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CMC TECHNICAL REFERENCE MANUAL
1X36003 Version 2.52
1996-1999 Ingersoll-Rand Company
Date of Issue: 18-Oct-1999
Choke —
Also know as stonewall. This is the maximum flow
that can be compressed by a given machine’s hardware
configuration.
Circuit Breaker —
An automatic switch that stops the flow
of electric current in a suddenly overloaded or abnormally
stressed electric circuit.
CMC —
Centac MicroController.
CMC System —
Any combination of CMC control
components which when combined create a control system.
The typical CMC system consists of a Base Control Module
(BCM), Operator User Interface (OUI), and Power Supply
(PS). A common variation on the typical system is the addition
of a Universal Communications Module (UCM).
Coast Timer —
The time interval, in seconds, between a
compressor stop or trip and the motor coming to a complete
stop. The timer is used to inhibit restarting.
Compressor Load, Load —
The power consumption of the
compressor. It is typically indicated in amps, kilowatts, SCFM,
etc.
COM Port —
See Serial Port.
Control Transformer —
The transformer that is used to
reduce the incoming voltage (for the prelube pump motor and
oil heater) to approximately 120 volts for controlling the CMC
electrical devices (relays, power supply, etc.).
Control Valve —
The inlet or bypass valve used to control
pressure or current.
Control Variable, Process Variable —
The variable being
regulated. When at MinLoad the control variable is load for the
inlet valve and System Pressure for the bypass valve. When
at MaxLoad the control variable is load and when loaded the
control variable is System Pressure.
CSA Approval —
Canadian Standards Association approval
is required for all electrical devices shipped into Canada. This
association is similar to UL for the United States and CE for
Europe.
CT —
Current Transformer.
CT Input Channel —
The current transformer input channel.
CT Ratio —
Current Transformer Ratio. The current
transformer ratio used in displaying the motor current; e.g.
600:5 = 120.
Current Transformer —
The electrical device used to
measure the amps of the main drive motor. For our standard
application, we only measure the current from one of the
three phases.
Daisy Chain —
A
method of wiring a communication
network. This method starts with the “master” and it is wired
directly to compressor #1. Compressor #2 is wired to
compressor #1, then compressor #3 is wired to compressor
#2.
Data Highway Plus —
A communication protocol used by
Allen-Bradley PLC 5 and SLC500 PLCs.
DCS —
See Distributed Control System.
degC —
Degrees Celsius, Centigrade.
degF —
Degrees Fahrenheit.
DH+ —
See Data Highway Plus.
Derivative Mode —
Provides a change in the control
variable (through the inlet or bypass valve) based on the
rate of change of the error (setpoint pressure minus
system pressure).
Derivative Constant —
Also know as the rate time, in
units of seconds.
Design Point —
The pressure and capacity required at
maximum ambient conditions.
Digital Device —
A device which is either on or off; e.g.,
the N.C. contact on the seal air switch.
Discrete Device —
See Digital Device.
Discharge Pressure —
The gas pressure between the
last stage of compression and the check valve.
Distributed Control System —
A system that attempts
to control an entire plant or process with multiple
independent local controllers by networking these local
controllers to a central computer through digital
communications. These central computers can be a PC,
PLCs or other larger systems. Some manufacturers of
these DCS products are Bailey, Honeywell, Allen-Bradley,
Siemens, and others.
Drain Wire —
An insulated wire in contact with a shield
throughout its length, and used for terminating the shield.
Dry Contacts —
A set of contacts that require a power
source supplied by others (customer). This is the normal
type of contacts that we provide.
Electro-pneumatic —
A term used to indicate a
combination of electronics and pneumatics. In the past, we
provided electro-pneumatic panels as standard equipment.
With the advent of digital computers, most all control panels
are electronic.
ERAM —
Erasable Random Access Memory.
FactoryLink —
One of many SCADA software packages
that can be used for air system integration.
FLA —
Motor Full Load Amps. The motor amperage at full
load, this value is found on the motor nameplate.
Flexible Conduit —
Small diameter hose, made of plastic
coated aluminum, which is used to enclose wire from the
control panel to machine mounted instruments.
Fused Disconnect —
As a safety precaution, this option
removes power from the panel before the door is opened.
By turning the rotary door handle, the panel power is
terminated. The disconnect would have to be mounted
external to the panel enclosure. The short circuit capacity,
maximum ground fault, motor full load amps, motor locked
rotor amps and motor voltage must be known to size the
disconnect properly.
Ground —
A connection to earth or to some extended
conducting body that serves instead of the earth.