Johnson Controls SABROE Unisab III Control, Инструкция по эксплуатации

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Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
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Compressor control and surveillance
3.9 Compressor control - electrical slide control
3.9.1 Electrical slide control
(SAB 330 screw compressors )
These screw compressors are fitted with a capacity slide (master slide) driven by an AC motor through
magnetic transmission, gearbox and spindle and a hydraulically Vi slide (baby slide) controlled by a sol-
enoid valve. The digital output for the valve is always controlled automatically by UniSAB III. Only the ca-
pacity slide is fitted with a position transmitter.
Note that the minimum pulse when moving the capacity slide is 1 second. For a SAB 330 L this corre-
sponds to a minimum capacity position change of 1.8%. Keep this in mind when adjusting the PID regu-
lators. Further, there is a pause of at least 1 second when changing the rotation direction of the motor.
3.9.2 Part load and full load
There are two operating modes for capacity control and Vi adjustment: Part load and full load.
At full load, the capacity is by definition 100%. By activating the solenoid valve, the Vi slide is forced in
mesh with the capacity slide. Vi is adjusted by changing the capacity slide position, which consequently
moves the Vi slide. Note that in the survey pictures, full load is indicated in the display by a solenoid
valve symbol:
At part load, the Vi slide is reset to minimum position by deactivating the solenoid valve. The capacity
slide is moved according to the capacity requirement.
UniSAB III changes from part load to full load when capacity exceeds the selected limit for Vi mode in-
cluded in the picture
Setup/Configuration/Compressor Block . The default limit is Vi mode = 97% but it
can be adjusted within the range 70 to 97%.
UniSAB III returns to part load when the capacity requirement decreases.
The changes described are automatically performed in any of the modes Manual , Auto and Remote .
3.9.3 Calculated Vi position
When changing to or running in full load mode, UniSAB III determines an optimum calculated Vi position
x
Vi
[%] according to suction pressure/discharge pressure ratio, compressor type, refrigerant and whether
there is an economiser. Furthermore, the corresponding capacity slide position is calculated:
x
cap
[%] x
Vi
=100 [%] -x
Vi
[%] *
(Vi-slide [mm] /Cap-slide [mm])
While in full load mode, the x
cap
[%] x
Vi
is the set point of the capacity slide position regulator.
3.9.4 Change to full load
When changing from part load to full load, UniSAB III will run through the following steps:
1. Move capacity slide if necessary (see below).
2. Activate solenoid valve of Vi slide to force Vi slide into mesh with capacity slide.
3. Move capacity slide (and thus Vi slide) to optimal position x
cap
[%] x
Vi
.
As regards point 1, UniSAB III compares the above defined x
cap
[%] x
Vi
with the actual capacity slide po-
sition. If the actual position is much higher than x
cap
[%] x
Vi
, the result would be an undesirable power
consumption if the Vi slide valve is activated immediately. Therefore, the capacity slide is moved as
quickly as possible down into the area where UniSAB III calculates that the power consumption will be
reasonable. After this, UniSAB III will move on to points 2 and 3.
3.9.5 Change to part load
When changing from full load to part load, UniSAB III will run through the following steps: