Design and Voltage Supply of High-Speed Induction - Aaltodoc

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28 Fig 2.3 Output voltages produced by PAM for a star connected three phase winding. Fundamental of phase-to-phase voltage also plotted. Fig. 2.4 Output voltages produced by PWM for a star connected three phase winding. Fundamental of phase-to-phase voltage also plotted. Np = 9 and ga = 0.8.
3 ROTOR CONSTRUCTIONS Starting from Francois Aragon’s experiments in 1824, electromagnetic induction and applications were studied and experimented with by Faraday, Ferraris and Tesla among others (Lindell 1994). Ferraris built several types of induction motors with a copper cylinder rotor in the 1880’s. He came to the conclusion that a maximum efficiency of 50 % could be achieved at 50 % slip. Tesla put his copper winding, or a cage, on a solid iron cylinder. In this way efficiencies higher than 50 % were achieved. In the 1891 Electrical Exhibition in Frankfurt, Germany, both Dolivo-Dobrowolski and Brown introduced three phase induction motors with efficiencies of around 90 %. Coming to the 20 th century, induction motor construction was principally the same as it is today. At some time, the lamination technique used in dynamos and transformers was adopted for the rotors of induction machines as well. In order to have a good efficiency, the rotor of an induction motor should usually provide the following two basic functions. • High permeability flux path is needed so that most of the magnetic field energy generated is usable at the air gap for the production of the torque. • The rotor has to have low resistivity flow paths for the electric currents induced so that the ohmic losses relating to torque producing currents are low. ⇒ Ferromagnetic materials have the high permeability needed but they lack the low resistivity if compared to other metals. This problem is usually solved so that the two functions are performed by different parts of the rotor. This kind of functional division calls for electromagnetic anisotropy in the rotor. Usually, the anisotropy is realized with mechanical design. The so-called core part is made of laminated ferromagnetic material and the current circuit part is made of high conductivity metal, usually copper or aluminum. The current part is usually referred to as a cage winding or a squirrel cage in an ordinary induction motor. Another way to realize the anisotropy would be the use of anisotropic materials or material matrixes as suggested by Ito et al. (1988) . Laminating the ferromagnetic core has some benefits. Firstly, it increases the resistivity seen by eddy-currents. The torque producing currents are forced to use the low resistivity squirrel cage and 29
Page 1 and 2: El 108 ACTA POLYTECHNICA SCANDINAVI
Page 3 and 4: PREFACE This thesis is the result o
Page 5 and 6: 5 Comparison of rotors for 60 kW 60
Page 7 and 8: LIST OF SYMBOLS a Number of paralle
Page 9 and 10: Rn Resistance of a parallel conduct
Page 11 and 12: 1 INTRODUCTION The need for high ro
Page 13 and 14: Conventional (high-speed) drive Hig
Page 15 and 16: Chapter 5 reports the comparison of
Page 17 and 18: Some penetration depth values are c
Page 19 and 20: 2.2 Stator windings for high-speeds
Page 21 and 22: ⎛ π ⎞ sin⎜ν ⎟ ⎛ π ⎞
Page 23 and 24: Table 2.3 Air gap characteristics o
Page 25 and 26: Cooling of the stator could need ax
Page 27: f sw N p = (2.9) fs The switching f
Page 31 and 32: and eddy-currents traveling on the
Page 33 and 34: support the squirrel cage winding,
Page 35 and 36: 3.1.3 Rotor loss and friction loss
Page 37 and 38: Table 3.1 High-speed induction moto
Page 39 and 40: critical speeds are passed relative
Page 41 and 42: Table 3.2 The free-free natural fre
Page 43 and 44: Table 3.3 The free-free natural fre
Page 45 and 46: 4 COMPARISON OF ROTORS FOR 65 KW 30
Page 47 and 48: Temperature [ºC] 110 109 108 107 1
Page 49 and 50: Temperature rise [K] 120 100 80 60
Page 51 and 52: improve the laminated design, more
Page 53 and 54: The copper coated solid steel rotor
Page 55 and 56: As reported in Lähteenmäki et al.
Page 57 and 58: Temperature rise [K] 100 80 60 40 2
Page 61 and 62: 6. The rest of the loss is defined
Page 63 and 64: Temperature rise [K] 100 80 60 40 2
Page 65 and 66: 5.2.7 About the mechanical robustne
Page 67 and 68: 6.1 Comparison of PAM and PWM for 6
Page 69 and 70: h d = , (6.2) I I h, PAM where Ih,P
Page 71 and 72: Fig. 6.4 Phase-to-phase voltage and
Page 75 and 76: Machines loss [W] 12000 10000 8000
Page 77 and 78: considerably higher than expected.
Page 79 and 80:
In order to improve the performance
Page 81 and 82:
l = + , (7.2) sλs 2leλ e l wλ w
Page 83 and 84:
gap of 1 mm would yield an effectiv
Page 85 and 86:
Table 7.1 Calculated effective leng
Page 87 and 88:
Input current [A] 170 160 150 140 1
Page 89 and 90:
8 CIRCULATORY CURRENTS IN A STATOR
Page 91 and 92:
Table 8.1 Circulatory current loss
Page 93 and 94:
Fig. 8.4 Strand currents in the two
Page 95 and 96:
8.2 Impedance of the circulatory cu
Page 97 and 98:
Because Φ l is approximately at th
Page 99 and 100:
Table 8.2 Circulatory current loss
Page 101 and 102:
Power loss [W] 3500 3000 2500 2000
Page 103 and 104:
k cc 600 500 400 300 200 100 0 0 50
Page 105 and 106:
9 OPTIMIZATION OF SOLID STEEL ROTOR
Page 107 and 108:
whole solution space determined by
Page 109 and 110:
the average time saving is 39 %. Th
Page 111 and 112:
Fig. 9.3 Cross sections of the 16,
Page 113 and 114:
Height of bar slot [mm] 8 6 4 2 0 R
Page 115 and 116:
The different rotor topologies were
Page 117 and 118:
possible. The coating practically v
Page 119 and 120:
Table 9.3. Optimization results for
Page 121 and 122:
Fig. 9.11 Initial (left) and opt. (
Page 123 and 124:
high-speed induction machine. Accor
Page 125 and 126:
Foelsch K. 1936. Magnetfeld und Ind
Page 127 and 128:
Pyrhönen J. and Kurronen P. 1994.
Page 129 and 130:
APPENDIX 129
Page 131 and 132:
currents in the solid iron flow mor
Page 133 and 134:
where the C sw E is the loss coeffi
Page 135 and 136:
B. CALCULATION OF THERMAL CHARACTER
Page 137 and 138:
Axial cooling duct Frame R fr3 Stat
Page 139 and 140:
Linear equalities Ax = b, (C3) wher
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Design and Voltage Supply of High-Speed Induction - Aaltodoc

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