Lab Information -- Direct Current Machine Experiments
EXPERIMENT NO. 12
SPEED-LOAD CHARACTERISTICS OF A SHUNT MOTOR
PURPOSE:
To study the speed load characteristics of a shunt motor at its rated speed.
APPARATUS REQUIRED:
1. One DM-100/A DC machine as a motor.
2. One DM-100/A DC machine as a generator.
3. One SLA-100/D Stobe tachometer.
4. One Hampden 0 to 150 volt DC voltmeter.
5. One Hampden DC 0 to 5A DC ammeter.
6. One Hampden DC 0 to 2.5 A ammeter.
7. One RL-100/A Hampden resistance load.
8. One Hampden 0 to 125 volt/5 amp. DC power supply.
9. One Hampden 0 to 150 volt/1 amp. DC power supply.
PROCEDURE:
1. Couple the DC motor to the DC generator and make the connections shown in Figure 12.
Adjust the motor's rheostat to its minimum resistance, fully counter clockwise position. Adjust
the generator's rheostat to its maximum resistance, fully clockwise position. Adjust the output of
the 150 volt DC supply to 115 volts.
2. Start the motor by slowly increasing the output of the 125 volt DC supply to 125 volts. Adjust
the motor's speed by means of its field rheostat. Adjust the output voltage of the generator to 115
volts by means of its field rheostat.
3. Perform a load test on the motor from no load to 1000 ohms, 500 ohms, 333 ohms, 250 ohms,
200 ohms, 166 ohms, and 142.8 ohms loads. As each load step is applied it will be necessary to:
1) Adjust the 125 volt DC supply to maintain a 125 volts input, and; 2) Adjust the generator's
rheostat to maintain a 115 volt DC output. Record the armature current, armature voltage, and
speed of the motor and the armature voltage and load current of the generator for each load step.
REPORT:
Using the data obtained, plot the speed and output power (armature volts times load amps) as
ordinates versus the motor's armature current as abscissa.
FIGURE 12