Hitachi RAC-25NH5, Service Manual

Page: 74 / 112

– 85 –
Drive
signal
Chopper
signal
Chopper
signal
DC
Current
level
DC current
Detection
resistor
5V
DC 260V
-360V
Reset circuit
Over-load external
setting circuit
Current amplified
circuit
Drive
Circuit
IP signal
Reset Voltage
Peak current
cut off circuit
Outdoor microcomputer
T
rip signal
synthesis circuit
Compressor
motor
Power
module
Fig. 8-2
●
The following describes the operations of each circuit in detail.
(1) Peak current cut off circuit
Fig.8-3 Peak Current Cut off Circuit and Waveforms at Each Section.
DC current Id
Voltage at point
1.05V
21A
Voltage at point
A
B
A
—
Fig.8-3
Detection
resistor
Negative
Terminal
DC
current
0V
0V
R43
0V
R41
QC
R42
SPM2
SPM2 — HIC
Main P.W.B
HIC
IC1
CN14
IP
Outdoor
microcomputer
F
R43
9 9
8
20 9 2 39 17
B
●
The Ip cut off circuit detects an instantaneous excessive current and stops inverter to protect parts such
as SPM2, etc.
●
As shown in diagram, if current exceeding 21A flows, voltage at point recognized by detecting resistor
is input to pin of SPM2 – HIC, and voltage divided by R41 and R43 is input to pin
of IC1. Since
threshold of IC1 is exceeded in this case, Lo signal is input from pin (Voltage at point . When Lo
signal is input to pin of microcomputer, microcomputer stops drive output.
●
When drive output from microcomputer is stopped, all drive output goes Hi, and microcomputer is initialized
to enter drive signal standby mode. 3 minutes later, microcomputer outputs drive signal again, to start
operation.
10
8
9
B
A
17