RXB PLUS ROTARY SCREW COMPRESSOR UNITS S70-101 IOM
Page 25
OPERATION
which is forwarded to the output modules. The instruction
triggers a solid state output device capable of handling con-
trol voltage and the instruction is executed. In some cases,
such as load and unload instructions, the computer displays
the instruction on the Operating display with an L (load) or
U (unload) symbol at the same time as the appropriate out-
put is energized.
If the microprocessor receives information that indicates an
abnormal operating condition has been reached or is
present, it will generate one or more of the following instruc-
tions:
1. If a subsystem on the compressor unit, such as the oil
heater(s) or liquid injection, can correct the problem, the
microprocessor will energize or de-energize this system.
2. If a prealarm setpoint has been reached the micro-
processor will trigger the prealarm and display this informa-
tion on the Operating display and the Annunciator display.
3. If a cutout setpoint has been reached, the microproces-
sor will shut down the compressor. The microprocessor will
indicate CUTOUT on the Operating display and the infor-
mation present on the Operating display at the moment of
cutout will be stored and can be retrieved by rotating dis-
plays to the Freeze display. Additional information will be
available through the Annunciator and Shutdown Record
displays.
A typical example of how the microprocessor responds can
be illustrated by the responses generated by the micropro-
cessor as oil temperature increases. Assume that the ambi-
ent temperature and compressor unit temperature are 45
O
F
and you have just pressed the [RUN] key to start the com-
pressor unit:
AT 45
O
F.
The microprocessor receives information that the oil
temperature is below 49
O
F, the Low Oil Temperature Cutout
setpoint, and and shuts down the unit. The microprocessor
will prevent the compressor package from running. The
microprocessor also instructs the oil heater(s) output to ener-
gize the oil heater(s).
AT 50
O
F.
When the oil temperature reached 50
O
F the microprocessor
would allow the Low Oil Temperature Cutout to be cleared
and the compressor unit could now be started. (Assume
that the [RUN] key has been pressed and that the com-
pressor has now started.) The Low Oil Temperature Alarm
would still be engaged and cannot be cleared until oil tem-
perature exceeds 58
O
F. The oil heater(s) shut off on com-
pressor start.
AT 113
O
F
The microprocessor instructs the liquid injection solenoid
output to deenergize the liquid-injection solenoid.
AT 122
O
F
The microprocessor instructs the liquid injection solenoid
output to energize.
AT 110
O
F TO 150
O
F.
Normal operating range. The microprocessor continues
monitoring oil temperature and reporting this information on
the Operating display.
LEAD-LAG OPTION (continued)
TYPICAL LEAD-LAG WIRING
ANY OTHER COMMUNICATIONS
LEAD-LAG, THEY CANNOT BE USED FOR
NOTE: WHEN USING THE RS422 PORTS FOR
ARE ON THE SAME SKID
WIRED AT FRICK IF BOTH UNITS
DE-9P DE-9P
(NOT USED)
ON BOTH CONNECTORS
JUMPER PIN 1 TO 6 AND 2 TO 7
SBCSBC
WIRING FOR LEAD-LAG SEQUENCING
WITH DBCH-9 HOOD (2 THUS)
CONNECTORS-#DE-9P MALE
FROM ALL OTHER WIRING
RS 422 WIRING SHALL BE SEPARATE
COLOR CODING SHOWN IS BELDEN #8777
USE BELDEN #8777 OR EQUAL (3 TWISTED PAIRS)
BLK
WHT
BLK
RED
BLK
GRN
4
5
8
9
33
9
8
5
4
+RX +RX
+TX +TX
-RX -RX
-TX -TX
COM COM
UNIT "B"
PORT 1
RS422
UNIT "A"
PORT 1
RS422
OPTIONAL
HOW THE MICROPROCESSOR WORKS
- SUMMARY -
The Frick microprocessor has 4 major components and a
variety of sensors. The major components are the SBC
(single board computer), two display screens, and the key-
board.
The SBC can be considered the brain of the microproces-
sor control console. The SBC contains the logic center which
provides the rules by which the microprocessor will oper-
ate, the integrated circuit chips which store the burned-in
memory of how the compressor unit is to behave, an analog
input to convert VDC from the various sensors into com-
puter binary language, and RAM (random access memory)
integrated circuit chips to store information which can be
readily changed by the microprocessor or, as in the case of
adjustable setpoints, by the operator. The SBC collects in-
formation, processes the information, and delivers instruc-
tions to the displays and to the output modules.
The SBC gathers information from several sources on the
compressor unit. Pressure transducers sense changes in
pressure and return a variable DC voltage of 1 to 5 VDC to
the SBC. The signals are converted into binary code which
the microprocessor understands. The microprocessor scans
the incoming data many times per second and compares
the information it receives with the instructions programmed
in the PROM chips, information stored in the RAM chips,
and instructions it has received from the console keyboard.
As operating conditions change, the microprocessor also
forwards the information it is receiving to the display screen.
When an operating condition or conditions develop which
the microprocessor program identifies as requiring a spe-
cific action, the microprocessor generates an instruction
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