INDUSTRIAL MATERIALS

Thin and High-Torque Axial Gap Motor Using Soft Magnetic Powder Cores

Asako WATANABE*, Tatsuya SAITO, Tomoyuki UENO, Hijiri TSURUTA, and Yuichi NAKAMURA

------Axial gap motors have been attracting attention as demand increases for thinner motors with a higher output. However, radial motors using laminated sheets remain dominant in the market, and the use of axial gap motors is still limited due to the difficulty in producing three-dimensional magnetic cores with laminated steel sheets. We have built an axial gap motor using soft magnetic powder cores that feature magnetic isotropy and high design flexibility. The motor offers high torque and cost efficiency compared with a conventional radial motor of the same size. ------Keywords: soft magnetic powder core, motor, axial gap, thin, high torque

1. Introduction 2. Overview of the Soft Magnetic Powder Core Due to a rise in the number of electric vehicles, The SMPC is made by compacting soft-magnetic performance advancement in electric appliances, and the powder coated with a very thin insulation film. Pure automation of factory work, motors that are the driving powder and ferrous powder are suitable for producing parts of these products and systems have been playing an soft-magnetic powder as they show high flux increasingly important role. The number of motors installed density*2 and high plastic deformation capacity when in vehicles is also increasing, mainly due to the growing compacted. Compacting this powder, in which each particle popularity of electric vehicles, but also because of the is insulated, to a high density creates an excellent soft conversion to electronic parts in gasoline-engine vehicles. , providing both high flux density and high elec- For example, cooling water pumps and cooling air fans are trical resistance at the same time. Table 1 shows the equipped with auto start/stop systems to keep the engine features of an SMPC compared to a core made of magnetic temperature low while the engine is not running. Not only steel sheets. Unlike the made of magnetic the number of motors but also that of vehicle components steel sheets, the core made of soft magnetic powder is in general is rising. This makes the space available for magnetically isotropic and, therefore, magnetic paths can actual motors increasingly small. One of the most effective be formed in any directions. Also, usage of powder enables solutions is to decrease the motor’s profile. However, the net-shape production*3 of the core through powder injec- currently most common motor is a radial gap motor tion into a variety of mold shapes. With this method, the (RGM), and if an RGM is made thinner, its torque is core can be shaped with a great freedom compared with reduced. To work on this problem, an axial gap motor when using magnetic steel sheets, making it suitable to (AGM) has come into focus as it is thin and delivers high create the wider shape of core needed for an AGM. The torque. A motor consists of a soft magnetic core, magnets, Japanese Industrial Standards (JIS) define magnetic proper- copper wire, and bearings. For an AGM, the soft magnetic ties for magnetic steel sheets. However, measurements are core needs to be designed with a three-dimensional taken for an individual sheet before it is layered, and it is approach. Magnetic steel sheets*1 have been traditionally used to produce the motor core; however, it is difficult to produce an AGM core using magnetic steel sheets. This is Table 1. Feature of soft magnetic powder core why the commercial adoption of AGMs has been limited. Soft magnetic Magnetic steel sheets To address this issue, Sumitomo Electric Industries, Ltd. powder core (conventional material) has created an AGM adopting a soft magnetic powder core Compacting powders Laminated sheets covered with insulating film coated by insulating layer (SMPC), which is easily shaped and isotopically magne- Low Joule heat along High Joule heat in plane tized compared with magnetic steel sheets. In tests, a thin any direction perpendicular to B B B AGM prototype with an SMPC demonstrated higher torque Schematic and higher efficiency compared with an RGM. This paper illustrations describes the features of the SMPC and performance assessment of the AGM prototype with the SMPC. We also Fe, Fe-Si, etc Fe-Si sheet Insulating film Insulating layer introduce our development efforts for new components (10~500 μm) (0.05~1.0 mm) and technologies. Magnetic isotropy good poor Shaping flexibility good okay Performance in product good okay/poor AC-magnetic propertiy good okay

106 · Thin and High-Torque Axial Gap Motor Using Soft Magnetic Powder Cores known that there are gaps between the design values and 3-2 Magnetic properties of the soft magnetic powder actual measurements of motor performance.(1),(2) This is core for the motor because the magnetic properties deteriorate due to the An SMPC for a motor is required to have high deformation caused by stress and thermal warping that magnetic flux density for an increased torque and low energy occur in press-cutting, caulking, and welding. On the other loss in the core (core loss) for improved work efficiency. hand, the magnetic properties of an SMPC are measured HB2, which is one of Sumitomo Electric’s SMPC grades, with a test piece created using the same compaction achieves high magnetic flux density and low core loss as a method as the final product. Thus, the gaps between the driving motor. This section describes the magnetic proper- design values and actual measurements of the motor’s ties of the HB2. Figure 2 shows the DC magnetization performance are small. Further, an SMPC with a high elec- curves of the HB2. Compared to the model made of trical resistance bears excellent high frequency properties. magnetic steel sheets, the HB2 has high magnetic flux Such SMPCs have been increasingly used in mass- density in a high magnetic field, retaining high perfor- produced high frequency products, such as fuel injection mance without having magnetic saturation. Next, compari- valves in diesel engines and boost converter reactors for sons of the core loss characteristics of the HB2 and a core electric vehicles.(3)-(5) In the same way, the SMPC used in a made of magnetic steel sheets are shown in Fig. 3. One of motor can suppress energy loss from the high-frequency noise generated by an inverter. Magnetic steel sheet: JIS 35A360 2.5 Magnetic steel sheet SMPC(HB2) (Single sheet test result)(6) 3. Application to Axial Gap Motors ]

[T 2.0 y 3-1 Overview of axial gap motor Magnetic steel sheet ns i t

e 1.5 (Toroidal piece test result)

An AGM is characterized by its thinness and high d x

torque. A structural diagram of an AGM is shown in Fig. 1. fl u

ic 1.0 In a commonly used RGM, and a rotor are posi- t e

tioned cylindrically, while in an AGM disc-shaped stators ag n and rotors are laid out in layers orthogonally around the M 0.5 rotating shaft. In a thin RGM, the facing area between the stators and the rotor is reduced, causing a reduction in 0.0 0 50 100 150 torque, whereas an AGM keeps the area unchanged, Applied magnetic field [kA/m] thereby maintaining a high torque. The following section explains the soft magnetic core Fig. 2. DC magnetization curve s of soft magnetic powder core for a motor of the motor . An RGM magnetic core can easily be produced using magnetic steel sheets as the magnetic paths in the RGM are two dimensional. On the other hand, in the Magnetic steel sheet: JIS 35A360 double-stator AGM shown in Fig. 1, three-dimensional Bm = 1.0 T Loss becomes larger due to processing of magnetic steel sheets magnetic paths need to be created between the rotor and 140 the two stators. It is very difficult to produce the magnetic Magnetic steel sheet core 120 (Measured with a toroidal test piece) core for this AGM using magnetic steel sheets as each g] sheet needs to be cut to a different width and the layering k 100 SMPC (HB2) has to be vertical rather than horizontal. Usage of powder 80 s [ W /

offers a highly flexible shaping capability and magnetic lo s

60 isotropy, which in turn delivers high productivity and high performance. Cor e 40 20 Magnetic steel sheet (Single sheet test result)(6) 0 Axial gap motor Radial gap motor 0 200 400 600 800 1000 Bm = 1.6 T Frequency [Hz] (Double-stator structure) Disk-shaped (IPM) Magnet poles magnetic poles are cylindrical 350 Magnetic steel sheet core Low profile & Making low 300 (Measured with a toroidal test piece) high torque profile reduces

power output g] 250 k Soft magnetic Magnet / SMPC (HB2) (Stator) W core (Stator) [ 200 Coil Coil s

Magnet (Rotor) lo s

150 Soft magnetic Magnetic core structural diagram core (Stator)

Cor e 100 Magnet core All sheets are Top view press-cut in 50 the same shape Magnetic SMPC →Laminated steel sheets 0 Flexible shaping Layering sheets all in different shapes ⇒ Easy shaping Easy to produce using magnetic steel sheets 0 200 400 600 800 1000 ⇒ Difficult shaping Frequency [Hz]

Fig. 1. Motor structures Fig. 3. Core loss characteristics of soft magnetic powder core for a motor

SEI TECHNICAL REVIEW · NUMBER 86 · APRIL 2018 · 107 the comparative items for the HB2 was a test piece made of magnetic flux of the stators to pass through the magnets, layers of 0.35-mm-thick magnetic steel sheets (JIS causing eddy currents by the electromagnetic induction 35A360), which are commonly used in motors, in a inside the Nd-sintered magnets of a low electrical resistance. toroidal form. Compared to this, the HB2 has excellent On the other hand, the AGM with Nd-bonded magnets characteristics in a high frequency condition and a high showed better overall efficiency with higher output (torque) magnetic flux condition. For example, the HB2 achieves despite a larger loss than that of the RGM. This is because 40% less core loss at Bm = 1.6 T/1kHz compared to the the high electrical resistance of the Nd-bonded magnets magnetic steel sheet core. suppresses the generated eddy currents. Sumitomo Electric provides the performance data of The above results suggest that the AGM with the the HB2 and other SMPC products, including temperature SMPC and Nd-bonded magnets is the best candidate to characteristics between –30°C and 150°C, to JMAG- achieve high torque and high efficiency as a thin motor. Designer. This data can then be utilized in the design and Figure 6 shows the relationship between the aspect ratio analysis of motors and electromagnetic components. and torque of the AGM with the SMPC and Nd-bonded 3-3 Design and appraisal of axial gap motor magnets and the RGM. In our analysis, we set the motor (1) Electromagnetic analysis and design of axial gap motor As described in the previous section, the HB2 is Sumitomo Electric’s low core-loss SMPC for motors. We 1.6 obtained actual performance data of the HB2 and compared Axial gap motor 1.4 (SMPC it with that of an RGM, which uses a core made of Average tor que 1.44 Nm, ripple 9.7% 1.2 + Nd sintered magnet) magnetic steel sheets. Both motors employed a permanent Axial gap motor magnet structure. The AGM was equipped with two stators 1.0 (SMPC [ N m] Average torque 1.15 N m , ripp le 6.7%

e + Nd bonded magnet) 0.8 along with a coreless rotor in which magnets were fixed on u i l Radial gap motor or q 0.6 Averag e torqu e 0.75 Nm, ripple 3.4% a non-magnetic support disc. The RGM was an inner-rotor T (Magnetic steel sheets IPM motor. The motor design specifications in this 0.4 +Nd sintered magnet) comparison were as follows: 0.2 1) Volume occupied by motor: 0.392 L 0.0 2) Magnet weight: 89.2 g 0 15 30 45 6 0 75 9 0 105 120 135 Ro tatio nal angl e [deg] 3) Coil space factor: 40% 4) Number of poles: 10; Number of slots: 12 Fig.4. Analysis results of instantaneous torque waves The above volume occupied by the motor is obtained by multiplying the external diameter by the height of the motor. The height of the RGM is the distance between the 140 98 top and bottom ends of the coil. Materials for the compo- 120 Efficiency Core loss 93 nents (other than the SMPC) were as follows: Magnetic 100 (Stator) steel sheets: JIS 35A360; Neodymium (Nd) sintered ] [% ]

W 80 4 y [ magnet:* NMX-37SH produced by Hitachi Metals, Ltd. c

s 88

(Data taken at Br = 1.14 T and 80°C); Nd bonded 60 ie n c 5 Lo s Core loss

magnet:* S5B-17ME produced by Aichi Steel Corporation E ffi 40 (Rotor) (Data taken at Br = 0.81 T and 80°C). 83 Two types of AGMs and an RGM were used for the 20 Copper loss comparison. One AGM was equipped with an SMPC and 0 78 Radial Axial: Nd bonded Axial: Nd sintered Nd sintered magnets for the rotor. The other AGM was Magnet Nd sintered Nd bonded Nd sintered Magnetic Core Magnetic powder core equipped with an SMPC and Nd-bonded magnets for the steel sheets Radial rotor. The RGM was made of magnetic steel sheets and Axial gap motor Nd-sintered magnets. Each motor was designed to be a thin Gap motor at an aspect ratio of 0.376 (outer diameter of 110 mm and Fig. 5. Loss and efficiency analysis results for each motor height of 41.3 mm). We first analyzed the electromagnetic fields of the AGMs and the RGM. The analysis conditions were as follows: operating temperature 80°C; rotation 1.4 Magnetic powder core + Nd bonded magnets 2 6,000 rpm; and current density 4 Arms/mm . Figure 4 1.2 1.15 Nm Axial gap motor shows the analysis results of instantaneous torque waves. 1.0 ]

The AGM that employed an SMPC and Nd-sintered m

N 0.8 [ Radial gap motor magnets showed nearly twice the torque of the RGM. The e 0.75 Nm Magnetic steel sheets u 0.6 AGM that employed Nd-bonded magnets, which have + Nd sintered magnet D

or q D weaker magnetic power, still showed 1.5 times more torque T 0.4 Axial gap motor Axial gap motor L L (D=85) than the RGM. These results demonstrate that this axial 0.2 (D=110) structure offers significantly improved torque even in a thin 0.0 design. Figure 5 summarizes the analysis results for both 0.3 0.376 0.5 0.7 0.814 0.9 the loss and efficiency of each motor. The AGM with Aspect ratio (L/D) Nd-sintered magnets showed a very large rotor loss. This was due to the coreless rotor in the AGM, which allows the Fig. 6. Torque and aspect ratio of each motor

108 · Thin and High-Torque Axial Gap Motor Using Soft Magnetic Powder Cores volume to be constant and varied the aspect ratio. In the possible to create the core as a single piece. Table 2 lists RGM, the torque is reduced by about 30% as the shape the appraisal results for the actual products. Although the becomes thinner. The AGM, however, retained high torque AGM prototype used the Nd-bonded magnets that have even with a low aspect ratio. The torque of the AGM weaker magnetic power, still it showed 1.6 times higher surpasses that of the RGM at an aspect ratio of 0.75. This torque than that of the RGM. The AGM’s efficiency was result suggests that the thinner the shape, the higher the superior to that of the RGM in all areas of frequency from torque efficiency in the AGM. the high-rotation and high-load area, where benefits from (2) Performance data of actual axial gap motor the SMPC are most obvious, to the low-load area. The total We then built the actual motors and examined their maximum efficiency was improved by 1%. The overall performance. Figure 7 lists all the production motors. The performance results of the actual motors confirmed that the motor was made to be thin at the same aspect ratio as the thin- AGM with an SMPC achieved high torque and high analysis model: 0.376 (outer diameter of 110 mm and efficiency, proving its excellent motor performance. height of 41.3 mm). The AGM employed Sumitomo Note that the results described in this section are Electric’s HB2 SMPC and Nd-bonded magnets, and the obtained from the joint research undertaken with RGM employed JIS 35A360 magnetic steel sheets and Masatsugu Takemoto, Associate Professor, Graduate Nd-sintered magnets. Figure 8 shows the SMPC compacted School of Information Science and Technology, Hokkaido specifically for this motor used in the performance test. University. The net-shape method simplified the core production despite its complicated form comprising teeth and back yoke. This core was made from six pieces as production Table 2. Performance results for the production motors motor also served as a trial for segment production, which Axial gap motor Radial gap motor will be used in the future commercialization of large high- Φ110×41.3 ←(Same aspect Motor dimensions (Aspect ratio power motors, such as driving motors. Note that it is also ratio) 0.376, thin shape) Magnetic steel SMPC Core sheets (HB2) (35A360) Axial gap motor Nd bonded Nd sintered Magnet Nd bonded Supporter Outer diameter: 110 mm (S5B-17ME) (NMX-37SH) (S5B-17ME) (SUS304) Analysis 1.23 (Nm) 0.81 (Nm) Torque*1 Measurement 1.18 (Nm) 0.74 (Nm)

S Max. Analysis 94.8% 93.8% Coil value Measurement*2 94.1% 93.1% N N S Efficiency Low Analysis 88.0% 87.3% SMPC: HB2 3 Load* 2 Rotor Stator Measurement* 87.5% 87.3% *1 Measurement condition: 1000 rpm, 4 Arms/mm2, *2 Mechanical loss was deducted by using a dummy rotor, Radial gap motor *3 Measurement condition: 1000 rpm, 0.3 Nm Core Nd sintered Coil Magnetic steel (35A360) (NMX-37SH) sheets: 35A360

4. Future Prospects for New Materials and Technology Shaft 4-1 Reduction of core loss and strengthening of soft (S45C) Outer diameter: 110 mm magnetic powder core Rotor Stator Improvement in the material properties of the SMPC is essential to achieve even better AGM performance. One Fig. 7. Production motors such material improvement is core loss reduction. The core loss performance of Sumitomo Electric’s new HX3 core is shown in Fig. 9. The HX3 realized lower core loss than the HB2 by controlling the composition of the metal powder and creating a super-thin insulation coating using the company’s exclusive technology. The performance results of the HX3 compare well with not only the actual measure- ment figures of the popular 0.35 mm-thick magnetic steel 1/6 of total component sheets, but also with those made of 0.3 mm- or 0.2 mm-thin Teeth sheets. Therefore, the HX3 core will surely contribute to improved motor efficiency. Back yoke Another motor performance improvement factor is the strengthening of the core. Figure 10 shows the strength comparison between the improved core and Sumitomo Fig. 8. Soft magnetic powder core for an axial gap Electric’s HB1. We improved the strength of the core by

SEI TECHNICAL REVIEW · NUMBER 86 · APRIL 2018 · 109 reducing the breaking points on the core surface through smoothing treatment and by suppressing crack formation 1.2 mm thick toroidal through internal hole structure control. The following (Outer diameter 50.0 mm, inner diameter 47.6 mm, three-point flexural test revealed that the core elasticity had height 15.0 mm) been improved 1.6 times over the HB1 and with three times better tensile strength. The strength improvement enhances 0.8 mm thick toroidal core shaping flexibility. For example, it is extremely diffi- (Outer diameter 20.0 mm, inner diameter 18.4 mm, cult to produce is a 0.8 mm-thin core using magnetic steel height 15.0 mm) sheets, however, it can easily be produced with magnetic powder as shown in Fig. 11.

Fig. 11. Thin wall soft magnetic powder core

0.35 mm magnetic steel sheet: JIS 35A360 0.30 mm and 0.20 mm magnetic steel sheet: 30HX1600 and 20HTH1200 produced by Nippon Steel & Sumitomo Metal Corporation 4-2 Insulation coating technology Bm = 1.0 T To install coils around the soft magnetic core for a 350 motor, the dielectric strength between the core and coil 300 0.20 mm sheets needs to be maintained using insulation paper or resin. ] actual value 250 However, such insulation is usually several hundred μm /k g 0.30 mm sheet

W actual values

[ 200 thick, which reduces the coil space factor and keeps the 0.35 mm sheets coil and core distance rather large, thereby reducing the o ss 150 actual value l motor power. Also, the said distance hinders thermal dissi- 100 or e

C pation from the coil to the core, limiting the maximum 50 0.20 mm single sheet test value(6) current, and this becomes a bottleneck to motor power 0 improvement. The effective solution to this problem is 0 500 1000 1500 2000 Frequency [Hz] insulation coating over the magnet core surface. Figure 12 shows an appearance view of the insulation-coated motor Bm = 1.7 T magnet core and a section view of the edge between the 350 core and the coat. The coat thickness is approximately 50 300 0.20 mm sheets actual value μm and the dielectric strength is 2,500 V at maximum. ] 250 0.30 mm sheets Thus, this thin coating technology with high dielectric /k g actual value strength further improves motor power by eliminating the W 200 [ 0.35 mm sheets 150 insulation components and increasing the coil space factor.

o ss actual value l

100 or e C 50 0 0 200 400 600 800 1000 Insulation Frequency [Hz] resin Top surface coating

Fig. 9. Core loss reduction in soft magnetic powder core for a motor*6

Internal wall Three-point bending strength Tensile strength 160 80 a]

P Fig. 12. Insulation coating appearance and section view

[ M 140 70 a ] P

g th 120 60 M n [

100 h 50 st r e g t n g 80 40

i n 4-3 Electromagnetic analysis and design of the motor d st r e

n 60 30 e This section explains the purpose for Sumitomo

40 ns il e 20 Electric, a manufacturer and seller of SMPCs, to conduct e T oi nt b p

- 20 10 electromagnetic analysis and design of an AGM. The shape e

r e 0 0 of an axial core is usually determined based on the h

T SEI standard Improved SEI standard Improved (HB1) (HB1) optimum electromagnetic design and does not take account of the actual production process due to the complexity of Fig. 10. Improvement of soft magnetic powder core's strength for a motor three-dimensional magnetic paths, which tends to cause problems in commercialization. It is, therefore, necessary to establish a design method to attain high motor perfor- mance in an easily producible form. When consideration to producibility and impact assessment (electromagnetic anal-

110 · Thin and High-Torque Axial Gap Motor Using Soft Magnetic Powder Cores 6. Acknowledgements ysis) of the actual motor performance are handled by different organizations or companies, it can take an We would like to express our appreciation to extended period of time to reach the optimum design as the Associate Professor Takemoto, Graduate School of two organizations may require a number of discussions and Information Science and Technology, Hokkaido University, subsequent adjustments. Sumitomo Electric has built its for his guidance and cooperation concerning the electro- own electromagnetic analysis technology in order to design magnetic analysis and performance appraisal of the motors. the optimum shape of axial magnet cores with a minimum time span. The company also offers a service to produce a motor based on given specifications (e.g. required torque, number of rotations, and size) through our exclusive elec- Technical Terms tromagnetic analysis and design. Figure 13 presents sample ＊1 Magnetic steel sheet core: A soft magnetic core made performance data of an actual motor produced based on our of layers of thin iron- alloy sheets. The thinner analysis and design. With the above service, we can the sheet thickness, the lower the core loss; however, quickly offer the benefits of an AGM with an SMPC, such producibility is also lowered, making production as profile reduction and torque improvement, to a wide more expensive. market. ＊2 Saturation flux density: The maximum magnetic flux density that can be generated in a magnetic material (the amount of magnetic flux per unit area). As the saturation flux density becomes higher, the smaller Torque properties Loss and efficiency analysis results the core size that can be produced. 5.0 90 Efficiency: 92.3% ＊3 Net-shape production: Powder metallurgy (metal- 80 4.0 forming technology) that produces a complicated

] 70 Copper loss m

] 60 form of a complete work without mechanical or other N 3.0 [

W [ e 50 post formation processing. u s 2.0 40 Rotor magnet loss

or q ＊4 Nd-sintered magnet: A magnet made of Nd magnetic Lo s T 30 ( loss) 1.0 powder with its density increased to almost 100% 20 Core loss (true density) through high heat treatment. The 0.0 10 (Stator) 0 2 4 6 8 10 12 0 magnetism is very high but the producible shapes are Current density [Arms/mm2] limited and post-processing is indispensable, therefore, production becomes expensive. The Fig. 13. Performance analysis results of AGM designed by Sumitomo Electric electrical resistance is low as it is bulk metal. ＊5 Nd-bonded magnet: An injection-molded or pressure- formed magnet made from kneaded Nd-magnetic powder and resin. Its magnetism is less than that of a 5. Conclusion sintered magnet, as the density of the bonded magnet This paper described performance analysis of an is lower. However, it has more flexibility in shaping, AGM using a SMPC and a performance appraisal using an and insulation from the resin provides high electrical actual AGM produced based on the analysis. resistance. A summary of the said performance analysis and appraisal results is as follows:

1. The SMPC has excellent features in (1) magnetic References isotropy, (2) shaping flexibility, (3) performance of (1) M. Yabumoto et al., Electrical Steel Sheet for Traction Motors of the production model, and (4) high frequency prop- Hybrid/Electric Vehicles, NIPPON STEEL TECHNICAL REPORT No. 87 pp.57-61 (July 2003) erties. (2) T. Wakisaka at el., Electrical Steel Sheet for Traction Motor of Hybrid/ 2. As a result of electromagnetic analysis, the AGM Electrical Vehicles, NIPPON STEEL TECHNICAL REPORT, No.103, with the SMPC and Nd-bonded magnets delivered pp.116-120 (May 2013) high torque and high efficiency at the same time. (3) Y. Shimada at el., Development of High-Performance P/M Soft 3. The lower the aspect ratio (i.e. the thinner the Magnetic Material, J-Jpn. Soc. Powder Powder Metallurgy, Vol.53, No.8, pp.686-695 (August 2006) shape), the higher torque efficiency deriving from (4) N. Igarashi at el., Pure Iron Based Magnetic Composite Core That the axial structure. Enables Downsizing Automotive Reactors, SEI Technical Review, No. 4. As a result of the actual motor performance 80, pp. 98-103 (April 2015) appraisal, the AGM achieved 1.6 times higher (5) T. Ueno at el., Development of a Soft Magnetic Powder Core with Distinct Magnetic Characteristics, Examples of Its Practical torque than the RGM made of magnetic steel sheets Applications, and Future Outlook, SEI Technical Review, No.82, pp.1-7 and Nd-sintered magnets. The AGM also showed (April 2016) better efficiency in all frequency zones. (6) NIPPON STEEL & SUMITOMO METAL, NON-ORIENTED 5. Sumitomo Electric has built a motor analysis and ELECTRICAL STEEL SHEETS catalog pp.25 design method alongside the development of mate- rials with better performance and better added value. This will contribute to the performance improvement of motors with SMPCs.

SEI TECHNICAL REVIEW · NUMBER 86 · APRIL 2018 · 111 Contributors The lead author is indicated by an asterisk (*).

A. WATANABE* • ‌Assistant Manager, Human Resources Division (Former Assistant Manager, Advanced Materials Laboratory)

T. SAITO • ‌Dr. Eng. Advanced Materials Laboratory

T. UENO • ‌Dr. Eng. Group Manager, Advanced Materials Laboratory

H. TSURUTA • ‌Sumitomo Electric Sintered Alloy, Ltd.

Y. NAKAMURA • ‌Group Manager, Analysis Technology Research Center

112 · Thin and High-Torque Axial Gap Motor Using Soft Magnetic Powder Cores