Hitachi RAS-E10H2 - Page 54

6-2.
Ov
er
load control circuit (O
VL control circuit)
Ov
er
load
control
is
to
decrease
the
speed
of
the
compressor
and
reduce
the
load
when
the
load
on
the
air
conditioner
increases
to
an
ov
er
load
state
,
in
order
to
protect
the
compresso
r,
electronic
components and po
wer break
er
.
Ov
er
loads are judged
by
comparing the DC current le
v
el and set
va
lue
Fig.6-4 sho
ws the
ov
er
load control system configuration and Fig.
6-7 is a character
istic diagram on
ov
er
load
judgement
v
alue
s.
There
are
two types
of
control
which
has
named
IS
OV
L
and
ID
OV
L.
IS
OVL
is
limiting
the
whole
input
of
this
room
air
conditioner
system
through
the
current
sensor
CT
1
in order to keep the maximum rating of components by reading total operating current.
ID
O
VL
is
wa
tching
and
limits
the
compressor
current
through
the
detection
resistor
,
which
is
b
uilt
in
IPM
in
order
to
control
the
compressor
reliability
.
reliability. reliability
Since
the
compressor
reliability
is
related
with
its
curve
.
All of O
VL operation v
alues were progr
ammed into EEPROM memor
y.
speed, the ID OVL value is also linked with the compressor speed. Fig.6-7 shows an ID OVL limitation
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
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
Fig. 6-7
Fig. 6-6
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
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