永磁直驱电机设计

Axial Flux Permanent Magnet Brushless Machines

Axial Flux Permanent MagnetBrushless Machines

by

JACEK F.GIERAS

United Technologies ResearchCenter,EastHartford, Connecticut, U.S.A.

RONG-JIEWANG

University ofStellenbosch,

Stellenbosch, WesternCape,SouthAfricaand

MAARTEN J. KAMPER

University ofStellenbosch,

Stellenbosch, Western Cape, South Africa

KLUWER ACADEMIC PUBLISHERS

NEW YORK,BOSTON, DORDRECHT, LONDON, MOSCOW

eBookISBN:Print ISBN:1-4020-2720-61-4020-2661-7

2005 Springer Science + Business Media, Inc.Print2004 Kluwer Academic PublishersDordrechtAll rights reserved

No part of this eBook maybe reproducedor transmitted inanyform or byanymeans,electronic,mechanical, recording, or otherwise, without written consent from the PublisherCreated in the United States of AmericaVisit Springer's eBookstore at:

and the Springer Global Website Online at:

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Contents

Preface

1.INTRODUCTION

1.1Scope1.2Features

1.3Development of AFPM machines1.4Types of axial flux PM machines1.5Topologies and geometries

1.6Axial magnetic field excited by PMs1.7PM eddy-current brake as the simplest AFPMbrushless machine

1.8AFPM machines versus RFPM machines1.9

Power limitation of AFPM machines

Numerical examples

2.PRINCIPLES OF AFPM MACHINES

2.1

Magnetic circuits

2.1.1Single-sided machines

2.1.2Double-sided machines with internal PM disc rotor2.1.3Double-sided machines with internal ring-shaped

core stator

2.1.4Double-sided machines with internal slotted stator2.1.5Double-sided machines with internal coreless stator2.1.6Multidiscmachines

2.2

Windings

2.2.1Three-phase windings distributed in slots2.2.2Drum-type winding

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viAXIAL FLUX PERMANENT MAGNET BRUSHLESS MACHINES

2.2.3Coreless stator winding2.2.4Salient pole windings2.3Torque production2.4Magnetic flux

2.5Electromagnetictorque and EMF

2.6

Losses and efficiency

2.6.1Stator winding losses2.6.2Stator core losses

2.6.3Core loss finite element model2.6.4Losses in permanent magnets2.6.5Rotor core losses

2.6.6Eddycurrentlosses in stator conductors2.6.7Rotationallosses

2.6.8Losses for nonsinusoidal current2.6.9Efficiency2.7Phasor diagrams2.8Sizing equations2.9

Armaturereaction

2.10AFPM motor

2.10.1Sine-wave motor2.10.2Square-wave motor

2.11AFPM synchronous generator

2.11.1Performancecharacteristics of a stand alone

generator

2.11.2Synchronization with utility gridNumerical examples

3.MATERIALS AND FABRICATION

3.1

Stator cores

3.1.1Nonoriented electrical steels3.1.2Amorphous ferromagnetic alloys3.1.3Soft magnetic powder composites3.1.4Fabrication of stator cores

3.2

Rotor magneticcircuits3.2.1PM materials

3.2.2Characteristics of PM materials3.2.3Operating diagram

3.2.4Permeances for main and leakage fluxes

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Contents3.2.5Calculation of magnetic circuits with PMs3.2.6Fabrication of rotor magnetic circuits

3.3

Windings

3.3.1Conductors

3.3.2Fabrication of slotted windings3.3.3Fabrication of coreless windings

Numerical examples

4.AFPM MACHINES WITH IRON CORES

4.1Geometries

4.2Commercial AFPM machines with stator ferromagneticcores4.3Some features of iron-cored AFPM machines4.4Magnetic flux density distribution in the air gap4.5

Calculation of reactances

4.5.1Synchronous and armature reaction reactances4.5.2Stator leakage reactance4.6Performance characteristics

4.7

Performancecalculation

4.7.1Sine-wave AFPM machine4.7.2Synchronous generator

4.7.3Square-waveAFPM machine4.8

Finite element calculations

Numerical examples

5.AFPM MACHINESWITHOUTSTATOR CORES

5.1Advantages and disadvantages

5.2Commercial coreless stator AFPM machines5.3

Performancecalculation

5.3.1Steady-state performance5.3.2Dynamic performance

5.4

Calculation of coreless windinginductances5.4.1Classical approach5.4.2FEM approach5.5Performance characteristics

5.6

Eddy current losses in the stator windings5.6.1Eddy current loss resistance

5.6.2Reduction of eddy current losses

5.6.3Reduction of circulating currentlosses

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viiiAXIAL FLUX PERMANENT MAGNET BRUSHLESS MACHINES

5.6.4Measurement of eddy current losses5.7ArmatureReaction

5.8

Mechanical design features

5.8.1Mechanical strength analysis

5.8.2Imbalanced axial force on the stator5.9

Thermal problems

Numerical examples

6.AFPM MACHINESWITHOUTSTATOR AND ROTOR CORES

6.1Advantages and disadvantages6.2Topology and construction6.3Air gap magnetic flux density6.4Electromagnetictorque and EMF6.5Commercial coreless AFPM motors

6.6

Case study: low-speed AFPM coreless brushless motor6.6.1Performance characteristics6.6.2Cost analysis

6.6.3

Comparisonwith cylindrical motor with laminatedstator and rotor cores6.7Case study: low-speed coreless AFPM brushless generator6.8

Characteristics of coreless AFPM machines

Numerical examples

7.CONTROL

7.1

Control of trapezoidal AFPM machine7.1.1Voltage equations7.1.2Solid-state converter7.1.3Currentcontrol7.1.4Speed control

7.1.5Highspeed operation

7.2

Control of sinusoidal AFPM machine

7.2.1Mathematical model and dq equivalent circuits7.2.2Currentcontrol7.2.3Speed control

7.2.4Hardware of sinusoidal AFPM machine drive7.3

Sensorless position control

Numerical examples

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Contents8.COOLING AND HEAT TRANSFER

8.1Importance of thermal analysis8.2

Heattransfer modes8.2.1Conduction8.2.2Radiation8.2.3Convection

8.3

Cooling of AFPM machines

8.3.1AFPM machines with self-ventilation8.3.2AFPM machines with external ventilation8.4

Lumped parameter thermal model8.4.1Thermal equivalent circuit8.4.2Conservation of energy8.5

Machine duties

8.5.1Continuous duty8.5.2Short-time duty8.5.3Intermittent duty

Numerical examples

9.APPLICATIONS

9.1Power generation

9.1.1High speed generators9.1.2Low speed generators

9.2

Electric vehicles

9.2.1Hybridelectric vehicles9.2.2Batteryelectric vehicles

9.3

Ship propulsion

9.3.1Large AFPM motors

9.3.2Propulsion of unmanned submarines

9.3.3Counterrotatingrotormarine propulsion system9.4Electromagneticaircraft launch system9.5Mobile drill rigs9.6Elevators

9.7MiniatureAFPM brushless motors9.8Vibration motors

9.9

Computer hard disc drives

Numerical examples

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xAXIAL FLUX PERMANENT MAGNET BRUSHLESS MACHINES

Symbols and AbbreviationsReferencesIndex

311321337

Preface

The drop in prices of rare-earth permanent magnet (PM) materials and pro-gress in power electronics have played an important role in the development ofPM brushless machines in the last three decades. These machines have recentlybecomemature and their high efficiency,power density and reliability has ledto PM brushless machines successfullyreplacing d.c. commutator machinesand cage induction machines in many areas.

The axial flux PM (AFPM) brushlessmachine, also called the disc-type ma-chine, is an attractive alternative to its cylindrical radial flux counterpart due tothe pancake shape, compact construction and high torque density. AFPM mo-tors are particularly suitable for electrical vehicles, pumps, valve control, cen-trifuges, fans, machine tools, hoists, robots and manufacturing. They have be-come widely used for low-torqueservo and speed control systems. The appli-cation of AFPM machines as generators is justified in wind turbines, portablegenerator sets and road vehicles. The power range of AFPM brushless ma-chines is now from a fraction of a watt to sub-MW.

Disc-type rotors can be embedded in power-transmission components orflywheels to optimize the volume, mass, number of parts,powertransfer andassembly time. For electric vehicles with built-in wheel motors the payoff isa simpler power train,higher efficiency and lower cost. Dual-function rotorsmay also appear in pumps, elevators, energy storages and other machinery,bringingadded values and new levels of performance to these products.

The authors believe that this first book in English devoted entirely to AFPMbrushless machines will serve as a textbook, useful reference and design hand-book of AFPM machines and will stimulate innovations in this field.

J.F. GIERAS,R. WANG AND M.J. KAMPER