Chinese Startup Shows EV Sedan Concept
NIO Inc, an electric vehicle (EV) venture firm based in China, aims to release an EV sedan in 2021.
NIO will sell the EV as the “ET” series. Its drive range will be 500km (approx 311 miles) or longer per charge, the company said. For the EV, NIO plans to employ an inverter using an SiC (silicon carbide) power semiconductor.
This time, NIO exhibited the “ET Preview” concept car, which had a shape of a mass-produced sedan, at Auto Shanghai 2019, which took place from April 16 to 25, 2019. The exterior design of the car was similar to that of Tesla Inc’s “Model 3” EV.
The ET Preview seemed to have two motors on the side of the front wheels and one motor on the side of the rear wheels. The motor is integrated with an inverter (including a circuit for driving the motor) and gear box (speed reducer and differential gear device) and functions as an electric axle.
Including the ET Preview, NIO’s EVs use different kinds of motors for the front and rear wheel sides. Specifically, they use a permanent magnet synchronous motor (PSM) on the side of front wheels and an induction motor (IM) on the side of rear wheels.
“In the low and middle speed regions, the driving force of PSM is mainly used,” NIO said. “At the time of acceleration or in the high speed region, IM is mainly used.”
Compared with PSM, IM has a larger volume but a high efficiency at the time of high-speed rotation.
NIO plans to apply the newly-developed electric axle to the ET series. To use PM, it will probably be used on the side of the front wheels. The maximum output and maximum torque are 220kW and 360N·m, respectively.
An SiC power semiconductor was employed for the inverter. As a result, compared with an existing product with a maximum output of 160kW, NIO increased output without increasing volume, the company said.
The new electric axle expected to be used on the side of the front wheels incorporates two PSMs and can control the right and left wheels separately. It is a coaxial type, and the axle connecting automotive shafts and the axle of the motor are located on the same line. A space for the two motors was created by using the SiC inverter for size reduction.
NIO has the “EP Platform” platform consisting of main EV components including an electric axle. Thus far, it applied the platform to the “ES8” and “ES6” SUV (sport utility vehicle)-type EVs but will expand the application range to the ET series sedan-type EV.
The EP Platform has lithium-ion (Li-ion) battery cells under the floor. The capacity of them is 84kWh. And the ES6 can travel 510km under the “NEDC (New European Driving Cycles)” mode. The ET Preview will have an equivalent drive range, according to NIO.