A new motor is expected to bring big
benefits to both electric vehicles and domestic appliances. Tom
Shelley reports
A flat, permanent magnet wheel motor and drive is claimed to have
about double the overall efficiency of other motors used or
proposed for electric vehicles.
Developed primarily for electric bicycles, the motor and drive
combination is unique in that back emf and surplus power is
extracted from non energised poles at all points in the drive
cycle. You could say that it saves energy by giving with one hand
and taking some of it back again with the other.
It is smoother and more efficient than conventional systems, and
is aimed at the growing electric and hybrid vehicle market,
including the nearly 3 million electric bicycles now made each
year in China.
The Ultra motor is in fact a whole family of motors invented
by Russian engineer Professor Vasiliy Shkondin, and made by him
and colleagues in a small firm 100km South of Moscow. Professor
Shkondin learned his trade as an electromechanical apprentice in
the Russian Navy, although he subsequently moved into academia.
The original inspiration may well have been advanced and super
quiet submarine motors, but nobody is saying.
The 750W motor shown to Eureka was mounted on the front wheel of
a bicycle, as part of an evaluation being undertaken by Chris
Roberts, a former Pera consultant now working for himself in a
small village near Melton Mowbray. The motor was between 40 and
45mm thick and 380mm in diameter and was enclosed in a solid
looking aluminium housing. It was powered by three 12V 10Ah
motorcycle batteries mounted in the cycle saddlebags. It was said
to have 10 ferrite permanent magnet poles on its rotor and 12
electromagnetic poles on its stator. Maximum output torque was
said to be 120Nm.
As well as regenerating power during braking, we were told that
it makes use of the fact that back emf is generated in each
electromagnet coil, when it is not powered. This energy is
extracted according to the amount of surplus power that the drive
decides it is supplying to the motor. The motor is said to
collect up to 30% of the power associated with back emf when
subjected to normal loads and speeds. This is claimed to at least
double the potential range of electric vehicles compared to those
powered using more conventional technology.
The motor exhibits relatively low field breakdown so torque and
back emf are less spiky than usual. The motor did exhibit some
slight cogging when the bicycle was ridden very slowly uphill,
but generally it runs very smooth and completely silent. Part of
the problem was, apparently, that your Eureka editor found it a
strange experience to ride a bicycle driven at the front, with
consequent wheelspin at the steering end, and so proceeded with
extreme caution. Motor performance was not helped by the
batteries being only partly charged. On a full charge, we were
told that range was about 25km.
Variant with stator poles on inside and magnets on outer
rotor
Motor with similar intended function but with outer stator poles
and magnets on inner rotor
Professor Shkondin has developed around 70 variants based on
the same basic technology. His factory, apparently, contains
prototypes of electric bicycles or different types and power,
electric motorcycles, wheelchairs and small cars reminiscent of
the 'Bond Bug'. One design, weighing 20kg, is intended to fit
into a 16in wheel rim. Power output is 4kW and maximum torque
600Nm. Torque generally is claimed to be two to four times
greater than that possible with conventional gearboxes.
According to Justin Martin, commercial director of the Ultra
Motor Company, an enterprise based in the Isle of Man, it will be
marketing four different concepts: Ultra slim, Ultra compact,
Ultra efficient and Ultra durable. "We think we can double
the range of battery electric vehicles from a typical 53 miles to
100 miles, and reduce the 0 to 30mph 7s acceleration time showed
by cars such as the Ford Thimk! to 4.5 to 5s. The bigger you go,
the more torque and output power you get per unit weight. With
sensible use of polymers it should be possible to reduce
weight."
Whereas personal electric vehicles remain under something of a
cloud in the UK, largely thanks to the Sinclair C5, other
countries, without the same bad experience, are grasping the
opportunities. There are now some 260 makers of electric bicycles
world-wide. In China, the bicycle is still the principle mode of
transport. The government there is not keen to encourage
universal use of cars, or even mopeds with 50cc internal
combustion engines, because of concerns about major pollution
problems in its cities. China is believed to have produced
between 2.5 and 3 million electric bicycles in 2002 the next
largest producers are Japan and India. In the USA, it is possible
to put 750W motors on bicycles, without getting into motorcycle
legislation. In Europe, the figure is 250W. A 250W electric
bicycle equipped with same 30Ah of batteries, should have a range
of about 75km. The company intends to offer DIY kits to convert
any make or model of bicycle into an adaptive 'pedelec' - a
regular bicycle with a motor attached to its frame and a throttle
on its handlebars.
Because the motors do not depend on rare earth metals, they are
cheap to make. As well as motor vehicles, Martin believes the
slim weight, high torque and smooth running low speed
characteristics make the motors and drives eminently suitable for
washing machines and other domestic appliances. The motors could
be mounted directly on the backs of the washing machine drums and
do away with the need for a belt drive, or the space required to
mount the motor beneath the drum. Martin and his colleagues, in
Isle of Man based Flintstone Technologies, have long experience
of technology transfer from Russia, previous successful transfers
include Keronite hard coatings for light alloys and Hardide fully
dense tungsten carbide.
Pointers
The motors are flat, multi-poled types optimised for low speeds
and high torque
The permanent magnets are ferrite, making the motors low cost
High efficiency and smooth running is ensured by using back emf
from the non-energised motor windings
Eureka says: "Its about time to took a
second serious look at the electric vehicle business as well as
seeing what other electrical products the new motor might allows
to be redesigned."
Euro motors zip along
Not only Russian and Chinese but leading European motor makers
continue to come up with ideas and products to meet the challenge
of designing commercially viable electric vehicles.
The Spingo, developed by Gloucestershire based Aphid designs,
powers kick scooters to speeds approaching 20mph, for up to 25
miles on a single charge. At its heart is a maxon RE40 motor
normally delivering 150W of power. The motor weighs only 480g
but, controlled electronically through Aphid's pulse width
modulator, it can produce almost 200W. Neodymium iron boron
magnets allow miniaturisation and a running efficiency of up to
92%. No load current at 48V is 5mA. The whole motor pack weighs
4kg including batteries.
AEG Lafert motors are also proving to be of interest to European
electric vehicle designers, again with permanent magnets. Fitted
to a Lepton electric scooter, 1.8kW motors give a top speed of
45km/h and 0 to 50km/h acceleration in 6.5 to 7s. Weight with
lead acid batteries is 133kg. On an electric micro car, 4kW
motors deliver a maximum torque of 50Nm and give a top speed of
45km/h. Range is 85km and weight is 440kg with batteries or 280kg
without.
Ultra
motor temporary web site
justinmartin@iom.com
For more technical
developments see www.eurekamagazine.co.uk