Hitachi RAS-50YH4 Service Manual page 74

5V
Reset circuit
Over-load external
setting circuit
DC 260V
-360V
Current amplified
circuit
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
27A
Voltage at point
A
1.35V
Voltage at point
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 27A flows, voltage at point
●
by detecting resistor is input to pin
of IC1. Since threshold of IC1 is exceeded in this case, Lo signal is input from pin
9
. When Lo signal is input to pin
B
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.
Reset Voltage
Chopper
signal
DC
Current
level
Negative –
Terminal
DC
current
A
Detection
resistor
0V
of SPM2 – HIC, and voltage divided by R41 and R43 is input to pin
10
of microcomputer, microcomputer stops drive output.
17
Chopper
signal
Drive
Circuit
IP signal
Peak current
cut off circuit
Detection
resistor
Fig. 8-2
SPM2 – HIC
R41
9
0V 0V
Fig.8-3
– 84 –
Drive
signal
Power
module
DC current
SPM2 Main P.W.B
B
CN14
R42
20 9 2
IC1
8
F
9
QC
recognized
A
(Voltage at point
8
Compressor
motor
HIC
39 17
IP
Outdoor
microcomputer