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American Institute of Electrical Engineers, Transactions of the

Issue 10 • Date Oct. 1939

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Displaying Results 1 - 7 of 7
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  • The Rating and Appication of Motors for Refrigeration and Air Conditioning

    Page(s): 519 - 527
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    This paper describes the procedure and practical results to date in applying single-phase motors to refrigeration compressors. The applications are primarily torque applications, temperature considerations being of secondary importance. A line of high-torque motors has been developed to meet the high starting and accelerating torques demanded by the compressors. Utilization of these torques results in running loads considerably higher than rated name-plate loads, without exceeding safe operating temperatures for the insulation life requirement. To meet these requirements a revised method of rating refrigeration motors on a starting and accelerating torque per horsepower and a starting efficiency basis is described. This method more clearly specifies a motor so that a more satisfactory application would be obtainable both from the standpoint of the user and the public utility company or code authority. View full abstract»

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  • Simplified Precision Resistance-Welder Control

    Page(s): 528 - 534
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    The types of resistance-welding applications requiring precision control heretofore characterized by electronic equipment are well-known. Attempts to extend the field of application to borderline operations have not met with complete success because of the initial expense and complicated nature of the control available. A simplified form of precision control consisting of a synchronized magnetic contactor and motor-driven timer overcomes these objections without compromise on results obtained. View full abstract»

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  • Load Ratings of Cable

    Page(s): 535 - 556
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    Operating and test data concerning the maximum safe loading of impregnated-paper-insulated lead-covered cable are presented. The results of the study may be summarized as follows: 1. The occasional operation of cable at higher temperatures than are permitted by present temperature rules effects considerable economy. 2. During emergencies, temperatures of 5 to 35 degrees centigrade (depending on kind of cable) above those permitted by the rules are safe for the insulation. 3. For extra-high-voltage solid-type cable, void formation in insulation and expansion of lead sheaths may limit allowable temperatures and temperature ranges. 4. Cracking of lead sheaths due t reciprocating cable movement into manholes may limit the temperature range for usual daily loading. Limitation is more severe for longer conduit lengths up to 500 feet, but changes little with increase from 500- to 1,000-foot lengths. 5. Cracking of sheaths in manholes due to cable movement may be reduced by improving manhole conditions. 6. For many cables a balanced design requires a lead-alloy sheath that gives increased resistance to effects of cable movement and of internal pressures. 7. Continuous field temperature surveys are essential to efficient use of large conduit and cable systems. 8. Only a small fraction of the cable ever operates at the higher temperatures. 9. Data on center empty-duct temperatures and on average heat losses over 24-hour periods give satisfactory results in heat calculations. 10. View full abstract»

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