Plug the motor into one of the
outlets in the box. Use the circuit breaker
include/exclude switch to turn the outlet on and off. Power up
the motor - it may be necessary to get it started by hand -
and display the voltage and current on the oscilloscope.
The current will lag the voltage by about 50 degrees.
Load the motor by holding the shaft with your fingers or by
pressing it against the block of wood. The current can
be seen to increase in amplitude and shift more closely into
phase with the voltage.
These images show the unloaded and heavily loaded cases.
Applied voltage is in yellow, current is in red.
NOTES
Display the voltage on Ch1. Braid the leads, and display
the current as the difference between Ch3 and 4 (labeled
"Math"). Set average = 4 to reduce the noise a bit.
Set the scope to measure and display the phase angle of "Math"
relative to Ch1.
The block of wood hooks over the edge of the table so it
doesn't get away.
