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SiC inverters halve the size of EV motor systems

Mitsubishi Electric says its silicon carbide inverter-equipped EV motor system is the industry's smallest

Mitsubishi Electric Corporation has developed a prototype electric vehicle (EV) motor system with a built-in SiC inverter.

The EV motor system is claimed to be the smallest of its kind; it measures just half the dimensions of Mitsubishi Electric's existing Silicon-based motor system that uses an external inverter.

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

The firm's existing Silicon-based system consists of separate motors and inverters driving the motors, which requires more space for these components and their wiring.


 SiC inverter-equipped EV motor system

The new motor system is expected to enable manufacturers to develop EVs offering more passenger space and greater energy efficiency. The company plans to commercialise the motor system after finalising 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 CO2 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.

Mitsubishi's newly developed cylinder-shaped inverter matches the diameter of the motor, enabling it to be connected coaxially within a chassis, resulting in a substantial downsizing of the motor system.

Silicon chips have been widely used in power devices for inverter switching. Silicon carbide, however, is now recognised 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.

The improved winding density and magnetic efficiency achieve a smaller motor with higher output. The new product has a permanent magnet motor that uses a neodymium magnet. Mitsubishi Electric's proprietary dense-winding structure enabled the company to utilise its poki-poki motor production technologies to reduce the size of the motor.

What's more, the size and configuration of the stator and rotator poles have been optimised using Mitsubishi Electric's high-level magnetic-design technology. As a result, magnetic efficiency has been increased and power output improved by 5% over the company's previous motors.
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