Study on effects of supply voltage asymmetry and distortion on induction machine

Performance of induction motor supplied with asymmetrical and nonsinusoidal supply voltages is studied in this thesis. Theory of induction motor is first presented for sinusoidal symmetrical supply voltages. Equations for the torque, losses, currents and efficiency are derived. Appropriate changes are made to apply this theory to induction motors operating at nonsinusoidal and asymmetrical supply voltages. Single phase equivalent circuit of the induction motor is presented for both asymmetrical and nonsinusoidal supply voltages. The equations governing operating characteristics are presented. Machine torque, losses, current and efficiency for asymmetrical and nonsinusoidal supply voltages are compared with the same for sinusoidal symmetrical supply voltages. Computer simulation in MATLAB is used to study the impacts of asymmetrical and nonsinusoidal supply voltages on induction machines. Machine torque, losses, current and efficiency are calculated for various levels of voltage asymmetry and distortion. Results of computer simulation are presented

Powers and Compensation in Three-Phase Systems with Nonsinusoidal and Asymmetrical Voltages and Currents

A contribution to power theory development of three-phase three-wire systems with asymmetrical and nonsinusoidal supply voltages is presented in this dissertation. It includes: • contribution to explanation of power related phenomena • contribution to methods of compensation The power equation of unbalanced Linear Time Invariant (LTI) loads at sinusoidal but asymmetrical voltage is first presented. The different current components of such a load and the phenomenon associated with these current components are described. The load current decomposition is used for the design of reactive balancing compensators for power factor improvement. Next, the current of LTI loads operating at nonsinusoidal asymmetrical voltage is decomposed, and the power equation of such a load is developed. Methods of the design of reactive compensators for the complete compensation of the reactive and unbalanced current components, as well as the design of optimized compensator for minimization of these currents are also presented. Next, the power equation of Harmonics Generating Loads (HGLs) connected to nonsinusoidal asymmetrical voltage is developed. The voltage and current harmonics are divided into two subsets, namely the subset of the harmonic orders originating in the supply, and the subset of the harmonic orders originating in the load. The load current is decomposed based on the Currents’ Physical Components (CPC) power theory, and the theory is also used for reference signal generation for the control of Switching Compensators used for power factor improvement. Results of simulation in MATLAB Simulink are presented as well