Comparison study of brushless doubly-fed motor and permanent-magnet synchronous motor

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Comparison study of brushless doubly-fed motor and permanent-magnet synchronous motor


Author: Weng, Xu
Title: Comparison study of brushless doubly-fed motor and permanent-magnet synchronous motor
Degree: M.Sc.
Year: 2015
Subject: Electric motors.
Electric motors, Brushless.
Permanent magnet motors.
Electric motors, Synchronous.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Electrical Engineering
Pages: 1 online resource (iv, 66 pages) : illustrations (some color)
iv, 66 pages : illustrations (some color)
Language: English
InnoPac Record:
Abstract: Electric motors, which are used in many areas, are very common. In this dissertation, I compare the operating speed ranges of two different motors, brushless doubly-fed motor (BDFM) and permanent-magnet synchronous motor (PMSM). There are many differences between these two motors. BDFM has two sets of three-phase windings, which are power windings and control windings. Control windings will be fed from a power. Its frequency can be changed. Power windings will be fed with a power with varying frequency. PMSM has one set of windings, which means that the speed adjustment totally depends on the power frequency. The permanent magnet in the PMSM makes the structure simpler, reduces the assembly costs and eliminates the brushes to increase the work reliability of the motor. Because of no excitation current, there is no excitation loss, then increasing the efficiency and power density of the motor. PMSM is widely used because of its simple configuration and high efficiency. Therefore, studying how to control it with an appropriate way is very necessary. Normally, we use DSP (digital signal processing) technique to control a motor. DSP technique can provide high-speed, high-resolution and sensorless algorithms to decrease system cost. In the dissertation, the speed ranges of BDFM and PMSM will be compared. I use the software Ansoft Maxwell to do the simulation of BDFM and PMSM. When giving different excitations (ideal sine excitation and PWM excitation) to the motors, we observe the changes of torque, current and induced electromotive force, then analyzing the results to get the speed ranges of BDFM and PMSM. After having compared the speed range of BDFM and PMSM with ideal sine excitation and PWM excitation, we alter the switching frequency when giving the PWM excitation to the motors to see the changes of torque, core loss, induced voltage and current. I also do some experiments on the hardware to prove the simulation results. When changing the switching frequency of PWM excitation to PMSM, the plots of torque and current will have a big difference. The hardware experiments with DSP technique have verified the most of software simulation results.

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