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(1) IS OVL
The voltage amp. circuit amplifies the DC current level detected by the detection transformer CT1.
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 61 of the microcomputer exceeds
the set value, the microcomputer decreases the rotation speed of the compressor and reduces the
load.
Voltage at microcomputer pin
Rotation speed of compressor
(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 60 . 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 → D C current: high
Fig. 6-4 shows the rotation speed control. When the voltage at pin 60 of the microcomputer exceeds
the set value, the microcomputer decreases the rotation speed of the compressor and reduces the
load.
Detection
DC Current
N
Resistor
37
35
Power P.W.B.
R906
R245
CT1
CN4B
CN4A
11
1
0V
C009
+
R005
D001
0V
0V
0V
12V
0V 0V 0V
Main P.W.B.
61
Decelerating
Judgment value according to rotation speed
(internal judgment value)
IPM
Direct Current
42
P
R003
R004
32
29
Q501
R513
R514
0V
R613
Microcomputer
0V
R612
0V
59
V d
5V
0V
0V
17
I p
5V
6
0V
7
R248
−
60
I d
5 +
+
IC4
5V
0V
0V
0V
R222
61
I S
0V
0V
R287
D208
5V
56
Reset output
2
1
0V
−
3 +
IC5
48
Reset
R288
R252
0V
Fig. 6-2
Accelerating
Decelerating
Accelerating
Fig. 6-3
Rotation speed
Fig. 6-4
- 60 -
Command rotation speed
Actual rotation speed
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