Studies on Multiphase Electric Motors

DESPRE CARTE

Cartea prezintă o comparație bazată pe analize cu elemente finite între patru mașini multifazate, cu număr diferit de faze statorice, și anume 3, 5, 7 și 9 faze, a două tipuri de mașini, și anume motoare asincrone și motoare sincrone cu magneți permanenți.

De asemenea, se prezintă proiectarea și procesul de fabricație a pachetului de tole statoric și a înfășurării statorice pentru a realiza un model fizic al motorului asincron cu 5 faze și cu colivie.

Testarea modelului fizic al motorului asincron cu 5 faze a fost realizată cu ajutorul unui invertor dedicat cu 5 faze.

Funcționarea motorului multifazat cu 5 faze în condiții de defect de fază deschisă a fost validată prin teste experimentale.

PREFACE

In this book is presented a comparison based on finite element analyses between four multiphase machines, with different number of stator phases, namely 3, 5, 7 and 9 phases, of two types of machines, namely induction motors and permanent magnet synchronous motors.

Also, the book presents the design and the manufacturing process of the stator laminated stack and of the stator winding in order to achieve a physical model of the 5-phase squirrel-cage induction motor.

The testing of the physical model of the 5-phase IM was achieved with the help of a custom made 5-phase inverter.

The operation under one open-phase fault of the 5-phase IM has been validated through experimental tests. In the book is described the change of the direction of rotation of a 5-phase motor.

The book follows the general objectives:

• the quantitative validation of the information in the literature regarding the behavior and advantages of multiphase machines;
• the identification of the number of phases, among those studied, which present the best performances for both for the synchronous and induction motors;
• the design and manufacture of a five-phase induction motor.

The book is structured in five chapters to which are added the introduction and general conclusions.

In the first chapter are described the studied cases of induction motors and analyzed the performances for the rated operating point.

In the second chapter are analyzed the behavior of the 3-phase, 5-phase, 7-phase and 9-phase induction motors, for both steady state tolerance and starting tolerance regarding one or many stator phase’s failures.

Chapter three presents an analysis of multiphase permanent magnet synchronous motors. Those models were developed starting from models of the analogue induction motors, described in the previous chapters.

In the chapter four are presented formulas and an analysis based on finite element model of five-phase induction motor for healthy operation. Also, an operation point is proposed and analyzed for continuous operation under one open-phase fault considering some criteria.

In the fifth chapter are presented the manufacturing process the stator laminated stack, the winding process of the stator, the test bench and the results measured on the physical model of the 5-phase squirrel-cage induction motor.

Author

CONTENTS

INTRODUCTION 23

CHAPTER 1. FINITE ELEMENT 2D MODELS OF THE MULTIPHASE (3-5-7-9) SQUIRREL-CAGE INDUCTION MOTORS 27
1.1. Introduction 27
1.2. Finite element analysis of the performances of the studied IMs 30
1.2.1. Electromagnetic field results 30
1.2.2. Stator currents and electromagnetic torque for rated motor’s operation and for starting 36
1.3. Remarks 40

CHAPTER 2. TOLERANCE REGARDING THE ELECTRIC SUPPLY FAILURES IN THE MULTIPHASE INDUCTION MOTORS 41
2.1. Steady state tolerance analysis 41
2.1.1. Steady state tolerance analysis of the 3-phase induction machine 42
2.1.2. Steady state tolerance analysis of the 5-phase induction machine 47
2.1.3. Steady state tolerance analysis of the 7-phase induction machine 54
2.1.4. Steady state tolerance analysis of the 9-phase induction machine 65
2.2. Starting tolerance analysis 71
2.2.1. Starting tolerance analysis of 3-phase IM with the Phase-1 failure 71
2.2.2. Starting tolerance analysis of 5-phase IM with one phase and two phases failures 72
2.2.3. Starting tolerance analysis of 7-phase IM with one phase and two phases failures 75
2.2.4. Starting tolerance analysis of 9-phase IM with up to three phase failures  79
2.3. Remarks 82

CHAPTER 3. RESEARCHES ON PERMANENT MAGNET SYNCHRONOUS MULTIPHASE MOTORS 84
3.1. Finite element 2D models of the multiphase permanent magnet synchronous motors 84
3.2. Cogging torque and Back-EMF in the studied multiphase PMSMs 85
3.2.1. Analysis of the Cogging Torque 85
3.2.2. Analysis of the Back-EMF 88
3.2.3. Remarks 97
3.3. Initial phase of the stator currents corresponding to the maximum value of the electromagnetic torque in PMSMs 98
3.4. Performances of rated operation of the multiphase permanent magnet synchronous motors 100
3.4.1. Magnetic field at rated operation and spatial harmonics of the magnetic field in the air gap 101
3.4.2. Electromagnetic torque for the rated PMSMs operation 107
3.4.3. Stator voltage for rated PMSMs operation 111
3.4.4. Efficiency of the PMSMs 115
3.4.5. Annotation 119
3.5. Remarks 123

CHAPTER 4. THE DESIGN OF A 5-PHASE SQUIRREL-CAGE INDUCTION MOTOR 125
4.1. Assumptions for preliminary motor design 126
4.2. The numerical model based on analytical formulas of the 5-phase IM 126
4.2.1. Verification criteria 127
4.2.2. The analytical computation of the 5-phase motor for rated operation 129
4.3. The finite element computation of the 5-phase IM 134
4.3.1. Healthy operation of the computed 5-phase IM 136
4.3.2. One open-phase fault operation of the computed 5-phase IM 143
4.4. Remarks 149

CHAPTER 5. THE MANUFACTURING AND TESTS OF A PHYSICAL 5-PHASE SQUIRREL-CAGE INDUCTION MOTOR 150
5.1. Manufacturing the stator laminated stack 150
5.1.1. Manufacturing the stator sheets 150
5.1.2. Packing the stator sheets on the mandrel 151
5.1.3. Mechanical consolidation of the stator laminated stack 152
5.2. Winding the stator core and the assembly of the motor 153
5.3. Experimental tests and results 155
5.3.1. Checking the insulation between the housing and the phase 155
5.3.2. Phase resistance measurement 155
5.3.3. The bench test 156
5.3.4. Healthy operation of the physical model of 5-phase IM 158
5.3.5. One open-phase fault operation of the physical model of 5-phase IM 162
5.3.6. Remarks 165
5.4. The direction of rotation for a 5-phase motor 165
5.5. Remarks 167

CONCLUSIONS 168

ANNEXES 172

REFERENCES180