Danfoss VLT CDS 303 User Manual

25-55 Alternation if Capacity < 50%
Option: Function:
Enabled [1]: The lead compressor function will be
alternated only if the numbers of compressors
running are providing less than 50% of total
compressor capacity.
Only valid if parameter 25-50 Lead Compressor
Alternation is dierent from [0] O.
25-56 Staging Mode at Alternation
Option: Function:
This parameter is only active if the option selected
in parameter 25-50 Lead Compressor Alternation is
dierent from [0] O.
Two types of staging and destaging of compressors
are possible. Slow transfer makes staging and
destaging smooth. Quick Transfer makes staging and
destaging as fast as possible; the variable speed
compressor is just cut out (coasted).
[0] * Slow At alternation, the variable speed compressor is
ramped up to maximum speed and then ramped
down to a standstill.
[1] Quick At alternation, the variable speed compressor is
ramped up to maximum speed and then coasted to
standstill.
Figure 6.36 is an example of the Slow transfer staging. The
variable speed compressor (top graph) and one xed
speed compressor (bottom graph) are running before the
staging command. When the [0] Slow transfer command is
activated, an alternation is carried out by ramping the
variable speed compressor to parameter 4-13 Motor Speed
High Limit [RPM] or parameter 4-14 Motor Speed High Limit
[Hz], and then decelerated to zero speed. After a “Delay
Before Starting Next Compressor” (parameter 25-58 Run
Next Compressor Delay) the next lead compressor (middle
graph) is accelerated and another original lead compressor
(top graph) is added after the “Delay Before Running On
Mains” (parameter 25-59 Run on Mains Delay) as a xed
speed compressor. The next lead compressor (middle
graph) is decelerated to Motor Speed Low Limit and then
allowed to vary speed to maintain system pressure.
Figure 6.36 Slow Transfer Staging
25-58 Run Next Compressor Delay
Range: Function:
0.5
sec*
[parameter 25-58 Run
Next Compressor Delay
– 5.0 sec]
This parameter is only active if the
option selected in
parameter 25-50 Lead Compressor
Alternation, is dierent from [0]
O.
This parameter sets the time
between stopping the old variable
speed compressor and starting
another compressor as a new
variable speed compressor. Refer
to parameter 25-56 Staging Mode
at Alternation and Figure 6.36 for
description of staging and
alternation.
25-59 Run on Mains Delay
Range: Function:
0.5
sec*
[parameter 25-58 Run
Next Compressor Delay
– 5.0 sec ]
This parameter is only active if
the option selected in
parameter 25-50 Lead Compressor
Alternation, is dierent from [0]
O.
This parameter sets the time
between stopping the old variable
speed compressor and starting
this compressor as a new xed
speed compressor. Refer to
parameter 25-56 Staging Mode at
Parameter Descriptions Operating Instructions
MG34M422 Danfoss A/S © Rev. 2013-07-03 All rights reserved. 119
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Danfoss VLT CDS 303 Specifications

General

Brand	Danfoss
Model	VLT CDS 303
Category	DC Drives
Language	English