The electrical variable transmission in a city bus

First, an electromechanical converter with two mechanical ports and one electrical port (consisting of two concentric machines and two invertors) is considered. This converter works as a continuously variable transmission between the mechanical ports and may, for example, replace the clutch, gearbox, generator, and starter motor in a motor vehicle. The working principle of this converter is explained. Next, a new converter, the electrical variable transmission (EVT), is presented. This converter has similar properties, but is smaller and lighter. The EVT may be seen as built up from two concentric induction machines with a combined, relatively thin yoke. So, we obtain one electromagnetic device instead of two magnetically separated devices. For the explanation of the principle of the EVT, different operation modes are examined by means of analytical two-dimensional field computations and the losses are discussed. The performance of the EVT in a city bus was simulated and compared with a bus with a conventional automatic transmission. The bus with the EVT uses less fuel because the combustion engine can operate with efficiency. The EVT is very well fit to be used in a hybrid configuration, which decreases the fuel consumption even more.