ABSTRACT increased the armature voltage (Ea) also increased. This

ABSTRACT

 

The experiment dealt with DC separately
excited shunt generator. The properties of this type of generator under no load
and full load conditions were studied. The effect to running speed of load and
no load was determined. Ways on how to do connections for the generator was
also examined.

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KEYWORDS

 

Armature – takes the place of the nail in
an electric motor. The armature is an electromagnet made by coiling thin wire
around two or more poles of a metal core.

 

Shunt – Parallel connection of small value
resistor across galvanometer which saves galvanometer from damage of huge
current flow

 

Excitation- The process of generating a
magnetic field by means of an electric current

 

Resistance – The ohmic resistance in the
main current-carrying windings of an electric generator or motor.

 

Commutator – their contacts are attached
to the axle of the electromagnet, so they spin with the magnet.

 

1 INTRODUCTION

 

The experiment aimed to show the properties of different DC
generators and the effects of load and no load conditions.

For a separately excited DC generator, a separate source
excites the field winding. 

A magnetic field is produced through the field windings
when the rotor is rotated the field is cut which induces electricity. The
voltage created will depend on the magnetic field and the speed of the rotor. A
separately excited generator will need an external DC power source. This type
of generator has a number of advantages such as variability in speed and
reversing the motor is easier.

 

2 RESULTS

 

The results showed in table 27-1 that as the field current
(If) increased the armature voltage (Ea) also increased.
This is due to Ohm’s Law which states that current and voltage have a direct
relationship.

The results showed in table 27-2 that as the resistance
load (RL) decreased the armature current (IA) minimally
increased, the armature voltage (Ea) decreased while the power
increased.

 

Table 27-1

IF (milliamperes)

EA (volts)

0

10

50

27

100

48.7

150

75

200

95

250

115

300

130

350

145

400

153

 

 

Table 27-2

RL (ohms)

IA (amps)

EA (volts)

POWER (watts)

?

0

135

0

600

0.2

126

25.2

300

0.45

125

56.25

200

0.6

123

73.8

150

0.8

120

96

120

1

118

118

100

1.2

115

138

80

1.35

112.5

151.875

75

1.42

119

159.04

 

 

6CONCLUSIONS

 

The experiment showed some characteristics of a separately excited
shunt DC generator. The output of polarity can be changed by either changing
the rotation of the generator or changing the direction of magnetic field. Also
Ohm’s Law and Kirchhoff’s current law were still instrumental in finding the
values from the experiment.