Review of Time and Space Harmonics in Multi-Phase Induction Machine

Abstract

Modern multiphase electric machines take advantage of additional degrees of freedom for various purposes, including harmonic current injection to increase torque per ampere. This new approach introduces a non-sinusoidal air gap flux density distribution causing additional technical problems and so the conventional assumptions need to be revised. The paper presents a methodology for synthesis of air gap magnetic field generated by a symmetrically distributed multiphase windings including the rotor field reaction due to the machine’s load. The proposed method is suitable either for single-layer or double layer windings and can be adopted either for full-pitched or chorded winding including slots effects. The article analyses the air gap flux density harmonic content and formulates conclusions important to multiphase induction motors. It also discusses effects of time harmonic currents and illustrates the principle of changing number of pole-pairs typical for harmonic currents being injected to increase torque.

Magneto-Motive Force and Performance Comparative Analysis Research for a Novel Pentacle-Star Hybird Winding Five-Phase Induction Motor

“…Hence, to obtain the same MMF magnitude from the two winding sets, for equal ampere turn for both windings N C1 I A1 = N C2 I A2 . The relation between the number of turns per phase for the two winding sets is expressed as N C2 = 1.902N C1 (12) where N C1 is the number of turns of star winding A1, and N C2 is the number of turns of the pentacle winding A2. This gives the same copper volume as in a conventional five-phase winding.…”

“…Further, the voltage or current waveform output by the inverter is not a standard sine wave, but contains a harmonic component which cannot be ignored, and the produced harmonic Magneto-Motive Force (MMF) has a great influence on the operational performance of the motor. Therefore, many research institutes and universities have paid attention to the following four aspects: 1) the structural design of multi-phase motors, as good structural design can effectively reduce the influence of spatial harmonics on motor performance (e.g., start-up performance and magnetic noise); 2) the relationship between harmonic current and the harmonic MMF of multi-phase motors with different structure under a non-sinusoidal power supply; 3) how to effectively use the harmonics to improve motor performance; and 4) fault diagnosis and fault-tolerant control of multi-phase motors [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…Magnetic Finite Element Analysis (FEA) and algebraic equation analysis based on the permeance model have been used to analyze the harmonic components of air-gap flux density distribution when designing induction motors [9,10]. Time and spatial harmonics have been researched using analytical methods and equivalent circuit methods [11,12]. Using four stator winding modes combined by even or odd number phase, symmetric or semi-symmetric winding construction can be analyzed [13].…”

Impact of Core Sheet Cutting Method on Parameters of Induction Motors

“…The determination of such characteristics requires complex tests, therefore another approximate method should be sought to enable calculations of the parameters and characteristics of the designed motors as close as possible to the values obtained as a result of laboratory tests of model motors. This particularly applies to the accuracy of calculating losses in the motor core and magnetizing current [35,36]. As demonstrated in [37], at motor load, core losses due to higher harmonics of induction far outweigh basic losses in teeth and stator yoke.…”

Comparison of AC-Superconducting Multi-Phase Symmetric-Winding Topologies for Wind Power Generators with Passive PM Rotors

“…Extra torque contributions are obtained because the air gap's flux distribution is flattened, avoiding the iron saturation and achieving a wider operational range. In summary, a MEM improves torque density, decreases cogging torque, reduces ripples, reduces rotor losses, and is more fault-tolerant [11]- [14].…”