Hitachi RAS-50WX8 Service Manual page 108

10. Outdoor DC Fan Motor control circuit
Main P.W.B.
FM-15V
R115
+
D101
5V
4 1
3 2
PQ102
0V
This model uses DC Fan Motor which is including controller circuit into the Motor shell.
This DC Fan Motor will rotate by control voltage apply to Vsp input. (Voltage range: 1.7 to 7V DC)
Vsp high : Faster ; Vsp low : slower ; Vsp lower than 1.7V : stop
Motor will output FG pulse by following this motor revolution.
Outdoor Microcomputer will output PWM control signal from pin
indoor Microcomputer.
This PWM control signal will convert to Vsp voltage by smoothing circuit (Q101 & RC filter)
Fan motor will start to rotate when Vsp was proceeding over than 1.7V, and generate FG pulse by rotation speed.
FG pulse will feed back to Outdoor Microcomputer through PQ102.
PQ102 is the isolator between Microcomputer circuit and DC Fan Motor circuit, which has to match the Fan Motor revolution
with instructed revolution. Such as...
FG feedback : Faster - Instruction : Slower ... Decrease pulse width
FG feedback : Slower - Instruction : Faster ... Increase pulse width
FG pulse is also used for Fan Motor fail detection.
Microcomputer will monitor FG pulse 30 seconds after start the fan motor. If there is no signal detected, it will consider that
the Fan Motor was malfunction and stop the operation. In this case, LD302 on main P.W.B. will blink 12 times. (Fan Motor
lock detected)
R107 and IC4 are used for Fan Motor over current.
Power board in system power module
+ + +
3 2 1 1 2 3
1 2 3
2A-Fuse
FM-15V
C102
R107
Q101
R101
R102
FM-0V
Ap 7V
5V
t
33.3KHz
R108
FM-0V
5V
T/2
T
Power supply for DC fan motor from smoothing
U
capacitor in system power module
V
W
4 5
RC Filter
1
2
3
0V
4
Vcc
5
PWM control voltage
6
VSP
FG Pulse
7
HIC
0V
0V
R283
61
60
59
R242
(FMCHOP) terminal by following the instruction from
– 148 –
Motor coil
BOARD
DC Fan motor with control board
12V
C208
0V
IC4
8
R244
2
- FAN
1 65
+
3 LIMITTER
+
R246
0V
0V
R297
Q201 75 FMCHOP
R298
0V FM-60 el
15
FG PULSE
input