The object of this experiment is to verify the factors , which affect Me building voltage In separately - cited generator , the external Characteristics and load saturation characteristics , regulating characteristics of the generator Characteristics of separately excited generator SAIF ALDIN ALI MADIN سيف الدين علي ماضي S96aif@gmail.com

1. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
1
[Electricity Laboratory II]
University of Baghdad
Name: - Saif Al-din Ali -B-

2. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
2
TABLE OF CONTENTS
Experiment Name................................................................I
Experiment Aim..............................................................II
Procedure.......................................................................V
Data and processes.......................................................VI
Calculations and Charts................................................VII
DISCUSSION……………….................................................VIII

3. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
3
1. Experiment Name: characteristics of separately excited generator
2. Experiment Aim: The object of this experiment is to verify the
factors , which affect Me building voltage In separately - cited generator
, the external Characteristics and load saturation characteristics ,
regulating characteristics of the generator
3. Procedure:
 Run (1): (No - load characteristics),
1. Connect the circuit as in fi l, switch (s) is open with the slide of the
rheostat al zero position in order to start with zero field current (if)
2. Run the generator at rated speed record the reading of voltmeter |
connected across armature terminals of the generator
3. Switch on d.c supply to the field winding and increase. If gradually
in approx. equal several steps , record Its value with the values of
the open - circuit voltage (E) between the outside terminal of the
generator which is operating in this case at N. L
4. Decrease I gradually in approx. equal several steps as in step 3 and
record the values of If and E specially at If=0
5. This value is e. t. due the residual magnetism
6. Phot armature voltage versus the field current
 Run (2): (External characteristics)
1. with the connection as shown in fig 2 operate the generator at rated
speed keeping It constant
2. Adjust the field rheostat to allow approx., the rated field current with
rated voltage say 220v
3. Change the load current by varying load starting from IL = 0 till n
rate value with 5 steps. Take reading of load terminal voltage
Observation table

4. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
4
4. Data and processes:
no If va If va
1 0 10 0 250
2 0.03 31 0.03 220
3 0.06 51 0.04 200
4 0.09 71 0.07 180
5 0.1 83 0.09 160
6 0.13 104 0.11 140
7 0.16 125 0.14 125
8 0.19 140 0.16 104
9 0.23 160 0.19 83
10 0.26 180 0.23 71
11 0.3 200 0.27 51
12 0.36 220 0.32 31
13 0.46 250 0.46 10
5. Calculations and Charts
Ra=0.9
no
Vl IL
Eg=Vl
External c.c
Eg=Vl+ILRa
Internal c.c
VR.A=220-Eg Ia*Ra
1 222 0 222 222 0 0
2 219 0.75 219 219.675 0.325 0.675
3 214 1.7 214 215.53 4.47 1.53
4 210 2.5 210 212.25 7.75 2.25
5 209 3.15 209 211.835 8.165 2.835
6 206 4.1 206 209.69 10.31 3.69
7 203 4.9 203 207.41 12.59 4.41

5. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
5
Charts
1. Relationship I(f) With V
2.
0
50
100
150
200
250
300
0 0.1 0.2 0.3 0.4 0.5
V
I(f)
growing
decreasing
-50
0
50
100
150
200
250
0 1 2 3 4 5 6
IL
Eg=Vl
Eg=Vl+ILRa
VR.A=220-Eg
Ia*Ra
ideal

6. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
6
6. Conclusions:
1. Got out the internal character. From the external character.
The interior is trying to get close to the ideal situation as we saw in the
chart it is rising
The relationship with the current in an external relationship is inverse as
the current is reduced by the amount of Eg = Vl
2. Explain the Effect of speed on the open circuit char
The speed is proportional to the emf, and the emf in turn is proportional to the current of the
field and finally the field current is proportional to the flow flux ... so the higher the speed the
greater the quantities and vice versa

7. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
7
a separately excited DC generator giving its no load voltage E0 for a constant field current. If
there is no armature reaction and armature voltage drop in the machine then the voltage
will remain constant. Therefore, if we plot the rated voltage on the Y axis and load current
on the X axis then the curve will be a straight line and parallel to X-axis as shown in figure
below. Here, AB line indicating the no load voltage (E0).
When the generator is loaded then the voltage drops due to two main reasons-
Due to armature reaction,
Due to ohmic drop (IaRa).
Internal or Total Characteristic of Separately Excited DC Generator
The internal characteristic of the separately excited DC generator is obtained by subtracting
the drops due to armature reaction from no load voltage. This curve of actually generated
voltage (Eg) will be slightly dropping. Here, AC line in the diagram indicating the actually
generated voltage (Eg) with respect to load current. This curve is also called total
characteristic of separately excited DC generator.
External Characteristic of Separately Excited DC Generator
The external characteristic of the separately excited DC generator is obtained by subtracting
the drops due to ohmic loss (Ia Ra) in the armature from generated voltage (Eg).
Terminal voltage(V) = Eg - Ia Ra.
This curve gives the relation between the terminal voltage (V) and load current. The external
characteristic curve lies below the internal characteristic curve. Here, AD line in the diagram
below is indicating the change in terminal voltage(V) with increasing load current. It can be
seen from figure that when load current increases then the terminal voltage decreases
slightly. This decrease in terminal voltage can be maintained easily by increasing the field
current and thus increasing the generated voltage. Therefore, we can get constant terminal
voltage.

8. SAIF AL-DIN ALI MADI
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
8