Hitachi RAM-68NP3B, Service Manual, Page: 45 / 79

■
RAM-68NP3B
Fig. 1-1
(Indoor unit 1)
(Indoor unit 2)
3P-Terminal
3P-Terminal
(Indoor unit 3)
Terminal block
2P Terminal
3P-Terminal
7
5
4
6
1
3
2
2
1
4
3
CN5
NV-4V
（WHT）
F8
F9
F10
BLU
YEL
GRY
ORN
PUR
PINK
BRN
RED
CN4
VH-7P
（WHT）
1. Main Power Supply Circuit
●
AC 220~240V power supplied to the 2P terminal block is supplied to DB2 via the noise filter circuit, 2A fuse (F3),
and varistor (VS5). High-voltage DC smoothed by DB2 and C023 is used to create DC voltage on the
transformer's secondary side by the switch control IC (IC1) and switching transformer.
●
Secondary side DC voltage is used in the following six systems:
⑴
B-15V : Power supply for communication circuits between outdoor and indoor
⑵
B-5V : Power supply for main microcomputer and peripheral circuits
⑶
B-12V : Operating power supply for electric expansion valve
⑷
16V : Power supply for compressor motor drive IPM and fan motor drive IPM
⑸
12V : Power supply for reversing valve relay, power relay, in-rush current relay, and operating
amplifier for compressor motor and fan motor current amplification
⑹
5V : Power supply for inverter microcomputer and peripheral circuits
●
Primary Components
⑴
C001, C002, C012, C013, C014, C007, C008, L004, L006
Absorb electrical noise generated during operation of the compressor, and reduce noise level emitted to the
power line.
(2) Surge absorber, varistor 1, 2, 5
Absorb external surges, such as induced lightning.
⑶
IC1
IC for control of switching power.
⑷
IC4
DC/DC converter IC for generating 5V from 12V.
⑸
IC9
DC/DC converter IC for generating B-5V from B-15V.
MAIN PWB
Microcomputer Standby output
L
N
BLK
BLK
WHT
SURGE ABSORBER
1
2
DESCRIPTION OF MAIN OPERATION CIRCUIT