Airwell ELECTRA AWAU-VDDE009-H11, Service Manual

Page: 27 / 64

12-2
CONTROL SYSTEMS
12.1.3 Compressor Frequency Control
The Compressor Frequency Control is based on the PI scheme.
When starting the compressor, or when conditions are varied due to the change of the room
condition, the frequency must be initialized according to the
ΔD
value of the indoor unit and the Q
value of the indoor unit.
Q value : Indoor unit output determined from indoor unit capacity, air flow rate and other factors.
1. P control
Calculate
ΔD
value in each sampling time (20 seconds), and adjust the frequency according to its
difference from the frequency previously calculated.
2. I control
If the operating frequency is not change more than a certain fixed time, adjust the frequency up and
down according to the
ΔD
value.
Obtaining the fixed
ΔD
value
When the
ΔD
value is small- decrease the frequency
When the
ΔD
value is large- increase the frequency
3. Frequency management when other controls are functioning
When frequency is drooping;
Frequency management is carried out only when the frequency droops.
For limiting lower limit
Frequency management is carried out only when the frequency rises.
4. Maximum and minimum limits of frequency by PI control
The frequency upper and lower limits are set depending on indoor unit.
When low noise commands come from the indoor unit or when outdoor unit low noise or quiet
commands come from indoor unit, the upper limit frequency must be lowered than the usual setting.
(see 12.1.3.1)
12.1.3.1 Frequancy range
The compressor frequency limitation is set by the following table
Mode
Minimum Frequency(MinFreq) Maximum Frequency(MaxFreq)
09 12 18
24
09 12 18
24
Cooling
TBC TBC TBC TBC TBC TBC TBC TBC
Heating TBC TBC TBC TBC TBC TBC TBC TBC
12.1.5.1 Frequency Changes Control
Frequency change rate is 1 Hz/sec.