Mitsubishi Electric MSZ-A09RV Service Manual page 37

9-14. Indoor fan motor control
The detected rotational frequency of the fan motor is feed backed to the microprocessor and then the microprocessor works
to keep the rotational frequency at a fixed value against load fluctuation.
(1) Circuit block diagram
Microprocessor
(2) Control system
<Output side>
The microprocessor outputs pulse
every 100Hz (every 50Hz in half wave).
(Fan speed varies according to the
time span between a Zero-cross point
on the commercial wave and a pulse
out put point.)
<Input side>
The microprocessor detects rotational
frequency of AC fan motor, using Hall
element in AC fan motor.
every 100Hz pulse output
actuator (SSR)
Rotational frequency
controller board
The microproces-
sor drives SSR on
relay P.C. board.
The microprocessor adjusts rotational
frequency.
If feed backed pulses are not detected for 12
seconds, fan motor becomes abnormal and
indoor POWER MONITOR lamp flashes to
show abnormality.
SSR output
AC motor
220~240V AC
Controlled voltage
is applied to AC
fan motor.
37
AC motor
Rotational
frequency
sensor
part
Output
Input