Resolver motivated sensorless rotor position estimation of wound rotor synchronous motors

This paper presents a novel approach to sensorless control of wound rotor synchronous motor drives. The proposed rotor position estimation strategy is motivated by principle function of a resolver and utilizes design similarity between the controlled motor and the resolver based rotor position sensor. The rotor circuit is fed by controlled three-phase bridge rectifier which produces an ac component of frequency of 300Hz in the rotor excitation (flux) current. This ac component of rotor excitation current can be understood like an injection signal. Its response on the stator is evaluated by phase-lock-loop (PLL) which estimates the rotor position. This paper describes physical principle and functionality of the proposed sensorless rotor position estimation technique and verifies the theoretical foundations by simulation and experimental results made on developed drive prototype of rated power of 10kW.