MXS Service Manual

Common Functions SiUS121736EA
49 Functions and Control
Inverter Principle To regulate the capacity, a frequency control is needed. The inverter makes it possible to control
the rotation speed of the compressor. The following table explains the inverter principle:
The following drawing shows a schematic view of the inverter principle:
Inverter Features The inverter provides the following features:
 The regulating capacity can be changed according to the changes in the outdoor temperature
and cooling/heating load.
 Quick heating and quick cooling
The rotation speed of the compressor is increased when starting the heating (or cooling). This
enables to reach the set temperature quickly.
 Even during extreme cold weather, high capacity is achieved. It is maintained even when the
outdoor temperature is 2°C (35.6°F).
 Comfortable air conditioning
A fine adjustment is integrated to keep the room temperature constant.
 Energy saving heating and cooling
Once the set temperature is reached, the energy saving operation enables to maintain the room
temperature at low power.
Frequency Limits The following functions regulate the minimum and maximum frequency:
Forced Cooling
Operation
Refer to page 222 for details.
Phase Description
1 The supplied AC power source is converted into the DC power source for the present.
2 The DC power source is reconverted into the three phase AC power source with variable
frequency.
 When the frequency increases, the rotation speed of the compressor increases resulting
in an increase of refrigerant circulation. This leads to a larger amount of heat exchange
per unit.
 When the frequency decreases, the rotation speed of the compressor decreases
resulting in a decrease of refrigerant circulation. This leads to a smaller amount of heat
exchange per unit.
Refrigerant circulation rate (high)
high f
low f
freq=variable
Refrigerant circulation rate (low)
high speed
low speed
(R2812)
Amount of heat
exchanged air (large)
freq=
constant
50 Hz
60 Hz
capacity=
variable
Amount of heat
exchanged air (small)
AC
power
DC
power
Amount of heat
exchanged air (large)
Amount of heat
exchanged air (small)
Frequency Functions
Low  Four way valve operation compensation. Refer to page 95.
High  Compressor protection function. Refer to page 96.
 Discharge pipe temperature control. Refer to page 96.
 Input current control. Refer to page 97.
 Freeze-up protection control. Refer to page 98.
 Heating peak-cut control. Refer to page 100.
 Defrost control. Refer to page 102.