Hitachi RAC-50DH7, Service Manual

Page: 61 / 101

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6. Rotor magnetic pole position detection circuit
C
A
B
D
E
18
19
20
Microcomputer of outdoor unit
+5V
+12V
C607
IC3
C606
R601
R603
R604
C604 C603 C602 C601
R605
R606
R607
R611
R608 R609 R610
R501
R505 R504
R503
R502
R602
0V
0V
0V
0V
C605
0V
4
5
6
7
3
11
12
8
9
1
2
13
14
10
V W
U
DC brushless motor
for compressor
lnverter
When the DC brushless motor is rotated, it also operates as power generator, generating reverse electromotive
force according to number of rotations. This reverse electromotive force is voltage-divided by R503 – R505
and R608 – R610, and appears as point
A
voltage. IC3 compares and digitalizes point
A
voltage with point
B
voltage (in which DC voltage (Vd) is voltage-divided by R501, R502 and R611), and inputs this to microcomputer
as position detection signals for points
C
,
D
and
E
. Microcomputer switches inverter using optimum timing
based on position detection signals, in order to control the rotation of the brushless motor.
Fig. 6-1 Rotor magnetic pole position detection circuit