Hitachi RAS-25SX8 Manuel De Maintenance page 157
5. Electrical expansion valve circuit
6
5
4
3
2
1
CN19
(unmounted)
6
5
4
3
2
1
Electrical
expansion
valve 1
Red
CN15
XA-6P
6
5
4
3
2
1
CN21
(unmounted)
・The electrical expansion valve is driven with a 12 V DC power source, which is designed specifically for
the expansion valve. Four phases of windings are energized for 1 or 2 phases, while the magnetic
poles of the windings are switched over to control the valve aperture. (It is insulated from
microcomputer potential.)
・The switchover direction of energization phases and the opening/closing direction are as shown in Table
5-1. When energized, pins ① to ④ of CN15 are at about 1.2 V, and when not energized, they are at about
12 V. When the power supply is reset, the expansion valve is initially operated for 30 to 40 seconds.
During initial operation, the pins ① to ④ of CN15 are measured with a tester. If there is any pin which
shows no change at 1.2 V or 12 V, then either the expansion valve or microcomputer should be
abnormal.
・Fig. 5-2 shows the logical waveform generated when the expansion valve is operating.
Downloaded from
www.Manualslib.com
C411
1
20
GND
VDD
2
19
ENABLE
RES
3
18
LATCH
CLK
4
17
S-OUT
S-IN
5
16
P-GND
P-GND
B-0V
6
15
COM2
COM1
7
14
05
04
8
13
06
03
9
12
07
02
10
11
08
01
IC11
C421
1
20
2
19
3
18
4
17
5
16
B-0V
6
15
7
14
8
13
12
9
10
11
IC12(unmounted)
B-0V
B-0V
manuals search engine
B-12V
＋
C401
B-0V
R416
R417
B-0V
B-0V
5V
４
１
２
３
PQ401
R411
B-0V
5V
R412
4
1
B-0V
2
3
PQ402
B-0V
5V
4
1
2
3
PQ403
R413
B-0V
Fig. 5-1
– 190 –
HIC
IC2
Microcomputer
R356
Clock signal
34
16
1
32
R357
Latch signal
15
2
35
33
R358
Serial signal
14
3
34
36
