Mitsubishi Electric MSZ-G09SV-E1 Service Manual page 40

9-13. Indoor fan motor control
The detected rotational frequency of the indoor fan motor (AC fan motor) is feeded-back 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
output point.)
<Input side>
The microprocessor detects rotational
frequency of AC fan motor, using Hall
element in AC fan motor.
every 100Hz pulse output
Rotational frequency
Electronic control P.C. board
The microproces-
sor drives solid
state relay on
Electronic control
P.C. board.
The microprocessor adjusts rotational frequen-
cy.
If feeded-back pulses are not detected for 12
seconds, it is detected as abnormality of AC
fan motor, and indoor OPERATION INDICA-
TOR lamp flashes to show abnormality.
AC motor
actuator
(Solid state relay)
40
Solid state
relay output
AC fan
motor
230V AC
rotational
frequency
sensor
part
output
input
Controlled voltage
is applied to AC
fan motor.