Five technologies to reinvent the electric motor
Modification of the magnetic flux, new cooling jacket ...
several innovations have been designed by companies to make electric motors
more efficient and lighter.
Magnax, the axial magnetic flux
The Magnax motor is an axial magnetic flux electric motor
that can provide a maximum power density of 15 kW / Kg. The high power
density is generated by an extremely compact and cordless axial flow.
It has a patented mechanical cooling system which extracts
heat from the coil more efficiently. “The heat extraction system is
directly connected to a water cooling jacket or air cooling fins which
dissipate heat instantly,” the company explains. Cordless Magnax axial
flow motors reduce iron loss by 85% due to very low amount of material
usage. It consists of two permanent flux magnet rotors which allow a
better torque / weight ratio of the motor. The fill factor of copper is
also high (90%) thanks to copper wires of rectangular section and a very
concentrated winding. The engine weighs only 16 kg.
The production process of the Magnax machine (core
production, winding, welding of bus bars, gluing of magnets, final assembly,
etc.) is carried out using standard manufacturing methods which can be
outsourced or automated. This decreases the production cost of an electric
motor which often requires manual interventions or highly adapted
machines. Its size is also variable, the motor can be more or less wide
and with more or less power. Thus it varies from 25 to 500 kW, 48 to 800 V
with a torque of 250 Nm.
Linear labs, the circumferential magnetic flux
The American company from Texas, Linear Labs, has designed
what it calls a Hunstable Electric Turbine or HET, named after
the founder of the company. According to their data, the continuous and
maximum power density of the engine using standard cooling can exceed 7.0 kW /
kg at a base speed of 3000 rpm.
The HET makes it possible to have "an engine torque
multiplied by two and a power three times higher" than a normal electric
motor. The HET is a permanent circumferential magnetic flux magnet machine
that incorporates four rotors. The technology relies mostly on a different
magnetic arrangement. "The coil is surrounded over its entire surface
by magnetic materials of the same polarity and all the magnetic fields created
are directed in the direction of the movement of the device," explains the
company. She explains: unlike existing conventional machines where torque
is only present at an optimum point when approaching a magnetic pole, the HET
does not have a single optimum point because all positions have maximum
torque. The engine power is therefore higher,
Compared to a normal electric motor, the HET uses 30% less
copper because only the copper within the coil is involved in the energy conversion. There
is no copper located outside the coil, and this reduces material
loss. Thanks to the constant magnetic flux, and the lower use of copper,
it also does not need mechanical reducers or a DC-DC converter,
which equalizes the different voltage levels, which further reduces the weight
of the motor. electric.
The plastic electric motor
Researchers from the Fraunhofer Institute for Chemical
Technology in cooperation with the Karlsruhe Institute of Technology have
developed a new cooling system in an engine made of reinforced plastic fibers,
instead of aluminum housings. This system makes it possible to create a
lighter engine.
"An electric motor consists of a rotating rotor and a
stationary stator. The stator contains coiled copper wires through which
current flows. This is where most of the electrical losses occur. The real
innovation of our concept is in the stator ", explains Robert Maertens,
scientist at the Fraunhofer Institute. Research teams have replaced the
use of round wire with a rectangular flat wire, which can be wound more tightly
on the stator. This creates more space for an adjacent cooling
channel. Heat loss dissipates through this internal cooling channel and
heat no longer needs to be transported through the metal housing to the outside
or to a cooling jacket. This is no longer necessary in this
concept. As a result, thermal inertia is lower and the motor achieves
higher continuous power. "We were able to show that we are already
able to cool more than 80% of the expected power loss", explain the
scientists.
A low voltage motor
Valeo presented
at CES 2018 an electric car with a low voltage 48 V motor. "The 100% electric
48V is also and above all more economical (20% cheaper) than an all-electric
solution operating at high voltage, because it does does not require certain
mandatory components and systems guaranteeing the safety of users of
high-voltage vehicles, ”explains the equipment manufacturer.
The new 48 V motor recovers energy during braking and is
stored in the lithium-ion battery, the starter-alternator also helps the
motor during acceleration phases thanks to the recovered energy and the
battery also supplies the network electric vehicle. "This offer can
be completed by adding a 48 V electric supercharger", adds Valeo.
Continental's compact engine
Continental has worked on a more compact, lighter and more
efficient electric motor. "The electric motor, gearbox and power
electronics are combined in a single unit," explains the
OEM. "The propulsion achieves a very high power density, with 150 kW
for a weight of only 75 kg", he adds. The compact model reduces the
space occupied by the motor and the level of integration does not use cables or
connectors.
According to Clean Automobile , Continental plans to
market two versions with 120 and 150 kW power and a maximum torque of 310 Nm.
"Continental offers its fully electric axle drive unit to vehicle
manufacturers in one module in the power categories up to 320 kilowatts and,
depending on the gear ratio, up to 6,400 Nm in output torque ", details Continental. “The
latter is presented by Continental as the equivalent of a classic 2-liter turbo
diesel unit,” adds Automobile Propre.
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