Time
-1.2
-0.8
-0.4
0
-1.2
Normalised
AC
-0.8
-0.4
Time
-1.2
-0.8
-0.4
0
-1.2
Normalised
AC
-0.8
-0.4
AC Current
AC input (V)
Phase Angle control uses a low frequency switch to chop an AC sine wave.
The firing angle of the switch is varied. (25% - 100%)
The average voltage is proportional to the area under the sine wave. Thus, the
average voltage is the integral from the firing angle to the zero crossing, the cosine
of the firing angle.
Phase Angle control provides a excellent method to control the average voltage of
an AC source. However, the low frequency AC waveform presented to the motor will
create some torque ripple and acoustic noise, to keep this to a minimum we keep
the range of control between 25% and100%.
note:
All universal motors operated from an AC source will have some torque
ripple.
Phase Angle Fan Speed Control
Time
-1.2
-0.8
-0.4
0
-1.2
Normalised
AC
-0.8
-0.4
Phase Angle set at 50%
Phase Angle set at 25%
Phase Angle Fan speed Control
17
