Carel k.Air, User Manual, Page: 65 / 192

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Functions k.air +030220981 rel. 1.2 - 01.12.2020
As soon as the controller recognises the compressor, it automatically writes the compressor motor electrical parameters to the
Power+ driver. If a Power+ driver that has already been confi gured is then used to manage a diff erent compressor, run the “write
default” command.
Note
: if replacing the Power+ inverter, the electrical parameters will be automatically updated only with the Auto- install
parameters option (Uc10); otherwise, following replacement and wiring, the “write default” command needs to be run in Uc08.
9.10.2 S afety times
k.air guarantees compressor safety times, such as:
• Minimum on time
• Minimum off time
• Minimum time between consecutive starts
These times are available in the Compressor menu, together with the PID parameters, and can be set by accessing the Service
level with the unit OFF.
9.10.3 Envelope
Parameters from Ub01 to Ub05 are read- only parameters that indicate the compressor status. The compressor operating limits
are controlled. This control cannot be disabled, so as to prevent the compressor from operating outside of the safety limits
defi ned by the manufacturer. All available compressors therefore contain envelope data. When selecting a specifi c type of com-
pressor, the following parameters are set based on the compressor manufacturer’s technical specifi cations:
• all the characteristic points that defi ne the shape of the compressor envelope
• maximum discharge temperature
• MOP and DeltaP minimum ExV opening management parameters
• set point control parameters (BLDC only)
• alarm prevention parameters
Note:
to view the graphs of BLDC compressor envelopes, see the CAREL document “BLDC compressor envelopes”, available
on ksa.carel.com
9.10.4 B L DC compressor start-up procedure
k.air manages the start-up of BLDC compressors in accordance with the manufacturer’s specifi cations: on starting, the com-
pressor is brought to start-up speed and kept at that speed, irrespective of the control request, for the entire minimum on time;
at the end of this period, the compressor is managed by the controller, modulating its speed in relation to the request and in
accordance with the conditions for managing the working point inside the envelope.
Note:
if at start-up the diff erential pressure is greater than the maximum allowed start-up threshold, the compressor remains
on call awaiting the diff erential pressure to drop below the threshold. If after 5 minutes the compressor has not yet started, a
specifi c alarm will be activated
9.10.5 B L DC compressor protectors
When the compressor working point is outside of the envelope, an alarm delay starts counting: if the working point remains outside
of the envelope, when the delay expires, a specifi c alarm is activated that stops the compressor; if, on the other hand, the working
point returns back inside the envelope limits, the alarm delay is reset. In addition to the operating limits defi ned by the shape of the
envelope, there is also a discharge temperature limit (Ub16, Ub17) that stops the compressor. See the following paragraph.
30220980_191_R01
Condensing
temperature
Evaporation
temperature
3 Custom
9
C
ust
om
3
2
9
8
7
1
4
5
6
Key
1 Zone inside the operating limits
2 Max compression ratio
3 Max condensing pressure
3 c Custom max condensing pressure threshold
4 Max motor current
5 Max evaporation pressure
6 Min compression ratio
7 Min diff erential pressure
8 Min condensing pressure
9 Min evaporation pressure
9 c Custom min evaporation pressure threshold
Fig. 9.u