User's Manual

012-07210A Permanent Magnet Motor

Part B: DC Generator

1. Review steps 1 and 5. Then remove the armature and install it with the split ring commutator

down between the brushes.

2. Connect the meter and rotate the armature slowly, at a rate of about one complete revolution in

two seconds.

a) How does the meter respond?

b) How does the meter respond when the armature is rotated in the opposite direction?

c) Why does the behavior of the split ring commutator differ in results from that of the dual slip

rings?

d) Which of the following describes the results? (a) AC (b) pulsating DC (c) steady DC

3. Spin the armature several more times, increasing the speed each time. Stop if this causes you to

exceed the range of the meter.

a) What is the effect of greater rotational speeds?

b) This result may be explained in terms of the ideas discussed above. Try to explain the effect of

greater speeds.