Resistance of Armature Winding...

 Aim:- Measurement of resistance of the armature winding, series field winding and shunt field winding of a DC machine.

NAME PLATE SPECIFICATIONS OF MACHINE:

BHP/KW = 75 HP

Voltage = 250V

Amperes = 15A

RPM = 1500 rpm.

Apparatus Required:-

S. No.

Name of Equipment

Type

Range

Quantity

1.

Ammeter

MC

0-15A

1

2.

Ammeter

MC

0 – 20A

1

3.

Voltmeter

MC

0 – 30V

1

4.

Voltmeter

MC

0-300V

1

5.

Rheostat

Single tube

500ohms, 5A

1

6.

Lamp load

Resistive

250V, 1KW

1

 

Theory:- According to Ohm's law, the resistance 'R' of a winding is given by:

                           R = I/V

Where,    

                    V = voltage drop across the winding

                    I= current through the winding

 

Circuit Diagram:-       

 

 

Diagram

Diagram

Diagram

 

PROCEDURE:

1. Measurement of armature resistance, series field resistance. Connections are made as shown in figure (a), the reading of various meters are recorded for different values of current flowing through the above winding. The variation in current is obtained with the help of lamp bank load. The readings are taken up to 125% of the rated current of the machine.

 

2. Measurement of shunt field resistance. Connections are made as shown in figure (b), the readings of various meters are noted down for various values of shunt field currents. The shunt field current is varied by a rheostat used a variable resistance.

 

 

Observation Table:-

                                (a) Armature Resistance:

S. No.

I (amp)

V (volts)

RA (ohms)

1.

2.4

4.6

1.92

2.

6

8.2

1.37

3.

8

9.4

1.175

                                                                                          Average RA = 1.44

                               (b) Series field Resistance:

S. No.

I (amp)

V (volts)

RY (ohms)

1.

6

1

0.17

2.

11.6

2.7

0.23

3.

16

3.6

0.225

                                                                                          Average RY = 0.625

                               (c) Shunt field Resistance:

S. No.

I (amp)

V (volts)

RZ (ohms)

1.

0.5

104

208

2.

0.75

152

202.67

3.

1

204

204

                                                                                          Average RZ = 204.89

 

 

Precaucation:-

1.     Make the connections properly.

2.     Note the readings of voltmeters and ammeters properly.

3.     Remove insulations from the connecting wire so as the current will flow properly

Post a Comment

0 Comments