New 5-phase concentrated winding machine with bi-harmonic rotor for automotive application

For a power range from 10 to 30 kW, 5-phase machines are well adapted to low-voltage (48V) supply thanks to their reduced current per phase. For three-phase machines but with higher voltages (>120V), machines with a number of slots per pole and per phase s_pp equal to 0.5 (as the 12slots/8poles combination) are widely used in hybrid automotive applications when a wide speed range is required. The reason is that the value of s_pp=0.5 guarantees no sub-harmonics and thus induces low level of permanent magnet rotor losses. In this paper a 20slots/8poles/5phases machine is chosen. With a winding factor of only 0.588 for the first harmonic, this machine is only interesting if its high third harmonic winding factor (0.951) is used. Thus, a new bi-harmonic rotor structure is presented. Thanks to adequate control with flux-weakening and ratio r between first and third harmonic currents, the maximum torque versus speed characteristic is determined.