GATE EE 2022 Set 1 — Question 65
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Electrical Machines → Three-Phase Induction Machines → Auto-Transformer
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Question
A 3-phase, , 4-pole, induction motor draws 5 times the rated current at rated voltage at starting. It is required to bring down the starting current from the supply to 2 times of the rated current using a 3-phase autotransformer. If the magnetizing impedance of the induction motor and no load current of the autotransformer is neglected, then the transformation ratio of the autotransformer is given by ____________. (round off to two decimal places).
Correct answer
0.61 to 0.65
Solution
1.Identify given parameters:
- Starting current at rated voltage () =
- Desired starting current from supply () =
The relationship between the starting current from the supply and the short-circuit current (starting current at rated voltage) when using an autotransformer with transformation ratio is:
3.Solve for :
Rounding to two decimal places, the transformation ratio is .Continue learning with Success Tracker
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