Current Characteristic Analysis and Diagnosis Method of Open-circuit Fault in Fractional Slot Permanent Magnet Machine With Y-Δ Hybrid Connection
Fractional slot permanent magnet machine(FS-PMM)with star-delta(Y-Δ)hybrid connection has a promising application prospect in the field of electric vehicles for its advantages of low harmonic and small torque ripple.However,due to the fact that the Δ-connected windings are located inside the machine,the current cannot be measured directly which resulting in faults in Δ-connected windings cannot be found in time.Therefore,a fault diagnosis method based on the magnitude of the third harmonic current is proposed for the single-phase open-circuit fault in Δ-connected windings of FS-PMM with Y-Δ hybrid connection.Firstly,the mathematical models with single-phase open-circuit fault in Δ-connected windings are established,and the influences of fault on the fundamental and third harmonic current are studied.Then,the magnitude of the third harmonic current of Y-connected windings is taken as the fault characteristic.Considering the noise interference under low speed condition,the magnitude of the third harmonic current is amplified and the fault phase location index is constructed by combining the threshold with the amplified magnitude of the third harmonic current.Finally,based on the fault phase location index,single-phase open-circuit fault detection and fault phase location are realized.The experimental results show that the proposed method can accurately diagnose single-phase open-circuit fault in Δ-connected windings in real time which shows good robustness.
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