Drive Circuit Of The Indoor Fan Motor; The Circuit Check; Typical Circuit Waveform; Fig - Hitachi RAC-18WEC Service Manual

3. Drive circuit of the indoor fan motor

Primary 18.5V
Power siganl of
indoor fan(from
3
pin 57 of
microcomputer)
Primary 0 V
Rotation speed feedback signal (to pin
Output signal of indoor fan (to pin
< The circuit check (For test) >
Name
Motor drive power
Motor contorl power
Motor speed signal
Motor rotation speed debug
* The voltage above is all motor operation vol. when yon start the test, take care
of your connector, do not touch the different pin together.
* The voltage of pin 6 - pin 4 , pin 7 - 4 maybe diffierent from above.
< Typical circuit waveform >
Voltage at pin $5 of microcomputer (between 0 V and pin $5 )
When slow (700min -
1.7ms.
5V
The indoor fan motor receives VDC (motor drive power supply), VCC (power supply for the control circuit inside the motor),
and VS (speed command voltage) from CN2. The indoor fan motor returns an FG signal of a frequency that matches the
rotation speed.
VCC stabilizes the primary 18.5 V power supply into 15 V by using Q201 and supplies it.
While on standby for a remote control signal, the Q201 shuts down the VCC and reduces the standby power.
The VS receives a command voltage from the microcomputer (IC601). The VS terminal undergoes an analog voltage that
matches the Lo level time ratio of the pulse signal from pin $5 of the microcomputer. (See Fig. 3-2.)
The FG terminal undergoes a signal of 12 pulses per revolution of the motor shaft. By counting the pulse rate, the
microcomputer (IC601) recognizes the motor speed, thereby performing feedback control.
14
of microcomputer)
68
of microcomputer)
45
Test point
CN2 1 pin- 4 pin
CN2 5 pin- 4 pin
CN2 6 pin- 4 pin
CN2 7 pin- 4 pin
When fast (1200min -
1 ) 1 )
1.7ms.
15V
5V
Primary 325V

Fig. 3-1

Test voltage
About 325V
About 15V
About 2-6V
About 7.5V
FG voltage of fan motor (between pins
When slow (700min -
When fast (1200min -
1 )
7.1ms.
4.2ms.
15V
Fig. 3-2
< Pin 6 - Pin 4 voltage one example >
1300min -
1
2.1V
Vsp voltage 「V」
* The different mode maybe have
different FAN rotation speed.
and of CN2)
1 )
Indoor fan motor
5.4V