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TOYOTA will trial the performance of silicon carbide power semiconductors in test vehicles on the streets of Japan.
Power semiconductors are found in power control units (PCUs), which are used to control motor drive power in hybrids and other vehicles with electric powertrains. The PCUs supply battery power to the motors during operation, and are also responsible for recharging the battery using energy recovered during deceleration.
Current generations of power semiconductors account for nearly 20 percent of a vehicle’s total electrical losses. Increasing their efficiency translates directly to improved powertrain efficiency.
Silicon carbide (SiC) power semiconductors exhibit less electrical resistance, and Toyota will be testing SiC technologies jointly developed by Denso, Toyota Central R&D Labs, and the company itself.
The test vehicles will consist of a Camry hybrid prototype and a fuel cell bus. Toyota will install SiC power semiconductors (transistors and diodes) in the Camry’s PCU’s internal voltage step-up converter and the inverter that controls the motor.
For the test period of a year, starting in February 2015, engineers will gather information about the PCU voltage and current, as well as driving speeds, driving patterns, and conditions such as outside temperature, and compare this data to current silicon semiconductors to determine the efficiency improvements achieved by the SiC technology.
Similarly, on January 9, 2015, Toyota began collecting operating data from a fuel cell bus currently in regular commercial operation in Toyota City. The bus features SiC diodes in the fuel cell voltage step-up converter, which is used to control the voltage of electricity from the fuel cell stack.