Batteries are usually the focus of technological advances when it comes to electric vehicles, but a new product announcement by Mitsubishi Electric reminds us that is not the only EV element that can be improved. The company has unveiled a new motor design that integrates the inverter – the electronics that regulate the flow of electricity between battery pack and motor – reducing the footprint of the drivetrain and freeing up space in a vehicle's architecture for passenger and cargo.

While less weight and size is pretty cool in itself, the new design doesn't stop there. Using silicon carbide (SiC) in place of silicon-based chips, it cuts energy losses by more than half. Traditionally, silicon has been used for power-switching chips but SiC is more resistant to heat, so thinner chips can be used. Less material means less electrical resistance which means less energy loss.

These innovations, in addition to earlier Pokémon "Poki-poki" manufacturing processes that increased power output through improved motor winding and lamination, all add up to a propulsion system that should be worthy of some of the battery breakthroughs that are coming down the line. Now, if only Mitsubishi Motors would complement its keiretsu kin's tech advances by developing an updated electric vehicle chassis to put it in, the tri-diamond brand might regain some of its former luster. Official press release awaits after the break.
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PRESS RELEASE

Mitsubishi Electric Develops EV Motor System with Built-in Silicon Carbide Inverter

Industry's smallest inverter-equipped EV motor system is half the dimensions of existing systems

Tokyo, March 8, 2012 - Mitsubishi Electric Corporation (TOKYO: 6503) announced today it has developed a prototype electric vehicle (EV) motor system with a built-in silicon carbide inverter. The EV motor system is the smallest of its kind, measuring just half the dimensions of Mitsubishi Electric's existing motor system that uses an external inverter, and loss is below half that of silicon-based systems.

The new motor system is expected to enable manufacturers to develop EVs offering more passenger space and greater energy efficiency. The company plans to commercialize the motor system after finalizing other technologies for motor/inverter cooling, downsizing and efficiency.

The global demand for EVs and hybrid EVs (HEVs) has been growing in recent years, reflecting increasingly strict regulation of fuel efficiency and growing public interest in saving energy resources and reducing carbon dioxide emissions. As EVs and HEVs require relatively large spaces to accommodate their robust battery systems, there is a strong need to reduce the size and weight of motor systems and other equipment to ensure sufficient room in passenger compartments.

Key Developments of New EV Motor System
1) Inverter-equipped design just half the dimensions of existing system
• Mitsubishi Electric's existing system consists of separate motors and inverters driving the motors, which requires more space for these components and their wiring.

• The newly developed cylinder-shaped inverter matches the diameter of the motor, enabling them to be connected coaxially within a chassis, resulting in a substantial downsizing of the motor system.

2) SiC inverter loss is reduced by more than 50% compared to silicon-based systems
• Silicon chips have been widely used in power devices for inverter switching. Silicon carbide, however, is now recognized as a more suitable material for chips owing to its electrical characteristics, including a breakdown electric field that is 10 times greater compared to silicon chips. This greater breakdown electric field enables thinner chips, which reduces electrical resistance and lowers loss.

• All power chips in the inverter are silicon carbide-based, resulting in over 50% reduction of loss compared to the company's silicon-based inverter system.

3) Improved winding density and magnetic efficiency achieve smaller motor with higher output
• The motor is a permanent magnet motor that uses a neodymium magnet. Mitsubishi Electric's proprietary dense-winding structure enabled the company to utilize its poki-poki motor production technologies to reduce the size of the motor.

• The size and configuration of the stator and rotator poles were optimized using Mitsubishi Electric's high-level magnetic-design technology. As a result, magnetic efficiency was increased and power output was improved by 5% over previous motors.

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