Magnetics Business & Technology - July/August 2021 - 34

VISIONS
Toshiba's New Magnetic Material Improves Motor Energy Conversion Efficiency
Figure 1: Flow of magnetic flux controlled by the developed magnetic material when used as a magnetic wedge in a motor
Researchers at Toshiba Corporation have developed a new
magnetic material that delivers major improvements in motor
efficiency at minimum cost, and with the potential to win
significant reductions in power consumption. It has been found
to greatly boost motor energy conversion efficiency when it
is used as the wedges in the motor, particularly in medium to
large induction motors. The material can be installed at minimal
cost with no need for design changes.
Through testing in an induction motor in railway rolling stock
drive systems, Toshiba confirmed an efficiency increase of
0.9 pt ( " pt " is the measure for comparing motor efficiency. It
indicates the difference in motor efficiency values) with an
improvement approaching the efficiency of permanent magnet
synchronous motors. The material can also be installed in
permanent magnet synchronous motors to realize much higher
efficiency.
The material also offers excellent heat resistance, suiting it for
applications such as railway rolling stock, automobiles, robots,
and industrial and medical equipment. If used in all motors
operating worldwide today, with the same level of improvement
in efficiency recorded by Toshiba, the material would allow the
elimination of ten 1 GW power plants, estimates Toshiba.
Wedges in motor prevent motor coils from falling out of their
slots. They are normally made of non-magnetic material, but
the use of magnetic material has been found to guide magnetic
flux toward the wedges, improving energy conversion efficiency.
However, the conventional magnetic material used as
the wedges is composed of spherical magnetic metal particles
with insufficient control of the magnetic flux, causing leaks to
the unwanted directions, as illustrated in Figure 1. The magnetic
wedge material itself also has high magnetic loss. It also
has low heat resistance, making it unsuitable for railway rolling
stock and other applications that require high heat resistance.
The unique characteristics of the new magnetic material deliver
excellent control of magnetic flux, ultra-low magnetic loss,
and high heat resistance. The material is composed of flaky
magnetic metal particles that have different magnetic property
depending on the direction, and ultra-low magnetic loss (Figure
2). Used as a magnetic wedge, magnetic flux can be efficiently
guided to the desired specific direction (Figure 1), reducing
energy loss and significantly improving energy conversion efficiency.
34
Magnetics Business & Technology * July/August 2021
Figure 2: Magnetic loss of the developed magnetic material
Figure 3: Weight change of the developed magnetic material during
heat treatment at 220°C
Toshiba also found that compacting flaky magnetic particles
with a heat-resistant binder heightens thermal stability, with
barely any weight decrease, even when held in a hot, 220°C
environment for a long period of time (Figure 3). This high heat
resistance opens the way to widespread the range of application
of the magnetic wedge. Toshiba targets commercializing
high-efficiency railway rolling stock motors equipped with magnetic
wedges by using the developed magnetic material.
For more info, see www.toshiba.com.
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Magnetics Business & Technology - July/August 2021

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