Hitachi RAS-50WX8 Service Manual page 96

5V
Reset circuit
Over-load external
DC320V
setting circuit
-360V
Current amplified
circuit
The following describes the operation of ecah circuit in detail.
(1) Peak current cut off circuit
Fig.7-3 shows peak current cut off ciruit and waveforms at each secition.
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 SPM, etc.
As shown in diagram, if current exceeding 24A flows, voltage at point
pin of SPM2 - HIC, and voltage divided by R41 and R43 is input to pin
this case, Lo signal is input from pin
microcomputer stops drive output.
When drive output from microcomputer is stopped, all drive output goes Hi, and microcomputer of SPM2-HIC 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
(AX-8T11)
Negative
Terminal
DC
current
A
Detection
resistor
0V
(Voltage at point
Chopper
signal Drive
Circuit
Peak current
cut off circuit
IP signal
Detection
resistor
Fig. 7-2
SPM2-HIC
R42
IC1
8
R41
9 9 QC
0V 0V
Fig. 7-3
recognized by detecting resistor is input to
of IC1. Since threshold of IC1 is exceedes in
. When Lo signal is input to pin
– 136 –
Drive
signal
Power
module
DC current
SPM2 Main P.W.B.
B
CN14
20 9 2 39 17
F
of microcomputer,
+
Compressor
motor
IP
Outdoor
microcomputer