Computationally Efficient Analysis and Optimization of Induction Motors

The goal of this dissertation is to establish computationally efficient large-scale design optimization procedures for induction motors that are not only computationally efficient, but also do not sacrifice the accuracy of the results. To achieve this goal, the topic of the lengthy numerical transient response of Time-Stepping Finite Element Analysis (TS-FEA) of induction motors was investigated. This is because this lengthy transient affects the computational efficiency aspect of the optimization process. The effect of different parameters on the numerical transient response phenomenon were studied, and two different techniques for mitigation of this numerical transient were evaluated. The superior one amongst the two techniques was highlighted and implemented on the case-study induction motor. This technique was also extended to induction motors under faults. Applying Maximum Torque Per Amp (MTPA) or constant Volts/Hz control on uncharacterized design candidates of a large-scale evolutionary optimization process that are assumed to be operating with a sine-wave current-regulated drive is a major challenge and process accuracy may suffer significantly. In this dissertation, a novel and computationally efficient technique was introduced that can apply the MTPA or constant Volts/Hz control on uncharacterized design candidates without any prior knowledge of the motor equivalent circuit parameters. A new computationally efficient VBR-based routine for calibration of the motor temperatures estimation was introduced in this dissertation. This hybrid approach is a fusion between the VBR-based TS-FE and the thermal network models of an induction motor and is aimed to enhance the accuracy of the induction motor optimization process. In addition, the sensitivity analysis for both purely magnetic and Multiphysics cases were performed to identify and deactivate the less impactful design variables to enhance the computational efficiency of the optimization process. Eventually, the techniques established throughout this dissertation are utilized to perform computationally efficient large-scale design optimization of induction motor that does not sacrifice on accuracy. The 5-Hp case-study induction motor was electromagnetically optimized under three different scenarios DE-based algorithm. In addition, a multi-physics design optimization routine was carried out with its own objective functions and design constraints that evaluated the motor in thermal, mechanical, and magnetic environments in real-time

On Shortening the Numerical Transient in Time-Stepping Finite Element Analysis of Induction Motors Under Static and Dynamic Eccentricity Faults

Modeling induction motors under static and dynamic eccentricity faults, arising from bearing wear and tear , through Time-Stepping Finite Element (TSFE) methods suffers from the resulting long numerical transient response before numerical convergence is achieved. In this paper, this lengthy transient phenomenon is substantially reduced through the so-called Virtual Blocked Rotor (VBR) approach implemented here. This approach starts with an initial calculation of the motor permeabilities and skin effect corresponding to the operating condition of the induction motor. Such calculations are performed in an FE Eddy-Current frequency-domain solver reflecting the voltage supply magnitude, value of slip, type and degree of eccentricity fault. The calculated permeabilities are imported into the TSFE simulation of the faulty induction motor and the performance characteristics of the faulty motor are extracted for further analysis. In this paper, static and dynamic eccentricities are applied to the induction motor under study. It is observed here that this approach successfully solves the problem of a lengthy numerical transient response and saves computational time in the analysis process

On Shortening the Numerical Transient in Time-Stepping Finite Element Analysis of Induction Motor Under Broken Rotor Bar Faults

In induction motors, broken rotor bar faults are common and represent an aggressively propagating phenomena in applications in which motors are subject to frequent line starts and stops. Fast and accurate analysis of induction motors under this type of faults is desirable. Time-Stepping Finite Element (TSFE) analysis of induction motors, as one of the most powerful tools of analysis, suffers from the lengthy numerical transient response and the large number of ac cycle periods that are needed to reach a steady-state level of flux build-up. That is, until a steady-state solution is reached. In this paper, this lengthy and undesirable transient time, as an obstacle, was successfully reduced through the implementation of the so-called Virtual Blocked Rotor (VBR) approach described in this paper. The VBR approach starts by determining motor permeabilities and skin effect corresponding to the operating condition of the induction motor. Permeability computation is performed in an FE Eddy-Current frequency-domain solver with the desired voltage supply magnitude and frequency, slip, and given broken rotor bar pattern. The computed permeabilities are then imported into the TSFE simulation model of the faulty induction motor and the performance criteria of interest are extracted for further evaluation. In this paper, a four adjacent broken bar fault pattern is studied in the given case-study induction motor. It was observed that this approach successfully and substantially mitigates the problem of the lengthy numerical transient response to reach a steady-state solution, and hence saves a large amount of time in the computational process