Hitachi RAS-E10H2 - Page 55

Compressor
Microcomputer EEPROM
Motor current (ID)
Whole current (IS)
Fig. 6-4 Overload Control System
Detection
resistor
A-D
converter
ID OVL
value
IS OVL
value
Motor
control
process
A-D
converter
Detection
transformer CT1
Amplifier
Smoother
Fig. 6-5
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P
P
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N
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Det ect ion re sis tor
DC voltage approx.
DC 235 V
IP M (Intelli g ent Powe r Module)
DC cur ren t
Microcomputer
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
ov
er
load control is required.
< Dur
ing
ov
er
load control
>
The
filter
consisting
of
R245
and
C217
remo
v
es
high
har
monic
components
from
the
v
oltage
generate
from
the
DC
current
flo
wing
to
the
detection
resistor
,
and
supplies
it
to
IC4
pin 5 .
IC4
fo
rm
s
a
non
-
in
ve
r
ting v
oltage am
p.
circuit together with the peripheral elements
.
The microcomputer stores the set v
alues which
va
ry
according to the rotation speed
.
When the DC
current le
ve
l e
xceeds the set v
alue
, the microcomputer enters the
ov
er
load control state
.
T
he set
Va
lue is deter
mined b
y the amplification of the v
oltage am
p.
circuit
Amplification
:
high
→
DC
current
:
lo
w
Amplification
:
lo
w
→
DC
current:
high
Fig. 6-7
(2) ID OVL
Fig.
6-5.
The
filter
consisting
of
R245
and
C217
rem
ov
es
high
ha
rm
onic
frequencies
from
the
vo
ltag
e
generated
by
the
current
flo
wing
to
Detection
resistor
;
R245
and
C217
av
er
age
the
v
oltage
.
This
compares
this
input
with
the
set
value,
and
if
the
input
exceeds
the
set
value,
it
enters
overloa
d
control status.
the
set
va
lue
,
the
microcomputer
decreases
the
rotation
speed
of
the
compressor
and
reduces
the
load.
Fig. 6-6
(1) IS OVL
voltage is then input to IC4 pin 5 and supplied to microcomputer pin
voltage is then input to IC4 pin 5 and supplied to microcomputer pin
6060
. The microcomputer
. The microcomputer
Fig. 6-6 shows the rotation speed control. When the voltage at pin
61
61
of the microcomputer exceeds
of the microcomputer exceeds
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
61
Rotation speed of compressor
61
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