2.2.42 Network connection to VSD shutdown
Compressors with VSD and Modbus drive communication
This shutdown (“Drive link error”) indicates that the Modbus communication between Unisab
III and the VSD drive has been disrupted for 10 seconds, and that the drive for security rea-
sons therefore has been stopped. When Unisab III goes into shutdown, the POV valve is
closed.
To secure that the drive too is stopped in case of communication error, the drive is set up to
stop the motor after 8 seconds.
The Danfoss drive must be set up as follows: 08-03 “Control word time out” set to 8 seconds
and 08-04 “Control word time out function” set to 5 “Stop and trip”.
The Leroy Somer drive must be set up as follows: "Serial link monitoring" set to Yes, "Moni-
toring period" set to 8 seconds and "Serial link fault" set to Major fault.
2.2.43 General drive error
Compressors with VSD and Modbus drive communication
This shutdown indicates that there is one or more faults in the Danfoss or Leroy Somer VSD
drives. The fault reason can be found in VSD menu no. 16-9 for the Danfoss drive and in
menu no. 18 for the Leroy Somer drive.
2.2.44 Forced speed alarm
SGC compressors (SAB 120→151 and SAB 193→355)
For these screw compressor types with frequency converter this alarm indicates that the
speed is forced up during the start-up phase. In this “forced speed” phase the frequency con-
verter will regulate up to a predefined speed and stay there as long as the main oil pressure is
low. When the main oil pressure is above its minimum limit this alarm is automatically reset.
2.2.45 Oil pressure diagrams
In the following diagrams, the absolute oil pressure (P
oil
) is the oil pressure displayed in the
oil picture + the suction pressure + 1 bar (atmosphere). The absolute suction pressure (P
suct
)
is the displayed suction pressure + 1 bar (atmosphere).
Alarms and shutdowns
54/319
Engineering manual - Unisab III 1.10
001930 en 2014.09
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