The IS200GGXDG1A is an Expander Diode Source Board designed by General Electric (GE) Industrial Control Systems for the Innovation Series™ medium voltage variable frequency drive system. As the core signal conversion hub between the Bridge Interface Control Board (BICI) and the diode source/dynamic braking (DB) circuit, the IS200GGXDG1A integrates multiple functions including fiber-optic communication, analog signal conditioning, status monitoring, and power management. This board is installed inside the control cabinet and exchanges gate commands and status information with the BICI board via RS-422 differential signals. Simultaneously, it directly connects to up to four Dynamic Braking Integrated Gate Commutated Thyristors (IGCTs) through fiber-optic interfaces, achieving high-speed, reliable communication with high-voltage isolation.
The IS200GGXDG1A is also responsible for receiving three-phase current feedback signals from the source current transformers, and aggregating voltage signals from the Voltage Feedback Scaling Board (NATO), the GDPA board power supply status signal, the 115 V control power status signal, and the onboard P5 power status signal, then sending them to the BICI board. This provides a comprehensive monitoring and protection data chain for the entire excitation control system.
System Architecture and Signal Flow
Within the drive system's control architecture, the IS200GGXDG1A occupies a key interface position between the BICI board and the power-level equipment:
Upstream Interface: Connects to the BICI board via a 50-pin PSRC connector, transmitting gate commands, status feedback, current and voltage monitoring signals, and board identification information.
Downstream Fiber-Optic Interface: Four duplex fiber-optic connectors (DB1 through DB4), each containing a transmitter (TX, blue) and receiver (RX, gray) channel, connect respectively to the gate drive units of four dynamic braking IGCTs.
Analog Input Interface: Six 3-terminal connectors are used for the primary and secondary side inputs of the three-phase source current transformers (CTs); three 2-terminal connectors are for user-configured CT burden resistors; and a 20-pin J1 connector receives voltage feedback signals from the NATO board.
Power and Monitoring Interface: A 6-pin J2 connector receives the high-frequency power supply (48 V AC, 27 kHz) and GDPA status signals from the GDPA board; a 2-pin J3 connector monitors the 115 V AC control power supplied to the GDPA board.
This multi-level interface design allows the IS200GGXDG1A to simultaneously handle high-speed digital fiber-optic communication, precision analog signal conditioning, and system-level status monitoring on a single compact board. This significantly simplifies intra-cabinet wiring and enhances system integration and reliability.
Detailed Core Functions
1. Fiber-Optic Gate Command and Status Feedback
The IS200GGXDG1A achieves isolated control of the dynamic braking IGCTs through four duplex fiber-optic interfaces. Gate commands from the BICI board arrive at the IS200GGXDG1A as RS-422 differential signals. They are converted into optical signals by the onboard logic and output to the corresponding IGCT gate driver module via the transmit fiber (TX), where a "Light ON" state indicates a command to fire the cell. Simultaneously, the IGCT status feedback optical signal returns to the IS200GGXDG1A via the receive fiber (RX). It is then converted back into an RS-422 differential electrical signal and transmitted to the BICI board, where "Light ON" indicates the IGCT is OK. Fiber-optic communication provides extremely high voltage isolation and immunity to electromagnetic interference, ensuring the integrity of control signals within the high-voltage, high-current power environment.
2. Source Current Transformer Interface and Burden Resistor Configuration
The IS200GGXDG1A provides complete primary and secondary side terminal blocks (3 terminals per phase, for primary positive, primary negative, and chassis ground) for the three-phase source current transformers. An onboard differential current detection circuit compares the primary and secondary CT currents, generating three-phase current imbalance signals (ACTP, BCTP, CCTP), which are sent to the BICI board via the PSRC connector. Users can connect external burden resistors through terminals TB19-TB24 based on the actual CT characteristics and configure the burden resistor selection using the three 2-pin Berg jumpers (JP1, JP2, JP3), enabling flexible system adaptation.
3. Voltage Feedback Signal Reception
The IS200GGXDG1A receives attenuated voltage signals from the Voltage Feedback Scaling Board (NATO) via the 20-pin J1 connector. These signals include:
Three-phase source voltages (SRCVAS, SRCVBS, SRCVCS)
Dynamic braking resistor positive terminal voltage (VDBR1S)
Dynamic braking resistor negative terminal voltage (VDBR2S)
NATO board cable-in-place indication signal (NATO CBL CHK)
All voltage signals are referenced to the signal common (LCOM). The IS200GGXDG1A sends these signals, along with the NATO board connection status, to the BICI board via the PSRC connector, providing foundational data for dynamic braking control algorithms and system protection.
4. System Status Monitoring and Aggregation
The IS200GGXDG1A possesses comprehensive system status monitoring capabilities, aggregating multiple critical status signals and reporting them uniformly to the BICI board:
GDPA Board Power Status: Receives a differential OK signal (GDPA1_OK_P and GDPA1_OK_N) from the GDPA board through the J2 connector. After opto-isolation, it outputs this signal (GDPA OK) to the PSRC connector. The front panel DS2 green LED indicates the GDPA power supply status.
115 V Control Power Status: Monitors the 115 V AC supply feeding the GDPA board via the J3 connector. The status signal is output after opto-isolation (CPOKS, 0 = OK). The front panel DS4 green LED indicates the 115 V power supply status.
Onboard P5 Power Status: Monitors the onboard +5 V DC supply. The status signal is output to the PSRC connector (P5 CHK). The front panel DS1 green LED indicates that the P5 power supply is OK.
NATO Board Cable-In-Place Detection: Receives the connection status of the NATO board cable through the J1 connector and sends this signal (NATOCHKS, 0 = OK) to the BICI board.
This centralized status monitoring design allows the BICI board to obtain comprehensive health information for the entire diode source/dynamic braking subsystem through a single interface.
5. Power Management
The IS200GGXDG1A receives its power from the GDPA board via a high-frequency 48 V AC supply (27 kHz) through the J2 connector. Onboard power conversion circuits generate the following DC supplies for the various functional modules:
+5 V DC (P5): Supplies power for the RS-422 transceivers, digital logic circuits, and some monitoring circuits.
+12 V DC (P12): Supplies power for the fiber-optic communication circuits and gate drive-related circuits.
+12 V Gating Circuit Supply (P12G): A switched 12 V supply dedicated to the gate firing circuits.
The board also provides seven isolated stab-on connectors for selective grounding, enhancing the system's noise immunity in complex electromagnetic environments.
Front Panel LED Indicators
The front panel of the IS200GGXDG1A features three LED indicators, providing fast and intuitive assessment of critical statuses:
LED | Color | Mnemonic | Description |
DS1 | Green | P5OK | Illuminates when the onboard +5 V supply is OK |
DS2 | Green | GDPAOK | Illuminates when the GDPA board power supply is OK |
DS4 | Green | 115VOK | Illuminates when the 115 V AC control power supply is OK |
The layout of these indicators allows on-site maintenance personnel to quickly judge the power supply status of the board and its peripheral devices without any tools.
Testpoints
The IS200GGXDG1A board is equipped with 15 testpoints, most of which are accessible from the front of the board for convenient debugging and fault diagnosis. The main testpoints are as follows:
Testpoint | Mnemonic | Description |
TP1 | DB4-TX | DB4 Gating Command (Dynamic Brake IGCT) |
TP2 | P12 | 12 V DC supply |
TP3 | P12G | 12 V DC for gating circuits (switched) |
TP4 | DB3-TX | DB3 Gating Command (Dynamic Brake IGCT) |
TP5 | DB2-TX | DB2 Gating Command (Dynamic Brake IGCT) |
TP6 | DB1-TX | DB1 Gating Command (Dynamic Brake IGCT) |
TP7 | CTA | Current difference between Phase A CT primary and secondary |
TP8 | CTB | Current difference between Phase B CT primary and secondary |
TP9 | CTC | Current difference between Phase C CT primary and secondary |
TP15 | DCOM | Signal common |
TP16 | DB1-RX | DB1 Status Feedback (Dynamic Brake IGCT) |
TP17 | DB2-RX | DB2 Status Feedback (Dynamic Brake IGCT) |
TP18 | DB3-RX | DB3 Status Feedback (Dynamic Brake IGCT) |
TP19 | DB4-RX | DB4 Status Feedback (Dynamic Brake IGCT) |
TP20 | P5 | Positive 5 V DC supply |
Adjustable Hardware Configuration
The IS200GGXDG1A uses Berg jumpers and wire jumpers for flexible configuration. JP1, JP2, and JP3 are 2-pin Berg jumpers used for selecting the CT burden resistors for the three phases. Users can adjust the jumper settings based on the actual application requirements to ensure the CT secondary current signals are within the optimal range. The board has no fuses and no adjustable potentiometers, simplifying field maintenance.
Connector Interface Summary
Connector | Type | Pins | Purpose |
TB1-TB3 | 3-Terminal Connector | 3 | Phase A CT Primary Input |
TB4-TB6 | 3-Terminal Connector | 3 | Phase A CT Secondary Input |
TB7-TB9 | 3-Terminal Connector | 3 | Phase B CT Primary Input |
TB10-TB12 | 3-Terminal Connector | 3 | Phase B CT Secondary Input |
TB13-TB15 | 3-Terminal Connector | 3 | Phase C CT Primary Input |
TB16-TB18 | 3-Terminal Connector | 3 | Phase C CT Secondary Input |
TB19-TB20 | 2-Terminal Connector | 2 | Phase A CT User Burden Resistor Input |
TB21-TB22 | 2-Terminal Connector | 2 | Phase B CT User Burden Resistor Input |
TB23-TB24 | 2-Terminal Connector | 2 | Phase C CT User Burden Resistor Input |
J1 | Plug Connector | 20 | Voltage Feedback Input from NATO Board |
J2 | Plug Connector | 6 | Power and Status Input from GDPA Board |
J3 | Plug Connector | 2 | 115 V AC Supply Monitoring |
PSRC | Plug Connector | 50 | I/O Interface with BICI Board |
DB1-DB4 | Fiber-Optic Duplex Connector | — | Dynamic Brake IGCT Gate Commands and Status Feedback |
Installation and Safety Precautions
The IS200GGXDG1A is mounted inside the control cabinet, secured by 11 screws onto eight plastic standoffs and three metal standoffs. The metal standoffs must be used with star washers to ensure any accidental high voltage is shunted to chassis ground through the protective circuit. The star washers must be seated against the metal surface with the metal standoffs, not with the plastic standoffs. When replacing the board, care must be taken to prevent electrostatic discharge (ESD sensitive). All power must be disconnected, and lockout/tagout procedures must be followed before operation. The board should be transported and stored using anti-static packaging.
