Experiments performed in Lab:

Circuit Diagrams:

Expected Curves:

Observations:

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Graphs:

1. Plot of Speed / V(v).

2. Plot of speed(rpm) / IM(A):

3. Plot of speed(rpm) / IF(A):

4. Plot of speed(rpm) / Torque(N-m):

Results and Inference:

1. With increase in the load, speed of the motor decreases.

2. “speed - torque” characteristics indicates that with increase in speed, the

applied torque decreases.

3. Reversing the polarity of applied voltage across motor, it reverses its

direction of motion.

4. Plot of speed (rpm) vs V(volt) indicates that the speed of the motor, w is

directly proportional to armature voltage.(As, this plot is linear).

5. Plot of speed (rpm) vs IF(A) is concave in nature. As, IF increases, speed of

motor, w decreases.

Conclusion:

1. Speed of the motor can be controlled by both either change in terminal

voltage, keeping field excitation constant or, by changing in field excitation

current, keeping terminal voltage constant.

2. Keeping field excitation constant, speed of motor increases with increase in

terminal voltage.

3. Keeping terminal voltage constant, speed of motor decreases with increase

in field excitation current.

Precaution:

1. Before switching on, circuit must be checked by instructor.

2. Speed of motor should be noted only after it becomes stable.

3. Voltage applied across motor should not be greater than rated voltage i.e.

230V

4. Reading from voltmeter and ammeter should be taken with great care.

5. Plots should be made carefully.