Toyota has revealed the details of a year-long trial, taking place in Japan, to evaluate the performance of new semiconductor technology in electric powertrain systems.
The new semiconductors, which use silicon carbide (SiC) materials, have been installed in a Toyota Camry hybrid saloon prototype. The OEM will monitor the performance of the vehicle during the trial to measure any improvements in efficiency that result from the SiC semiconductors. Toyota has also installed the components in a hydrogen fuel cell-powered bus.
The technology has been jointly developed by Toyota, Denso, and Toyota’s Central R&D Labs (CRDL). Engine Technology International spoke to a Toyota representative about the project.
“Toyota CRDL and Denso began basic research in the 1980s, with Toyota participating from 2007 to jointly develop SiC semiconductors for practical use,” the spokesperson reveals. “In December 2013 Toyota established a clean room for dedicated development of SiC semiconductors at its Hirose plant – a facility for research, development and production of devices such as electronic controllers and semiconductors.”
Power semiconductors are used in the control units of electric drivetrains – in hybrid and all-electric systems – sending power from the battery to the motor for drive, and from the motor back to the battery during energy recovery.
“A key way to improve fuel efficiency in vehicles fitted with electrified powertrains is to improve the efficiency of the power semiconductors used to control electrical power, which means reducing resistance of the passing current and reducing electrical power loss,” explain Toyota’s spokesperson. “As power semiconductors account for an estimated 20% of the total electrical power loss in hybrid vehicles, Toyota has been working on in-house development of power semiconductors and on improving fuel efficiency since launching the Prius gasoline-electric vehicle in 1997.”
The OEM has already set benchmarks for the SiC project. “Through the use of SiC semiconductors, Toyota aims to improve hybrid vehicle fuel efficiency by 10% under the Japanese MLIT test cycle, and reduce power control unit size by 80% compared with current PCUs with silicon-only semiconductors.”
The results of the year-long trial, held in Toyota City, will be closely monitored, but the company already feels that the technology has great potential. “There are still many issues remaining before all power semiconductors can be replaced by silicon carbide, and before the technology can be commercialized to maximize its effect, but Toyota plans to work toward commercialization over the medium- to long-term.”
There are currently no plans for further trials in different locations, or with different vehicles. But Toyota has also been trialing the components in a hydrogen fuel cell-powered bus, currently in commercial operation in Toyota City. “The trial began on January 9 and is scheduled to continue until March 31,” the spokesperson confirms. “This trial is to verify the feasibility and effectiveness of the fuel cell bus through testing involving commercial operation on regular routes and on public roads. The results will be used by our R&D department.
“The power semiconductors can reduce boost-converter losses, supporting effective use of power from the fuel cell, and we believe that this will increase efficiency.”