SiMT041509E Control Specification
Function and Control 34
4. Determine prohibited frequency
There is a certain prohibited frequency such as a power supply frequency.
Initial Frequency When starting the compressor, the frequency is initialized according to the ∆D value of the
indoor unit.
<∆D signal: Indoor frequency command>
The difference between the room thermistor temperature and the target temperature is
recognized as the ∆D signal and is used for frequency command.
∗OFF = Thermostat OFF
PI Control 1. P control
The ∆D value is calculated in each sampling time (20 seconds), and the frequency is
adjusted according to its difference from the frequency previously calculated.
2. I control
If the operating frequency does not change for more than a certain fixed time, the frequency
is adjusted according to the ∆D value.
When the ∆D value is low, the frequency is lowered.
When the ∆D value is high, the frequency is increased.
3. Frequency control when other controls are functioning
When frequency is dropping;
Frequency control is carried out only when the frequency drops.
For controlling lower limit;
Frequency control is carried out only when the frequency rises.
4. Upper and lower limit of frequency by PI control
The frequency upper and lower limits are set according to the command of the indoor unit.
When the indoor or outdoor unit quiet operation command comes from the indoor unit, the
upper limit frequency is lower than the usual setting.
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
–2.0 ∗OFF0 42.084.0C
–1.5 1 0.5 5 2.5 9 4.5 D
–1.0 2 1.0 6 3.0 A 5.0 E
–0.5 3 1.5 7 3.5 B 5.5 F
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