Hitachi RAC-10G5, Service Manual, Page: 49 / 62

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10. Temporary Switch
●
The temporary switch is used to operate the air conditoner temporarily when the wireless remote control
is lost or faulty.
●
The air conditioner operates in the previous mode at the previously set temperature. However, when the
power switch is set to OFF, it starts automatic operation.
Fig. 10-1
11. DC Fan Motor Drive Circuit
●
Fig. 11-1 shows the indoor DC fan motor drive circuit.
Fig. 11-1
●
The circuit produces the fan motor drive voltages, 8-33V, from 35V DC supplied from power supply and
controls the fan motor speed.
●
Q901 is switched on and off according to the signal at fan PWM output pin
57
to control the voltage
which is smoothed by D902, L901 and C901 to drive the fan motor.
●
The output voltage is divided by R919 and R920 and is input to divided voltage output pin
8
; the micro
computer controls the fan PWM output so the output voltage is set to the specifi ed value. The chopper
frequency of the fan PWM output is 15.7kHz.
●
In the Fan current detection circuit, 35V line current is detected by R906 and input to fan current detection
pin
9
. Microcomputer detects overcurrent comparing it with the current judgment value corresponding
to the fan rotation speed.