Power flow in an induction machine based electrical variable transmission

An electrical variable transmission (EVT) is an electromagnetic device with dual mechanical and electrical ports. In hybrid electric vehicles (HEV's) it is used to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. The most important feature is that the power splitting is done in an electromagnetic way. This has the advantage over mechanical power splitting devices of reduced maintenance, high efficiency and inherent overload protection. Depending on the operating point part of the power is transmitted in an electromagnetic way, while the rest is transmitted electrically using two back to back inverters. The power flow determines the power rating of the inverters, the cooling and the machine design. This paper gives an overview of the different operating points and the corresponding power flow.