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EWCM9900
COMPRESSOR CONTROL
TIMINGS FOR STEP COMPRESSORS
Example of step activation in the case of four homogeneous step
compressors with 126-FdLy =0:
The switching on/off of a compressor must satisfy the following
requirements:
Power steps requested
4
3
• Minimum off-on time 121-oFon.
This is the minimum delay between switching off and switching on;
• Minimum on-off time 122-donF.
This is the minimum delay between switching on and switching off;
• Minimum on-on time 123-onon.
This is the minimum delay between switching on and switching on again;
2
1
0
Time
Time between steps
Time
Compressor 1
Activating and deactivating power steps must respect the activation/release
times for resources 124-don and 125-doF and is a function, not only of the
type of compressors (HOMOGENOUS STEPS or NON-HOMOGENEOUS),
but also of parameters 126-FdLy and 127-FdLF.
Time
Compressor 2
HOMOGENEOUS STEPS - activation
Time
Compressor 3
• if 126-FdLy=0 is NO it is sufficient that the increment interstep time 124don be observed, which starts when each resource is activated;
• if 126-FdLy=1 we have two cases:
- If the increment interstep time count was already underway due to a
previous step being activated, then this delay must expire before
another resource can be activated;
- If the increment interstep time count has already expired, the
increment interstep time is reloaded when a resource is called by the
controller;
HOMOGENEOUS STEPS - deactivation
• If 127-FdLF=0 it is enough that the decrement interstep time 125-doF be
observed, which starts when a resource is switched off;
• If 127-FdLF=1 we have two cases:
- If the decrement interstep time count was already underway due to a
previous step being deactivated, then this delay must expire before
another resource can be deactivated;
-If the decrement interstep time has already expired, then it is
reloaded when the controller calls for another resource to be
deactivated;
Time
Compressor 4
Time
NON-HOMOGENEOUS STEPS - activation
• If 126-FdLy=0 it is sufficient that the increment interstep time 124-don be
observed, which starts when each resource is activated;
• If 126-FdLy=1 the increment interstep time is reloaded when a resource is
called by the controller only if the activation would result in quitting the
dead band;
NON-HOMOGENEOUS STEPS - deactivation
• If 127-FdLF=0 it is enough that the decrement interstep time 125-doF be
observed, which starts when a resource is switched off;
• If 127-FdLF=1 then the decrement interstep time is reloaded when the
controller calls for another resource to be deactivated, if this would
result in quitting the dead band.
SEGMENTATION OF HOMOGENEOUS STEP COMPRESSORS
Example of step activation in the case of three homogeneous step
compressors with 126-FdLy =1:
The configuration of a circuit with segmented compressors is done with
parameters 502-PC1 to 513-PC12 which define the number of steps of each
compressor (number of segmentations plus one).
Up to 5 segmentation relays can be handled.
Parameter 118-PtSE defines the mode of actuation of the segmentations
(see table).
• If, for example, 502-PC1 = 1 segmentation is not available, hence the
compressors are full and can deliver 0% or 100% of their power only.
Power steps requested
3
• If, for example, 502-PC1 = 4 (4 power steps), 3 segmentations are
available, hence the compressors are full and can deliver 0%, 25%, 50%,
75% or 100% of their power.
2
1
0
Time
Time between steps
Power
118 - PTSE = 0
118 - PTSE = 1
118 - PTSE = 2
Segmentation
Segmentation
Segmentation
ACC
Time
1
Compressor 1
Time
100%
ON
75%
ON
50%
ON
25%
ON
0%
ON
2
3
1
2
ON
3
ON
1
2
3
ON
ON
ON
ON
ON
Compressor 2
Time
Compressor 3
Time
ON
ON
ON
ON
ON
ON
ON
ON