Samsung Electronics DVM Series Technical Manual page 11

2) PWM (Pulse Width Modulation) valve
PWM valve is the valve to take away the fixed scroll by lifting up through the difference of pressure after the digital
scroll compress being connected to the outlet and inlet of suction. Therefore, the capacity of compressor is controlled
automatically according to the operation status such as loading when the valve is closed or unloading when the valve
is opened. PWM means the control of ON/OFF signal to the valve for loading/unloading.
Relationship between PWM valve and loading/unloading
compression
non-compression
(rotating in vain)
(4) Refrigerant flow rates control
Refrigerant flow rates through the electronic expansion valve are controlled by the 2 factors, which are the
temperature difference between inlet and outlet of evaporator and the difference between room and set temperature.
a. An electronic expansion valve optimally distributes refrigerant flow rates to each room and the fuzzy logic enables
the unit to cool precisely; refer to the figure below.
b. The air conditioner senses the temperature difference between inlet and outlet of evaporator, plus the temperature
difference between room and set temperature. It calculates the superheat and the room temperature status, then
adjusts refrigerant flow rates by deciding the required steps for the valve to open.
1
0.5
0
-0.5
-1
PWM valve open PWM valve close
Unloading
Period (Cycle Time, T)
Falling room temperature
Rising room temperature
Open electronic expansion valve
Close electronic expansion valve
Ι
9
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