– 136 –
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.
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 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 exceedes 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 of SPM2-HIC is initialized to
enter drive signal standby mode. 3 minutes later, microcomputer outputs drive signal again, to start operation.
Fig. 7-2
Fig. 7-3
DC320V
-360V
DC
Current
level
Over-load external
setting circuit
Detection
resistor
Current amplified
circuit
+
DC current Id
Voltage at point
Voltage at point
27A
1.35V
A
A
B
9
9
8
20
9
0V
0V
0V
Detection
resistor
DC
current
Negative
Terminal
R41
SPM2-HIC
SPM2
Main P.W.B.
IP
Outdoor
microcomputer
R42
CN14
QC
IC1
F
R43
C43
2
39
17
5V
Reset circuit
Drive
Circuit
IP signal
Power
module
Compressor
motor
Peak current
cut off circuit
(AX-8T11)
Reset Voltage
DC current
Outdoor microcomputer
Tr
ip signal
synthesis circuit
Chopper
signal
Chopper
signal
Drive
signal
B