The IS200EACFG2A is an Exciter AC Feedback Board designed by General Electric (GE) for its EX2100 Excitation Control System. This board is a medium-high voltage version within the EACF series, primarily used to measure the exciter PPT AC supply voltage and current, providing precise feedback signals for the excitation control system. The IS200EACFG2A board incorporates transformers for three-phase voltage measurement, two input terminals for Flux/Air Core coils, and three DB9 connectors for cables connecting to the controllers (M1, M2, and C). The output signals from the voltage and current circuits are distributed to the controllers via these three connectors.
The IS200EACFG2A board is typically located in the exciter auxiliary cabinet and connects to the EBKP backplane via cables, which can be up to 90 meters in length. The board features high-precision voltage measurement capabilities and robust anti-interference design, providing high-frequency noise suppression near the signal entry points to ensure the accuracy and stability of the measured signals. The board design meets industrial-grade standards and is suitable for critical applications in power plant excitation systems.
II. Main Functions
The primary functions of the IS200EACFG2A include, but are not limited to, the following:
1. Exciter Voltage Measurement
The IS200EACFG2A board supports one three-phase AC voltage input, specifically designed for a nominal voltage level of 1000 V rms. Its specific specifications are as follows:
Nominal Input Voltage Range: Up to 1000 V rms
Overvoltage Capability: +20% (i.e., continuously sustainable input up to 1200 V rms)
Frequency Range: 50/60 Hz
Output Voltage: Onboard Potential Transformer (PPT) secondary output is nominally 1.6 V rms
Transformers T1 through T4 on the board are used for three-phase voltage conversion. Input voltages are connected via three independent screw terminals: TB1, TB2, and TB3. The voltage measurement circuits are precisely designed to provide highly reliable voltage feedback signals to the excitation control system for regulation, protection, and synchronization purposes.
2. Air Core CT/Flux Coil Inputs
The IS200EACFG2A board provides two independent Flux/Air Core coil input channels for measuring current or flux signals from the excitation system. These input signals typically originate from Air Core Current Transformers (CTs) or flux coils, with the following typical output characteristics:
Nominal Output Voltage Range: 0 ~ 0.8 V rms (50/60 Hz)
Input Terminal: Terminal block TB4, providing two input groups (each with high and low terminals)
Air Core CT input signals are subjected to high-frequency noise suppression at the board's entry point to eliminate the impact of on-site interference on measurement accuracy. The shields of the input cables can be connected to chassis ground via nearby grounding screws to ensure signal integrity.
3. Signal Outputs and Interfaces
The IS200EACFG2A board routes the measured voltage and current signals to the control system's EMIO boards (via the EBKP backplane) through three 9-pin Sub-D connectors (J504, J509, J514). These three connectors correspond to:
J504: Connects to the M1 controller
J509: Connects to the M2 controller
J514: Connects to the C controller
The pin assignments for each connector are identical, ensuring that the signals received by the three controllers are consistent, meeting the requirements of redundant control systems.
4. Test Points
The board features voltage test rings TP1 through TP4 for measuring the phase-to-phase voltage outputs from the potential transformers:
Between TP1 and TP2: Measure Line Voltage A-B
Between TP3 and TP4: Measure Line Voltage B-C
Between TP4 and TP1: Measure Line Voltage C-A
These test points facilitate on-site commissioning and troubleshooting, allowing technicians to take direct measurements with a multimeter or oscilloscope without disconnecting external wiring.
III. System Applications
1. Application in EX2100 Excitation Control System
The IS200EACFG2A is a key board within the EX2100 Excitation Control System for acquiring AC feedback signals from the exciter. Its roles within the system include:
Voltage Feedback: Measures the three-phase AC voltage from the exciter PPT, providing voltage feedback signals to the Automatic Voltage Regulator (AVR) for closed-loop control and voltage regulation.
Current/Flux Feedback: Receives signals from Air Core CTs or flux coils to monitor exciter current or flux status, providing inputs for excitation protection and monitoring systems.
Redundant Signal Distribution: Simultaneously distributes the measured signals to three controllers (M1, M2, C), meeting the redundancy requirements of the EX2100 system and enhancing system reliability.
2. Typical Application Scenarios
Synchronous Generator Excitation Systems
Steam Turbine Generator Excitation Control
Hydro Turbine Generator Excitation Control
Gas Turbine Excitation Systems
Industrial Synchronous Motor Excitation
IV. Installation and Configuration Instructions
1. Mounting Location
The IS200EACFG2A board is mounted inside the exciter auxiliary cabinet and secured to the cabinet's standoffs using three screws. Ensure sufficient space around the board for wiring and maintenance access during installation.
2. Wiring Instructions
3. Output Connections
Use three cables to connect J504, J509, and J514 to the corresponding EMIO board interfaces on the EBKP backplane. The maximum cable length is 90 meters. Shielded cables are recommended to ensure signal quality.
4. Using Test Points
The TP1-TP4 test rings on the board can be used to measure the line voltages from the potential transformer secondaries:
Probe tips of an oscilloscope or multimeter can directly contact the test rings for measurement.
Typical output: Under nominal input voltage, the secondary output is approximately 1.6 V rms.
V. Board Replacement and Maintenance
1. Preparation Before Replacement
De-energize and Discharge: Power to the excitation system must be turned off before replacing the board. Follow the complete de-energizing procedures outlined in the appropriate User's Guide (GEH-6631) and adhere to all local Lock-out/Tag-out practices. Allow time for capacitors to discharge.
ESD Precautions: The EACF board contains static-sensitive components. ESD handling procedures must be followed:
2. Replacement Procedure
Verify Power Off: Before opening the auxiliary cabinet door, test electrical circuits to ensure power is off.
Disconnect Cables:
Remove voltage input wires from TB1, TB2, and TB3.
Remove coil input wires from TB4.
Disconnect connectors J504, J509, and J514.
It is recommended to label all cables and wires before disconnection to simplify reconnection.
Remove Old Board: Remove the three screws securing the EACF board and take out the old board.
Install New Board: Orient the new board in the same position as the removed one, place it onto the standoffs, and secure it with the three screws.
Reconnect Cables: Reconnect all cables and wires to the corresponding terminals and connectors on the new board as labeled. Ensure connections are secure and fully seated.
Restore Power: Close the auxiliary cabinet door and follow procedures to restore power to the system after verifying all connections.
3. Maintenance Recommendations
Periodically inspect connectors on the board for looseness and check wiring for signs of aging.
During system operation, monitor voltage signals via the test points to verify normal board function.
If abnormal measurements or system alarms occur, first check input signals and shield grounding integrity before suspecting board failure.
