An analytical method of calculating back-emf in dual consequent hybrid excitation synchronous machine

In order to solve the problem of asymmetric bidirectional flux control capability in hybrid excitation machine, a novel structure called dual consequent hybrid excitation synchronous (DCHES) machine is presented in this paper. Generally, the analysis of back-EMF for the machine with complex electromagnetic structure such as DCHES machine should utilize 3-D finite element analysis (FEA), which will require huge resources and computing time. In order to avoid using 3-D FEA to analyze the back-EMF of complex structure, an analytical method of calculating back-EMF is presented in this paper. The electromagnetic field in 3-D space can be simplified as a 2-D field by dividing the 3-D field into several simple zones, the resultant effect equals to the summation of every single 2-D field's effect. According to electromagnetic theory, the analytical formula of back-EMF is obtained on the basis of Fourier series. The influence of main parameters on back-EMF waveform under sine and trapezoidal flux distribution is discussed respectively. The theoretical result shows that the trapezoidal air-gap flux distribution would generate a sine back-EMF. Finally, the presented analytical method is verified and evaluated with experimental results.