Hitachi RAS-18YH4 Service Manual page 41

MODEL RAC-18YH4
1. The electrical parts for the outdoor unit is composed of two P.W.B (a power P.W.B. and main P.W.B.)
and a harmonics improvement circuit as shown in Fig. 1-1.
• MAIN P.W.B.
This P.W.B. is equipped with the rectification diode, DC fan motor control circuit and the circuits
around the micro computer which take various controls.
• POWER P.W.B.
This P.W.B. is equipped with the noise filter, ICP power circuit, interface circuit, smoothing capacitor,
expansion valve control circuit and four-way valve control circuit.
• HARMONICS IMPROVEMENT CIRCUIT
This circuit is composed of the capacitor at the bottom of the electrical parts box and two reactors
attached to the BULKHEAD.
POWER P.W.B.
A
B
SWITCHING
POWER SUPPLY.
C
INTERFACE
CIRCUIT
D
REVERSING VALVE
CONTROL CIRCUIT
ELECTRIC EXPANSION VALVE
CONTROL CIRCUIT
MAIN P.W.B.
HARMONICS
IMPROVEMENT
CIRCUIT
FAN MOTOR
CONTROL
CIRCUIT
Fig. 1-1
– 44 –
IPM
INVERTER
CONTROLCIRCUIT
RESET
CIRCUIT
MICRO
COMPUTER
THERMISTOR
DETECTION
COMPRESSOR
POSSITON
DETECTIVE
CIRCUIT
CIRCUIT