Danfoss AK-CH 650 - Page 103

AK-CH 650 Capacity controller RS8ER302 © Danfoss 2016-02 103
Compressor application 5 – 1 x Speed + single step
The controller is capable of controlling one speed-regulated
compressor combined with one-step compressors of the same or
dierent sizes.
Preconditions for using this compressor application are:
• A speed-regulated compressor that can be of a dierent size
than the following one-step compressors
• Up to 11 one-step compressors of the same or dierent capacity
(depending on coupling pattern)
This compressor combination can be handled in accordance with
the following coupling patterns:
• Sequential
• Cyclical
• Best t
Handling the speed-regulated compressor.
For more information on the general handling of the speed-regu-
lated compressor, refer to section "Power pack types".
Cyclical operation - example
Here, the one-step compressors are of the same size.
The speed-regulated compressor is always the rst to start and the
last to stop.
One-step compressors should be cut in and cut out in accordance
with the First-In-First-out principle in order to equalise operating
hours.
The speed-regulated compressor is used to ll the capacity gaps
between the one-step compressors.
Example:
Increasing capacity:
- The speed-regulated compressor starts when the desired
capacity equals the start speed
- The following one-step compressor with the smallest number
of operating hours cut in when the speed-regulated compres-
sor is running at full speed (90 Hz)
-When a one-step compressor cuts in, the speed-regulated com-
pressor reduces speed (40 Hz) equivalent to the capacity of the
one-step compressor.
Decreasing capacity:
- The following one-step compressors with the most operating
hours should be cut out when the speed-regulated compressor
reaches minimum speed (30 Hz)
- When a one-step compressor is cut out, the speed- regulated
compressor’s speed increases (80 Hz), equivalent to the capac-
ity of the one-step compressor
- The speed-regulated compressor is the last compressor to be
cut out when the preconditions for this are fullled.
Best t - example:
Here, at least two of the one-step compressors are of dierent
sizes.
The speed-regulated compressor is always the rst to start and
last to stop.
The capacity distributor cuts in and cuts out the one-step com-
pressors in order to achieve the best possible capacity t (least
possible capacity jump)
The speed-regulated compressor is used to ll out the capacity
gaps between the one-step compressors.
Example:
Increasing capacity:
- The speed-regulated compressor starts when the desired
capacity matches the start speed
- The smallest one-step compressor is cut in when the speed-
regulated compressor runs at full-speed (90 Hz).
- When the speed-regulated compressor again reaches max.
speed (90 Hz), the smallest one-step compressor is cut out (C2)
and the big one-step compressor (C3) is cut in.
- When the speed-regulated compressor again reaches max
speed (90 Hz), the smallest one-step compressor (C2) is cut in
again.
- When the one-step compressor is cut in, the speed is reduced
on the speed-regulated compressor (40 Hz) equivalent to the
capacity of the cut in capacity
Decreasing capacity:
- The small one-step compressor is cut out when the speed-regu-
lated compressor has reached minimum speed (30 Hz)
- When the speed-regulated compressor again reaches minimum
speed (30 Hz), the smallest one-step compressor (C2) is cut out
and the big one-step compressor (C3) is cut in.
- When the speed-regulated compressor again reaches min.
speed (30 Hz), the large one-step compressor (C3) is cut out
and the small one-step compressor (C2) is cut in again.
- When the speed-regulated compressor again reaches min.
speed (30 Hz), the small one-step compressor (C2) is cut in.
- The speed-regulated compressor is the last compressor to be
cut out when the requirements for this are fullled.
- When the one-step compressor’s capacity is cut out, the speed-
regulated compressor increases speed (80 Hz) equivalent to
the cut out capacity.