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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 siliconchip.com.au 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. siliconchip.com.au June 2009  17