Overview
Configured for electro-hydraulic servo valve control in Mark VI turbine control systems, the General Electric IS200VSOH1B (IS200VSOH1B Servo Control Board) provides direct physical and electrical execution of servo loop algorithms. The board controls four electro-hydraulic servo valves associated with steam or fuel valves and processes linear variable differential transformer (LVDT) feedback for valve position control. It interfaces with associated servo terminal boards and the VME processor rack through dedicated front-panel and backplane connectors.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | IS200VSOH1B |
| Brand | General Electric |
| Series | Mark VI |
| Product Type | Servo Control Board |
| Base Model | IS200VSOH1B |
| Origin | United States (USA) |
| Control Function | Electro-hydraulic servo valve loop control |
| Controlled Channels | Four servo valve channels |
| Feedback Input | Linear variable differential transformer (LVDT) |
| Terminal Board Support | TSVO or DSVO servo terminal boards |
| Signal Configuration | Simplex and TMR signal distribution |
| VME Interface | VME processor rack connectors |
| Front Panel Connector | J5 |
| VME Rack Connectors | J3 and J4 |
| TMR Terminal Connectors | JR1, JS1 and JT1 |
| External Trip Inputs | JD1 or JD2 |
| Status Indicators | RUN, FAIL and STATUS LEDs |
| RUN Indication | Flashing green |
| FAIL Indication | Solid red |
| STATUS Indication | Normally off; flashing orange during an alarm condition |
Backplane Communication and Servo I/O Architecture
The IS200VSOH1B operates within the GE Mark VI hardware architecture and exchanges control and diagnostic information through its VME rack interface. The board executes servo loop algorithms locally while coordinating field connections through associated TSVO or DSVO terminal boards.
Three cables connect to the VSVO board through the J5 front-panel plug and J3/J4 VME rack connectors. The JR1 connector supports simplex terminal board connections, while JR1, JS1 and JT1 support TMR signal fan-out arrangements.
In addition, the board interrogates identification devices installed on the terminal board connectors. Each read-only device stores terminal board information including serial number, board type, revision number and plug location. If the detected identification data does not match the expected configuration, the board generates a hardware incompatibility fault.
The architecture also supports diagnostic monitoring of servo current, LVDT feedback, excitation voltage and TMR signal differences. Therefore, the control system can isolate abnormal feedback inputs and continue using a valid sensor input when the configured diagnostic logic permits.
Frequently Asked Questions
Q: How does the IS200VSOH1B monitor servo valve feedback?
A: The board processes LVDT feedback signals to determine valve position. If one regulator feedback sensor becomes abnormal, the diagnostic logic can remove that sensor from the feedback calculation and use the valid sensor input.
Q: What happens when a servo output current does not respond correctly?
A: The board monitors servo output current for excessive current or abnormal response conditions. When the diagnostic criteria detect a fault condition, the board generates the associated diagnostic indication.
Q: Does the IS200VSOH1B verify the connected terminal board configuration?
A: Yes. Terminal board connectors JR1, JS1 and JT1 include identification devices containing board and installation information. A detected mismatch generates a hardware incompatibility fault.
Field Installation Guidelines
- Turn off power to the VME processor rack before installing or removing the IS200VSOH1B board.
- Align the board with the designated VME rack slot before applying insertion pressure.
- Use the top and bottom board levers to seat the edge connectors evenly. Do not force the board into the connector.
- Tighten the captive screws at the top and bottom of the front panel after the board is fully seated.
- Verify that J5, J3 and J4 cables are connected according to the Mark VI system configuration.
- Check JR1, JS1 and JT1 terminal board connections before applying system power, especially in TMR configurations.
- Route LVDT feedback and servo wiring separately from high-energy conductors where practical to reduce electrical interference.
- Inspect cable shields and grounding arrangements according to the installed Mark VI panel wiring practice.
- After power-up, verify the front-panel LEDs. Normal operation uses a flashing green RUN indication, while a solid red FAIL indication requires diagnostic review.
- Review individual diagnostic signals through the control system toolbox when the STATUS LED flashes orange. Diagnostic conditions can include servo current faults, LVDT signal limits, excitation voltage faults, A/D converter calibration faults and TMR differential faults.
