Switching Control between 3-coil and 5-coil modes for 6-pole Active Magnetic Bearings

6-pole active magnetic bearings (AMBs) have fewer poles than usual 8-pole AMBs, then, it is easier to miniaturize and suitable for small motors. In this paper, we propose the novel control method for the 6-coil AMB, which switches between 3-coil and 5-coil modes. The 3-coil mode uses three coils to generate bearing force and can reduce power consumption. On the other hand, the 5-coil mode uses five coils, and can generate larger maximum force than that of the 3-coil mode. By switching between the two modes, it is possible to realize both lower power consumption and larger bearing force. This paper introduces the coil currents in the 5-coil mode and shows the results of levitation and rotation tests. The results show that the proposed method realizes stable levitation with lower current limit compared with other methods.