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3-1-5. Control Method of Rotational Speed
Sine wave control makes the current transformers conduct real time detection of the value of the current running into the mo-
tor, locates the rotor position from the detected value and decides if voltage should be impressed and if frequency should be
changed.
Compared to the conventional control and rotor position detection method, sine wave control can provide fi ner adjustment of the
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.
3-2. EXPANSION VALVE CONTROL (LEV CONTROL)
Linear expansion valve (LEV) is controlled by "Thermostat ON" commands given from each unit.
Indoor unit status
LEV opening
Stop of all indoor unit
Opening before stop
→
500 pulse in 15 minutes
When outdoor unit is operating, some
indoor units stop and some operate.
COOL: 5 pulse (fully closed)
HEAT: 59 pulse (slightly opened) (
MXZ-2B
), 100
→
52 pulse (
MXZ-3B/4B71/3C/4C71VA
),
100 59 pulse (
MXZ-4B80/5B/4C80/5C/6C
)
Thermostat OFF in
COOL or DRY mode
When the outdoor unit operates (When the other indoor unit operates): 5 pulse.
When the outdoor unit stops. (When the other indoor unit stops or thermo OFF):
Maintain LEV opening before stop
→
500 pulse in 15 minutes
Thermostat ON in
COOL or DRY mode
• LEV opening for each indoor unit is determined by adding adjustment according to the
number of operating unit and the capacity class to standard opening, based on the operation
frequency:
e.g.) Opening 130 pulse in standard opening 1
→
Minimum 80 pulse, Maximum 205 pulse.
(Capacity code 4 at 1 unit operation) (Capacity code 1 at 4 units operation)
• After starting operation, adjustment according to intake superheat, discharge temperature is
included in standard opening. 1
NOTE
: LEV opening in each frequency at DRY operation and COOL operation is the same.
However, velocity and compressor operation frequency controls are different. (Refer
to 3-3. OPERATIONAL FREQUENCY RANGE)
(As far as the indoor unit velocity control goes, refer to DRY operation in MICRO-
PROCESSOR CONTROL in indoor unit.)
Thermostat OFF in HEAT mode
• When the outdoor unit operates. (When the other indoor unit operates):
59 pules (
MXZ-2B
), 140 pulse (
MXZ-3B/4B/5B/3C/4C/5C/6C
).
• When the outdoor unit stops. (When the other indoor unit stops or thermo OFF):
Maintain LEV opening before stop
→
500 pulse in 15 minutes.
Thermostat ON in HEAT mode
• LEV opening for each indoor unit is determined by adding adjustment according to the
number of operating unit and the capacity class to standard opening, based on the operation
frequency:
e.g.) Opening 120 pulse in standard opening 1
→
Minimum 70 pulse, Maximum 165 pulse.
(Capacity code 4 at 1 unit operation) (Capacity code 1 at 4 units operation)
• After starting operation, opening becomes the one that adjustment according to discharge
temperature that was added to basic opening. 1
1 LEV opening when the outdoor unit is operating: Upper limit 500 pulse, Lower limit 59 pulse
(
MXZ-2B/4B80/5B/4C80/5C/6C
), 53 pulse (
MXZ-3B/4B71/3C/4C71
).
3-1-4. Characteristics of sine wave control in case of brushless DC motor
●
Although ordinary 3-phase induction motor requires energy to excite the magnetic fi eld of rotor, brushless DC motor does not
need it. So, higher effi ciency and torque are provided.
●
This control provides the most effi cient waveform corresponding to the rotational speed of compressor motor.
●
The rotation can be set to higher compared to the conventional motor drive system. So, the time in which air conditioner can
be operated with less energy is longer than conventional models. This can save annual electric consumption.
●
Compared to square wave control, the torque pulsation is reduced at rotation so that the motor operates more quietly.
●
Since the response and effi ciency of motor are enhanced in sine wave control, fi ner adjustment can be provided.
DC Motor
AC Motor
Rotor
Permanent magnet is embedded.
Excited by magnetic field of stator
Rotor Position Signal
Necessary
Unnecessary
In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it does not require energy to excite the rotor
like AC motor does. However, it is necessary to control the frequency of 3-phase AC current supplied to the stator accord-
ing to the polar direction of magnet embedded in the rotor so as to drive the motor effi ciently. Controlling 3-phase AC current
frequency also means controlling the timing to switch the polarity of stator. Therefore, the polar direction of rotor needs to be
detected.
