Afma motor reconfigures itself constantly for optimum performance
http://www.drives.co.uk/fullstory.asp?id=3804
[image] Novel 23-phase motor optimises itself continuously in real time
[Apr 8 2013]
[image
http://www.drives.co.uk/images/news/news-2012/Axiflux-motor-web.jpg
]
An Australian start-up company has developed a novel multi-phase motor
that,
it says, can be optimised in real time for efficiency or for power, at any
time and for any speed. Melbourne-based Axiflux’s Afma (adaptive magnetic
flux array) machines contain 23 coils, each independently controlled by
its
own microprocessor.
The machines – which could be configured in various ways, including as
single-phase AC motors, DC motors and three-phase high-voltage AC motors
or
generators – are essentially axial-flux permanent magnet machines. Their
disc-like structure allows several rotors to be stacked together to double
or triple the output. All of the poles and magnets are on the same axis as
the rotor and inverter electronics can be integrated with the motor.
Traditionally, decisions have had to be made when designing a motor to
optimise it for a specific maximum power, maximum torque at a given speed,
and maximum efficiency at that speed. By contrast, the Afma motor
reconfigures itself constantly for optimum performance across a wide range
of operating speeds and loads. “Design decisions that were traditionally
locked in at the factory, are now made in real time,” Axiflux says. This
avoids the need for compromise, it adds.
If less power is needed, sections of the machine can be disabled so that
only those coils best aligned with the magnets are turned on. Similarly,
if
one of the 23 coils fails, the machine re-optimises itself without the
coil.
In some configurations, such as generators, the coils could be
hot-swappable, allowing the machine to continue operating without any
downtime. The motors can operate with almost half of their coils turned
off.
Because the Afma motor uses more coils and magnets than traditional
machines, the current through each coil is smaller, allowing less copper
to
be used, cutting losses and producing less heat. The motors also need less
steel and can be smaller than conventional machines of a similar rating.
Although the current through each coil is small, the total current for the
whole system is said to scale linearly, along with the quantity of
material
and the cost of the machine. This should allow large motors to be built
“at
an affordable price,” says Axiflux.
Part-load efficiencies are claimed to be as high as 95%, compared to 70%
for
some conventional designs.
Another advantage – especially for applications such as electrical
vehicles
– is that the Afma motor can do away with the need for heavy gearboxes and
separate inverters. It should be easy to manufacture using established
techniques and materials.
The motor is the brainchild of Axiflux’s chief technology officer, David
Jahshan, who has been working on the technology since 2008. One reason
that
it is economic for each of the 23 coils to have its own microcontroller is
that mass-market products such as plasma TVs have brought the price of
these
devices down from around $50 to about $2 each. The low-cost processors
allow
the use of techniques such artificial intelligence and neural network
processing to produce the ideal waveform for each coil under the current
operating conditions.
Axiflux has built several prototype machines and is currently working on a
150kW version.
It is also collaborating with several other Australian companies to test a
150kW, 2.8kNm motor in an electric vehicle. In addition, Axiflux is
planning
to build its own electric sportscar that will have two 300kW in-wheel
motors
– each motor being a similar size to a conventional brake assembly.
The Axiflux team has also developed concept designs for direct-drive wind
turbines (avoiding the need for heavy, costly gearboxes) and efficient
industrial crushers and fans that would reduce energy requirements at
remote
mining locations.
Axiflux is talking to several potential joint venture partners around the
world and is securing global patent protection for its technology.
“The electric motor has really not changed since its invention in the late
1800s,” says Airflux CEO, Chris Mosely. “What David (Jahshan) has done is
invert the design approach to motors and generators and, in the process,
created a modular, dynamically reconfigurable electric machine. The
applications and benefits which will accrue are extremely significant.”
[© DFA Media]
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