Electrical Machines-I 4th Sem EE/EEE/2520/May2019 PSBTE Paper

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SECTION-A

Q1. Do as directed.                                                                                                     15×1=15

1. Transformer core is made of silicon steel to reduce
2. Laminations are used in armature of DC machines to reduce losses.
3. In DC machines, maximum efficiency occurs when variable losses are to constant
4. The generator operates on the principle of induced
5. DC series motor is used for .
6. The DC motors are best suited where almost constant speed is
7. Very small transformers are generally
8. Transformer steps up or steps down the Input Voltage
9. Transformer has no           Losses.
10. Transformers are always rated in KVA

SECTION-B

Q2. Attempt any five questions.                                                 5×6=30

1. Why starter is necessary for a DC motor?
2. What are the conditions for parallel operation of single phase transformer?
• Why the efficiency of the transformer is higher than other AC machines?
1. A 4 pole, 1200 rpm generator with a lap wound armature has 65 slots and 12 conductors per slot. The flux per pole is 0.01 weber. Find the EMF induced in the
2. Why DC series motors cannot be started without load?
3. The no load ratio of a 50 Hz, single phase transformer is 3000/250 V. Determine the number of turns in each winding, if the maximum flux is 0.06 Wb in the
• Explain the differences between Auto Transformer and single phase

SECTION-C

Q3. Attempt any three questions.                                                            3×10=30

1. Explain the methods of speed control of DC shunt Motor
2. A 40 KVA transformer has iron losses of 450 W and full load copper losses 850 W. If P.F. of load is 0.9 lagging. Find full load efficiency, KVA load at which maximum efficiency occurs and the maximum
3. Explain the working of 3 point DC shunt motor starter with neat
4. Explain parallel operation of three phase Transformer.
5. A 25 KW, 250 V, DC shunt generator has armature and field resistance of 0.05 ohm and 100 ohm respectively. Find total armature power developed when working (i) as a generator delivering 25 KW output and ii) as a motor taking 25 KW

BASIC ELectronics be may 2018 DIPLOMA PAPER SOLUTION

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Section a FILL IN THE BLANKS be paper

Pentavalent Impurity

40.6%

Center-Tap transformer

ac component

Knee Voltage of Silicon diode is 0.7V

Zener Breakdown Region

Temperature.

True

Potential Divider or Voltage Divider Biasing.

Junction Field Effect Transistor

Voltage Controlled device.

Emitter is Highly Doped and Collector is Moderate Doped.

Valence Band

Saturation Region

Section B : BE PAPER MAY 2018 PAPER

What is Zener diode? Draw its symbol and characteristics

hybrid Parameter) of transistor

Temperature variations affect the operating point of a transistor

Phase reversal of output voltage with respect to input voltage in an Amplifier

BASIC ELECTRONICS DIPLOMA MAY 2018 PAPER

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Section c solved bee paper

Light Emitting Diode

Drift and Diffusion current

Filter Circuit

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