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InsemMar 20252019 patternSE Electrical

Electrical Machines-1 SPPU Insem Question Paper Mar 2025

All 4 questions from this SPPU insem paper, as printed. Read them here or open the PDF.

Open the PDFMost repeated Electrical Machines-1 questions
Subject code
203146
Pattern
2019 pattern
Exam
Insem
Session
Mar 2025
Max. marks
30
Time
1 Hour
Semester
IV
Paper code
[6409]-207

Printed for: S.E. (Electrical Engineering) (Insem)

Instructions to the candidates

  1. Solve Q1 or Q2; Q3 or Q4.
  2. Figures to the right indicate full marks.
  3. Neat diagrams must be drawn wherever necessary.
  4. Assume suitable additional data, if necessary.
  5. Use of a non-programmable calculator is allowed.

Questions

  1. Q1

    1. a)

      State an importance of open and short circuit test on transformer over direct load test on transformer to find out efficiency and regulation of it. Explain the reasoning behind, how wattmeter reading in open circuit test and in short circuit test is taken as iron loss and copper loss of transformer respectively?

      [8]
    2. b)

      Open and short Circuit test is performed on single phase transformer having voltage and power rating as 250/500 volts, 25KVA. The test results are as below: Open Circuit Test: (with HV winding open) 250 volts 5A 200 watts Short Circuit Test: (with HV winding shorted) 6 volts 100A 180 watts Draw an equivalent circuit diagram of transformer referred to LV winding and write the values of respective parameters in equivalent circuit as calculated from the tests

      [7]

  2. Q2

    1. a)

      Derive an expression for “Copper Saving” in step-down Single Phase Auto-Transformer in comparison with Two Winding Single Phase Transformer. State any Two disadvantages of autotransformer.

      [8]
    2. b)

      State the names of losses taking place in single or three phase transformers. Explain in brief about factors affecting on these losses. Write only formula for “All Day Efficiency” for transformer. 2

      [7]

  3. Q3

    1. a)

      What is the necessity of parallel operation of transformers? State the necessary and desirable conditions for satisfactory parallel operation of single phase transformers.

      Also asked:Mar 2026

      [7]
    2. b)

      Two single phase transformers with equal voltage ratios have impedances of (0.82+ j 2.51) ohms and (0.8+j 2.31) ohms with respect to the secondary. If they operate in parallel, how they will share a total load of 2000 KW at power factor 0.8 lagging?

      Also asked:Mar 2023

      [8]

  4. Q4

    1. a)

      With the neat sketch and phasor diagram explain Open Delta or V-V Connection of the transformer.

      Also asked:Mar 2026 ·Mar 2023

      [8]
    2. b)

      Explain in brief an importance of ‘Polarity Test’ on transformer in practice. Draw the relevant circuit diagrams for any single phase transformer to obtain resultant voltage from ‘additive polarity’ and ‘subtractive polarity’ connection. 

      [7]