A General Mathematical Formulation for the Determination of Differential Leakage Factors in Electrical Machines with Symmetrical and Asymmetrical Full or Dead-Coil Multiphase Windings

This paper presents a simple and general mathematical formulation for the determination of the differential leakage factor for both symmetrical and asymmetrical full and dead-coil windings of electrical machines. The method can be applied to all multiphase windings and considers Görges polygons in conjunction with masses geometry in order to find an easy and affordable way to compute the differential leakage factor, avoiding the adoption of traditional methods that refer to the Ossanna's infinite series, which has to be obviously truncated under the bound of a predetermined accuracy. Moreover, the method described in this paper allows the easy determination of both the minimum and maximum values of the differential leakage factor, as well as its average value and the time trend. The proposed method, which does not require infinite series, is validated by means of several examples in order to practically demonstrate the effectiveness and the easiness of application of this procedure

Voltage source inverters: an easy approach for fast fault detection

Peer Reviewe

Closed-loop bandwidth impact on MVSA for rotor broken bar diagnosis in IRFOC double squirrel cage induction motor drives

This paper investigates the detectability of rotor broken bars in indirect rotor flux oriented control (IRFOC) for variable speed double cage induction motor drives, using vibration signature analysis techniques. The Impact of the closed loop control system cannot be neglected when the detection of rotor asymmetries in the machine is based on the signature analysis of electrical or mechanical variables. Therefore, the investigation of rotor fault components for different bandwidths of closed-loop regulators is necessary to evaluate its relevance in the above listed variables. This paper investigates the impact of the control system on relevance of the fault components computed from axial and radial vibration signals. Experimental results show the validity of this impact, and more specifically, the bandwidth PI regulators. Due to its relevance, axial vibration analysis shows a more robust fault signature, under the control impact, in separating healthy from rotor bar breakage in double squirrel cage induction motors

Quantitative Rotor Broken Bar Evaluation in Double Squirrel Cage Induction Machines under Dynamic Operating Conditions

Advanced monitoring techniques leading to fault diagnosis and prediction of induction machine faults, operating under non-stationary conditions have gained strength because of its considerable influence on the operational continuation of many industrial rocesses. In case of rotor broken bars, fault detection based on sideband components issued from currents, flux, instantaneous control or power signals under different load conditions, may fail due to the presence of inter-bar currents that reduce the degree of rotor asymmetry, especially for double squirrel cage induction motors. But the produced core vibrations in the axial direction, can be investigated to overcome the limitation of the classical technique using appropriate time-frequency analysis for these purposes. Unlike previous approaches, the presented technique is based on optimized use of the Discrete wavelet transform to overcome the limitation of classical frequency approaches under non-stationary operating conditions. The developed approach is best suited for automotive or high power traction systems, in which safe-operating and availability are mandatory. Experimental results are provided, showing the validity of the investigated technique, leading to an effective diagnosis procedure for incipient rotor broken bars in double or single cage induction machines under dynamic operating conditions