In the past, various companies have already tried developing disruptive zero-emission motors, for instance with motors hidden in the wheel. This frontier has not technically found its benefit, yet, especially owing to the weight hindrance.
Hitachi, more precisely its subsidiary Hitachi Astemo, is trying giving a solution to the problem with the Direct-Drive. In practice, the manufacturer is going to integrate everything in a single component, placing in the wheel the motor, the inverter and the brake to achieve a power/weight ratio of 2.5 kW for each kg. In this way, they can partially eliminate wirings, as well as transmission gears, so improving efficiency up to 30%.
The prototype wheel is 19″, with maximum torque of 960 Nm, operation at 420 volt and maximum power of 60 kW: multiplied by four wheels, the total value would amount to 240 kW.
To avoid undesired contacts between the inverter components and the liquid, the cooling oil circulates in a ring among the various parts, by means of tubes, directly acting on power semiconductors, and then it is conveyed to the motor to cool coils.