Design and Voltage Supply of High-Speed Induction - Aaltodoc

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102 account when calculating the scaling factor ksc. The average temperatures measured for the windings in Chapter 6 were also taken into account. The estimation model presented in Section 8.3 (Eq. 8.8) was used to calculate the values for ksc. The current spectra measured in Chapter 6 were modified by square root of kcc, thus yielding the effective current spectra for the power loss. Results for PWM with 15 pulses per half cycle and PAM are presented. Fig. 8.11 shows the average value of kcc for the three phase winding as a function of frequency. It is seen that the model gives very high values for kcc. It is clear that the extrapolation from 450 Hz is inaccurate. It is reminded here that the frequency of the fundamental was already 835 Hz. The coupling between the current distribution, circulatory emf ecc and temperature distribution is not present in the model. If the coupling was modeled, the kcc curve in Fig. 8.11 might saturate at some higher frequency. Thus, the result on the effect of the circulatory currents is only qualitative. Fig. 8.12 shows the current spectra measured at full load points. It shows that PAM has steadily decreasing amplitude for the components. The PWM has low amplitudes for 5 th and 7 th order harmonics but higher amplitudes at higher frequencies. The rms-values of the harmonic currents are 32.8 A for PAM and 20.6 A for the PWM, as measured in Chapter 6. Fig. 8.13 shows the same spectra corrected with the square root of kcc, yielding an effective current spectra for power loss. It shows how the higher order currents for the PWM have a major effect on total harmonic content. The rms-values of the effective harmonic currents are 175 A for PAM and 265 A for the PWM. Using DC-resistance of the stator winding, the harmonic loss due to the circulatory currents is calculated. The effective currents would give harmonic loss of 800 W for PAM and 1870 W for the PWM. These loss values are much too high. The total harmonic loss measured in the motor was only 700 W for PAM and 770 W for the PWM. Even if the values for kcc and effective currents are too high at higher frequencies, the result shows that the circulatory currents could be one thing to decrease the usefulness of PWM for high speed induction machines. On the other hand, if the kcc - curve shown in Fig. 8.11 saturates at higher frequencies, the situation might be different. The harmonic currents of 5 th and 7 th order could increase more relative to higher harmonics. Thus, PWM might win the comparison after all. This is an interesting issue and subject for further studies.
k cc 600 500 400 300 200 100 0 0 5000 10000 15000 20000 25000 30000 35000 Frequency [Hz] Fig. 8.11 kcc estimated according to the model presented in Section 8.3. I [A] 200 180 160 140 120 100 80 60 40 20 0 PAM 15 pulses 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 harmonic order Fig. 8.12 Measured current spectra for PAM and PWM with 15 pphc. Current [A] 200 180 160 140 120 100 80 60 40 20 0 PAM 15 pulses 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 harmonic order Fig. 8.13 Effective current spectra for PAM and PWM with 15 pphc. 103
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El 108 ACTA POLYTECHNICA SCANDINAVI
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PREFACE This thesis is the result o
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5 Comparison of rotors for 60 kW 60
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LIST OF SYMBOLS a Number of paralle
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Rn Resistance of a parallel conduct
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1 INTRODUCTION The need for high ro
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Conventional (high-speed) drive Hig
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Chapter 5 reports the comparison of
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Some penetration depth values are c
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2.2 Stator windings for high-speeds
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⎛ π ⎞ sin⎜ν ⎟ ⎛ π ⎞
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Table 2.3 Air gap characteristics o
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Cooling of the stator could need ax
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f sw N p = (2.9) fs The switching f
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3 ROTOR CONSTRUCTIONS Starting from
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and eddy-currents traveling on the
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support the squirrel cage winding,
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3.1.3 Rotor loss and friction loss
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Table 3.1 High-speed induction moto
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critical speeds are passed relative
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Table 3.2 The free-free natural fre
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Table 3.3 The free-free natural fre
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4 COMPARISON OF ROTORS FOR 65 KW 30
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Temperature [ºC] 110 109 108 107 1
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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 59 and 60: Temperature rise [K] 140 120 100 80
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 73 and 74: Temperature rise [K] 120 100 80 60
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: Power loss [W] 3500 3000 2500 2000
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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