Condition monitoring of the insulation health of electric machines is usually performed with offline tests. In recent years, online condition monitoring methods for the groundwall insulation have been introduced. The majority of these works are based on leakage current measurements, requiring additional equipment compared to the standard one in converters. The condition monitoring method in this work instead relies on the high-frequency ringing of stator currents occurring after a converter switching transition. This work evaluates the method experimentally in a randomly-wound stator winding of an induction machine prototype equipped with taps. The insulation condition change is forced by inserting external capacitors. Through the analysis of different metrics for the health monitoring and a detailed discussion of the hardware and software requirements for an electric drive, a viable way forward for the practical implementation of the approach is proposed.

An interturn short-circuit in the stator windings can lead to the breakdown of electrical machines. In the case of induction machines, several fault detection methods and faulted models have been developed in the recent decades. These models differ mainly in how the leakage inductances of the faulted winding are modeled. This work provides a generalized model for interturn short-circuit faults, using different assumptions for the leakage inductances. The model is validated with experimental results for an exhaustive set of fault parameters, and the leakage inductances influence is analyzed. Moreover, the model is used to analyze the drawbacks of the negative-sequence fundamental current as a traditional fault signature. A high-frequency injection method for converter-fed machines is presented to overcome these limits. The proposed fault signature is the negative-sequence current at the injection frequency and it is evaluated experimentally at different operating conditions. The fault severity and its location are proved to be related to the proposed fault signature.

Induction machines are the working horses in a lot of industries. Inter-turn short-circuit (ITSC) fault is one of the most common failure modes taking place in them. It can generate large fault currents that lead to a local temperature rise in the faulty stator slot, which deteriorates the working performance of the machine or even cascades to a complete machine breakdown. This article focuses on developing transient thermal models for an induction machine under ITSC faults. The aim of these thermal models is to understand the thermal behaviour of the induction machine at different ITSC fault propagation stages. The first thermal model is based on finite element method (FEM) simulation that includes a physics-based model for the thermal contact resistance. The second thermal model is a lumped parameter thermal network that models the stator as inter-connected slot-number parts. They are both capable of modelling the characteristic of non-uniform temperature along the circumferential direction for the induction machine operating under ITSC fault conditions. After area-weighted averaging the results of the FEM simulation, it is found they are quantitatively consistent, with an average relative error magnitude of 5%, as well.

Condition monitoring of the insulation health of electric machines is usually performed with offline tests. In recent years, online condition monitoring methods for the groundwall insulation have been introduced. The majority of these works are based on leakage current measurements, requiring additional equipment compared to the standard one in converters. The condition monitoring method in this work instead relies on the high-frequency ringing of stator currents occurring after a converter switching transition. This work evaluates the method experimentally in a randomly-wound stator winding of an induction machine prototype equipped with taps. The insulation condition change is forced by inserting external capacitors. Through the analysis of different metrics for the health monitoring and a detailed discussion of the hardware and software requirements for an electric drive, a viable way forward for the practical implementation of the approach is proposed.

This work investigates stator interturn short-circuit faults in induction machines. The goal is to examine possible fault signatures used in detection methods for interturn short-circuit faults. For this purpose, a faulted induction machine is analysed through a finite-element model. Great attention is given to the sequence components and harmonic content of the stator currents. Finite-element-based results are provided and discussed for an extensive set of fault conditions. The stator-current negative sequence and the rotor slot harmonics are dependent on the fault presence. An induction machine prototype with tapped windings is used for experimental tests where an extensive amount of fault conditions is implemented. The experimental tests validate the finite-element model and the fault signatures.

As the working horse in the industrial world, induction motors are widely applied in many important areas. Hence, it is crucial to investigate the fault operation conditions that would cause their deterioration of working performance or even failures, such as the inter-turn short-circuit (ITSC) fault. This study aims at analyzing the extra generated loss and induced thermal response in an 11kW induction motor under such a fault scenario. Specifically, a new finite element model with separated conductors in the stator slot is built, which characterizes the physics of ITSC fault propagation at different stages by varying the numbers of shorted conductors. In addition, the ITSC fault is implemented in different positions of the stator slots and the consequent motor temperature distributions are analyzed as well.