Lab Information -- Direct Current Machine Experiments
EXPERIMENT NO. 5
LOAD CHARACTERISTICS OF A SEPARATELY-EXCITED SHUNT GENERATOR
PURPOSE:
To study the load characteristics of a separately-excited shunt generator at rated speed and
voltage.
APPARATUS REQUIRED:
1. Two DM-100/A DC Machine (one as generator, one as motor).
2. One SLA-100 D Tachometer
3. One 0 to 150V DC Voltmeter
4. One 0 to 2.5A DC Ammeter
5. One 0 to .5A DC Ammeter
6. One Resistance load RL-100/A
7. One 0 to 125 Volt/5 Amp DC Power Supply
8. One 0 to 150 Volt/1 Amp DC Power Supply
PROCEDURE:
1. Couple the DC generator to the DC motor and make the connection shown in Figure 5. Make
sure Power Supply is in the OFF position.
2. Adjust the generator's field rheostat to its maximum resistance, fully CW. position. Adjust the
motor's field rheostat to its minimum resistance, fully CCW position.
3. Adjust the output of the 150 volt DS supply to 125 volts. Have the instructor check your
connections and then start the motor.
4. Adjust the speed to 1800 RPM by slowly increasing the output of the 125V DC supply to 125
volts and then use the motor's rheostat knob to bring the motor up to speed. Adjust the
generator's output to 130 volts by means of its rheostat.
5. Perform a load test on the generator from no-load to approximately 1.35 amperes load. This is
done by decreasing the resistance load, first no-load and then from 1000 ohm to approximately
83.33 ohm. It is necessary to adjust the 125V DC supply after each load step is applied to
maintain 1800 RPM. Record the armature volts, load current, field current, and speed.
REPORT:
Using the data obtained, plot the armature terminal voltage as ordinate versus the load current as
abscissa.
QUESTIONS:
1. What are the causes of voltage dropped in a separately-excited generator?
2. What is the percent voltage regulation of the generator?