Design and Voltage Supply of High-Speed Induction - Aaltodoc

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64 Temperature rise [K] 140 120 100 80 60 40 20 0 26 bars 16 bars Coated 0 10 20 30 40 50 60 Input power [kW] Fig. 5.16 Measured temperature rise of the rotor surface. Magnetization 85 % of nominal. Slip [%] 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 26 bars 16 bars Coated 0 10 20 30 40 50 60 Input power [kW] Fig. 5.17 Measured slip. Magnetization 85 % of nominal. Power loss [W] 12000 10000 8000 6000 4000 2000 0 26 bars 16 bars Coated 0 10 20 30 40 50 60 Input power [kW] Fig. 5.18 Total loss measured. In the measurement for the motor with the 26 bar rotor, a rotor with 16 bars was used in the generator. Magnetization 85 % of nominal.
5.2.7 About the mechanical robustness As a last operation characteristic it should be mentioned that all the tested rotors gave no sign of mechanical detoriation or fault. The 50000 1 /min and 150 °C limits for the squirrel cage rotors were adequate and higher speeds and temperature could be tested in the future. With the squirrel cage rotors, a trade-off must be made between the maximum speed and the amount of copper in the cage. This is because the amount of copper is limited by the centrifugal forces acting on the rotor. For a certain rotational speed, the squirrel cage has to be designed so that it gives a good performance while meeting the mechanical limitations. Basically this means the selection of an optimal height, width and number for the bars. This is done in a numerical optimization case in Chapter 9. 5.3 Conclusion Three different solid rotor constructions for a high-speed electric motor were tested. Two solid steel rotors with a surface mounted squirrel cage were presented and compared against a commercially used copper coated solid steel rotor. The results showed that the squirrel cage rotors could increase the utilization factor and efficiency if properly designed. In the application considered, the limiting characteristic for use of the squirrel cage rotors was the mechanical coupling of copper and steel in the rotor and thus the measurements were made at 835 Hz for a 1000 Hz drive. The squirrel cage rotors have better magnetization properties. They yielded a lower temperature rise for the stator winding, a smaller input current and a better power factor. The copper coated solid steel rotor had the smallest rotor and total loss and best efficiency at maximum load. Also, the copper coated rotor has a mechanical advantage. The full potential of the 1000 Hz drive could not be reached with the squirrel cage rotors because of the mechanical limits. Only a properly designed squirrel cage rotor will have an electromagnetic advantage at the high speed/power range. Because the differences in performance were relatively small, it is hard to make any definitive judgment. The stator and rotor constructions were not optimized together or separately. It is perhaps safe to say that both approaches have possibilities. A properly designed squirrel cage rotor could be an electromagnetically better option, especially at a lower speed range. The coated rotor should probably be emphasized at higher speeds because it is mechanically stronger. 65
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El 108 ACTA POLYTECHNICA SCANDINAVI
Page 3 and 4:
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
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 and 28: f sw N p = (2.9) fs The switching f
Page 29 and 30: 3 ROTOR CONSTRUCTIONS Starting from
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: Temperature rise [K] 100 80 60 40 2
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
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possible. The coating practically v
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Table 9.3. Optimization results for
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Fig. 9.11 Initial (left) and opt. (
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high-speed induction machine. Accor
Page 125 and 126:
Foelsch K. 1936. Magnetfeld und Ind
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Pyrhönen J. and Kurronen P. 1994.
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APPENDIX 129
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currents in the solid iron flow mor
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where the C sw E is the loss coeffi
Page 135 and 136:
B. CALCULATION OF THERMAL CHARACTER
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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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