DGC Brushless Excitation - Emerson Process Management

DGC Brushless Excitation
System Description
3.3.a Single Board Computer
The computers used in each channel of the DGC are state-of-the art, industrial grade Single Board
Computers (SBC), featuring a high-speed Pentium processor, a serial port, an Ethernet port and
various other features. System operating software and calibration constants are stored in nonvolatile
“Flash” memory so that all programming is retained on power loss. The SBC uses no
moving parts to ensure rugged and reliable performance.
The two processors share information via the Ethernet port. The video output is normally
connected to a flat panel display. Keyboard and mouse connectors are available on the front of the
module.
All field I/O communication is accomplished across the bus connections on the VMEbus Backplane
to the adjacent ADIOU module.
3.3.b Analog and Digital I/O Unit (ADIOU)
The Analog and Digital I/O Unit (ADIOU) module provides analog and digital input and output
capabilities for the DGC using “Industry Pack” (IP) technology. IP modules are small circuit cards
that provide specific I/O functions that can be mixed and matched to create a system with the
desired types and quantities of I/O. The ADIOU circuit card is a “carrier card” that provides
mechanical support and electrical interfaces to support four IP modules.
The four IP modules utilized on the ADIOU are:
• Slots A and B: 48-Point Programmable Digital I/O modules. Of the 96 available points,
36 are configured as digital inputs and 60 are configured as digital outputs. The digital
inputs provide the controllers with the ability to monitor switch positions, breaker
positions and alarm conditions. The digital outputs enable the controllers to energize
lamps, generate alarms, warnings and generator trips. Digital inputs and outputs
operate at 5 VDC level.
• Slot C: 16-channel A/D Converter which allows the controllers to monitor a variety of
analog signals. The module supports monitoring of both AC and DC field signals in the
range of + 10 Volts.
• Slot D: 16-channel D/A Converter module which provides the controllers with the ability
to generate + 10 VDC signals for control and indication.
Communication with the single board computers is carried out across the VMEbus Backplane.
Field input and output signals are connected through ribbon cables on the front of the card to the
front edge of the I/O Interface Control Unit (IOICU).
3.3.c I/O Interface Control Unit (IOICU)
The IOICU module provides the circuitry to scale, buffer and filter the signal types associated with
synchronous machine voltage regulators. In a single channel system, all of the field connections
are made through a single IOICU, whereas a redundant unit has two IOICU modules whose outputs
must be paralleled to fully implement the redundancy features. When configured as a redundant
unit, the IOICU ultimately determines which DGC channel is in control of the system outputs.
The IOICU receives and conditions analog input signals from the field in three ranges: 150 VAC, 6
VAC and + 10 VDC, converting them to the range of + 10 Volts.
The IOICU buffers the outputs and provides the capability to “tristate” each of the analog outputs as
part of the redundancy features of the DGC.
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