Historical Evolution of Motor Technology
38
Historical Evolution of Motor Technology
Hiroyuki Mikami, Dr. Eng.
Kazumasa Ide, Dr. Eng.
Yukiaki Shimizu
Masaharu Senoo
Hideaki Seki
OVERVIEW: Driven by a strong desire to produce electric motors using
domestic rather than foreign technology, Hitachi’s founder, Namihei Odaira,
produced three 5-HP electric motors in 1910. Now, a century later, electric
motors incorporate a variety of different technologies and have undergone
significant changes in their size, performance, and other features. They have
become a key device that underpins society in a wide range of fields including
power generation, industry, transport, and home appliances.
INTRODUCTION
2010 marked the 100th anniversary of Hitachi’s
formation and it is widely known that the company’s
first product was a 5-HP (horse power) induction motor
(see Fig. 1). Although most electric motors in Japan
at the time were imported from overseas, Hitachi’s
founder, Namihei Odaira, embarked on development
driven by a strong desire to produce electric motors
using his team’s own technology developed locally
in place of foreign technology. After overcoming
numerous technical challenges, the result was
three 5-HP motors produced in 1910. This was the
beginning of Hitachi’s activities in the field of electric
motors as well as its starting point in motor technology
development.
Now, a century later, the electric motor has become
a key device that underpins society in a wide range of
fields including power generation, industry, transport,
and home appliances (see Fig. 2). In particular,
in conjunction with advances in microelectronics
technology and power semiconductor devices since
the 1980s, rapid progress has been made in the field
of inverters (a form of electrical conversion system)
and the drive control systems that combine inverters
with motors. Along with control functions that have
made it possible to supply motors with operating
characteristics tailored to specific system applications,
it also seems likely that this progress was helped along
by the desire for greater energy efficiency. Almost all
power generation involves the use of generators and
electric motors are widely used as power sources in
factories, railways, and home appliances, and even
in vehicles and data processing equipment. It is also
widely known that motors account for approximately
Field
Application
Output (W)
1
10
100
1k
10k 100k 1M 10M 100M 1G
EPT (main motor)
Automotive
(HEV)
Auxiliary
(EPS, pump, etc.)
Household AC
Home
appliances
Refrigerator
Washing machine
Vacuum cleaner
General purpose
(pump, blower, etc.)
Industrial
Fig. 1—5-HP (horse power) Induction Motor.
After building up experience and skills through the repair of
electrical machinery, Hitachi produced three induction motors
with an external diameter of approximately 400 mm and a
weight of approximately 150 kg. The motors were designed
by Naosaburo Takao (who later became Vice-President) and
manufactured from parts made using a sheet steel processing
machine imported from the UK and a coil winding machine
they built themselves.
Elevator
Railroad
Steel mill
Power
systems
Wind power
Thermal power
EPT: electric power train HEV: hybrid electric vehicle
EPS: electric power steering AC: air conditioner
Fig. 2—Examples of Hitachi Electric Motor Products.
Motors and generators have advanced to become key devices
that help underpin society.
39
Hitachi Review Vol. 60 (2011), No. 1
CHANGES IN MOTOR TECHNOLOGY
Fig. 3 shows the history of motors and associated
technology. This history goes back nearly two
centuries to a series of inventions inspired by Faraday’s
laws of electromagnetic induction in the first half of
the 19th century. Because early motors were powered
by batteries, most progress focused on DC (direct
current) motors. This was followed subsequently by
the invention of practical induction, synchronous, and
other AC (alternating current) motors as AC power
technology became more advanced. The principles
behind the motors used today were largely worked
out during the 19th century and they have undergone
steady progress since then by drawing on advances
in the three key enabling technologies of design,
materials, and production techniques.
The 5-HP electric motor described above was also
part of this history of progress. Fig. 4 shows a graph
indicating how the weights of 5-HP motors made by
1830
1900
2000
Hitachi 5-HP induction motors
Motor development at Hitachi
5-HP motor
▲: Steinmetz ▲: Kron coordinate ▲: 2D magnetic analysis
transformation
▲: 3D magnetic
▲: Concordia theory analysis
Systematization
Design
technology
of motor theory
▲: DC generator / Magneto
▲: DC generator /
▲: Electrical steel ▲: Rare-earth
Dynamo
sheet
permanent magnet
▲: AC generator
▲: SMC
▲: Induction motor
▲: Amorphous steel sheet
Invention of “motor”
Material technology
▲: Insulation
▲: High-space-factor winding
Production technology ▲: Segment core
Period of invention
Period of
scientific initiatives
Period of industrial
initiatives
2D: two-dimensional 3D: three-dimensional DC: direct current
AC: alternating current SMC: soft magnetic composite
Fig. 3—History of Motors and Associated Technologies.
The electric motor was invented in the 1830s and underwent
scientific and industrial advances during the 20th century.
5-HP (3.7-kW) 4-pole induction motor
1910
1916
80
60
40
1951
Journal bearing
1955
1963
1970
1991 1994
Ball bearing
Copper
bar rotor
Aluminum
diecast rotor
Class E
insulation
Class A
insulation
Steel plate Aluminum
frame
frame
Cast iron frame
20
0
1935
2001
1977
Total prod. = 20 M Total prod. = 40 M
100
Ratio of mass (%)
40% of all electricity consumption (1) . As well as
playing a major role in industrial progress, it is no
exaggeration to say that rotating machinery in the form
of motors and generators form part of the foundations
of modern society.
This article reviews the historical evolution of
the technology used in electric motors together with
generators, inverter control, and other associated
components, describes examples of work being done
on the ongoing development of motors, and looks at
the outlook for the future.
New
JIS
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Year
JIS: Japanese Industrial Standards
Fig. 4—Changing Mass of Hitachi 5-HP Motor.
Numerous technical developments have made motors smaller
and lighter.
Hitachi have changed over time. The adoption of a
wide range of technologies has reduced motor size
to about one-fifth that of the first motor made back
in 1910 and advances in production techniques have
seen cumulative production pass 45 million motors in
January 2010.
The following sections describe the changes that
have taken place in the key technologies of design
(analysis), materials, and production techniques that
have underpinned the evolution of the electric motor.
Design and Analysis Technologies
This section takes as an example the use of
electromagnetic field analysis in electrical and
magnetic design which is considered the most
important design and analysis technology for motors
and generators.
Fig. 5 plots the progress in electromagnetic
field analysis alongside the changes in the capacity
of turbine generators which are the largest of all
rotating machines. Because conducting studies on
full-scale prototypes is impractical when developing
large generators, electromagnetic field analysis
has played a role in design investigations since the
technique was first invented. Quasi two- and threedimensional analyses were first used in the 1960s and
three-dimensional analysis using the edge-elementbased finite element method is now widely used (2).
Computing speeds have also been improved, not only
because of the obvious improvement in the capabilities
of the computers themselves, but also through the
adoption of a number of computational techniques.
A relationship is evident between this trend and the
Rotor
100
0
eH
0
arm
n
Or
60
Tim
onic
on
ic
250 MVA
70 MVA
Ord
er
3D analysis
Electromagnetic field
Parallel computing
Improvements of edgeelement FEA formulation
108
104
10
Application of FEA
to electromagnetism
Quasi-3D
formulation
Robust algorithms
for solving non-linear
problem
2
1
1960
Invention of edge-element FEA
1970
1980
Year
1990
2000
2010
0
m
End
cover
Spectral force resolution
Base
Structural vibration
Cal. by complete stator model
70
60
50
40
Pick up points
for noise
30
20
0
2,000
4,000
6,000
8,000
10,000
Noise
Frequency (Hz)
Fig. 6—Motor Electromagnetism and Noise Analysis.
Motor noise can be estimated quantitatively based on a
coupled electromagnetic force, structure, and fluid analysis.
analysis, structural analysis, and vibration and noise
analysis and it has become possible in recent years to
analyze motor noise through coupled electromagnetic
force, structure, and fluid analysis (5) (see Fig. 6).
Materials and Production Techniques
Materials and production techniques have made
a major contribution to improvements in motor
performance over recent years. In terms of materials,
mass production of electrical steel commenced in the
1960s and this material was quickly adopted for use
in motors. Similarly, rare-earth magnets invented in
Max. energy
product (kJ/m3)
increase in the capacity of the turbine generators
made by Hitachi, which has utilized electromagnetic
field analysis from its very beginnings, and this
corroborates the role that analysis techniques have
played in increasing capacity.
The ability to use two-dimensional electromagnetic
field analysis to analyze the mechanical movement
of the rotating part of the motor (rotor) dates back
to the latter half of the 1980s. This analysis took a
considerable length of time in those days meaning
that it could not necessarily simulate all the different
motor operating conditions and accordingly it was
only used in a limited way. To eliminate restrictions
like this, Hitachi developed techniques for shortening
the calculation time by taking advantage of the various
cyclic aspects of internal motor operation based on
motor theory(3). These expanded the range of cases that
could be analyzed and allowed a complete cycle of the
waveform to be calculated from analysis information
for a particular region only, including analysis of
situations that combined both long-wavelength
components and very short-wavelength components
as occur in induction motor rotor currents. Based on
analysis techniques like these, it became possible to
calculate losses caused by short-wavelength/highfrequency components that occur due to the motor
structure and to separate fully the electromagnetic
force components associated with each mode and
frequency(4). Progress has also been made on coupled
analysis techniques such as electromagnetic field
60
Cal. by simplified stator model
Meas.
80
p. u.: per unit FEA: finite element analysis
Fig. 5—Advances in Analysis and Design Techniques Relating
to Electromagnetic Field Analysis.
Large and complex analyses have facilitated the development
of motors, generators, and other machines thanks to advances
in the computing environment.
de
r
−60
400
106
Amn
0
Quasi 3D analysis
2D analysis
Relative calculation speed (p. u.)
200
1,120 MVA
800 MVA
940 MVA
800
40
Frame
Stator
1,570 MVA
1,300 MVA
arm
1,200
Conventional 4-pole
Conventional 2-pole
Air-cooled 2-pole
Sp
ac
eH
1,600
Sound pressure level (dBA)
Hitachi turbine generator
Max. capacity (MVA)
Historical Evolution of Motor Technology
480
NdFeB magnet
320
SmCo magnet
160
0
1910
1950
AlNiCo magnet
Ferrite magnet
2000
Air conditioner compressor motor
Stator
Ferrite magnet
Rotor
NdFeB magnet
q-axis
cut
Concentrated
Rotor core
winding
with q-axis cut
Performance 3 kNm/m3, 94% 7 kNm/m3, 95% ← , 95.5%
Feature
Distributed
winding
Thin slot
insulation
← , 96.0%
NdFeB: neodymium iron boron SmCo: samarium cobalt
AlNiCo: aluminum nickel cobalt
Fig. 7—Advances in Motors Due to Rare-earth Magnets.
The invention of the neodymium magnet led to a major step
forward in motor performance.
Hitachi Review Vol. 60 (2011), No. 1
1983 have played a major role in reducing motor size
and improving performance.
Fig. 7 shows the history of permanent magnet
development and advances in permanent magnet
motors. Magnet energy product improves progressively
from ferrite through alnico and samarium-cobalt
magnets. While the most commonly used magnet in
earlier times was the low-cost ferrite magnet, use of
neodymium magnets (the strongest type of magnet)
grew rapidly after their invention. Looking at the
influence these magnets have had on Hitachi’s air
conditioner compressor motors, initially these motors
used ferrite magnet rotors combined with distributedwinding stators. The arrival of the neodymium magnet
saw the adoption of concentrated windings for the
stator and, as shown in the figure, smaller coil end
size. Although coil ends with concentrated windings
are smaller, because they produce large harmonic
components in the magnetic flux distribution, the
stator and rotor shape become important design
considerations. Consequently, advances in the
electromagnetic field analysis techniques described
above have been complementary with those in magnet
materials and have allowed both axial length to be
roughly halved and efficiency to be improved.
One example of production technology is a
technique for achieving a high space factor (winding
density) through use of a split core. Fig. 8 shows an
example of a technique for increasing the density of
wires in the winding slots by using a press-forming
machine to pressure-mold an aligned pre-wound core.
This achieves a high space factor by molding the wire
into the shape of the slot that is to hold the winding
without compromising the insulation performance
High-density wire molding technology
I
Clinging
by energizing
Press die
Winding frame
AC servo motor (2001)
• High space factor: 75%
• High accuracy
roundness: 0.03 mm
of the coil wound around the mold. Technology was
also developed to ensure that the stator core is put
together with a high degree of roundness when it is
separated and reassembled, resulting in small size and
low cogging torque. This technology has been used in
industrial servo motors since 2000 (6).
INVERTER AND DRIVE CONTROL
TECHNOLOGIES
Changes in Variable-speed Systems
Whereas DC motors had previously been the
mainstay for variable-speed motor control, a major
shift to AC motors took place in the 1980s. Fig. 9
shows the history of advances in motor drive control.
The major factors behind these advances are the
performance improvements in microcomputers and
the main circuit elements used in inverters. The main
control method changed progressively to AC motor
vector control and, in terms of precision, response, and
speed range, the performance of AC motors came to
surpass that of DC motors.
Sensorless Control
Fig. 10 shows how vector control of induction
motors has evolved. The general-purpose inverter has
provided the driving force behind induction motor
control technology. Sensorless vector control was
incorporated in general-purpose inverters in 1989.
1960
Motor
• Small size
• Low cogging torque
• High speed response:
500 Hz
State in slot section
Fig. 8—Split Core and Winding with High Space Factor.
Better motor performance was achieved by improving the coil
space factor and the precision of split core assembly.
1970
1980
DCM
Control
circuit
Analog
Sequence control,
PI control
ACM 1.0
Precision DCM
(%)
0.25
Speed DCM
range 1:5
2000
Cycloconverter
PWM invertor
Analog-digital
Digital (microprocessor), ASIC
hybrid
Control
algorithm
Response DCM
(rad/s) 2
1990
ACM (IM, SM)
Power M-G Thyristor Leonard
converter
Performance
Self-bonding wire
41
15 – 20
Vector control
Anti-vibration control
0.05
60
0.01
500 – 1000
ACM
1:40
ACM
1:200
1:1000 –
DCM: DC motor ACM: AC motor IM: induction motor
SM: synchronous motor M-G: motor-generator
PWM: pulse width modulation
ASIC: application specific integrated circuit PI: proportional/integral
Fig. 9—History of Advances in Motor Drive Control.
The performance of variable-speed AC motor systems has
improved with advances in control and power conversion
equipment (Reference: 2001 Annual Conference of Industry
Applications Society, The Institute of Electrical Engineers of
Japan, S11-1).
Minimum
frequency at
200% torque
(Hz)
Historical Evolution of Motor Technology
Sensorless vector control
V/F
constant • HITACHI • HITACHI • HITACHI
5.0
1.0
0.0
HFC-VWA
1970
1980
1989
1990
2006
Zero-speed
sensorless
vector
SJ700
200% torque at 0.3 Hz,
150% torque at 0 Hz
Torque (%)
0.3 Hz 200
100
0
−100
−200
HFC-VWA
SJ700
2000
1999
Speed sensorless
vector control
SJ300
300
600
900
1200
Speed (min-1)
SJ300
V/F: voltage/frequency
Air conditioner
COP
Fig. 10—Advances in Vector Control for Induction Motors.
Advances in vector control provided improvements in motor
functionality.
6.0
4.0
Induction
motor
2.0
1970
PM motor
• PAM
• 120° control
1980
1982
1990
• Less & less
2000
2002
PM
Conventional
Less & less
Position Current sensor Sensorless
sensor
Controller
Sensorless
MPU
PMSM
Development of positionsensorless control with 120°
commutation, use of PM
motors in air conditioners.
Soft
based
sensor
Sin-wave
current
Ideal sine wave current drive
introduced in consumer appliances
using “less & less” technology.
COP: coefficient of performance PM: permanent magnet
PAM: pulse amplitude modulation MPU: microprocessor unit
Fig. 11—Advances in Sensorless Control of Permanent Magnet
Motors.
Advances in control techniques for permanent magnet motors
that do not use position and current sensors and which were
developed for use in air conditioners.
Compared to V/F (voltage/frequency) control used
previously which kept the flux swing constant, vector
control achieves a significant improvement in low-speed
torque by controlling the torque components. Zerohertz sensorless technology was first commercialized
in 1999 and succeeded in performing vector control at
0 Hz, something that was not previously possible.
Fig. 11 shows the history of sensorless control
techniques for permanent magnet motors. Development
of permanent magnet motor control was undertaken
primarily for air conditioning appliances. The size and
efficiency of permanent magnet motors underwent a
sudden improvement with the invention of rare-earth
magnets, but because they cannot be started without an
inverter, the applications for these motors have grown
with the help of control technology.
42
Permanent magnet motors were introduced in
Hitachi air conditioners in 1982 and mass-market
models have used sensorless control since that time.
Since then, permanent magnet motors and sensorless
control have become the industry standard for air
conditioners. PAM (pulse amplitude modulation)
control which varies the amplitude of voltage pulses
was developed subsequently and technology for
driving motors with an ideal sine wave current was
developed in 2002. A form of sensorless control that
used neither the position sensor nor current sensor
originally required when using vector control to drive a
motor was developed at the same time, resulting in the
ultimate circuit configuration for an ideal drive (7).
Sensorless control without position or current
sensors is now being widely adopted in home
appliances such as refrigerators, cordless cleaners, and
washing machines as well as in other fields such as in
industry or for auxiliary automotive motors.
EXAMPLE INITIATIVES FOR FUTURE
Concerns in recent years about how to prevent
global warming are driving demands to reduce motor
energy consumption by making motors even smaller
and more efficient. To achieve both smaller size and
higher efficiency, it is necessary to minimize as far as
possible the various types of energy loss that occur
inside motors while simultaneously dealing with the
reduction in heat dissipation performance that results
when motors are made smaller.
Against this background and on the occasion of
the 100th anniversary of the company’s founding,
Hitachi, Ltd. in collaboration with Hitachi Industrial
Equipment Systems Co., Ltd. produced a prototype
concept motor in 2010 with the intention of achieving
even smaller motor sizes in future. The prototype
involved the development of technology to improve
heat dissipation, a coupled magnetic field and thermal
analysis technique that simultaneously analyzes the
magnetic flux and heat flow in the motor, and design
optimization techniques that are based on this analysis
technology. It is this analysis technology that makes
the greatest contribution to the design of motors for
small size and the following sections describe the
technology itself together with the prototype motor
that was investigated with its aid (8).
Coupled Magnetic Field and Thermal Analysis
and Shape Optimization Techniques
Because the objective was to make a smaller motor,
a permanent magnet configuration was chosen for the
Hitachi Review Vol. 60 (2011), No. 1
prototype. The technologies required for permanent
magnet motor design can be broadly divided into
electrical design, cooling design, and demagnetization
analysis (demagnetization: the loss by a magnet of its
magnetism). Conventionally, the most common design
approach has been to treat electrical design, cooling
design, and demagnetization analysis separately and
base the design on individual analyses that dealt
with losses, temperature, or other parameters. Also,
design conditions such as the variation in material
characteristics or dimensional tolerances often have
specific ranges. Accordingly, it was essential to
run analyses based on severe conditions to ensure
performance could be achieved even under worst-case
conditions. This design methodology meant that excess
margins were built into the motor’s structural design
and performance, in which case a series of prototypes
would be produced after the design stage to adjust
the extent of these structural design and performance
margins.
Typically, the structural design of a motor is
determined by the required torque performance and
permitted temperature rise. Problems that arise when
a motor is made smaller while keeping the same
output and efficiency include that losses remain the
same despite the smaller chassis and the excessive
rise in temperature due to the reduction in surface
area for dissipating heat. The problems associated
with higher temperature include loss of magnetism
in permanent magnets and an increase in winding
resistance, resulting in a deterioration in motor torque
characteristics. In other words, there is a trade-off
between motor size and temperature. Accordingly,
striking a good balance between temperature rise and
torque performance is a key point when designing
motors for small size and it is considered essential that
the temperature in the actual environment where the
motor is to be used be considered in the analysis if a
design that achieves this balance is to be obtained.
In response, Hitachi has developed analysis
technologies that can be used to design smaller
permanent magnet motors by linking magnetic field
analysis using the two-dimensional finite element
method with thermal analysis using the equivalent
thermal network method and combining these with
shape optimization using mathematical programming
methods. Fig. 12 shows a flow chart of this analysis
technique. The analysis starts by setting assorted
motor variables which are used as the basis of a twodimensional magnetic field analysis which is followed
by a thermal analysis. The results of the analysis are
43
Stator core
x6
x8
Coil
x7
x9
x5
x2
Rotor core
x4
x1
x3
x10
Permanent magnet
(a) Optimized variables in magnetic field analysis model
Variable x
Objective function
(1) Calculation of material
constants
History of
temperature rise
(2) Generation of finite
element mesh
(3) 2D-magnetic field analysis
Optimization
engine
Read previous
values.
(4) Calculation of motor losses
(5) Calculation of thermal
resistances
History of
core length
(6) Steady-state thermal
network analysis
(7) Calculation of motor
characteristics
Set new values.
Objective function F(x)
(b) Flow of proposed method
Fig. 12—Newly Developed Coupled Magnetic Field and
Thermal Analysis and Shape Optimization Techniques.
Linked analysis of heat and magnetic fields together with shape
optimization achieved both a shorter design time and a smaller
motor.
set in the objective function and the calculation is
repeated until the objective function criterion (which
in this case is the minimum motor size) is satisfied,
with the optimization engine used each time to set the
variables for the next iteration subject to the specified
restrictions.
Prototype Results
A prototype 5-HP permanent magnet motor
produced using the above techniques achieved a
volume only one-fifteenth that of Hitachi’s original
5-HP induction motor from 1910 (and only one-third
Historical Evolution of Motor Technology
Hitachi’s first motor (IM)
Current model
(IM)
Prototype
(PM)
Fig. 13—Comparison of Original 5-HP Motor, Current
Production Model, and New Prototype.
The body of the prototype motor is only one-fifteenth the size of
Hitachi’s original motor.
Prototype
5-HP motor
designed by
Design
Division
Fig. 14—Prototype Motor on Show at Hitachi uVALUE
Convention 2010 held in Japan.
The prototype motor was included in the 100th Anniversary
Exhibit and was made using a design prepared by Hitachi’s
Design Division.
the volume of current 5-HP induction motors) (see
Fig. 13). The motor development also drew on the
leading-edge materials of the Hitachi Group including
the use of neodymium magnets from Hitachi Metals,
Ltd. in the rotor, enameled wire from Hitachi Cable,
Ltd., and organic chemical materials from Hitachi
Chemical Co., Ltd.
An example of the prototype motor produced
using a design from Hitachi’s Design Division was
unveiled to the public at the “Hitachi uVALUE
Convention 2010” held in July 2010 in Japan where it
was included in an exhibit celebrating the company’s
100th anniversary (see Fig. 14).
44
D e sp it e h av i ng su ch a h ig h d eg r e e of
miniaturization, the motor achieved a very high
efficiency of approximately 94% in continuous
operation tests.
FUTURE OUTLOOK
The evolution of the electric motor has been
underpinned by design, production, and material
technologies. In recent years in particular, motor
performance has received a major boost from a variety
of simulation techniques and other advances such as
in materials technology, particularly in the field of
permanent magnet motors. Prompted by concerns
about reducing the burden on the environment, it is
anticipated that, in addition to the expected further
improvements in efficiency, the future will also
see further research into motor structure aimed at
reducing material usage through smaller motor sizes
and making available materials that do not include
scarce resources (9) . With use of electric motors
and inverters becoming standard practice, it is also
anticipated that motors, inverters, and motor control
will become integrated in both a structural and design
sense. In terms of control, vector control has entered
widespread use starting with 120° commutation
control, and it seems likely that control techniques
that take account of motor non-linearity caused
by magnetic saturation will enter practical use in
order to combine controllability with small size and
light weight (10) . In the field of design technology,
meanwhile, it is anticipated that integrated design
methods will be adopted using techniques based on
overall optimization instead of designing the inverter,
motor, and control separately as in the past and then
having to tune their combined operation.
CONCLUSIONS
Motors and generators are examples of products
that utilize magnetism in their operation. This article
has reviewed the historical evolution and future
outlook for these machines along with the inverterbased control systems used to drive them.
As with the relationship between motors and
control and motors and inverters, it is anticipated that
electric drive will continue to make rapid advances
in the future through the ability to produce designs
that are even better at balancing reliability, structural
design, and value by designing motors and inverters
as a single unit.
Hitachi Review Vol. 60 (2011), No. 1
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ABOUT THE AUTHORS
Hiroyuki Mikami, Dr. Eng.
Kazumasa Ide, Dr. Eng.
Joined Hitachi, Ltd. in 1990, and now works at the
Department of Motor Systems Research, Hitachi
Research Laboratory. He is currently engaged in
research and development of motors, generators,
and drive systems. Dr. Mikami is a member of The
Institute of Electrical Engineers of Japan and The
Institute of Electrical and Electronics Engineers, Inc.
(IEEE).
Joined Hitachi, Ltd. in 1988, and now works at
the Department of Power Electronics Systems
Research, Hitachi Research Laboratory. He is
currently engaged in research and development of
power electronics equipment including motors. Dr.
Ide is a senior member of The Institute of Electrical
Engineers of Japan and IEEE.
Yukiaki Shimizu
Masaharu Senoo
Joined Hitachi, Ltd. in 1972, and now works at
the Motor Power Systems Division. He is currently
engaged in a project to strengthen motor and inverter
development.
Joined Hitachi, Ltd. in 1975, and now works at the
Motor Power Systems Division. He is currently
engaged in a project to strengthen motor and inverter
development. Mr. Senoo is a member of The Institute
of Electrical Engineers of Japan.
Hideaki Seki
Joined Hitachi, Ltd. in 1979, and now works at the
Motor Power Systems Division. He is currently
engaged in a project to strengthen motor and inverter
development.