PASCO SE-8658A PERMANENT MAGNET MOTOR - Manual (Page 27)

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012-07210A Permanent Magnet Motor
tape. Slip the square part far enough way down the split ring commutator so you can grip
the plastic bushing to spin the armature. Position the photogate so the corners of the square
interrupt the photogate’s beam 4 times per revolution.
8. Set the voltage to 8 volts and the frequency of the alternating current to 16 Hz. Start the motor
and use the stroboscope or photogate to determine the rotational speed of the motor. What is the
rotational speed of the armature? If the result is not already expressed in revolutions per second,
convert it to these units.
9. While the motor is running, lower the voltage to 6 volts. Does the rotational speed of the
armature change when you change the voltage?
10. Return the voltage to 8 volts and change the frequency of the alternating current to 20 Hz, and
then 24 Hz, determining the rotational speed each time. (Manually restart the motor each time if
needed.)
Does the rotational speed of the armature change when you change the current frequency?
11. If the room is lit with fluorescent lights, you can also see the effect changing the current
frequency on the motor’s speed. Fluorescent lamps flash twice during each cycle of the AC
power that supplies them. When the motor operates at a submultiple of this rate, multiple
images will appear to be stationary, so the armature will appear to be stationary. Observe the
armature at current frequencies of 15, 20, 24, and 30 Hz (or at 16.67, 20, and 25 Hz in locations
with 50 Hz AC power).
➤ Notice that the motor is not self-starting. Immediately after you apply the AC
power, start the motor manually by grasping the black plastic bushing at the top of
the armature assembly between thumb and forefinger and spinning the armature.
It may take several attempts to successfully start the motor because you must spin
the armature at a speed that approximately matches the frequency of the power
➤Note: with the PASCO 6500 Series Power Amplifier, the motor may stop and
need to be restarted manually.