Magnetic coupling analysis of four-quadrant transducer used for hybrid electric vehicles

A four-quadrant transducer (4QT), which is a hybrid electric vehicle power train concept, is a structural integration of two permanent-magnet synchronous machines. It comprises three parts: stator, outer rotor, and inner rotor. As the outer rotor is a structural and magnetic common part of the two radial-flux machines, the magnetic circuits of the two machines are coupled. A new method is put forward to solve the permanent-magnet operating point when considering the magnetic coupling during machine design, and a 4QT prototype machine of 60 kW is designed. The influences of the magnetic coupling on flux distribution and electromagnetic torque are discussed by analytical method and finite-element method, respectively. It can be concluded that the decoupling is easy to perform. The magnetization-direction choice of the two layers of the permanent magnets on the outer rotor is also discussed, and the consistent magnetization is preferred.