– 29 –
(3) Contents of operation command signal (Serial
signal) from indoor unit controller to outdoor unit
controller
The following three types of signals are sent
from the indoor unit controller.
• Operation mode set on the remote control
• Compressor revolution command signal defined
by indoor temperature and set temperature
(Correction along with variation of room
temperature and correction of indoor heat
exchanger temperature are added.)
• For these two types of signals ( [Operation
mode] and [Compressor revolution] ), the
outdoor unit controller monitors the input
current to the inverter, and performs the
followed operation within the range that
current does not exceed the allowable value.
• Temperature of indoor heat exchanger by indoor
heat exchanger sensor
(Minimum revolution control)
(4) Contents of operation command signal (Serial
signal) from outdoor unit controller to indoor unit
controller
The following signals are sent from the outdoor
unit controller.
• The current operation mode
• The current compressor revolution
• Outdoor temperature
• Existence of protective circuit operation
For transferring of these signals, the indoor
unit controller monitors the contents of signals,
and judges existence of trouble occurrence.
Contents of judgment are described below.
• Whether distinction of the current operation
status meets to the operation command
signal
• Whether protective circuit operates
When no signal is received from the
outdoor unit controller, it is assumed as a
trouble.
8-1-1. Capacity Control
The cooling capacity is varied by changing compres-
sor motor speed. The inverter changes compressor
motor speed by changing AC 220–230–240V power
to DC once, and controls capacity by changing
supply power status to the compressor with transis-
tor module (includes 6 transistors). The outline of the
control is as follows: The revolution position and
revolution speed of the motor are detected by
detecting winding electromotive force of the com-
pressor motor under operation, and the revolution
speed is changed so that the motor drives based
upon revolution speed of the operation command by
changing timing (current transfer timing) to ex-
change inverter output voltage and supply power
winding.
Detection of the revolution position for controlling is
performed 12 times per 1 revolution of compressor.
The range of supply power frequency to the com-
pressor differs according to the operation status
(COOL, DRY).
Table 8-1-1 Compressor revolution range
Operation
No. of
Combination
Compressor
operating
revolution
mode
unit
of indoor units
(rps)
1 unit
M10
—
13 to 45
COOL
M13
—
13 to 69
2 units
M10
M10
13 to 91
M13
M10
13 to 91
1 unit
M10
—
13 to 72
HEAT
M13
—
13 to 92
2 units
M10
M10
13 to 120
M13
M10
13 to 120
8-1-2. Current Release Control
The outdoor main circuit control section (Inverter
assembly) detects the input current to the outdoor
unit. If the current value with compressor motor
speed instructed from indoor side exceeds the
specified value, the outdoor main circuit control
section controls compressor motor speed by reduc-
ing motor speed so that value becomes closest to
the command within the limited value.
8-1-3. Power Factor Improvement Control
Power factor improvement control is performed
mainly aiming to reduce the current on much power
consumption of cooling / heating operation. Control-
ling starts from the time when input power has
reached at a certain point. To be concrete, IGBT of
the power factor improvement circuit is used, and
the power factor is improved by keeping IGBT on for
an arbitrary period to widen electro-angle of the
input current.
