The GE IS200EDEXG1AEA Exciter De-Excitation Control Board is the main board in the de-excitation module of the EX2100™ Excitation Control system. The primary function of the IS200EDEXG1AEA Exciter De-Excitation Control Board is to remove stored energy from the generator field when an emergency shutdown occurs and the field breaker or contactors open. The board provides SCR firing, conduction sense feedback, and voltage retention to ensure operation even in the event of a power failure, making it a critical safety and protection component within the excitation system.
The IS200EDEXG1AEA Exciter De-Excitation Control Board is identified by the GE part numbering convention used throughout the Industrial Control Systems product line. The "IS200" prefix identifies the board as a GE Industrial Control Systems product, with "200" specifically indicating that the board is a base-level board. The "EDEX" acronym identifies the board's functional designation as an Exciter De-Excitation Control Board. The "G1" designation identifies the hardware group and normal coating, with Group 1 specifically designed for SCR de-excitation, while Group 2 is designed for diode de-excitation. The "AEA" suffix identifies the artwork and functional revision combination. All digits are important when ordering or replacing any board, as boards of different revision levels may not contain identical hardware, and GE ensures backward compatibility of replacement boards while noting that different revision levels may not contain identical components.
The de-excitation control scheme operates as follows: the EMIO board initiates de-excitation on the EXTB board, the EXTB board opens the 41dc contactor (MDA/MDB) or breaker, and then transfers de-excitation signals from the auxiliary contacts to the SCR firing circuits on the IS200EDEXG1AEA Exciter De-Excitation Control Board. With redundant control, two firing commands come in through the EXTB and activate the firing circuit. Upon firing, the circuit produces a high-frequency square wave which is connected to the SCR gate and causes conduction. If this circuit fails or is delayed, a self-firing circuit fires the gate; this circuit consists of a break-over diode network controlled by the SCR anode voltage and connected to the SCR gate.
This product introduction provides detailed technical information, functional descriptions, connector assignments, configuration guidance, and comprehensive specifications for the GE IS200EDEXG1AEA Exciter De-Excitation Control Board, serving as an essential reference for excitation control engineers, maintenance technicians, and system integrators working with GE industrial control equipment.
Functional Architecture and Signal Processing
The IS200EDEXG1AEA Exciter De-Excitation Control Board is built around a robust architecture that combines dual redundant firing control circuits, self-firing protection, conduction sensing, and voltage hold-up capability to ensure reliable de-excitation of the generator field under all operating conditions, including emergency shutdown and power failure scenarios.
The board level architecture of the IS200EDEXG1AEA Exciter De-Excitation Control Board includes two independent control circuits, designated Control Circuit A and Control Circuit B. Control Circuit A receives the firing command from the KDEP on the EXTB board through connector J8 and receives power from the M1 power supply through connector J17M1, which provides P24, COM, and N24. Control Circuit B receives the firing command from the KDEP on the EXTB board through connector J8 and receives power from the M2 power supply through connector J17M2, which provides P24, COM, and N24. This dual-redundant arrangement ensures that a failure in one control circuit does not prevent the de-excitation function from operating, because the second control circuit remains available to fire the SCR.
Both control circuits feed a common firing transformer arrangement that drives the SCR gate. The self-firing circuit is provided as a backup to the normal firing control circuits. If the normal firing circuits fail or are delayed, the self-firing circuit fires the gate. This circuit consists of a break-over diode network controlled by the SCR anode voltage and connected to the SCR gate. The firing commands M1, M2, and the break-over diodes are wired together and connected to the gate of the SCR through the DEPL connector. The SCR anode firing voltage is selectable for the voltage and type of SCR used, with both the break-over diodes (BODs) and current limiting resistors set with wire jumpers on stab connectors E1B through E12.
Voltage Hold-Up Circuit
The voltage hold-up circuit is one of the most critical features of the IS200EDEXG1AEA Exciter De-Excitation Control Board. The board retains voltage on the positive 24 V DC and negative 24 V DC supplies so that it can fire the SCR in the event of a total power failure. Voltage for wetting the external de-excitation contacts is also provided by the voltage hold-up circuitry. This ensures that the firing command is available for de-excitation after a power failure, which is essential because the de-excitation function must operate precisely when the normal power supplies may have been lost due to the emergency shutdown condition.
The hold-up circuitry ensures that the energy required to fire the SCR gate is stored on the board and remains available even when the external power sources have collapsed. This design philosophy recognizes that the most critical time for de-excitation is during a loss of power or an emergency trip, and the IS200EDEXG1AEA Exciter De-Excitation Control Board is engineered to remain functional and effective precisely under those adverse conditions.
Conduction Sensors
The IS200EDEXG1AEA Exciter De-Excitation Control Board detects current in the field circuit using Hall Effect sensors. A mechanical ring, also referred to as a flux concentrator or conduction ring, couples magnetic flux to the sensors located at the top edge of the board. Both sensor circuits 1 and 2 have separate circuits detecting bi-polar current flow. The M1 and M2 current sense signals are sent to the EXTB board and then to control, providing the control system with positive confirmation that the de-excitation SCR has begun conducting and that the field current is being extinguished.
For diode de-excitation applications, the mechanical ring is set to detect unidirectional current flow, adapting the board to the requirements of the Group 2 diode de-excitation configuration. Two red LEDs on the board indicate the status of both current sense circuits, and the indicators light whenever current flow is detected, providing maintenance personnel with a clear visual indication that the conduction sensors are functioning and that the field circuit is carrying current.
SCR Firing Voltage Selection
The SCR anode firing voltage of the IS200EDEXG1AEA Exciter De-Excitation Control Board is selectable for the voltage and type of SCR used in the application. Both the break-over diodes and the current limiting resistors are set with wire jumpers on the stab connectors E1B through E12, allowing the board to be adapted to the specific SCR characteristics of the de-excitation module. Stab connector E1A is wire jumped to the SCR anode.
A critical caution applies to the break-over diode configuration: if a break-over diode's break-over voltage is exceeded and the BOD is not connected to the gate of the SCR, the EDEX board will be destroyed. Before attempting to fire the SCR by exceeding the break-over voltage of the BOD, it is essential to make sure that the firing control circuit will fire the SCR. This precaution protects the board from damage during commissioning and testing.
Multiple Board Configurations
For large field current applications, it is necessary to use multiple de-excitation SCRs, with each SCR controlled by an IS200EDEXG1AEA Exciter De-Excitation Control Board connected in a master-follower configuration. The master board receives the M1 and M2 power through connectors J1 and J2, while the follower boards receive +24 V DC, −24 V DC, and common from the master board over the EPL cables, and no connections to J1 and J2 should be made on the follower boards. The master and follower boards are configured with jumpers JP1 and JP2 as either master or follower, with jumpers JP3 through JP6 always connected.
The EPL1 and EPL2 connectors are 25-pin D connectors that carry the master pulse signals, the common from M1 and M2, the positive and negative 24 V DC from the M1 and M2 supplies, and the positive 24 V DC supplied from the EXTB for the conduction sense circuits. This master-follower architecture allows the IS200EDEXG1AEA Exciter De-Excitation Control Board to be scaled to any field current requirement by adding follower boards, while the master board coordinates the simultaneous firing of all de-excitation SCRs to ensure that the stored energy is removed evenly and rapidly from the generator field.
Application Suitability and System Integration
The IS200EDEXG1AEA Exciter De-Excitation Control Board is an essential safety and protection component of the EX2100™ Excitation Control system, providing the controlled removal of stored energy from the generator field during emergency shutdowns and trips. Its dual redundant firing control circuits, self-firing backup, voltage hold-up capability, and Hall Effect conduction sensing ensure that the de-excitation function operates reliably even under the most adverse conditions, including total power failure.
In the de-excitation control scheme, the EMIO board initiates de-excitation on the EXTB board, and the EXTB board opens the 41dc contactor or breaker and transfers the de-excitation signals from the auxiliary contacts to the SCR firing circuits on the IS200EDEXG1AEA Exciter De-Excitation Control Board. The board then fires the de-excitation SCR, which provides a low-impedance path across the generator field to dissipate the stored magnetic energy rapidly and safely. The conduction sensors confirm that the SCR has begun conducting and that the field current is being extinguished, providing positive feedback to the control system.
For large field current applications, multiple IS200EDEXG1AEA Exciter De-Excitation Control Boards are connected in a master-follower configuration, with each board controlling a separate de-excitation SCR. The master board coordinates the simultaneous firing of all SCRs, ensuring that the stored energy is removed evenly and rapidly from the generator field. The follower boards receive their power and firing commands from the master board over the EPL cables, simplifying the wiring and ensuring synchronized operation.
The IS200EDEXG1AEA Exciter De-Excitation Control Board is designed for easy installation and maintenance. Its PEM Snap Top fasteners allow the board to be quickly installed on and removed from the intermediate mounting panel, and its removable conduction ring provides access to the Hall Effect sensors for inspection and replacement. The two red conduction LEDs provide a clear visual indication of the current sense circuit status, and the wire jumpers on the stab connectors allow the SCR firing voltage to be adapted to the specific SCR characteristics of the application.
Maintenance and Lifecycle
The IS200EDEXG1AEA Exciter De-Excitation Control Board is designed for long service life with minimal maintenance. The board contains no moving parts other than the removable conduction ring, and its solid-state construction ensures high reliability in continuous industrial operation. Routine maintenance consists of periodic visual inspection of the board, connectors, and conduction ring, verification of the red conduction LED indications, and confirmation that the wire jumpers are set correctly for the application.
If a board fails, replacement requires careful attention to safety procedures. After de-energizing the panel and verifying that no power exists on the board, all cables must be labeled with the correct connector name to simplify reconnection. All cables must be disconnected from the board, and the stab-on wire jumper must be removed from connector E1A while leaving the other wire jumpers in place. The conduction ring must be removed from over the Hall Effect sensors, and the PEM Snap Top fasteners that hold the board to the intermediate mounting panel must be opened so that the board can be removed. The wire jumpers on the replacement board must be placed in the same position as on the old board, and the jumpers JP1 through JP6 must be checked. The replacement board must be oriented in the same position on the mounting panel as the one removed, the Snap Top fasteners must be closed, the conduction ring must be replaced, and all cables and the wire jumper to E1A must be reconnected as labeled and properly seated at both ends. Finally, the auxiliary cabinet door must be closed.
GE Industrial Systems ensures compatibility of its replacement boards, even though boards of different revision levels may not contain identical hardware. When ordering a replacement IS200EDEXG1AEA Exciter De-Excitation Control Board, provide the complete part number and description, the exciter serial number, and the Material List (ML) number. The factory may substitute later versions based on availability and design enhancements, but backward compatibility of replacement boards is guaranteed.
Conclusion
The GE IS200EDEXG1AEA Exciter De-Excitation Control Board is a reliable, robust, and safety-critical module for the EX2100™ Excitation Control system. Its dual redundant firing control circuits, self-firing backup, voltage hold-up capability, Hall Effect conduction sensing, and master-follower scalability provide the controlled removal of stored energy from the generator field under all operating conditions, including emergency shutdown and power failure. The board's selectable SCR firing voltage, removable conduction ring, and clear visual indicators simplify installation, configuration, and maintenance.
With its clearly labeled connectors, configurable wire jumpers, redundant control circuits, and comprehensive documentation, the IS200EDEXG1AEA Exciter De-Excitation Control Board is an essential component in EX2100 Excitation Control installations worldwide. Backed by GE's quality manufacturing, global support network, and commitment to backward compatibility, the IS200EDEXG1AEA Exciter De-Excitation Control Board continues to deliver the performance, durability, and safety that industrial users expect from GE. Whether used in a new installation or as a replacement for an existing board, the IS200EDEXG1AEA Exciter De-Excitation Control Board provides the de-excitation control functionality required for reliable and safe excitation system operation.
