Mitsubishi Electric PURY-P200 Service Handbook page 96

4. Frequency control
• Depending on the capacity required, the frequency of the compressor is controlled to keep constant the evap-
oration temperature (0˚C = 0.71MPa) during cooling operation and condensing temperature (49˚C = 2.88MPa)
during heating operation.
• The capacity of the P200-P400 is controlled solely by the inverter-driven compressor, and the capacity of
P450-P650 is controlled by No.1 and No.2 compressors.
• The following table shows the frequency change of the inverter compressor during normal operation.
Model Frequency/cooling
P200 type
P250 type
P300 type
P350 type
P400 type
P450 type (50/60Hz)
P500 type (50/60Hz)
P550 type (50/60Hz)
P600 type (50/60Hz)
P650 type (50/60Hz)
✻
The maximum frequency during heating operation is affected by the outdoor air
temperature to a certain extent.
(1) No. 2 compressor operation/stop (P450-P650 types only)
1 No. 2 compressor going from stop to in-operation
When No.1 compressor does not meet the capacity requirement, No.2 compressor will start its operation.
2 No. 2 compressor going from in-operation to stop
When an operation of both No.1 and No.2 compressors exceeds the capacity requirement, No.2 compres-
sor will stop its operation.
(2) Pressure limit
The maximum limit of high pressure (Pd) is set for each frequency level. If this limit is exceeded, the frequency
will be reduced every 30 seconds.
(3) Discharge temperature limit
The discharge temperature (Td) of the compressor in operation is detected, and if it exceeds the upper limit,
the frequency is reduced by 5 Hz.
• Control is performed 30 seconds after compressor start-up and every 30 seconds thereafter.
• Operating temperature is 105˚C for P200 type and 115˚C for P250-P650 types.
(4) Periodic frequency control
Frequency control other than the ones performed at startup, upon status change, and for protection is called
periodic frequency control (conversent control) and is performed in the following manner.
1 Periodic control cycle
Periodic control is performed after the following time has passed
(a) 30 seconds after either compressor start up or the completion of defrost operation
(b) 30 seconds after frequency control by discharge temperature or by pressure limit
2 The amount of frequency change
The amount of frequency change is controlled to approximate the target value based on the evaporation
temperature (Te) and condensing temperature (Tc).
Frequency/heating
30~81Hz 30~92Hz
20~69Hz 20~85Hz
20~83Hz 20~98Hz
20~95Hz 20~102Hz
20~100Hz 20~103Hz
20~70/56Hz 20~83/73Hz
20~85/73Hz 20~92/84Hz
20~96/88Hz 20~99/93Hz
20~104/98Hz 20~109/105Hz
20~112/107Hz 20~110/113Hz
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Speed
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.
3Hz/sec.