Mitsubishi Develops Compact EV Motor With Built-in SiC Inverter

Feb 19, 2014
Yoshiro Tsuruhara, senior editor, Electronics/Mechanical Group
The newly-developed motor
The newly-developed motor
[ If it clicks, the expanded picture will open ]
A conventional motor using a Si inverter
A conventional motor using a Si inverter
[ If it clicks, the expanded picture will open ]
The pathway of cooling water
The pathway of cooling water
[ If it clicks, the expanded picture will open ]

Mitsubishi Electric Corp developed an electric vehicle (EV) motor incorporating an inverter whose components such as transistors and diodes are all made by using silicon carbide (SiC).

With an output power of 60kW, it has a size of 14.1L, which is the smallest in the industry. The company aims to commercialize the motor in about 2018.

SiC inverters have higher efficiencies than Si inverters and, thus, generate less heat, making miniaturization easier. The volume of the latest EV motor (14.1L) is 44% smaller than that of Mitsubishi Electric's EV motor that uses a separate inverter (about 25L including the volume of the inverter). Also, the new motor enables to improve efficiency by several percents, the company said.

To reduce size, Mitsubishi Electric employed a new cooling system. Its conventional cooling system uses a method that first sends cooling water to a high-temperature inverter and then to a motor. On the other hand, the new system passes water along the perimeter of the cylindrical housing so that the inverter and motor units can be cooled in parallel. Because the inverter unit generates more heat than the motor unit, a larger amount of water flows near the inverter unit.

For commercialization, the costs of SiC devices need to be lowered. But Mitsubishi Electric expects that they will be close to the costs of Si devices in 2018.