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Electrical Practice in Collieries; A Manual for Colliery Managers, Under-Managers, Engineers, and Mining Students

Electrical Practice in Collieries; A Manual for Colliery Managers, Under-Managers, Engineers, and Mining Students


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About the Book

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...33T000 = 6-9'say7 To allow for friction of gear, starting, 4c., add about 50 per cent., this will give a motor of about 10 B.H.P. as the size required. Such a motor will be of ample strength for the work, and might run about 630 revolutions per minute, at this speed the gear would be-ix; that is, 7tol. 90 Suppose that in the above example the motor has an efficiency of 80 per cent., and it has to be supplied with current at 380 volts, what size of cables would you put in? What would be the voltage at the pit bottom, and how many amperes of current would the motor require? Ten B. H. P. is required, and this represents 80 per cent, of the current energy. 10 x 100 _ amperes x 380 80-746 10 x 100 x 746 .. Amperes = 380-80 = 24-5. On consulting the tables given in Chapter I. we find a cable of 19/19 will carry this current safely. Since the pump is 400 yards from the pit bottom the cables will have a total length of 800 yards from that point, and the drop in voltage will be 24-5 x 1-786 = 44 volts per mile nearly, 44 x 800 which for 800 yards gives 60--= vlts The voltage at the pit bottom will thus be 380 + 20 = 400. The efficiency of electrical pumping installations, taken as & whole, differs widely in different cases, but may be taken as from 45 to 75 per cent. according to conditions. Under ordinary circumstances, with not too great a distance between the pumps and the generator, an average of from 55 to 60 per cent. should be obtained. Alternate currents are now being applied to the driving of pumps, three-phase motors being the class generally used. Where adopted, good work is, as a rule, being done, and the future will see a more extended use of the system, especially in cases where power has to be carried over long distances. The principle of t...


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Product Details
  • ISBN-13: 9781156073964
  • Publisher: Rarebooksclub.com
  • Publisher Imprint: Rarebooksclub.com
  • Height: 246 mm
  • No of Pages: 78
  • Spine Width: 4 mm
  • Width: 189 mm
  • ISBN-10: 1156073960
  • Publisher Date: 01 May 2012
  • Binding: Paperback
  • Language: English
  • Returnable: N
  • Weight: 154 gr


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