Real-Time Detection of the Dynamic Eccentricity in Permanent-Magnet Synchronous Motors by Monitoring Speed and Back EMF Induced in an Additional Winding

We developed a real-time method to detect the dynamic eccentricity of a rotor in a permanent-magnet (PM) motor by monitoring a fault detection signal induced in an additional winding, without performing any further postprocessing, even under a nonstationary rotational speed. After deriving a mathematical equation of the back electromotive force (EMF) induced in a tooth-coil winding, we proposed a fault detection signal, which is the back EMF in an additional winding divided by the rotational speed, when the additional winding is wound around the teeth corresponding to an even number of pole pitches. We used the 2-D finite-element model of a three-phase PM motor with eight poles and 12 slots to verify the proposed method. We also developed an experimental setup which can change the dynamic eccentricity of a PM motor and we performed the experiment for PM motors with dynamic eccentricities of 0%, 25%, and 50% to verify the proposed method. Through the mathematical equation, numerical simulation, and experiment, we confirmed that the fault detection signal proposed in this paper can successfully detect the dynamic eccentricity in a PM motor in real time.