GE DS200NATOG2A Voltage Feedback Scaling Board

The DS200NATOG2A is a Voltage Feedback Scaling Board designed by General Electric (GE) Motors & Industrial Systems for its LCI (Load Commutated Inverter) systems and SCR bridge control systems. Belonging to the NATO (Voltage Feedback Scaling Board) series, this board is part of the G2 group and represents revision A. It serves as a critical component in GE high-voltage drive systems for precisely measuring and providing feedback of SCR bridge voltages.

The primary function of the NATO Voltage Feedback Scaling Board is to attenuate the high-voltage AC (three-phase) and high-voltage DC (positive and negative bus) signals from the SCR bridge to low-voltage levels that can be processed by the control system, enabling the control boards on the VME backplane to accurately acquire bridge voltage feedback signals. The board contains five identical, series-connected strings of precision resistors, corresponding to the three-phase AC voltages (phases A, B, C) and the positive and negative DC bus voltages. By selecting different input stab connectors and wire jumper combinations, the board can be configured to accommodate various input voltage levels from 1200 V to 6900 V, providing a unified low-voltage output to the control system.

The DS200NATOG2A board is the G2 group version. The main difference from the G1 version is that the G2 version uses wire jumpers to replace the bottom two resistors in each resistor string, reducing the number of resistors per string to four, making it suitable for lower voltage applications. The board is designed to meet the demands of high-voltage industrial environments and features the following characteristics:

• High-Precision Resistor Strings: Utilizes precision resistors connected in series to ensure accuracy and stability of voltage attenuation.

• Flexible Voltage Configuration: Supports various input voltage levels from 1200 V to 6900 V through combinations of stab connectors and wire jumpers.

• Five Independent Attenuation Channels: Processes three-phase AC voltages and positive/negative DC bus voltages separately, totaling five independent channels.

• Overvoltage Protection: Each resistor string output is equipped with a Metal Oxide Varistor (MOV) to prevent excessive output voltage if the output cable is disconnected.

• Compact Design: Outputs all attenuated voltage signals through a single 20-pin ribbon cable connector, simplifying wiring.

• Passive Design: The board contains no fuses, LEDs, or user-replaceable components, ensuring high reliability.

This product is widely used in LCI load-commutated inverter systems, medium and high-voltage variable frequency drives, large synchronous motor starting systems, and various industrial power electronics applications requiring precise SCR bridge voltage measurement.

II. Key Functions

1. High-Voltage Voltage Attenuation

The core function of the DS200NATOG2A board is to attenuate high-voltage signals from the SCR bridge to low-voltage levels that can be processed by the control system. The board contains five precision resistor strings, each corresponding to one input voltage signal:

The attenuation ratio of each resistor string is configured by selecting different input stab connectors and wire jumper combinations, ensuring that the output signals fall within the acceptable range of the control system.

2. Flexible Voltage Level Configuration

The DS200NATOG2A board supports configuration for various input voltage levels. By selecting different input stab connectors (Jx, JxA, JxB) and wire jumper combinations (WJ1-WJ10), the board can accommodate the following voltage levels:

The G2 group version uses wire jumpers to replace the bottom two resistors in each string, reducing the number of resistors per string from 6 to 4, making it suitable for lower voltage levels such as 4200 V, 2200 V, and 1200 V.

3. Overvoltage Protection

Each resistor string output is paralleled with a Metal Oxide Varistor (MOV). If the output ribbon cable is disconnected while input voltage is present, the MOV prevents the output voltage from becoming excessively high, protecting downstream control circuits from damage. One end of each MOV is connected to the ground stab connector JG via pins 2, 14, and 20 of the JV connector.

4. Signal Output

The attenuated output voltages from the five resistor strings are output to the VME backplane (VBPL) via a single 20-pin ribbon cable connector JV. The pin assignments for the JV connector are as follows:

5. Passive Design

The DS200NATOG2A board employs a purely passive design, containing no fuses, LEDs, adjustable components, or user-replaceable parts. This design enhances board reliability and reduces the probability of failure. However, if the board fails, it must be replaced as a complete unit.

III. Hardware Architecture

1. Board Structure

The DS200NATOG2A board uses a standard printed circuit board structure with a simplified design, containing only the essential high-voltage attenuation circuits. The board includes:

• Five Precision Resistor Strings: Each string consists of multiple precision resistors connected in series.

• Input Stab Connectors: 15 total (3 per string) for connecting high-voltage input signals.

• Wire Jumpers: 10 total (2 per string) for configuring G2 group voltage levels.

• Output Ribbon Cable Connector JV: 20-pin connector for outputting attenuated voltage signals.

• Metal Oxide Varistors: 5 (MV1-MV5), one per string, providing overvoltage protection.

• Testpoints: 5 (TP1-TP5) for factory low-voltage testing only.

2. Resistor String Composition

In the G2 group version, each string contains 4 precision resistors, with the positions of the bottom two resistors replaced by wire jumpers. Taking String A as an example, resistors R1-R4 are the effective resistors, while R5 and R6 are replaced by wire jumpers WJ1 and WJ2. Similar arrangements apply to the other resistor strings.

3. Stab Connectors

The board has 15 input stab connectors, divided into five groups of three. The naming convention and functions are as follows:

Note: For G2 group boards, the bottom two resistors are replaced by wire jumpers, so the actual number of resistors is reduced, but the input connector naming remains unchanged.

4. Wire Jumpers

The G2 group board uses 10 wire jumpers to replace the bottom two resistors in each string. The functions of each wire jumper are as follows:

IV. Detailed Interface Description

1. JV Output Connector

JV is a 20-pin ribbon cable connector used to output the five attenuated voltage signals to the VME backplane (VBPL). Pin assignments are as follows:

2. Input Stab Connectors

The board has 15 input stab connectors, divided into five groups of three. The naming and function of each connector are as follows:

Note: For G2 group boards, the bottom two resistors are replaced by wire jumpers, so the actual number of resistors is reduced, but the input connector naming remains unchanged.

3. Wire Jumpers

The G2 group board uses 10 wire jumpers to replace the bottom two resistors in each string. The functions of each wire jumper are as follows:

V. Configuration and Settings

1. Voltage Level Configuration

The voltage level of the DS200NATOG2A board is configured by selecting combinations of input stab connectors and wire jumpers. For the G2 group board, the configurable voltage levels and corresponding configuration methods are as follows:

2. Configuration Examples

Configuring for 4200 V Input Voltage:

• Ensure all 10 wire jumpers (WJ1-WJ10) are installed.

• Use JxA stab connectors (JAA, JBA, JCA, JDA, JEA) to connect the input power.

• Each string has 4 resistors, and the output voltage is approximately 1.820 V rms.

Configuring for 2200 V Input Voltage:

• Ensure all 10 wire jumpers (WJ1-WJ10) are installed.

• Use JxA stab connectors (JAA, JBA, JCA, JDA, JEA) to connect the input power.

• Each string has 2 resistors, and the output voltage is approximately 1.905 V rms.

Configuring for 1200 V Input Voltage:

• Ensure all 10 wire jumpers (WJ1-WJ10) are installed.

• Use JxB stab connectors (JAB, JBB, JCB, JDB, JEB) to connect the input power.

• Each string has 2 resistors, and the output voltage is approximately 2.075 V rms.

3. Board Replacement Considerations

When replacing a NATO board, ensure that the wire jumper settings on the new board match those on the board being replaced. Since the G1 and G2 group boards have different hardware configurations (number of resistors and wire jumper settings), replacement boards must be of the same group.

VI. Installation and Maintenance

1. Mounting Location

The DS200NATOG2A board is typically installed in the high-voltage area near the SCR bridge, connecting directly to high-voltage signals via stab connectors, and to the control system’s VME backplane via the JV ribbon cable.

2. Installation Steps

1. Verify Power is Off: Turn off system power, wait several minutes for high-voltage capacitors to discharge, and use high-voltage test equipment to verify no power is present.

2. Open Cabinet Door: Access the printed wiring board area.

3. Locate Mounting Position: Identify the installation position for the NATO board.

4. Install the Board: Align the NATO board with the standoffs and secure with lock washers.

5. Connect Input Cables: Select the appropriate stab connectors based on configuration and connect the high-voltage input cables.

6. Connect Output Cable: Connect the JV ribbon cable to the gate distribution and status board or VME backplane.

7. Power On Verification: After completing installation, perform power-on verification according to system commissioning procedures.

3. Removal Steps

1. Verify Power is Off: Ensure the system has been de-energized and test to verify no power is present.

2. Disconnect Cables: Carefully disconnect the JV ribbon cable and all input stab connectors.

3. Remove Lock Washers: Remove the lock washers securing the board.

4. Remove the Board: Keep the board level and carefully remove it with both hands.

4. Maintenance Recommendations

• High-Voltage Safety: Always be aware of high-voltage hazards during maintenance; even after system power-off, high-voltage capacitors may still retain charge.

• ESD Precautions: Always wear a grounding strap when handling boards. Store boards in anti-static bags.

• Periodic Inspection: Check that stab connectors are secure and ribbon cables are intact.

• Spare Parts Management: It is recommended to keep at least one identical NATO board on-site as a spare to minimize downtime.

VII. Applications

The DS200NATOG2A Voltage Feedback Scaling Board is widely used in the following industrial applications:

• LCI Load-Commutated Inverter Systems: Provides precise voltage feedback signals for SCR bridges.

• Medium and High-Voltage Variable Frequency Drives: Provides voltage measurement in 4.16 kV and higher voltage drives.

• Large Synchronous Motor Starting Systems: Monitors bridge voltage during motor starting.

• Gas Turbine Starting Systems: Provides voltage feedback in static starters.

• Industrial Power Electronics Equipment: Various applications requiring measurement of SCR bridge high voltages.