Electrical Steels: Volume1: Fundamentals and basic concepts

Cover
Contents
Acknowledgements
Preface
Common acronyms, symbols and abbreviations used in the text
Introduction to Volume 1
About the authors
1 Soft magnetic material
1.1 Range and application of commercial bulk magnetic materials
1.2 Industrially important characteristics of soft magnetic materials
1.3 Families of commercial soft magnetic materials
1.4 Electrical steels
1.5 Global impact of energy wastage in electrical steels
References
2 Basic magnetic concepts
2.1 Magnetic fields, flux density and magnetisation
2.1.1 Magnetic field (H)
2.1.2 Magnetic dipole moment (m)
2.1.3 Magnetic polarisation (J)
2.1.4 Magnetic flux density (B)
2.1.5 Permeability (µ)
2.1.6 Relationships between H, B and M
2.1.6.1 Hysteresis models
2.1.7 Demagnetising effects
2.2 Units in magnetism
2.3 Dimensional analysis of magnetic quantities
2.4 Crystal planes and directions
References
3 Magnetic domains, energy minimisation and magnetostriction
3.1 Magnetic dipole moments and domains
3.2 Weiss theory and molecular field
3.3 Minimisation of free energy
3.4 Domain wall structure and motion
3.5 Domain changes occurring during magnetisation
3.6 Anisotropy energy
3.6.1 Anisotropy energy in materials with cubic crystal structure (Ek)
3.6.2 Uniaxial anisotropy energy (Eu)
3.7 Magnetostatic energy (Ems)
3.8 Fundamentals of magnetostriction
3.8.1 Stress–strain relationship in soft magnetic materials
3.8.2 Origin of magnetostriction in soft magnetic materials
3.9 Magnetoelastic energy (Eme)
3.10 Domain wall energy (Ew)
3.11 Work and energy in the magnetisation process
3.12 Static domain structure with minimum stored energy
3.13 Domain changes occurring during magnetisation
3.14 Energy (Eh) due to an externally applied field
3.15 Effect of an applied field on a domain wall
3.16 Magnetostriction in soft magnetic materials
3.16.1 Saturation magnetostriction along principal crystal axes
3.16.1.1 Saturation magnetostriction along the [100] direction
3.16.1.2 Saturation magnetostriction along the [111] direction
3.16.1.3 Saturation magnetostriction along the [110] direction
3.16.2 The special case of (110) [001] oriented silicon–iron
3.16.3 Saturation magnetostriction of a polycrystalline material
3.16.4 Variation of magnetostriction with flux density
3.17 The Barkhausen effect
References
4 Methods of observing magnetic domains in electrical steels
4.1 Introduction
4.2 Powder techniques
4.3 Optical methods of surface domain observation
4.3.1 The magneto-optic effect
4.3.2 Domain observation using the longitudinal KMO effect
4.3.3 Observation of rapid domain wall motion using the KMO effect
4.4 Magnetic force microscope
4.5 Domain visualisation from surface field sensors
4.6 Observation of sub-surface domain features
4.6.1 Electron microscope techniques
4.6.2 X-ray techniques
4.6.3 Freeze-in techniques for observing sub-surface structures
4.6.4 Visualisation of sub-surface domain structures using neutron irradiation
4.7 Use of magnetic bacteria for domain observation
4.8 Magneto-optical indicator films
4.9 Comparison of methods for observations on electrical steels
References
5 Electromagnetic induction
5.1 Faraday's law
5.2 Lenz's law
5.3 Expressions for an induced e.m.f.
Reference
6 Fundamentals of a.c. signals
6.1 Waveform terminology
6.2 Distortion factor
6.3 Distorted voltages on power systems
6.4 Distorted B or H waveforms due to non-linear magnetisation curves
6.5 Effect of the electric circuit on waveform distortion
6.6 General relationship between harmonics in B and H waveforms
6.7 Calculation of flux density under distorted magnetisation conditions
References
7 Losses and eddy currents in soft magnetic materials
7.1 Physical and engineering approaches to magnetic losses
7.2 Energy dissipation derived from the area enclosed by a B–H loop
7.3 Derivation of the dependence of loss on B and H using the Poynting vector theorem
7.4 Hysteresis loss
7.5 Eddy current generation in a rod of conducting material
7.6 Eddy currents in a thin sheet
7.6.1 Skin depth and equivalent depth of uniform magnetisation
7.7 Classical eddy current loss
7.7.1 Reduction of eddy current loss by use of laminations
7.8 Separation of losses into eddy current and hysteresis components
7.8.1 Hysteresis loss components
7.8.2 Separation of total loss into two or three components
7.9 Total loss within a sheet
7.10 Total power loss of a strip expressed in terms of B and H
References
8 Rotational magnetisation and losses
8.1 Vector representation of a pure rotating magnetic field
8.2 Rotational flux density
8.3 Torque curves and stored magnetocrystalline energy
8.4 Rotational hysteresis loss
8.5 Magnetic domain structures under rotational magnetisation
8.6 Combined alternating, rotational and d.c. offset magnetisation
8.6.1 Combined alternating and rotational magnetisation
8.6.2 Alternating magnetisation combined with d.c. offset fields
8.7 Rotational loss at power frequency
8.7.1 Distinction from rotational hysteresis loss
8.7.2 Total rotational loss in terms of B and H
8.7.3 Loss separation under rotational magnetisation
8.8 Magnetostriction under rotational magnetisation
8.8.1 Multidirectional magnetostriction
8.8.2 Simulation of rotational magnetostriction
8.9 Three-dimensional magnetisation
References
9 Anisotropy of iron and its alloys
9.1 Magnetisation at an angle to a preferred crystal direction
9.2 Magnetisation at angles to an easy direction under a.c. magnetisation
9.3 Effect of strip width on magnetisation direction in anisotropic material
9.4 Effect of stacking method on apparent loss of anisotropic strips cut at angles to an easy axis
References
10 Magnetic circuits
10.1 The basic magnetic circuit
10.2 Magnetic reluctance
10.3 Field and flux density distribution in a circular core
10.4 Iron cored solenoid
10.5 Flux density in a magnetic material measured by an enwrapping search coil
10.6 Field and flux density at the interface between two media
10.7 Forces between magnetised laminations
References
11 Effect of mechanical stress on loss, permeability and magnetostriction
11.1 Effect of stress on simple magnetic domain structures
11.2 Stress sensitivity derived from domain structures
11.3 Effect of biaxial stress
11.4 Stress sensitivity of GO steel
11.5 Stress sensitivity of NO steel
11.6 Effect of bending stress
11.7 Effect of normal stress
11.8 Effect of stress on components of loss
11.9 Effects of building stresses in electrical machine cores
11.9.1 Clamping stress
11.9.2 Wound cores
11.9.3 Stacked cores
11.10 Slitting and punching stress in electrical steel
11.10.1 Background
11.10.2 Practical aspects of the cut edge region
11.10.3 Other cutting methods
11.10.4 Modelling the effect of the cut edge effect
11.10.5 Shrink fitted stator cores
References
12 Magnetic measurements on electrical steels
12.1 Introduction
12.2 Effect of sample geometry (toroids, single strips, rings and single sheet)
12.2.1 Epstein frame
12.2.2 Single sheet tester
12.2.3 Rings and toroids
12.3 Sensing methods
12.3.1 Flux density sensing
12.3.2 Magnetic field measurement
12.4 A.C. magnetic measurements of losses and permeability
12.4.1 The wattmeter method
12.4.2 Digital interpretation of the wattmeter method
12.4.3 Localised measurements
12.4.4 Measurements under simulated operational conditions
12.4.5 D.C. biased a.c. measurements
12.5 2D and rotational magnetic measurements
12.5.1 Measurement principles
12.5.2 Magnetisation systems
12.5.3 Loss measurement
12.6 Magnetostriction measurements
12.6.1 Magnetostriction parameters
12.6.2 Magnetostriction measurement transducers
12.6.3 Rotational magnetostriction
12.7 On-line measurements
12.7.1 Practical challenges
12.7.2 Non-enwrapping systems
12.8 The d.c. magnetic measurements
12.8.1 Quasi-static measurements
12.8.2 Point-by-point measurement
12.8.3 Vibrating sample magnetometer
12.8.4 Coercimeters
12.8.5 Demagnetisation
12.9 Surface insulation testing
12.10 Barkhausen noise measurement
References
13 Background to modern electrical steels
13.1 History and development of electrical steels
13.1.1 Laminations
13.1.2 Increased resistivity
13.1.3 Purification
13.1.4 Grain size
13.1.5 Crystal orientation
13.1.6 Coatings
13.2 Metallurgical requirements and control
13.2.1 Thickness
13.2.2 Chemical composition
13.2.3 Grain size
13.2.4 Crystal orientation
13.2.5 Coatings
References
14 Production of electrical steels
14.1 Chemical composition
14.2 Hot rolled coil production
14.3 Cold mill processing
14.3.1 Grain oriented electrical steel
14.3.2 Non-oriented electrical steel
14.4 Final property assessment
14.5 Future development
14.5.1 Grain oriented electrical steel
14.5.2 Non-oriented electrical steels
References
15 Amorphous and nano-crystalline soft magnetic materials
15.1 Amorphous materials
15.1.1 Production of amorphous magnetic materials
15.1.2 Composition
15.1.3 Magnetic structure
15.1.4 Coatings and surface treatment
15.1.5 Stress sensitivity
15.1.6 Magnetostriction
15.1.7 Consolidated Fe-based amorphous material (POWERCORE)
15.1.8 Bulk amorphous material
15.2 Nano-crystalline magnetic materials
15.2.1 Production of nano-magnetic material
15.2.2 Magnetic properties
15.2.3 Coating and surface treatment
15.2.4 Stress sensitivity
15.3 General properties of amorphous and nano-materials
15.3.1 Families of amorphous materials
15.3.2 Commercial materials
15.4 High silicon micro-crystalline ribbon
15.5 Applications of amorphous and nano-crystalline ribbons
References
16 Nickel–iron, cobalt–iron and aluminium–iron alloys
16.1 Introduction
16.2 Iron, cobalt and nickel
16.2.1 Iron
16.2.2 Nickel
16.2.3 Cobalt
16.3 Nickel–iron alloys
16.4 Perminvar
16.5 Cobalt–iron alloys
16.5.1 Stress dependence of magnetic properties of Co–Fe alloys
16.6 Aluminium–iron alloys
16.7 Applications
16.7.1 Ni–Fe alloys
16.7.2 Co–Fe alloys
References
17 Consolidated iron powder and ferrite cores
17.1 Background
17.2 Consolidated iron and SiFe powder cores
17.2.1 Production
17.2.2 SMC compositions for power applications
17.2.3 Magnetic properties
17.2.4 Loss components in SMCs
17.2.5 Applications of iron-based SMCs
17.2.6 Opportunities for future developments
17.3 Soft ferrites
17.3.1 Basic structure
17.3.2 Production
17.3.3 Magnetic properties
17.3.4 Loss components in ferrite cores
17.3.5 Applications
References
18 Temperature and irradiation dependence of magnetic and mechanical properties of soft magnetic materials
18.1 Effects of temperature on structure insensitive magnetic properties
18.1.1 Saturation magnetisation Ms
18.1.2 Resistivity
18.1.3 Magnetocrystalline anisotropy constants
18.1.4 Magnetostriction constants
18.2 Effect of temperature on permeability, coercivity and losses
18.3 The d.c. and a.c. properties of silicon steels at elevated temperatures
18.4 Temperature dependencies of magnetic properties of various material
18.5 Modelling high temperature performance
18.6 Magnetic properties at cryogenic temperatures
18.7 Effect of non-uniform temperature gradients in magnetic core laminations
18.8 Effect of irradiation on soft magnetic materials
References
Index
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