Design of IPMSM with eccentric rotor and search coils for absolute position sensorless drive

In this paper, a design methodology of IPMSM for absolute position sensorless drive is proposed. In conventional researches on the absolute position estimation, initial motion of the rotor was required, which was not allowed in many applications. To eliminate the initial motion, an IPMSM with eccentric rotor with search coils is devised. In the proposed design, the information of the absolute position is included in the voltage signals at the search coils. By measuring the search coil voltages and analyzing them, the absolute position can be estimated without the initial motion of the rotor. The overall performances of the proposed motor design are evaluated by rigorous finite element analyses and experimental tests.