Johnson Controls SABROE Unisab III Control, Инструкция по эксплуатации

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Engineering manual - UniSAB III 1.10.8
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Compressor control and surveillance
3.4.5 Oil heating
Oil heating is not a configuration point, but it has various functions depending on whether the compres-
sor in question is configured as a reciprocating or a screw compressor.
For a reciprocating compressor the heating element output is powered by decreasing oil temperature.
This function is active both at compressor standstill and when the compressor is in operation.
The set point of this value is set in the picture Control values/Oil/Temperature/Control , Set point 2 . The
set point has a fixed hysteresis of 5K.
SMC/CMO: Set point 2 = 35 ° C: Heating starts at 35 ° C and stops at (35+5) = 40 ° C.
HPC/HPO: Set point 2 = 55
°
C: Heating starts at 55
°
C and stops at (55+5) = 60
°
C.
3.4.6 Rota (VSD)
A reciprocating compressor can be fitted with a frequency converter (VSD) for additional capacity con-
trol. In Johnson Controls Denmark documentation this unit type is called a RecipRota. The cooling ca-
pacity is a combination of the number of engaged steps and the rotation speed set by the frequency
converter.
A RecipRota can be controlled in two ways:
• With limited frequency control where all steps are engaged before the frequency control is en-
abled, i.e. increased from minimum speed.
• With full frequency control on (between) all steps.
In the Setup/Configuration/Drive menu (see subsection 6.4.1 Drive ) the rota method can be configured
to either the step (limited) or speed (full) control method.
Note: The Speed configuration is only recommended for compressors with Centa coupling. For com-
pressors with other coupling types VSD operation might cause torsional vibration problems at some part
load frequencies (especially when not all steps are engaged).
The
Speed configuration is not available for TCMO and TSMC reciprocating compressors.
With VSD operation the capacity step in/out is controlled by the PID or I capacity regulator following the
set point signal. The
Delay Up and Delay Down timers are not used. To make sure that the compressor
cannot engage the cylinders too fast, a ramp function will limit the maximum capacity (Yield) change to
2.0%/sec for step up and 3.0%/sec for step down. This means that a yield increase from 0% to 100% will
take minimum 50 seconds, and a yield decrease from 100% to 0% will take minimum 33 seconds.
The step method is the standard Rota control method for reciprocating compressors. It works this way:
The compressor starts with the first step engaged then it ramps up to minimum speed. It remains at mini-
mum speed until all steps are engaged and not until then, the speed can be ramped up to maximum.
With a setting where minimum speed is set to 700 [rpm], motor rpm min. 2 is set to 700 [rpm] and maxi-
mum speed is 1500 [rpm], the reciprocating compressor will be step regulated up to 47% and then
speed regulated between 47% and 100%.
With a setting where minimum speed is set to 500 [rpm], motor rpm min 2 is set to 700 [rpm] and maxi-
mum speed is 1500 [rpm], the reciprocating compressor will be step regulated up to 47% and then
speed regulated between 47% and 100%. But in this case the compressor can run at a lower minimum
capacity.
The speed method can only be used on reciprocating compressors equipped with VSD and the soft
Centa coupling. It is not recommended for reciprocating compressors equipped with the standard Re-
xnord coupling as it may lead to torsional vibration problems.
It works this way: The compressor starts with the first step engaged at low speed then it ramps up to
minimum speed, i. e. 500 [rpm]. At the first capacity step, it ramps up speed until the capacity corre-
sponds to the second step at minimum speed. Then the second step is engaged and at the same time
speed is ramped down to minimum. It will then ramp up speed, engage the next step, slow down and so
on until all steps are engaged at minimum speed. Then speed is ramped up to maximum speed.