The IS200EMIOH1A is an Exciter Main I/O Board designed by General Electric (GE) for its EX2100™ Excitation Control System. This board features a single-slot, double-height (6U) VME-style form factor and mounts in the EX2100 control rack. The IS200EMIOH1A is the core I/O processing board of the EX2100 excitation control system, responsible for data exchange with multiple terminal boards, processing various field input signals, and outputting control commands to actuators.
The IS200EMIOH1A board communicates with several I/O terminal boards, including EPCT, ECTB, EXTB, and EACF, via the control backplane (EBKP). These terminal boards handle tasks such as generator voltage and current measurement, relay outputs, contact inputs, de-excitation control, AC feedback, and gate pulse amplification. The IS200EMIOH1A integrates these signals and simultaneously sends logic-level gate pulse signals to the ESEL board via the backplane. The ESEL board then transmits these signals to the EGPA board in the power conversion cabinet to achieve SCR firing control.
Key features of the IS200EMIOH1A board include:
Centralized I/O Processing: Unified handling of analog and digital inputs and outputs from multiple terminal boards.
Gate Pulse Generation: Sends logic-level gate pulse signals to the ESEL board via the backplane.
Redundant Architecture Support: Supports both simplex and redundant control systems; supports online replacement in redundant systems.
Jumperless Design: The board has no configuration jumpers; all configuration is achieved through backplane connectors.
Status Indication: Front panel features Power and Status LED indicators.
The IS200EMIOH1A board includes two backplane connectors (P1 and P2). It communicates with other control boards via P1 and interfaces via P2 with I/O terminal board cables connected to the lower part of the EBKP. The board design meets industrial-grade standards and is suitable for critical control applications in power plant excitation systems.
II. Main Functions
The primary functions of the IS200EMIOH1A include, but are not limited to, the following:
1. Generator Voltage and Current Measurement Interface
The IS200EMIOH1A receives generator voltage and current measurement signals via the EPCT terminal board:
Potential Transformer (PT) Signals: 2 channels, for measuring generator voltage.
Current Transformer (CT) Signals: 2 channels, for measuring generator current.
These signals are used for feedback control of the voltage regulator and system protection.
2. AC Feedback Interface
The IS200EMIOH1A receives AC feedback signals from the exciter via the EACF terminal board:
Power Potential Transformer (PPT) Signal: 1 channel, measures exciter voltage.
Air Core CT Signals: 2 channels, measure exciter current.
3. Relay Drive and Contact Input Interface
The IS200EMIOH1A implements the following functions via the ECTB terminal board:
Trip Relay Drive: 2 channels, drives external lockout relays.
General Purpose Relay Drive: 4 channels, Form-C contact outputs.
General Purpose Contact Inputs: 6 channels, for monitoring external device status.
Dedicated Contact Inputs: 52G (generator breaker) and 86G (lockout relay) contact inputs.
4. De-excitation and Flashing Control Interface
The IS200EMIOH1A implements the following functions via the EXTB terminal board:
Flashing Control: Drives 53A and 53B pilot relays.
Close Control: Drives the 41 pilot relay.
Trip Control: Drives the 41T pilot relay.
De-excitation Control: Drives the KDEP de-excitation pilot relay.
Status Feedback: Receives status feedback from the EDEX de-excitation control board.
Status Feedback: Receives status feedback from the Crowbar board.
Auxiliary Contact Feedback: Receives auxiliary contact status from 53A, 53B, and 41.
5. Gate Pulse Control and Feedback Interface
The IS200EMIOH1A communicates with the ESEL board via the backplane, thereby controlling the EGPA board:
Gate Pulse Output: Sends logic-level gate pulse signals to ESEL via the backplane. ESEL distributes them to EGPA boards for up to 6 power bridges, with 6 firing signals per bridge.
Conduction Feedback Reception: Receives three-phase current conduction feedback from EGPA for the power bridges via ESEL.
Temperature Feedback Reception: Receives power bridge temperature fault and alarm status from EGPA via ESEL.
6. Status Indication
The front panel features two LED indicators:
Power LED (Green): Indicates whether the board's +5 V dc power is normal.
Status LED (Green): Indicates the IMOK signal status output by the FPGA, signifying normal board operation.
III. System Applications
1. Application in EX2100 Excitation Control System
The IS200EMIOH1A is the core board for centralized I/O signal processing within the EX2100 Excitation Control System. Its roles within the system include:
I/O Data Concentration: Communicates with multiple I/O terminal boards via the backplane, concentrating various signals such as generator voltage/current, exciter voltage/current, contact inputs, and relay feedback.
Control Command Output: Based on calculations from the DSPX controller, sends gate pulse commands to the ESEL board via the backplane, and drives pilot relays and trip relays via EXTB and ECTB.
System Status Monitoring: Receives conduction feedback and temperature status from power bridges, as well as status feedback from de-excitation and crowbar circuits, for monitoring and protection by the control system.
Core of Redundant Architecture: In redundant systems, M1, M2, and C each have an EMIO board, processing I/O signals for their respective sections. If any board fails, it can be replaced online without affecting system operation.
2. Typical Application Scenarios
Voltage and current measurement for synchronous generator excitation systems
Relay control and contact status monitoring for excitation systems
Generator de-excitation and flashing control
SCR firing pulse generation for power bridges
Conduction status and temperature monitoring for power bridges
IV. Detailed Interface Description
1. Backplane Connectors P1 and P2
The IS200EMIOH1A board connects to other parts of the control system via two backplane connectors:
| Connector | Function Description |
| P1 | Communicates with other control boards in the same rack (e.g., DSPX, EISB), exchanging control data and status information. |
| P2 | Connects to I/O terminal board cable interfaces located on the lower part of the EBKP backplane, enabling signal exchange with boards such as EPCT, ECTB, EXTB, and EACF. |
2. Supported I/O Terminal Boards and Signals
The following I/O terminal boards are connected via P2 and EBKP, along with the signals they carry:
| I/O Board | EMIO Function | Input/Output Signals |
| EPCT | Measures generator voltage and current | 2 PT, 2 CT |
| ECTB | Drives relays, accepts contact inputs | 2 Trip Relay Drives, 4 Form-C Contact Outputs, 6 General Purpose Contact Inputs, 52G/86G Contact Inputs |
| EXTB | Controls flashing and de-excitation relays | 53A/53B/41/41T/KDEP Pilot Relay Drives, EDEX Status Feedback, Crowbar Status Feedback, 53A/53B/41 Auxiliary Contact Feedback |
| EACF | Receives exciter AC voltage and current | 1 PPT, 2 Air Core CTs |
| EGPA | Indirectly controlled via ESEL and backplane | Up to 6 Power Bridges × 6 Firing Signals, 3-Phase Conduction Feedback per Bridge, Temperature Fault/Alarm |
V. Indicators and Status
1. Front Panel Indicators
The IS200EMIOH1A front panel features two green LED indicators (refer to Figure 1 in the document for locations):
| LED | Label | Color | Description |
| Upper | POWER | Green | Lights when board +5 V dc power is normal. |
| Lower | STATUS | Green | Lights when the FPGA's IMOK signal is active, indicating normal board operation. |
During normal operation, both LEDs should be steadily lit. If the STATUS LED is off, it indicates an internal board fault, and replacement may be necessary.
2. Coordinated Indication with Other Boards
The IS200EMIOH1A has no other indicators. Its operational status can be indirectly determined by:
Viewing I/O signal status via Toolbox diagnostic software.
Observing indicator status on other boards in the same section (e.g., DSPX, EISB).
Observing the operation of driven relays.
VI. Installation and Replacement
1. Mounting Location
The IS200EMIOH1A board inserts into a designated slot in the EX2100 control rack. Simplex systems use one slot (typically corresponding to M1). Redundant systems use three slots (M1, M2, C). During installation, ensure the board is inserted into the correct slot; incorrect insertion may damage board electronics.
2. Offline Replacement Procedure (System De-energized)
Safety Warnings:
WARNING: To prevent electric shock, turn off power to the excitation system and follow the complete de-energizing procedures outlined in the Installation and Startup Guide (GEH-6631). Adhere to all local Lock-out/Tag-out practices. Allow time for capacitors to discharge.
CAUTION: To prevent component damage caused by static electricity, treat all boards with static sensitive handling techniques. Wear a wrist grounding strap and store boards in anti-static bags.
Replacement Steps:
Verify Power Off: Ensure the excitation system is completely de-energized. Test circuits before opening the control cabinet door.
Remove Old Board:
Loosen the screws at the top and bottom of the faceplate near the ejector tabs (screws are captive).
Unseat the board by raising both ejector tabs.
Gently pull the board straight out of the rack using both hands.
Install New Board:
Align the new board with the correct slot and push it in along the guides.
Using thumbs, firmly press the top and bottom of the faceplate simultaneously to initially seat the board.
Alternately tighten the top and bottom faceplate screws evenly to ensure the board is squarely seated.
Restore Power: Close the cabinet door, restore power to the excitation system following procedures, and test operation.
3. Online Replacement Procedure (Redundant System)
In a redundant control system, a failed EMIO board can be replaced while the excitation system is running.
Risk Warning: During online replacement, other controllers, power supplies, and terminal boards remain energized and active. Extreme caution must be taken to avoid touching other live parts or causing short circuits.
Replacement Steps:
Identify Failed Board: Confirm the section (M1, M2, or C) containing the failed EMIO board using Toolbox diagnostic software and indicators on adjacent controller boards.
De-energize Section: Open the control cabinet door. On the EPDM (Exciter Power Distribution Module), turn off the power switch for the section corresponding to the failed board, de-energizing that section.
Verify De-energized: Before touching the EMIO board, verify that the LED indicator for the corresponding EPDM section is off, EPSM indicators are off, and all power indicators on boards within that section are off.
Remove Failed Board: Same as offline procedure, but note that all cables remain in place.
Install New Board: Same as offline procedure.
Restore Power: Re-apply power to the section from the EPDM. Check that the EMIO board's Power LED lights up, the green Status LED lights up, and the green power LEDs on adjacent controller boards light up.
Functional Test: Verify the replaced EMIO board's functionality by transferring control from the active master to the inactive master and observing correct system operation.
