Year: 2005
Type: dissertation
Abstract: Multi-phase motors have several advantages over the traditional three-phase motors.\nIn this study, the additional degrees of freedom available in five-phase permanent\nmagnet motors have been used for three purposes: 1) enhancing the torque producing\ncapability of the motor, 2) improving the reliability of the system, and 3) better adjusting\nof the torque and flux linkages of the five-phase direct torque controlled system.\n1) Due to the fact that space and time harmonics of the same orders will contribute\npositively to output torque, a five-phase permanent magnet motor with quasi-rectangular\nback-EMF waveform is supplied with combined fundamental and third harmonic of\ncurrents. For modeling and analysis of the motor a 0 3 3 1 1 q d q d frame of reference is\ndefined where 1 1q d rotates at the synchronous speed and 3 3q d rotates at the three times\nsynchronous speed. Based on the mathematical model in the 0 3 3 1 1 q d q d frame of\nreference, it is shown that this system while having a higher torque density with respect\nto a conventional permanent magnet synchronous machine, is also compatible with\nvector control algorithm.\n2) A resilient current control of the five-phase permanent motor with both sinusoidal\nand trapezoidal back-EMF waveforms under asymmetrical fault condition is proposed.\nIn this scheme, the stator MMF is kept unchanged during healthy and faulty condition.\nTherefore, the five-phase permanent magnet motor operates continuously and steadily\nwithout additional hardware and just by modifying the control algorithm in case of loss\nof up to two phases. The feature is of major importance in some specific applications\nwhere high reliability is required.\n3) High torque and flux ripple are the major drawbacks of a three-phase direct\ntorque controlled system. The number of space voltage vectors directly influences the\nperformance of DTC system. A five-phase drive, while benefiting from other advantages\nof high order phase drives, has inherently 32 space voltage vectors which permits better\nflexibility in selecting the switching states and finer adjustment of flux and torque. A\nsensorless direct torque control of five-phase permanent magnet motor is implemented.\nSpeed information is obtained based on the position of stator flux linkages and load\nangle.\nExperiments have been conducted on a 5kW five-phase surface mount permanent\nmagnet motor and a 3kW five-phase interior permanent magnet motor by using\nTMS320C32 DSP. The results obtained are consistent with theoretical studies and\nsimulation analysis, which further demonstrate the feasibility and practical significance\nof the five-phase permanent magnet motor drives.
Author: Leila Parsa
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2752296711