97
w
The operation frequency in COOL mode is restricted the upper limit frequency after 1 hour as shown below for
dew prevention.
It is rated frequency or less.
1Hr
Time
Maximum
frequency
Upper limit
frequency
Rated frequency or less
6-22-5. Control Method of Rotation Times
Sine wave control makes the current transformers conduct real time detection of the value of the current running into the motor,
locates the rotor position from the detected value and decides if voltage should be impressed and if frequency should be chan-
ged.
Compared to the conventional control and rotor position detection method, sine wave control can provide finer adjustment of the
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.
Rotor
Rotor Position Signal
Permanent magnet is embedded.
Necessary
DC Motor
Excited by magnetic field of stator
Unnecessary
AC Motor
6-22-4. Characteristics of sine wave control in case of brushless DC motor
●
Although ordinary three-phase induction motor requires energy to excite the magnetic field of rotor, brushless DC motor
doesn't need it. So, higher efficiency and torque are provided.
●
This control provides the most efficient waveform corresponding to the rotation times 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 energy saved 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 response and efficiency are enhanced in sine wave control, finer adjustment can be provided.
w
In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it doesn't require energy to excite the rotor
like AC motor does. However, it's necessary to control the frequency of three-phase AC current supplied to the stator
according to the polar direction of magnet embedded in the rotor so as to drive the motor efficiently. Controlling three-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.
6-23. OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT
1. Outline
The operational frequency is as following:
First, the target operational frequency is set based on the difference between the room temperature and the set tem-
perature.
Second, the target operational frequency is regulated by discharge temperature protection, high pressure protection,
electric current protection and overload protection and also by the maximum/minimum frequency.
2. Maximum/minimum frequency in each operation mode
Applied
model
COOL
DRY
HEAT
Minimum
frequency
Minimum
frequency
Minimum
frequency
Rated
frequency
Rated
frequency
Maximum
frequency
Maximum
frequency
Maximum
frequency
20
20
20
81
96
66
71
87
62
30
30
20
98
102
79
108
108
84
98
102
79
20
20
20
MUZ-GA50VA
MUZ-GA60VA
MUZ-GA71VA
OBT06D--4qxp 07.3.2 9:53 AM Page 97
