Johnson Controls SABROE UniSAB III Engineering Manual page 193

Set-up
4: Display
Amp or kW
The measured signal can be displayed either as ampere or as a kW signal. Select Amp for Amp signal
input. Select kW for kW signal input. The Amp signal can be read as either 0-1 A or 4-20 mA. Use Motor
input signal to choose between the two sources.
5: Motor input signal
0-1 A/4-20 mA
Select 0-1 A when the measured motor current is supplied from a current transformer with ampere ratio
xxx/1 amp connected to the terminals X1/Motor current trafo.
Select 4-20 mA when the measured motor current is supplied from a 4-20 mA transmitter, e. g. a fre-
quency converter or other equipment. The terminals X1/Motor current are used here.
6: Rotatune
Yes
No
Select Yes if UniSAB III is fitted on a compressor with frequency converter. Select No for all other com-
pressors. For further information, please see UniSAB III sequence manual, which describes the use of
frequency converters with UniSAB III.
It should be noted that compressors running variable speed (VSD) are at higher risk of facing vibrational
problems than similar fixed speed applications. Johnson Controls Denmark and the Sabroe factory have
gained comprehensive experience in VSD and we are integrating this knowledge into both the mechani-
cal design and control systems of our products. For this reason we cannot accept liability for any dam-
age related to vibration or variable speed drive on non-factory built equipment. This includes both
mechanical and electrical equipment meaning that VSD equipment must be purchased as complete fac-
tory built and tested packages to ensure optimum reliability and to attain full factory warranty coverage.
It should be noted that vibration may appear as structural vibration in frames, piping, instrumentation
etc. or as torsional vibration in rotating equipment (compressor shaft, coupling and motor rotor).
Note that for SAB 120, 151, 157 HR, 193, 233, 283 and 355 with frequency converter you must set in a
minimum capacity limit when running half speed, i.e. at 1500 rpm or below. The minimum capacity must
be set to:
20 % when 1500 rpm
30 % when 1000 rpm
40 % when 600 rpm
Enter the minimum capacity limit setting in the configuration point Manual zero, see subsection 6.4.3
Compressor block.
For SAB 120, 151, 157 HR, 193, 233, 283, 355 the configuration of Manual zero is now made automati-
cally when Rotatune is selected. Based on the setting of Motor RPM min. the value of Manual zero is
calculated to a value, lying within the range 0 to 40%.
Manual zero = (50 - 0.02 x Motor RPM min.) %
Note that for SAB 120, 151, 157 HR, 193, 233, 283 and 355 with frequency converter you may see a
problem with low oil pressure at compressor start-up at low rpm.
To avoid this problem a new function Forced speed has been built into the UniSAB III code as from ver-
sion 1.0.7.0. This function regulates speed up to a predefined value, as long as the main oil pressure is
low. See subsection 6.4.1 Drive - 9: Forced speed for further description.
Up to UniSAB III version 1.0.7.0 this problem was handled by an external timer relay connected to the
frequency drive input and a set-up in this frequency converter input which ensured that the drive would
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