Today's electric drives are usually designed without transmission; at the most, they may include a reduction gear to lower rpm speed. In addition, the absence of a gearbox makes the drive units simpler and thus more robust and cheaper. They are also more compact than a unit with a transmission.
Ricardo's engineers took exactly the opposite approach when developing their scalable Electric Drive Unit (EDU), which they intend to present at CTI Shanghai on September 24. The unit is intended to provide state-of-the-art power and torque density as well as system efficiency, and all of that with high noise, vibration and harshness (NVH) performance.
Why chose the Ricardo engineers such an adversarial approach? “A multi-speed transmission is clearly more costly than a single speed unit, but it's use can give benefits in terms of weight reduction and more compact sizing of the electric motor, improved whole system cost, energy efficiency, and a hence the potential for a reduced battery size or extended range”, explained a company spokesperson. He was convinced that “the use of multi-speed EDUs is likely to be an increasing trend in the market in the coming 5 years.”