Voltage Amp. Circuit; During Overload Control - Hitachi RAS-25CNH1 Service Manual

2
Vd
Micro computer
(AX-8E21)
3
Id
4
Is
Cool 44
Voltage at HIC
Voltage at HIC
Rotation speed of compressor
2

. Voltage amp. circuit

The voltage amp. circuit amplifies the DC current level detected by the detection resistor after being
converted to a voltage and supplies it to the micro computer. Receiving this, the micro computer converts
it to a digital signal and compares it with the internal data to judge whether or not overload control is
required.
< During overload control >
The filter consisting of R201 and C202 removes high harmonic components from the voltage generated
from the DC current flowing to the detection resistor, and R205 and C206 average the voltage and supplies
it to OP1 pin 5 OP1 forms a non-inverting voltage amp. circuit together with the peripheral elements.
The micro computer stores the set values which vary according to the rotation speed as shown in Fig. 8-
8. When the DC current level exceeds the set value, the micro computer enters the overload control state.
The compressor motor is controlled in the same way as in external judgement described previously.
The set Value is determined by the amplification of the voltage amp. circuit.
{
Amplification : high [ DC current : low
Amplification : low [ DC current: high
HIC - 1
64
+
ZZZ C204
-
OV
9
5V
R204
VRI
8
R208
OV
OV
47
R222
OV
8
9 9
Deceleration
Power module
positive terminal
+
R229
R230
R231
OV
5V
Q203
D202
FANC
R203
Q202
Fig. 8-8
Acceleration Deceleration
Fig. 8-7
– 81 –
R205
5
+
7
+
-
6
C206
ZZZ
-
4
OPI
OV
R211
OV
R206
R207
OV
Q201
OV
Commanded rotation speed
Actual rotation speed
Acceleration
DC current
R201
R806
OV