Danfoss AK-PC 351 Instructions Manual page 3

The capacity from the digital scroll compressor
The capacity is divided into period times as "PWM per". 100% capacity is delivered when cooling takes place for the whole period.
An off time is required by the capacity control valve within the period and an on time is also permitted. There is "no cooling" when the
valve is on.
The controller itself calculates the capacity needed and will then vary it according to the cut-in time of the capacity control valve.
A limit is introduced if low capacity is needed so that the cooling does not go below 10%. This is because the compressor can cool
itself. This value can be increased if necessary.
The capacity can similarly be limited so that the compressor cannot deliver 100% capacity. It is not normally necessary to limit this
max. capacity.
Sd monitoring
When regulating with Sd monitoring, the controller will increase capacity if the temperature nears the Sd limit. This will result in better
cooling of the digital scroll compressor.
Refrigeration
No refrigeration
Stream kompressor
The PWM signal can also be used to control one stream compressor with one relief valve.
The compressor capacity is distributed by up to 50% for one relay and the remaining 50-100% for the unloader. The unloader is con-
nected to DO6.
Sd can be monitored like a scroll compressor.
AK-PC 351
PWM period time
PWM Min. Cycle
Instructions RI8RB2ML © Danfoss 09/2014
Only DO6
PWM Max. Cycle
3