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Under the Hood of a MiniE Electric Vehicle. AC Propulsion Systems


Mini E

Mini E

AC propulsion systems based in California supplies the and battery technology for the MINI E electric vehicle made by Mini who is owned by the BMW Group.


The MINI E uses a specially-developed version of AC Propulsion’s proprietary tzero™ technology to provide high performance, high efficiency, and fast charging. AC Propulsion’s air-cooled copper-rotor induction motor produces maximum torque from zero to 5,000 rpm and spins all the way up to 13,000 rpm.

 The IGBT inverter drives the motor to produce peak power of 150 kW. Even with this high power rating, according to the company, the AC Propulsion drive system operates with high efficiency in normal driving. Powerful regenerative braking adds to the efficiency and driving appeal. When the car decelerates, the kinetic energy of motion is converted back to electrical energy in the battery.

AC Propulsion CEO Tom Gage had his to say about their product and relationship with BMW group.

Working with BMW Group on the MINI E project has been a great opportunity. The schedule was tight and required a lot of discipline and coordination. We really pushed our manufacturing operation to meet the production schedule. I drove one of the cars in Munich and our drive system delivers the power, I couldn’t stop smiling. We’ve had cars with our drive systems on the road since 1992, and some have well over 100,000 miles on them, so we’ve seen our systems handle the rigors of daily use. This is a big step for electric vehicles.

AC Propulsion

AC Propulsion

Ac Propulsion systems also supplies the battery for the MINI E. The battery is made up of 48 Li Ion modules. AC Propulsion assembles each module from 106 small Li Ion cells using proprietary assembly techniques and battery management technology. Each module sends voltage and temperature information to the management system which controls for optimal battery operation under driving and charging conditions. Battery data are logged to provide information for analysis and evaluation.

Gage added,

Our Li Ion modules are developed specifically for electric vehicles, not hybrids,so they are lighter and less costly than hybrid batteries for the same amount of energy. Combine the high energy of our batteries and the high efficiency of our drive system, and we deliver excellent range capability at a good price.

AC Propulsion’s patented battery charger is an integral part of the AC Propulsion drive system used in the MINI E, so wherever the car goes, the charger goes. When the wallbox outlet is connected to the charge port on the MINI E, charging proceeds automatically.

The AC Propulsion charger is flexible and can use 120V, 208V, or 240V outlets. Convenience charging from any 110V wall outlet reduces range anxiety by providing plug-in-anywhere capability. AC Propulsion’s tzero™ technology provides an additional state of the art feature available only with the AC Propulsion drive system – the charger works both ways – it is bi-directional. The charger can discharge the battery as well as charge it. In effect, the charger can serve as a regulated power source with many possible applications including, battery pack self-diagnosis, back-up power, car-to-car charging, and, perhaps most importantly in the future, providing ancillary services to the power grid. Engineers have a term for this – vehicle-to-grid or V2G – and it promises to make smart grids of the future more efficient in providing electric power for cars as well as buildings.

V2G does not discharge the battery, so the car is always available for driving. But with each vehicle sourcing or sinking small amounts of power while plugged in, a fleet of V2G-capable vehicles can buffer natural variations in supply and demand on the grid, and even allow for higher utilization of solar and wind power.

AC Propulsion is working with V2G research and development programs throughout the US to supply V2G-capable vehicles, evaluate V2G functionality, and develop the communications and control systems that will necessary to enable electric vehicles to support the power grid.

AC Propulsion was founded in 1992 by Alan Cocconi. It has headquarters, engineering, manufacturing, and test facilities in San Dimas, CA (Los Angeles County), and operates a wholly-owned manufacturing plant in Shanghai PRC. Total employment is over 100 persons and production capacity is over 2000 drive systems per year. AC Propulsion sells propulsion systems and components, technical services, and technology licenses to automotive and other clients throughout the world.

The tzero™ is AC Propulsion’s trademark for proprietary electric vehicle technology including the AC Propulsion drive system with integrated, bi-directional charger, AC Propulsion Li Ion battery assemblies, and AC Propulsion integrated battery management systems. AC Propulsion is the owner of 6 issued patents on EV technology, which have been licensed to other companies, including Tesla Motors. Some of this technology was originally developed by AC Propulsion for its tzero™ electric sports car which achieved 0-60 mph acceleration in 3.6 seconds and 300 mile range while driving 60 mph.


The AC Propulsion drive system includes a power electronics unit and AC-induction traction motor featuring proprietary and patented tzero™ technology to provide high performance, high efficiency, and rapid, convenient charging capabilities for electric vehicle applications. The system delivers up to 150 kW (200 hp) motor output, yet maximizes vehicle operating range with high efficiency over a broad operating range and comprehensive energy recovery through regenerative braking. The tzero™ technology includes patented control and construction techniques that allow the power electronics and motor windings to be re-configured as a high-rate Reductive™ battery charger. By using existing componentry, the Reductive™ Charger reduces vehicle cost and weight. By allowing safe charging from existing 110V to 240V outlets at rates as high as 20 kW, the Reductive™ Charger reduces infrastructure installation requirements and costs, and its innovative bi-directional power capability allows self contained vehicle battery diagnostics and standby power generation.


Advanced Drive Control Circuitry

•”Glass smooth” torque under all load and

speed conditions

•Natural and transparent driving feel

•Driver adjustable regeneration

•Traction control, speed control available

•Integral power distribution and fusing for accessory drive, cabin heater, and hybrid or fuel cell APU

Integrated Reductive™ Charger

•Charge from any source, 100-250 VAC

•Charge rate controllable from 200W up to 20kW (with 240 V line)

•Unity power factor, sine wave current draw

•GFI outlet compatible

•Automatic mode switching (recharge mode activated when charge power is connected)

•Controlled battery discharge into power line for battery diagnostics and V2G

•UPS mode for backup power and energy transfer to other electric vehicles.

Designed-in Safety

•No exposed high voltage surfaces

•All control wiring is grounded, 12 V or less

•Protection against over-current, over-voltage and over-temperature conditions.

•Battery floats with respect to vehicle chassis

•Double insulated motor

•Zero motor back-EMF when excitation removed

•Interlocks prevent accidental operation


Voltage 350 V nominal

240 V min, 450 V max

Current 580 Adc max (drive)

200 Adc max (regeneration)

Torque 225 Nm max, 0-5,000 rpm (drive)

115 Nm max (regeneration)

Power 150 kW max 6,000-12,000 rpm

50 kW continuous


Drive: 91% peak

86% road load (30 kW, 8500 rpm)

Charge: >90% (240 V line, 10 kW)


Pulse-width-modulated, voltage fed, IGBT inverter with current mode, sine-modulated controls; battery charging circuitry; auxiliary 13.5V power supply; and interfaces for control pedals and dash instruments. Environmentally rugged forced

air-cooled design.

Dimensions*: 186 x 313 x 760 mm

Total weight: 30 kg (incl blower)

Cooling: Forced-air with pwm control

Power connectors: Aircraft-style circular

Control connectors: automotive

Control inputs: Ground-referenced signals for key switch, accelerator pedal, regenerative sensitivity, forward, neutral, and reverse; and RS-232 for recharge/discharge control

Instrumentation outputs: RS-232 for battery voltage, inverter, hybrid and drive current, inverter temp, motor temp, motor rpm, motor direction, line voltage, line current, battery isolation, and 12V bus voltage

Power supply current**: 100 A @ 13.5 V


Four-pole induction, high frequency design with inverter-controlled magnetic flux.

Dimensions*: 245mm dia x 350 mm long

Total weight: 50 kg (incl blower)

Maximum rpm: 13,000

Insulation: Class H, double-insulated

Cooling: Forced-air with pwm control

Sensors: Winding temp, tachometer

* dimensions exclude blower and connectors

** up to 30 A allocated for cooling blowers

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