A 15 kw squirrel cage motor having a maximum efficiency of 90% on a continuous full load has temperature rise of 42 degrees celcius after 30 min and 52 degrees celcius after 1 hr under the above operation conditions. a) calculate its final steady state temperature rise on continuous load and the heating time constatnt. b) if the motor is operated on a short load for 9 min estimate its temperature rise. c) calculate the maximum overload that can be applied on a short, 9 min rating so that the temperature rise is the same as the final steady state temperature rise on continuous load.

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What is the meaning of STAR POINT? Why this important in CT and VT?

2 Answers   L&T,

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3ph motor running with unequal kw and different pf what are the reasons

0 Answers   UltraTech,

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Can anyone please give me the parameters , formula needed to calculate the circuit breakers for building services.Thanks

0 Answers   Bhel,

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in three pin plug point, whats the reason that one plug point is bigger in size

4 Answers  

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My question is whether bellow formula is correct to find bus size for 46kA for 0.5 second & what is RT in bellow formula. formula to calculate the size of busbar to withstand the thermal stresses due to currents with duration of 0.2 sec to 5 sec. Sp = RT( I x I x t) / K Where Sp – is the cross sectional area of bus bar in millimeters. I -    is the value of AC fault current. t -    is the operating time of disconnecting device in seconds. K –  is the factor depending on the material of the conductor, insulation and initial and final temperature. Value of ‘k’ for copper is 143.

0 Answers   Premier,

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why frequency should be constant?

2 Answers  

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what happen if i change the polarity of ac when it is connected with motor

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What are hrc fuses and where it is used?

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how to check the insulation for motor using megger?

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How to calculate load requirement of a 50 flat apartment with 5 kw each unit,sizing of cable,transformer

1 Answers  

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