

0.6

61.9%
0

2000

4000
6000
8000
Rotation speed [r/min]

SS-SRM

AA-SRM

10
2000

1p.u.=70W(rated output)

4000
6000
Rotation speed [r/min]

8000

0.2

0.4
0.6
0.8
Output Pout_m [p.u.]1

5.4
Comparison results between measurement and FEA
Fig.15 shows the comparison between the measurement results andthe FEA results of the iron losses of (a) SS-SRM and (b) AA-SRM.
As shown in Fig.15, there is an error of approximately 15% between
the measurement results and the FEA results in both SS-SRM and
AA-SRM. These errors will be due to the accuracy of FEA analysis
and the accuracy of measurement results. The characteristics of theblanked SRM is analyzed from the data of the characteristics of theblanked ring cores. However, the impact of the blanking process
will be not always the same as that of the ring core, especially incomplicated parts such as motor teeth. In addition, the iron loss inmeasurement results is the value calculated indirectly from othermeasured values by Eq.(11). However, there are errors in the value
calculated iron loss due to the unconsidered loss such as the strayload loss and the AC copper loss.
Fig.16 shows the separation results of the iron loss of (a) SSSRM and (b) AA-SRM at rated power (70W). The errors between
the measurement results and the FEA results are 15% or less in both
SS-SRM and AA-SRM. In SS-SRM, the eddy current loss is 59.9%,
whereas the hysteresis loss is 40.1% of 5.77W of the total iron loss.
On the other hand, in AA-SRM, the eddy current loss is 25.5%,
whereas the hysteresis loss is 74.5% of 1.23W of the total iron loss.
Therefore, the eddy current loss dominates the iron loss in SS-SRM,
whereas the hysteresis loss dominates the iron loss in AA-SRM. In
general, the eddy current loss dominates the iron loss of the general
high-speed motor as shown in Fig.16(a) since the eddy current loss
is proportional to the square of the electrical frequency. In theamorphous alloy, the eddy current loss is 1/10 and the hysteresis
loss is 1/2 compared with the silicon steel. Therefore, the dominant
eddy current loss at high-speed motor is dramatically reduced.

3

0

0.4

(b) AA-SRM

Reduced byapproximately 75%

2Error isapproximately 15%

Fig. 15. Comparison results of measurement and FEA in all output
range at 10000r/min.

7

4

0.6

0

Fig. 13. Efficiency characteristics of SS-SRM and AA-SRM
in all speed range at 1p.u. torque.

5

FEA

0

10000

(b) Regarding the mechanical loss as a part of the shaft output (Eq.(10))

6

1
0.8

0.2

0.55

Iron loss Wi [W]Experiment

1.2

0.85
0.8

1

1.4

90.4%

AA-SRM

0.9

0.4
0.6
0.8
Output Pout_m [p.u.]

10000

Fig. 14. Iron loss characteristics of SS-SRM and AA-SRM
in all speed range at 1p.u. torque.
Fig.13 shows the motor efficiency characteristics of SS-SRM and
AA-SRM in all speed range at 1p.u. torque. The mechanical loss is
not regarded as a part of the shaft output (i.e. use of Eq.(9)) in
Fig.13(a), whereas the mechanical loss is regarded as a part of the
shaft output (i.e. use of Eq.(10)) in Fig.13(b). As shown in
Fig.13(a)(b), the motor efficiency of AA-SRM is higher than thatof SS-SRM in all speed range. In addition, as shown in Fig.13(a),the motor efficiency is leveling off at approximately 10000 r/min
due to the mechanical loss. As shown in Fig.9(b), the motor
efficiency of AA-SRM is improved by 8.3% compared with that of
SS-SRM at 10000r/min, while the motor efficiency of AA-SRM is
improved by 6.0% compared with that of SS-SRM at 2000r/min.
Therefore, the efficiency improvement thanks to the low iron loss
characteristic of the amorphous alloy becomes greater at higher
speeds.
Fig.14 shows the iron loss characteristics of SS-SRM and AASRM in all speed range at 1p.u. torque. The iron loss of AA-SRM
is reduced by approximately 75% compared with that of SS-SRM
in all speed range.

8

IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)6.

Conclusion

7

(3)

(4)

(5)

(6)

(7)

(8)

(9)

Iron loss [W]59.9%of the total

4
3

1.03

Eddy (rotor)

2.94

Eddy (stator)

0.61

Hys (stator)

2.05

Hys (stator)

5.77

2

40.1%
of the total

0
MeasureFEA(a) SS-SRM

1.4
Error: 13.1%

Iron loss [W]

1.2

1

25.5%
of the total

0.8
0.6

1.23
74.5%
of the total

0.4

0.07
0.20

Eddy (rotor)
Eddy (stator)

0.19

Hys (stator)

0.61

Hys (stator)

0.2
0MeasureFEA(b) AA-SRM

Fig. 16. Iron loss separation results of rated power (70W) at
10000r/min.

(10)

(11)

(12)

(2)

5

1

References(1)

Error: 14.9%

6This paper provided the characteristics of the ring cores and theswitched reluctance motors (SRMs) made by blanking (a)20HX1300 of the high grade low-iron-loss silicon steel (0.20mm
thickness) and (b) 2605SA1 of the amorphous alloy (0.025mm
thickness). The blanking of the amorphous alloy is an innovativetechnology for the mass production of the high efficiency
amorphous-alloy-motor. The impacts of the processing methods onthe magnetic properties were evaluated with the ring coresprocessed by two methods: the wire cutting and the blanking. On
the other hand, the experiment with the SRMs processed by theblanking evaluated the characteristics depending on the material.
As first prototype, 70W-SRM (40mm thickness) was manufactured
by blanking 1600 sheets of the amorphous alloy and adhesively
laminating them. These experiments reveal the following
characteristics of the entire motor by blanking the amorphous alloy:(ⅰ) the amorphous alloy is expected to be 1/10 of the eddy current
loss and 1/2 of hysteresis loss compared with the silicon steel
according to the measured parameters of Steinmetz equation.
(ⅱ) the hysteresis loss is expected to dominate of the iron loss inthe amorphous ally motor even with the high speed operation.
(ⅲ) the blanking of the amorphous alloy impacts the hysteresis
loss rather than the eddy current loss, which is the important factor
for the high efficiency with the high speed operation.
(ⅳ) the blanking of the amorphous alloy is expected to increase
the hysteresis loss by 23.0% according to the measured parametersof Steinmetz equation, which is not a serious problem in practicaluse.
(ⅴ) the iron loss of the amorphous-alloy-SRM was greatly
reduced by compared with that of the silicon-steel-SRM. In addition,
the motor efficiency of the amorphous-alloy-SRM is improved
compared with that of the silicon-steel-SRM.

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Takahiro Kumagai(Student
member)received the B.S. degree in electrical, electronics andinformation engineering from Nagaoka University ofTechnology, Niigata, Japan, in 2017, where he iscurrently working toward the Ph.D. degree. He is a
student member of IEEJ and IEEE. His current
research focuses on the driving method and the motor
design method for switched reluctance motor.
Hirotaka Sakurai(Student
member)received the B.S. degree in electrical, electronics andinformation engineering from Nagaoka University ofTechnology, Niigata, Japan, in 2021. He has beenwith Nagaoka University of Technology as a M.S.
course student in electrical, electronics andinformation engineering. He is a student member of
IEEJ and IEEE.
Taisuke Shioi(Student
member)received the B.S. degree in electrical, electronics andinformation engineering from Nagaoka University ofTechnology, Niigata, Japan, in 2020. He has beenwith Nagaoka University of Technology as a M.S.
course student in electrical, electronics andinformation engineering. He is a student member of
IEEJ and IEEE.
Hirotaka kato(Student member) is
currently working for the B.S. degree in electrical,
electronics and information engineering from
Nagaoka University of Technology, Niigata, Japan.
He is a student member of IEEJ.

Jun-ichi Itoh
(Seniormember)received his M.S. and Ph.D. degree in electrical andelectronic systems engineering from Nagaoka
University of Technology, Niigata, Japan in 1996,
2000, respectively. From 1996 to 2004, he was with
Fuji Electric Corporate Research and Development
Ltd., Tokyo, Japan. He was with Nagaoka Universityof Technology, Niigata, Japan as an associate
professor. Since 2017, he has been a professor. His research interests arematrix converters, dc/dc converters, power factor correction techniques,energy storage system and adjustable speed drive systems. He received IEEJ
Academic Promotion Award (IEEJ Technical Development Award) in 2007.
In addition, he also received Isao Takahashi Power Electronics Award in
IPEC-Sapporo 2010 from IEEJ, 58th OHM Technology Award from The
Foundation for Electrical Science and Engineering, November, 2011,
Intelligent Cosmos Award from Intelligent Cosmos Foundation for the
Promotion of Science, May, 2012, and Third prize award from Energy
Conversion Congress and Exposition-Asia, June, 2013. Prizes for Scienceand Technology (Development Category) from the Commendation for
Science and Technology by the Minister of Education, Culture, Sports,
Science and Technology, April 2017. He is a senior member of the Instituteof Electrical Engineers of Japan, the Society of Automotive Engineers ofJapan and the Institute of Electrical and Electronics Engineers.

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IEEJ Trans. ●●, Vol.●●, No.●, ●●●Evaluation of Blanked-Amorphous-Alloy-SRM (Takahiro Kumagai et al.)Keisuke Kusaka(Member) received
the B.S. and M.S. degrees in electrical, electronics
and information from Nagaoka University ofTechnology, Niigata, Japan in 2011, 2013,
respectively. From 2015 to 2016, he was with Swiss
Federal Institute of Technology in Lausanne (EPFL),
Switzerland as a trainee. In 2016, he received the
Ph.D. degree in energy and environment science from Nagaoka Universityof Technology. He was with Nagaoka University of Technology, Niigata,Japan as a researcher from 2016 to 2018. Since 2018, he has been with
Nagaoka University of Technology, Niigata, Japan as an assistant professor.
His current research interests include the areas of IPT systems and highfrequency converters. He is a member of Institute of Electrical Engineers ofJapan, Society of Automotive Engineers of Japan and the IEEE.
Takashi Yamaguchi(Non-Member)iscurrently Chief Executive Officer with Yamaguchi
Manufacturing Co., Ltd. He is engage in precisionmold manufacturing and precision press processing.

Masayuki Nakagawa(Non-Member) joined
Industrial Research Institute of Niigata Prefecture in
1996. He currently belongs to the Research andDevelopment Center. He is engaged in measurement
and analysis work requested by companies, including
research on metal joining and surface modification.

Daisuke Sato
(Member) received
the B.S. and M.S. degrees in electrical, electronics
and information from Nagaoka University ofTechnology, Niigata, Japan in 2012, 2014,
respectively. In August 2016, he established
Nagaoka Motor Development Co., Ltd. In 2017, hereceived the Ph.D. degree in energy and environment
science from Nagaoka University of Technology. His
current research interests include the areas of rotating machines.

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IEEJ Trans. ●●, Vol.●●, No.●, ●●●