Application guidelines
7
FRCC.PC.023.A7.22
Single compressors
Variable speed compressors
Variable speed offers more flexibility in
compressor selection than fixed speed
compressors. Selection of the right variable
speed compressor size can be done by different
methods:
1. Maximum cooling capacity: Select a
compressor size which achieves the peak load
system cooling capacity demand at its maximum
speed.
2. Nominal cooling capacity: Select a compressor
size which achieves the nominal system cooling
capacity at a rotational speed of 3600 - 4500 rpm
(60-75 rps).
3. Best Seasonal Efficiency Ratio: Select a
compressor size which achieves the minimum
system cooling demand at its minimum speed.
Ensure that the compressor is able to cover the
peak load system cooling capacity. This selection
makes the compressor to run for a maximum of
time at part load where the system efficiency is
highest.
Performance tables at 3 speeds can be found
in the following pages. Detailed performances
can be found in datasheets and in selection
programs.
Compressor size
Different frequency converter variants are
available according to:
1. Main supply voltage
2. IP class (CDS303 drives are available in IP20 or
IP55 housings)
3. RFI class (Radio Frequency Interference) H2
or H3
4. Printed Circuit Board (PCB) coated or not
coated.
When the compressor size and mains voltage
have been defined with above selection
criteria, the code number tables from section
“Ordering information and packaging” give
the appropriate frequency converter sizes and
up to 8 corresponding code numbers for each
compressor model.
Note this compressor is equipped with
a four poles electrical motor so the applied
frequency from the inverter will be 50 Hz for
25 rps (1500 rpm) up to 200 Hz for 100 rps
(6000 rpm).
Frequency converter
variants
Compressor and frequency
converter combinations
