Introduction to the GE IS200VAICH1C Analog I/O Board

The IS200VAICH1C from General Electric belongs to the Mark VI turbine control system series. This VME Analog Input/Output (VAIC) board serves as a processor board for gas and steam turbines. Engineers use the IS200VAICH1C to create both TMR and simplex control configurations. Its versatile design makes it one of the more adaptable Mark VI products. Furthermore, the board accepts 20 analog inputs while controlling 4 analog outputs simultaneously.

Mark VI Series Context

The Mark VI series represents one of GE’s most advanced Speedtronic systems. Many Mark VI components, including the IS200VAICH1C, are now in legacy status. Original equipment manufacturer (OEM) support is no longer available from GE. Nevertheless, this board remains essential for maintaining existing turbine installations. It represents a functional step up from the previous Mark V series. The Mark V series had more limited applications for gas and steam turbine assemblies.

Functional Description

The IS200VAICH1C converts analog inputs to digital values for processing. It transfers these values over the VME backplane to the VCMI board. From there, the controller receives the data for turbine management. For outputs, the VAIC converts digital values back to analog currents. These currents drive through the terminal board into the customer circuit. The board contains signal conditioning, an analog MUX, an A/D converter, and a D/A converter.

Channel Configuration

This VAIC board provides 24 channels in total for system integration. Specifically, 20 channels function as analog inputs for field signals. The remaining 4 channels serve as analog outputs for control commands. Each terminal board accepts 10 inputs and 2 outputs. Cables connect the terminal board to the VME rack. The IS200VAICH1C processor board resides in this rack for centralized processing.

Simplex Configuration

In simplex configuration, the terminal board provides input signals to a single VAIC. This single IS200VAICH1C provides all output currents for the system. Simplex suits less critical applications where redundancy is not required. Installation costs are lower with simplex configurations. Maintenance is also simpler with fewer boards to manage. Therefore, simplex works well for smaller or non-critical turbine installations.

Triple Modular Redundant (TMR) Configuration

TMR configuration provides high availability for critical turbine control. Input signals fan out to three VME board racks labeled R, S, and T. Each rack contains its own IS200VAICH1C board for triple redundancy. In the event of hardware failure, the failed VAIC removes itself from the output. The remaining two boards continue producing the correct current seamlessly. A proprietary circuit creates the desired current using all three VAICs working together. The actual output current is measured with a series resistor. This resistor feeds a voltage back to each VAIC for verification. The resulting output becomes the voted middle value (median) of the three currents.

Terminal Board Compatibility

Two generations of the VAIC board exist with corresponding terminal boards. The original generation includes all versions prior to and including VAICH1C. The IS200VAICH1C belongs to this original generation. For 20 mA outputs, these boards support up to 500 ohm load resistance. This rating applies at the end of 1000 feet of #18 wire. This generation requires terminal board TBAIH1B or earlier for proper operation. These boards also work properly with all revisions of DTAI terminal boards. Newer VAICH1D and subsequent releases support higher load resistance. Those newer boards require TBAIH1C or later terminal boards.

Compressor Stall Detection

The IS200VAICH1C firmware includes gas turbine compressor stall detection. This detection executes at a rate of 200 Hz for rapid response. Two different stall algorithms can be selected based on turbine type. Both algorithms use the first four analog inputs scanned at 200 Hz. One algorithm suits small LM gas turbines using two pressure transducers. The other algorithm suits heavy-duty gas turbines using three pressure transducers. PS3 represents the compressor discharge pressure in these algorithms. A drop in PS3 pressure indicates a possible compressor stall. The algorithm also calculates dPS3dt (rate of change of discharge pressure). These values compare with configured stall parameters (KPS3 constants). The IS200VAICH1C initiates the compressor stall trip signal. This signal sends to the controller where it initiates a shutdown. The shutdown signal can set all fuel shut-off valves through any relay output.

Status LEDs

Three LEDs at the top of the VAIC front panel provide status information. The normal RUN condition displays as a flashing green light. The FAIL condition displays as a solid red light. The third LED displays STATUS and normally remains off. However, this LED shows a steady orange if a diagnostic alarm condition exists on the IS200VAICH1C.

Diagnostic Features

Each analog input has hardware limit checking based on preset high and low levels. These levels are set near the ends of the operating range. If this limit exceeds, a logic signal activates. The input then stops being scanned. Each input also has system limit checking based on configurable high and low levels. These limits can generate alarms for operator notification. Configuration options include enabling/disabling and latching/non-latching settings. In TMR systems, the IS200VAICH1C compares each signal to the voted median value. If one signal varies by more than a predetermined limit, a fault is created. This provides early indication of developing problems in one channel. Diagnostics also monitor D/A outputs, output currents, total current, suicide relays, and 20/200 mA scaling relays. The TBAI terminal board has its own ID device interrogated by the VAIC. This ID device contains the board serial number, type, revision number, and connector location.

Physical Characteristics

The IS200VAICH1C features a single-width front faceplate for rack mounting. Three status LEDs provide visual diagnostics on the front panel. Two clips keep the unit secure after rack installation. The rear edge contains two horizontal connectors for backplane interface. The board is populated with capacitors, resistors, processor chips, transistors, and diodes. Most components carry original manufacturer marks and reference designations. Surface codes on the board assist with positioning and wiring. Conformal coating protects the PCB from environmental contaminants. This C-rated revision represents a specific version of the VAIC board.

Installation Procedure

Follow these steps to install the IS200VAICH1C correctly.

1. Power Down the Rack: Ensure the VME processor rack is completely de-energized. Lock out the main power source for safety.

2. Insert the Board: Slide the IS200VAICH1C into the selected VME rack slot. Align the board with the card guides carefully.

3. Seat the Connectors: Push the top and bottom levers with your hands. The edge connectors will seat properly into the backplane.

4. Secure the Board: Tighten the captive screws at the top of the front panel. Also tighten the captive screws at the bottom.

5. Connect Terminal Board Cables: Attach cables from the terminal board to the IS200VAICH1C. Verify correct connector orientation for each cable.

6. Apply Power: Restore power to the VME processor rack. Then observe the three status LEDs for normal operation.

Package Contents

Your IS200VAICH1C shipment includes the following items:

• One GE IS200VAICH1C analog I/O board (VAIC processor board)

• One anti-static protective bag

• One handling instruction sheet

Common FAQs

1. Is the IS200VAICH1C still supported by General Electric?
No, most Mark VI components including the IS200VAICH1C are now legacy status. OEM support is no longer available from GE.

2. Can the IS200VAICH1C be used for both gas and steam turbines?
Yes, the IS200VAICH1C works for both gas and steam turbine applications. It supports both TMR and simplex control configurations.

3. What terminal board works with the IS200VAICH1C?
This generation of VAIC requires terminal board TBAIH1B or earlier. The IS200VAICH1C also works properly with all revisions of DTAI terminal boards.

4. What is the maximum load resistance for 20 mA outputs?
The IS200VAICH1C supports up to 500 ohm load resistance. This rating applies at the end of 1000 feet of #18 wire.

5. How does TMR configuration handle a board failure?
The failed board removes itself from the output automatically. The remaining two IS200VAICH1C boards continue producing the correct current.

Conclusion

The General Electric IS200VAICH1C delivers versatile analog I/O capability for Mark VI systems. Its 20 inputs and 4 outputs support both simplex and TMR configurations. Compressor stall detection enhances turbine safety and protection. Comprehensive diagnostics monitor both hardware and system limits. For Mark VI turbine control applications, choose the IS200VAICH1C analog I/O board.