Projects:2019s2-25401 Line-Start Axial-Flux Permanent-Magnet Motor

The aims of this project is to design line-start axial-flux permanent-magnet synchronous motors using the Finite Element Method (FEM), simulate radial-flux and axial-flux permanent-magnet synchronous motors using ANSYS software, analyse and compare the steady-state and transient-state performance of conventional radial-flux permanent-magnet synchronous motors with axial-flux permanent-magnet synchronous motors.

Introduction

The line-start axial-flux permanent-magnet synchronous motor has a higher torque density than that of the radial-flux motor, resulting in lower cost. Besides, it is more efficient than standard induction motors at rated output power from 0.55 kW to 7.5 kW. It also adds a squirrel cage to the rotor of an axial-flux permanent-magnet motor for providing self-starting capability, which could improve start-up performance and high efficiency in the steady-state operation. Furthermore, this type of model can reduce the cost more compared with the permanent-magnet synchronous motors.

Project team

Project students

• Cheng Zhang
• Hengyi Zhang
• Seetharaman Kavasseri Sankaranarayanan

Supervisors

• Prof. Wen Soong
• Dr. Solmaz Kahourzade

Objectives

This project aims to design and analyse the line-start axial-flux permanent-magnet motors using the ANSYS Maxwell and Simulink method.

Induction motors

Induction motors are widely used in a variety of industrial, commercial and domestic applications because they have many advantages, which are self-starting, economical and reliable [1]. The induction motor works on Faraday’s law of electromagnetic induction. When a three-phase power source is supplied to the stator, a rotating magnetic field is generated that operates at a synchronous speed [1]. This field is cut by the rotor conductors and back-EMF is induced in the rotor winding. As the rotor circuit is closed, current flows through the winding and mechanical force act on the conductors. Besides, In the stator and the rotor of the induction motor, the current will cause a large mechanical force, which will break the insulation or the conductor. This mechanical force produces a torque which tends to move the rotor in the same direction as the rotating field [2].

Permanent-magnet motors

Permanent magnet synchronous motors are commonly used in industrial applications that require rapid torque response and high-performance operation, such as automation for traction, robotics and aerospace [3]. The permanent magnet synchronous motor is an AC synchronous motor whose field excitation is provided by permanent magnets and has a sinusoidal back-EMF waveform. Besides, it has a permanent magnet rotor and windings on the stator. However, the structure of the stator with windings configured to produce a sinusoidal magnetic flux density in the air gap of the motor resembles that of an induction motor. Compared with the conventional synchronous motor, for the stator, it is symmetrical three-phase windings, but for the rotor, it uses a unique shape of rare-earth permanent magnet instead of the excitation winding [4]. This means that the permanent magnet synchronous motor has the characteristics of simple structure, small size, lightweight and high overload capacity, which means the motor is compact, efficient, and has high torque density and high dynamic performance [5]. Furthermore, permanent magnet synchronous motors must operate with a drive because they require a drive to operate. The drive uses the current-switching technique to control the motor torque and the mathematically intensive conversion between one coordinate system and another coordinate system to control the torque and flux current simultaneously [6].

Line-start permanent-magnet motors

The name of line-start permanent magnet synchronous motors comes from its ability to start directly when connected to the source. This type of motor has permanent magnets on its rotor, and a squirrel cage starting winding. To be specific, it means that line-start permanent-magnet synchronous motors have permanent-magnet with induction rings for self-starting to avoid inverter fed mechanism. Besides, this type of motor combines the high efficiency and ease of use of permanent magnet synchronous motors with design simplicity and high starting capacities of induction motors [7]. However, due to the braking torque caused by permanent magnets, the starting torque of the line-start permanent magnet motors can be very poor [8] [9].

Method

MATLAB / Simulink ANSYS Maxwell