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Reliable stator winding faults diagnosis is important for machine drives. This work presents an inter-turn short-circuit (ITSC) winding faults detection method for permanent magnet synchronous motors (PMSMs), based on the percentage of the second harmonics in phase instantaneous reactive powers (IRPs), defined in the abc frame of reference. In particular, the proposed indicator can locate the phase with ITSC for the PMSM with neutral conductor. The feature of ITSC in phase IRP is analyzed theoretically first, and a simulation setup is established in MATLAB/Simulink using the faulty PMSM model widely used for ITSC detection. From the theoretical analysis and the simulations, the second harmonic in phase IRP is proven to be the characteristic feature for fault detection. Simulations at different operating conditions show that the percentage of the second harmonic to its dc component in phase IRP, which is the proposed indicator in this article, is more reliable than the second harmonic amplitude itself for the ITSC detection and location. Experimental tests are carried out on a 3 kW motor with ITSC to investigate the effectiveness of the proposed indicator under different working conditions. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines work with controllers and controller parameters affect the machine's voltages and currents and, thus, the diagnosis of stator winding fault. One such parameter is the current controller bandwidth that affects the harmonic content in these signals. In the literature, the second harmonics in both $dq$ -axis currents and voltages have been used for fault detection, and the main advantage is that interturn short-circuit (ITSC) winding fault with a few shorted turns, specially one turn, can be detected. One indicator that combines the fault information in voltages and currents is the instantaneous reactive power (IRP). However, it has been shown that IRP does not perform robustly with respect to current controller bandwidth. The main contribution of this article is that it proposes and validates a new mathematical function for ITSCs detection, Rayleigh quotient, which combines the fault information present in voltages and currents to make ITSCs detection robust to current controller bandwidth. The validations from both cosimulation and experiment show that the proposed method is robust to the bandwidth and can detect ITSC faults faster than IRP. [ABSTRACT FROM AUTHOR]

With the wide application of inverter-fed motors (IFMs), it is necessary to monitor the groundwall (GW) insulation status to guarantee the reliable operation of motor drive system. This article first proposes a mathematical model of leakage current in IFM to analyze its time domain characteristics, and then an online GW insulation monitoring method is proposed based on the transient characteristics of leakage current. By using the initial oscillation amplitude, oscillation period, and attenuation time of leakage current, the phase, position, and severity of GW insulation degradation can be identified. The proposed method is validated using an IFM, and the experimental results agree well with theoretical analysis. [ABSTRACT FROM AUTHOR]

The electrical performance of ac contactor degrades under electric load stress, and the degradation data contains the information concerning the residual electrical life (REL). This article proposes an online reliability evaluation method that relates contact erosion loss (CEL) to electric load stress, performance degradation process, and electrical life prediction. First, the degradation variable of normal distribution is constructed by segmenting accumulation of CEL, and a degradation model based on Wiener process is established. With the knowledge of the first accumulation of CEL beyond failure threshold, the probability density function (PDF) of REL for ac contactor is presented, and the point estimation value and an interval estimation value of REL are calculated. Second, a simulation electrical life test is conducted using Monte Carlo method, and results show that the electrical performance degradation model and the prediction method of REL raised in this article are effective. Finally, CELs weighed in the electrical life test are applied in the prediction process of REL of ac contactor and the prediction error is proven acceptable in practical application. Compared with the neural network-based methods, the proposed method provides an intuitive and simple mathematical model with clear physical interpretations. [ABSTRACT FROM AUTHOR]

With the increasing of switching frequency in pulsewidth modulated motor system, common mode current (CMC) seriously affects the reliable operation of motor system and it has become a problem that cannot be ignored. This paper proposes a mathematical model of CMC and conducts detailed time–frequency characteristics analysis of CMC. The influence of several key parameters of motor system, such as distributed capacitance, dc bus voltage, and inverter switching frequency, on CMC characteristics has been analyzed in detail, and the corresponding variation rule of CMC oscillation amplitude and attenuation period/time has been summarized. The experimental results are presented to verify the correctness of theoretical analysis. The conclusions of this paper can lay theoretical foundation for the effective suppression of CMC in various practical applications. [ABSTRACT FROM AUTHOR]

Electrical life is an important performance indicator of ac contactor, and it is influenced by various factors, among which the most important one is arc erosion caused by arc current. This paper proposes a general contact erosion model based on arcing phase angle to simulate the electrical life distribution characteristics of ac contactor under random breaking operations. For the same type of ac contactor, different individuals have different electrical life due to the manufacturing dispersion, so the normal distribution is utilized to simulate the manufacturing dispersion under $3\sigma $ standard. The simulation results show that the electrical life distribution is closely related to the manufacturing dispersion degree. When the dispersion degree of manufacturing processes is relatively low, the electrical life obeys three-parameter Weibull distribution. Otherwise, the electrical life of contactors obeys normal distribution. Finally, the electrical life test is performed, and the test results are consistent with the theoretical analysis results. The abovementioned conclusion provides theoretical foundation for the reliability evaluation and experimental study of ac contactor. [ABSTRACT FROM AUTHOR]