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At last, a fair-dinkum electric vehicle
conversion using an induction motor . . .
Mal’s EV
By LEO SIMPSON
Malcolm Faed has produced the first electric vehicle conversion
using an industrial 3-phase induction motor controlled by a
variable frequency, variable voltage converter. As far as we
know, it is the first such road-registered DIY conversion in
Australia and it is probably one of the first in the world.
12 Silicon Chip
siliconchip.com.au
B
ack in the December 2008 issue we reported on the
Australian Electrical Vehicle Association’s field day
held in October. We commented that all the vehicle
conversions on display appeared to be based on DC motors
with wound fields and ratings up to about 70kW.
But we have always felt that the ideal conversion should
be based on a 3-phase induction motor, as in hybrid electric
vehicles and in larger commercial electric vehicles as well
as modern diesel locomotives.
So when we heard that Malcolm Faed was engaged in a
conversion which would use an industrial grade 3-phase
induction motor and matching drive (the inverter), we
watched his internet blog with keen interest. Just recently
he has completed it and is now happily driving a registered
electric vehicle on Sydney’s roads. He dropped into our
offices to show it off.
It is based on a Toyota Hilux Xtracab utility, a rugged
commercial vehicle with an aluminium tray body with
plenty of space for the battery bank. To look at the finished
vehicle, the conversion looks surprisingly straightforward
although Malcolm would have undoubtedly spent hundreds of hours thinking about each step in the process
before actually doing it.
The conversion can be summarised as having a whopping orange induction motor mounted in the now very spacious engine bay and the battery bank and inverter system
mounted on the rear tray under a large canopy.
With the bonnet down and the canopy closed, the only
clue that this might be an electric vehicle is the plastic
cover for a standard 230VAC mains 3-pin male socket on
Just to prove the point, here’s the rego sticker, placed just a
couple of months ago. It shows a gross vehicle mass (GVM)
of a little over two tonnes.
the side of the tray body, used for battery charging.
Perhaps another clue, if you see the black Hilux pulled
up next to you in traffic, is that you won’t hear the motor
running – because it isn’t! That is not to say that the motor
is silent because once it is above walking speed, the motor
can certainly be heard – and nor is it particularly quiet.
But before we get too
far ahead, let’s discuss
more of the basics of
the conversion. The
battery bank consists
of 50 12V 20Ah sealed
lead acid cells giving
a total battery supply
Unlike today’s petrol engines shoe-horned into the bay, this under-hood shot shows a lot of space, even with a grunty
3-phase industrial motor. It has an electric fan fitted because the internal cooling just isn’t enough at low engine speeds.
Inset top right is the ratings plate for the ASEA motor. It’s showing its age but can still be read.
siliconchip.com.au
June 2009 13
On the face of it, this electric vehicle conversion is pretty
simple. The execution proved to be a tad more difficult!
off-peak electricity, so the cost of energy for this vehicle
is particularly low.
Total capacity of the battery bank is 12 kilowatt-hours
and this gives a driving range of about 40km – fairly modest
but adequate for Malcolm’s short daily commute.
Most readers will be aware that the speed of an induction motor is more or less locked to the frequency of the
AC driving voltage. Hence, a 4-pole induction motor connected to a 50Hz mains supply will normally run at about
1440 RPM; slightly less than the so-called synchronous
speed of 1500 RPM.
Incidentally, the synchronous speed of an induction
motor can be calculated using the formula:
rail of 600V. This is fed to a Danfoss VLT5042 frequency
converter intended to drive 3-phase induction motors up
to 48kW (peak).
Now the cunning aspect of Malcolm’s conversion is that
it feeds the 600V DC directly to the VLT5042 converter.
Why is this cunning? Because when used normally, the
VLT5042 is fed with 3-phase 415VAC which is then internally rectified by a 6-diode bridge to obtain 586V DC and
it is this DC which is then converted to variable frequency,
variable voltage AC.
What Malcolm has done is to bypass the internal 3-phase
bridge rectifier and feed the frequency converter with DC
from the batteries instead.
The 600V battery supply is split into ±300V rails and so
there are three supply leads into the VLT5042 converter:
+300V, 0V & -300V.
For charging from 230VAC, the battery bank is split
into 12 banks of four (48V) and one bank of two (24V)
and these banks are charged by 13 intelligent switchmode
chargers. Each night the battery bank is charged using
n = 120f
P
where n = RPM, f = frequency and P = number of poles
of the motor.
Similarly, a 2-pole induction motor will run at about
2880 RPM, again slightly less than the synchronous speed
of 3000 RPM. The difference between the motor speed and
synchronous speed is known as “slip” and this is dependent
on the load on the motor (or the torque produced).
Hence, in order to drive the motor over a wide range of
RPM, the frequency converter must have a similarly wide
output. In the case of the Danfoss VLT5042 used here, the
drive frequency is configured to vary from 0.5Hz to 132Hz
and the voltage must also be varied, from quite low at low
frequencies up to a maximum of 415V (3-phase AC) at 50Hz
and then fixed for higher frequencies.
The VLT5042 is able to work in open or closed-loop mode
and has a speed pickup input. On Malcolm’s conversion
the speed pickup is a toothed wheel on the output shaft
of the motor and a Hall Effect sensor. At this stage though,
CHARGERS
CHARGERS
25 x
300V 12V 20Ah
SLA
300V
25 x
12V 20Ah
SLA
VARIABLE
FREQUENCY,
VARIABLE
VOLTAGE
CONVERTER
3-PHASE
INDUCTION
MOTOR
CONTACTORS, SAFETY LOCKOUTS ETC NOT SHOWN
Mal Faed drying off the electronics while we took photos of his EV conversion on a (very!) wet day. This is looking across
the battery bank with the Danfoss VLT5042 controller under his right elbow.
14 Silicon Chip
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QUICK FACTS
Vehicle:
Range:
Charge time:
Cost to run:
Efficiency:
Performance:
Converted weight:
Motor nominal:
Motor peak:
Braking:
Controller:
Batteries:
Battery energy:
Chargers:
Top speed:
Modifications:
1992 Toyota Hilux Extra Cab. 2WD (RN90R)
35km to 70% discharge – hilly terrain (Collaroy to Terrey Hills return)
Deeper discharges will significantly affect the life of the batteries.
1 – 5 hours depending on distance travelled.
1.39¢/km (off-peak 1 electricity tariff); 4.9¢/km (peak electricity tariff)
Battery cost ~10¢ per km. (Total 11.39 to 14.9¢/km)
Compared to petrol, 13¢ per km – 11l/100km <at>$1.18/l Add 5 to 15¢/km for servicing Total 18 to 28¢/km
Hilly terrain – battery to wheels: 238Wh/km
Flat terrain – battery to wheels: 200Wh/km
Peak power – 35kW at wheels (48kW electrical)
Peak torque – 1615Nm at wheels. Peak motor torque 315Nm
Originally: Power 75kW <at> 4800 RPM; Torque 185Nm <at> 2800 RPM
1544kg (Original weight 1250kg; GVM [Gross Vehicle Mass] 2050kg)
15kW / 99Nm, ASEA, aluminium frame, 3-phase induction motor.
~48kW / ~350Nm
Regenerative and original vacuum assisted hydraulic.
Danfoss VLT5042 3-phase Inverter (aka Variable Speed Drive / VSD). Provides regenerative braking.
50 x 20Ah (<at> 2hr rate) Greensaver SLA
12kWh
13 x 2.5A switch-mode smart chargers
75km/h on flat
• Manual steering
• Electric heater
• 5:125:1 differential
the VLT5042 is being used in open-loop mode, with the
motor speed pickup being connected for speedo operation
only. Even though it’s road registered and drivable, it’s still
a work-in-progress!
The VLT5042 uses a bank of high-voltage insulated
gate bipolar transistors (IGBTs) in a 6-way bridge to give a
3-phase drive to the 4-pole motor which is delta-connected.
The motor is a second-hand ABB unit with a nameplate
rating of 15kW at 415VAC. That might seem low but remember that such a motor can deliver at least three times
its rated power for short periods.
The motor sits in the engine bay of the Toyota Hilux in
virtually splendid isolation. The only modification is that
it has been fitted with a standard 12V radiator fan which
is controlled by a thermostatic switch on the motor body.
The fan replaces the internal fan, which was ineffective at
low speeds and too noisy at the higher speeds the motor
is now required to run at.
Even so, the 12V fan does not cut in frequently and
would only be expected to be running when the Hilux is
climbing a steep hill.
The motor drives the differential of the Hilux directly;
there is no intermediate gearbox. However, Malcolm has
increased the diff ratio to 5.125:1 to obtain a better hill
climbing capability – necessary for his Sydney northern
beaches’ location. Top speed is about 75km/h.
Engine braking & regeneration
One aspect of this conversion which is not immediately
obvious is that the combination of the Danfoss VLT5042 and
the 3-phase motor can provide substantial engine braking,
dependent on the throttle setting. The engine braking is an
siliconchip.com.au
The large knob in the foreground is the Forward/Neutral/
Reverse switch, with the Danfoss keypad and display. It
is not possible to inadvertently throw the car into reverse
while under way. This is prevented by a key interlock
which must be used to change motor direction.
June 2009 15
This shot shows the 12V battery (right corner) which provides power to all the ancillaries. Above it is the blue vacuum
reservoir, included so that the vacuum pump, adjacent to the power brake booster, does not cycle frequently. The vacuum
pump is fitted with a gauge – just to show it is working. Centre right of the photo (circled) is the throttle potentiometer.
The pot is 10kΩ (linear) and provides 60° of rotation.
inherent function of induction motor slip, whereby when
the motor is being “over-run” by the drive shaft (as when
coasting down a hill), the motor is effectively generating
reverse torque.
But since the motor is being driven by the rear wheels,
it also provides worthwhile regeneration, delivering significant current to the batteries on long downhill runs.
The battery charging evidently takes place via the substrate reverse diodes in the IGBTs. A meter inside
the vehicle monitors the battery drain and the
regeneration.
Regeneration is a particular advantage of using a 3-phase motor and one
which cannot easily be provided in
conversions using series DC motors.
Ultimately, an AC conversion such
as this should be very quiet because
the motor is not subject to the high
frequency pulse drive normally
employed in DC conversions.
The 3-phase sinewave is synthesised by higher frequency switchmode pulsing so high frequency
whistling is evident from outside
the vehicle.
to run the ancillaries such as the vehicle’s instrumentation,
windscreen wipers and washers and lighting.
This is provided by a 12V SLA battery, identical to those
sitting in the rear tray. It is charged by a pair of switchmode regulators, one of which is connected to the +300V
rail while the other is connected to the -300V rail. Both
their floating outputs are connected in parallel to charge
the battery.
As well as lighting, it also provides power to
a 12V vacuum pump which runs the power
brake booster. It also drives a 12V blower
for the ceramic core heater. The heater
is run from the 600V supply and
provides demisting for the windscreen.
There is no air-conditioning
for the driver and passengers
though... That might be in a
subsequent EV conversion perhaps.
Ancillaries
All electric vehicle conversions
need to provide a 12V battery supply
16 Silicon Chip
Not something you see every day!
Driving it
Driving the converted Hilux is
a bit of an art because the throttle
and braking response needs to be
learned. If you’re too hard on the throttle, the motor slip goes to a high value
and it loses power.
Having said that, the vehicle evidentsiliconchip.com.au
ly has adequate power to keep up with other traffic and is no
slouch when climbing hills. However the battery drain
goes up alarmingly at these times, rapidly reducing the
available capacity. On the level, the car trickles along.
Where it is disconcerting is that the motor is not as
smooth as you would expect and has significant vibration
conducted through the cabin – almost a cogging effect.
This is probably a consequence of the motor being solidly mounted to the chassis without any rubber mounts
to provide isolation. Perhaps that might be a later modification.
When climbing hills the motor also becomes quite
strident – surprisingly so. We measured a peak of 78dBA
inside the cabin. Of course, large 3-phase industrial motors
are never silent; it is just that you are seldom aware that
they produce any noise since it is normally drowned out
by the machinery they are driving.
Overall, we are very impressed with this EV conversion.
Not only is it the first using an induction motor but Malcolm’s choice of vehicle is very appropriate. It is a strong
commercial vehicle and should provide good protection
in the event of a crash. Even if it rolled over, you could
fairly confident that the battery pack would be securely
held in place. Having back seats, it also provides for four
occupants, something that most prior conversions using
SC
conventional cars cannot provide.
Much more detail can be found on Malcolm’s EV Blog:
http://a4x4kiwi.blogspot.com/
This view shows 10 of the 13 individual battery chargers.
This shot show the Danfoss VLT5024 frequency converter with the top cover removed. In the foreground you can see the
two 13.8V 25A switchmode power supplies which are used to charge the 12V ancillary battery. They occupy the space
originally taken up by the 415V 3-phase rectifier filters.
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June 2009 17
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