General Electric Review Volume 15

General Electric Review Volume 15

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 edition. Excerpt: ...are plotted in Fig. 7. The drawn curve in Fig. 8 is calculated from the equations on the assumption that c2: ci = 50, and taking 63 kilovolts the measured arc-over voltage of a single unit alone (Test 1, Fig. 3), as the voltage on the line insulator. This curve can be obtained directly from Fig. 7, by taking 03/100 of the voltage values given there. The crosses are actual measured values from the test in Fig. 3. The check is much closer than would be expected, as when the voltage is brought nearly to arc-over, corona appears first on the line insulator. This generally increases c2 in greater proportion than c, and hence tends to improve the balance. In this way a sort of automatic grading seems to take place. Test values show this in Fig. 9, where the measured points shift to better ratio curves as the string length is increased. It can thus be seen that, on account of this automatic grading effect, high arc-over voltages do not always mean good balance at operating voltages. It is important to have a high efficiency, or good balance, before leakage starts; otherwise it seems that in case of lightning or surge the porcelain of the line unit is likely to be punctured. Automatic grading would not help in this case, as puncture would probably occur before the formation of corona. Conclusions (1) Where the mutual capacity c2 of an insulator is small compared to its 'to ground' capacity cu the voltage balance along a string of such units will be bad. The line unit will take the greatest voltage, and the tower unit the least. THE POWER-FACTOR OF LOW-SPEED POLYPHASE MOTORS By H. M. Hobart, M. Inst. C. E. Consulting Engineer, General Electric Company The arguments and data given in this paper may assist power users in determining the more

Product details

  • Paperback | 402 pages
  • 189 x 246 x 21mm | 717g
  • United States
  • English
  • black & white illustrations
  • 1236955781
  • 9781236955784