– 50 –
(1) IS OVL
Current transformer CT1 reads the input flowing current and detected to the microcomputer as a voltage
signal. Receiving this, the microcomputer converts it to a digital signal and compares it with the internal
data to judge whether or not overload control is required.
Fig. 6-3 shows the rotation speed control. When the voltage at pin u of the microcomputer exceeds
the set value, the microcomputer decreases the rotation speed of the compressor and reduces the
load.
(2) ID OVL
Fig. 6-2. The filter consisting of R245 and C217 removes high harmonic frequencies from the voltage
generated by the current flowing to Detection resistor; R245 and C217 average the voltage. This voltage
is then input to IC4 pin 5 and supplied to microcomputer pin t . The microcomputer compares this
input with the set value, and if the input exceeds the set value, it enters overload control status.
The set Value is determined by the amplification of the voltage amp. circuit
Amplification : high → DC current : low
Amplification : low → DC current: high
Fig. 6-4 shows the rotation speed control. When the voltage at pin t of the microcomputer exceeds the
set value, the microcomputer decreases the rotation speed of the compressor and reduces the load.
Fig. 6-4
Fig. 6-2
Fig. 6-3
Judgment value according to rotation speed
(internal judgment value)
Rotation speed
DC current
Decelerating Accelerating Accelerating
Actual rotation speed
Command rotation speed
Decelerating
Voltage at microcomputer pin
Rotation speed of compressor
IPM
11
42
R003
R004
R514
R513
P
2932
35
37
0V
Q501
R613
R612
0V
0V
R906
R905
C91
9
N
5V
0V 0V
V
d
I
p
I
d
I
S
Reset
Reset output
Microcomputer
0V
R252
R288
IC5
1
2
3
0V
5V
C215
R289
D208
R287
C204
R285
C226
R292
R284
R286
0V 0V 0V
12V
0V
R222
CN4A
CN4B
R221
C010
D204
C218
C224
C210
0V
0V
R248
IC4
7
6
5
R249
R241
R608
C222
D204
5V
0V
5V
0V
0V
R245
C217
R24
7
R005
D001
0V0V
0V
0V
CT1
C009
R006
Power P.W.B.
Detection
Resistor
59
17
60
61
56
48
1
DC Current
Direct Current
Main P.W.B.
61
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