Last year I covered Season 3 of Formula E racing in NY on EDN in ‘Formula E: The electric vehicle moves to the racing circuit’
Formula E racing now kicks off it’s 2017/18 Season 4 with the first race in Hong Kong on December 2, 2017.
The only USA races this year will be in New York City again on July 14 and 15, 2018 and I am planning to attend.
In this article, I would like to take a look at the DC/DC converter in the Electric Vehicle (EV) motor drive architecture. This power architecture enables lower current and voltage ripple with high power density. It is an important stage between the battery and the motor DC link bus of the EV. The converter handles power flow from the battery while driving and returns energy to the battery when regenerative braking occurs.
An important aspect of a good design for an EV would be low loss power switches in both conduction and switching functions. The use of SiC power devices running at high frequency and with low switching losses makes it an excellent candidate for an EV inverter design.
ROHM is supplying SiC power modules to the Venturi Formula E racing team which will reduce the size and weight of the inverter in their racing car. The higher frequency of which these SiC power elements are capable will also reduce the size, cost and weight of any filtering components in the vehicle. With the low losses in a SiC device, cooling requirements are reduced as well, which translates to more space in the vehicle at a lower weight.
The Venturi Team racing machine
In Season 2 (2015/16) of Formula E racing inverters were typically weighing 15 kg with a maximum power of 200kW. Season 3 (2016/17) inverters shrunk in size by 19% and dropped in weight to 13 kg. Now in Season 4 (2017/18), using a full SiC module, the weight dropped to 9kg which is 4kg less than last year with a 30% reduction in size, but with a 10% increase to 220kW power capability.
As opposed to conventional IGBT modules with similar current ratings, the Season 4 module reduces switching losses by 75% (at a chip temperature of 150°C). This greatly increases the energy efficiency for the whole application. With the addition of more compact peripheral components throughout the high-frequency drive, along with the effect of reductions in switching losses, the system now has a more compact cooling system as well.
The Advantage of Using SiC Products
The SiC power module used in the inverter of the VENTURI Formula E team racing car enables a large power throughput, due to a new package with an improved internal module structure, as well as an optimized thermal management architecture.
The ROHM SiC power module architecture (Image courtesy of ROHM)
About VENTURI Formula E Team
VENTURI Automobiles (The ‘company’) is one of the pioneers in designing electric powertrains and has been systematically pursuing a sustained electric vehicle innovation policy since 2000. The company develops the highly advanced technologies available for extreme-performance electric powertrains. In 2013, VENTURI Automobiles entered the FIA Formula E series under the VENTURI Formula E Team name and became an FIA-approved manufacturer in 2015. The company supplies full powertrain systems for the VENTURI Formula E Team. VENTURI Automobiles holds the FIA World Land Speed record for an all-electric vehicle. In 2016, the VENTURI Buckeye Bullet 3 set the official top recorded speed achieved by an electrically-driven car of 549 km/h on the Bonneville Salt Flats in Utah.
McLaren Applied Technologies
McLaren has a wide variety of products for the Formula E racing car architecture: McLaren Formula E products
McLaren’s E-motor is a starting point for many Formula E teams who will modify that design within FIA Formula E rules and standards to get an edge over the competition.
McLaren’s 120kW E-Motor is a synchronous permanent magnet motor/generator for use in hybrid and electric vehicles. The motor power supply is a high voltage, three-phase output from an inverter. such as McLaren Applied Technologies’ MCU-500, but in the case of the Venturi Team, they are using a ROHM Inverter powered by SiC power elements. (Image courtesy of McLaren)
The motor architecture uses an advanced liquid cooling scheme that enables the motor to achieve constant high-power operation even with its reduced size and weight.
When this 20,000 RPM motor is combined with an efficient inverter like ROHM’s which is seated on top of the 28 kWHr battery pack and powered from a high voltage DC bus by that battery pack, the system can be controlled using torque and/or speed demands via a standard CAN bus. See the following video.
Watch for my article on EDN in which I will discuss the Formula E racing car design concept and architecture in detail.