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(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
No. of Combination of Compressor
operating unit indoor units revolution (rps)
RAS-M16UKCV-E 16 to 77
1 unit RAS-M13YKCV-E 16 to 72
RAS-M10YKCV-E 16 to 45
2 units
¡
*
19 to 84
3 units
¡
*
23 to 92
*
: In case that any multiple indoor units are combined.
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 operation. Controlling 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 arbi-
trary period to widen electro-angle of the input
current.
8-1-4. Prevent-Freezing Control
The indoor heat exchanger sensor detects refriger-
ant vapor temperature in COOL/DRY operation. If
the temperature is below the specified value, com-
pressor motor speed is reduced so that operation is
performed in temperature below the specified value
to prevent-freezing of indoor heat exchanger.
8-1-5. P. M. V. (Pulse Modulating Valve)
Using P.M.V., refrigerant flow of refrigeration cycle is
varied for the optimum temperature. Controlling
each unit separately by three P.M.V. corresponds to
difference of pipe length, fan speed, and unit tem-
perature.
If an error occurs on cycle temperature when power
source of the air conditioner has been turned on,
and if start/stop times of the outdoor unit are 30
times, move the valve once until it hits on the
stopper for positioning of the valve. In this case,
ticktack sound may be heard.
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