Question Paper: Electrical Technology and Instruments Question Paper - May 2015 - Instrumentation Engineering (Semester 4) - Mumbai University (MU)
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## Electrical Technology and Instruments - May 2015

### MU Instrumentation Engineering (Semester 4)

Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

### Solve any four:

1 (a) What is the difference between a generator and a motor? 5 marks

1 (b) Explain power flow diagram for an Induction Motor. 5 marks

1 (c) State the advantages and disadvantages of moving iron instrument. 5 marks

1 (d) Explain the applications of CRO. 5 marks

1 (e) Explain the basic principle of ADC. 5 marks

2 (a) Two series motors run at a speed of 700 r.p.m. and 750 r.p.m. respectively, when taking 70A at 500 V. The terminal resistance of each motor is 0.5Ω. Calculate the speed of the combination, when connected in series and coupled mechanically. The combination is taking 70A at 500V supply. 5 marks

2 (b) Derive the following torque rations in terms of slip and rotor parameters. <mi>i</mi><mo stretchy="false">)</mo><mtext> </mtext><mstyle displaystyle="true" scriptlevel="0"><mfrac><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>S</mi><mi>T</mi></mrow></msub><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>n</mi><mi>t</mi></mrow></msub></mfrac></mstyle><mtext> </mtext><mi>i</mi><mi>i</mi><mo stretchy="false">)</mo><mtext> </mtext><mstyle displaystyle="true" scriptlevel="0"><mfrac><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>F</mi><mi>L</mi></mrow></msub><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>n</mi><mi>t</mi></mrow></msub></mfrac></mstyle>[/itex]" role="presentation" style="font-size: 125%; text-align: center; position: relative;">i) TSTTnt ii) TFLTnt<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mi>i</mi><mo stretchy="false">)</mo><mtext> </mtext><mstyle displaystyle="true" scriptlevel="0"><mfrac><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>S</mi><mi>T</mi></mrow></msub><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>n</mi><mi>t</mi></mrow></msub></mfrac></mstyle><mtext> </mtext><mi>i</mi><mi>i</mi><mo stretchy="false">)</mo><mtext> </mtext><mstyle displaystyle="true" scriptlevel="0"><mfrac><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>F</mi><mi>L</mi></mrow></msub><msub><mi>T</mi><mrow class="MJX-TeXAtom-ORD"><mi>n</mi><mi>t</mi></mrow></msub></mfrac></mstyle>[/itex]<script type="math/tex; mode=display" id="MathJax-Element-1"> i) \ \dfrac {T_{ST}}{T_{nt}} \ ii) \ \dfrac {T_{FL}}{T_{nt}} </script> 5 marks

3 (a) Explain how rotating magnetic field is produced in 3&Straightphi; induction motor. 5 marks

3 (b) Explain the working at attraction type and repulsion type moving iron instrument with neat diagram. 5 marks

4 (a) Derive the bridge balance equation for the basic a.c. bridge. 5 marks

4 (b) What is Hay's bridge? Derive the balance equation. When it is preferred over Maxwell bridge? 5 marks

5 (a) A 3ϕ, 12 pole, induction motor has rotor resistance of 0.15Ω and standstill reactance of 0.25Ω per phase. On full Load it is running at a speed of 480 r.p.m. The rotor induced e.m.f. per phase at standstill is observed to be 32V. Calculate (i) Starting Torque (ii) Full load torque (iii) maximum Torque (iv) Speed at maximum torque. 5 marks

5 (b) Explain variable frequency drive. List its applications. 5 marks

### Write short notes on (any two):

6 (a) A.C. voltmeter. 5 marks

6 (b) Shaded pole induction motor. 5 marks

6 (c) Applications of a.c. potentiometer. 5 marks

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