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9. OPERATION DESCRIPTION
9-1. Outline of Air Conditioner Control
This air conditioner is a capacity-variable type air
conditioner, which uses DC motor for the indoor fan
motor and the outdoor fan motor. And the capacity-
proportional control compressor which can change
the motor speed in the range from 9 to 120 rps is
mounted. The DC motor drive circuit is mounted to
the indoor unit. The compressor and the inverter to
control fan motor are mounted to the outdoor unit.
The entire air conditioner is mainly controlled by the
indoor unit controller.
The indoor unit controller drives the indoor fan motor
based upon command sent from the remote control-
ler, and transfers the operation command to the
outdoor unit controller.
The outdoor unit controller receives operation
command from the indoor unit side, and controls the
outdoor fan and the pulse motor valve. (P.M.V)
Besides, detecting revolution position of the com-
pressor motor, the outdoor unit controller controls
speed of the compressor motor by controlling output
voltage of the inverter and switching timing of the
supply power (current transfer timing) so that motors
drive according to the operation command.
And then, the outdoor unit controller transfers
reversely the operating status information of the
outdoor unit to control the indoor unit controller.
As the compressor adopts four-pole
brushless DC motor, the frequency of the
supply power from inverter to compressor is
two-times cycles of the actual number of
revolution.
(1) Role of indoor unit controller
The indoor unit controller judges the operation
commands from the remote controller and
assumes the following functions.
• Judgment of suction air temperature of the
indoor heat exchanger by using the indoor
temp. sensor. (TA sensor)
• Judgment of the indoor heat exchanger
temperature by using heat exchanger sensor
(TC sensor) (Prevent-freezing control, etc.)
• Louver motor control
• Indoor fan motor operation control
• LED (Light Emitting Diode) display control
• Transferring of operation command signal
(Serial signal) to the outdoor unit
• Reception of information of operation status
(Serial signal including outside temp. data) to
the outdoor unit and judgment/display of error
• Air purifier operation control
(2) Role of outdoor unit controller
Receiving the operation command signal (Serial
signal) from the indoor unit controller, the out-
door unit performs its role.
• Compressor operation control
• Operation control of outdoor
fan motor
• P.M.V. control
• 4-way valve control
Operations followed to
judgment of serial signal
from indoor side.
• Detection of inverter input current and current
release operation
• Over-current detection and prevention operation
to IGBT module (Compressor stop function)
• Compressor and outdoor fan stop function
when serial signal is off (when the serial signal
does not reach the board assembly of outdoor
control by trouble of the signal system)
• Transferring of operation information (Serial
signal) from outdoor unit controller to indoor
unit controller
• Detection of outdoor temperature and opera-
tion revolution control
• Defrost control in heating operation (Temp.
measurement by outdoor heat exchanger and
control for four-way valve and outdoor fan)
(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.)
• Temperature of indoor heat exchanger
• For these signals ([Operation mode] and
[Compressor revolution] indoor heat exchanger
temperature), 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 allow-
able value.
(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.