| Summary: | This paper presents how to diagnose faults in static and dynamic eccentricity of a rotor by observing the vibration of permanent magnet synchronous motor. The radial electromagnetic force density of the permanent magnet synchronous motor is represented as the square of the air-gap flux density based on the Maxwell stress tensor, which is applied to the stator to cause the vibration. The distribution of air-gap flux density changes with the static and dynamic eccentricity so the changes of vibration order and frequency of radial electromagnetic force density will be considered with formulas. In result, the static eccentricity changes the vibration order while the dynamic eccentricity changes both vibration order and frequency. By applying it to the target model, 6-pole and 9-slot permanent magnet synchronous motors, the static eccentricity generates the vibration order of the original frequency, r = 2. In addition, the dynamic eccentricity generates vibration order, r = 2, not at the original frequency, but at the sideband frequency. It means that the static eccentricity increases the vibration of the original frequency and the dynamic eccentricity generates the sideband frequency while the vibration of the original frequency changes relatively little. The last proposal was verified with the finite element analysis and tests. Keywords: Permanent magnet synchronous motor (PMSM), Static eccentricity (S.E.), Dynamic eccentricity (D.E.), Radial electromagnetic force density, Vibration, Sideband frequency
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