Shark -new motor design concept for energy saving- applied to - VBN

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18 Chapter 2 Linear analysis of the Shark switched Reluctance Motor The analysis of this structure encouraged the authors to claim that the SRM with a toothed air gap exhibits an efficiency some10 [%] bigger than that of an equivalent cylindrical air gap SRM. In [1] the Shark concept is initially studied by the means of a simple structure, as shown in Fig.2.2. The air gap of this model has a saw-toothed profile. Measurements on this model showed that such a configuration exhibits increased air gap permeance and lower acoustic noise, compared to the model of Fig.2.1, with cylindrical air gap. The same paper also presents a prototype SRM with toothed air gap, as shown in Fig.2.3. As for the air gap shape design of the Fig.2.3 motor was not optimised, the measured results did not reach the predictions for torque production. However, the static measurement of the flux linkage characteristics indicated that for similar excitation conditions, the flux linkage is higher, than in the cylindrical air gap SRM, as long as the material does not saturate. The authors concluded that optimisation is necessary in order to reap all the benefits of adopting such a structure. winding winding Fig. 2. 1 Cylindrical air gap structure [1] Fig. 2. 2 Simplified Shark structure [1] Fig. 2. 3 Toothed air gap Shark SRM [1] Despite the improved performances measured on different Shark structures a detailed study of the Shark configuration has not yet been reported. In the present work, a step-by-step analysis is conducted. The first step consists of a simplified analysis assuming linear magnetic material properties. To introduce the subject, the Shark configuration is presented and the main geometric parameters are defined. 2.1.2 Shark configuration The terms used in the analysis of the Shark SRM are defined in this section. The geometric conditions and the electromagnetic assumptions are discussed and the evaluation criteria are defined. Geometric conditions The philosophy of the Shark concept is an extension of the geometry of a cylindrical air gap SRM (CSRM), shown in Fig.2.4. The main geometric dimensions of the CSRM, as defined in Fig.2.4, are: Ds –stator outer diameter, Dbs – stator slot bottom diameter, Dr1 – rotor diameter, Dbr - rotor bottom diameter, lstk – length of the lamination stack, g – air gap length in the aligned position and (gi+g) – air gap length in the unaligned position.
Chapter 2 Linear analysis of the Shark switched Reluctance Motor The Shark SRM, illustrated in Fig.2.5, is obtained by redistribution of the magnetic material between the stator and the rotor bodies. This means that a certain amount of material is removed from the stator in order to shape the Shark profiles of the stator body. The same amount of material is added to the rotor in order to form the Shark profiles of the rotor body. This process is carried out keeping the main dimensions of the radial cross-section unchanged, except the rotor diameters. Whilst the original dimension Dr1 remains unchanged, an additional dimension, Dr2, which helps in specifying the Shark profile, is defined. It is worth mentioning that the Shark teeth may be generated inwards or outwards on the rotor body. The second configuration is used throughout this work. Even if the air gap area were to be identical in the two cases, as the width of the poles is kept unchanged, the unaligned inductance will be slightly increased by the Shark air gap, reducing the benefit of the Shark air gap. Dbs Dbr Ds Dr1 Fig.2.4 View of a CSRM Fig.2.5 View of a Shark SRM The main geometrical dimensions remain unchanged. This means that: • the stack length, lstk, of the Shark SRM is the same as in the equivalent CSRM • the stator diameter, Ds, of the Shark SRM is the same as in the equivalent CSRM • the air gap length, g, of the Shark SRM is the same as in the equivalent CSRM Under these conditions, the core volumes of the CSRM and Shark SRM are identical, defined as: 2 g gi y x z lstk Ds Vcore = π ⋅ ⋅l stk (2.1) 2 The amount of material used in the two motors was also identical as the Shark structure is obtained simply by redistributing the iron material between stator and rotor. No material was added or removed from the machine. The excitation circuit of the two motors is assumed to comprise similar Dbs Ds Dbr g/cos Dr1 y z lstk 19
Page 1: Shark -new motor design concept for
Page 6 and 7: Abstract The aim of this thesis is
Page 8 and 9: i instantaneous current Ψ ϕ flux
Page 13 and 14: Table of contents Preface………
Page 15 and 16: Chapter 1 Introduction Chapter 1 In
Page 17 and 18: Chapter 1 Introduction Table 1.1 Fu
Page 19 and 20: Chapter 1 Introduction The magnetic
Page 21 and 22: Chapter 1 Introduction Fig.1.7 Illu
Page 23 and 24: [Wb] O Wf Wconv Fig. 1.9 Conversion
Page 25 and 26: Chapter 1 Introduction 1.5 Area of
Page 27 and 28: Chapter 1 Introduction Based on the
Page 29 and 30: Chapter 1 Introduction Chapter 3, F
Page 31: Chapter 2 Chapter 2 Linear analysis
Page 35 and 36: ( y) Chapter 2 Linear analysis of t
Page 37 and 38: Chapter 2 Linear analysis of the Sh
Page 45 and 46: ksquare Lsquare L0 Chapter 2 Linear
Page 47 and 48: L Chapter 2 Linear analysis of the
Page 49 and 50: inductance gain 4 3.5 3 2.5 2 1.5 C
Page 53 and 54: Chapter 3 Chapter 3 Finite Element
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Page 73 and 74: 1 Chapter 3 Finite Element modeling
Page 79 and 80: flux linkage [Wb] Chapter 3 Finite
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Chapter 3 Finite Element modeling o
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Chapter 4 Chapter 4 Analytical mode
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Chapter 4 Analytical modelling of t
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N s because there are ph Chapter 4
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where where λ ( , θ ) 102 Chapter
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104 energy gain Chapter 4 Analytica
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106 Chapter 4 Analytical modelling
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112 radial force [N] 1900 1800 1700
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114 radial force [N] Chapter 4 Anal
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120 Chapter 5 Measurement and compa
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turn on angle [deg] 128 10 8 6 4 2
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140 copper loss [W] Chapter 5 Measu
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142 d. Power factor Chapter 5 Measu
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144 f. Specific torque Chapter 5 Me
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148 Chapter 6 Manufacturing conside
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158 Chapter 7 Summary and Conclusio
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Appendix A Design data of Induction
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170 Appendix B Definition of the ai
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178 air gap flux density [T] Append
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Appendix C 180 Appendix C Analytica
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A A A w1 w2 w3 182 = w ⋅ v = w =
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Appendix C.4 184 Appendix C Analyti
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Appendix C.5 Permeance ratio 186 Ap
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Appendix D Appendix D.1 188 Appendi
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190 References [16] T.J.E. Miller,
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192 References Conference, , 27 Jul
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194 Volume: 2 , 1996 , Page(s): 715
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196 References [96] F. Abrahamsen,
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188 References
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