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# Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paper

`Electrical Machine-I 4TH SEM DIPLOMA PSBTE MAY 2018 PAPERÂ  Â    `

## Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â SECTION A

Â  Â  Â  Â  1. Fill in the blanks :

1. As the load increases, the speed of DC series motor will Decreases
2. For step-up transformer, the transformation ratio is More then Unity.
3. Brushes of DC machines are made up of Carbon.
4. Wave winding has Two Parallel paths.
5. Working principle of a transformer is Faraday\’s Law of Electromagnetic Induction.
6. The ratio of KW to KVA is known as Power Factor.
7. A transformer has no Core and Copper Losses.
8. Silicon steel is used to reduce Eddy Current Losses.
9. Transformer will give maximum efficiency when copper losses are equal to Iron Losses.
10. The shaft of DC machine is made up of mild Steel.

## Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  SECTION-B

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

1. Explain why DC series motor cannot be started without load?

2. What are the applications of DC motors ?

3. Explain how electromagnetic torque is developed in DC Motors.?

4. Name various methods of cooling transformers. Explain any one in Details ?

5. Explain the speed control methods of DC shunt Motor ?

6. Following data is obtained on a 5KVA 220/440V,1-Ð¤ transformer

Â  Â  Â  Â  Â  Â  Open circuit test: 220V, 2A, 100W on LV sideÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â

Â  Â  Â  Â  Â  Â  Short circuit test: 40V, 11.4A, 200W on HV side. Determine full load efficiency at 0.9pf.

Â  Â  Â  Â  Â 7.Derive e.m.f equation of a Transformer ?

## Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â SECTION-C

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

1. Why is there necessity of a starter? Name different types starters used in dc motors. Explain working of 3 point starter with

2. Write a note on: a) Parallel operation of transformersÂ Â Â Â Â  b) Auto transformer

3. Explain various types of losses occurring in DC Machines ?

4. The armature of a 12 pole DC shunt generator has 50 slots and is wave wound with 12 conductors per slot. The generator is running at a speed of 625rpm and supplies a resistive load of 115ohm at a terminal voltage of 300V, the armature resistance is 0.5ohm and field resistance is 60ohm. Find armature current, generated e.m.f. and flux per Pole ?

5. Explain various types of DC machines on basis of different types of excitations.

## Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paper

### Section a :-Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paperem Exam ECE/CSE/IT/EEE/0064/Nov 2015

As the load increases, the speed of DC series motor will Decreases

Â

For step-up transformer, the transformation ratio is More then Unity.

Â

Brushes of DC machines are made up of Carbon.

Wave winding has Two Parallel paths.

Â

Working principle of a transformer is Faraday’s Law of Electromagnetic Induction.

Â

The ratio of KW to KVA is known as Power Factor.

Â

A transformer has no Core and Copper Losses.

Â

Silicon steel is used to reduce Eddy Current Losses.

Â

Transformer will give maximum efficiency when copper losses are equal to Iron Losses.

Â

The shaft of DC machine is made up of mild Steel

### Section B :Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paper

why DC series motor cannot be started without load

applications of DC motors

How electromagnetic torque is developed in DC MotorsÂ

Various methods of cooling transformers.

speed control methods of DC shunt MotorÂ

Open circuit test: 220V, 2A, 100W on LV sideÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â

Short circuit test: 40V, 11.4A, 200W on HV side. Determine full load efficiency at 0.9pf.

Â  Â  Â  Â Â

e.m.f equation of a TransformerÂ

## Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paper

Get Started

### Section c Electrical Machines-I 4th Sem EE/EEE/2520/May 2018 Paper

Why is there necessity of a starter

Â

a) Parallel operation of transformersÂ Â Â Â Â

b) Auto transformer

Â

Various types of losses occurring in DC MachinesÂ

Â

DC shunt generator Numerical

Types of DC machines on basis of different types of excitations