IS200VAICH1D - VME ANALOG INPUT CARD

Functional Description

The IS200VAICH1D is a Contact Input Group Isolation terminal board developed by General Electric. It is designed to interface with the VME rack and plays a critical role in handling analog inputs and outputs in control systems.

Key Functions and Features

1. The VAIC (Analog Input/Output Control) board accepts 20 analog inputs and controls four analog outputs. Each terminal board provides 10 inputs and 2 outputs.
2. The terminal board is connected to the VME rack, which houses the VAIC processing board, through cables.
3. The VAIC board converts analog inputs to digital values and sends them to the VCMI board. The VCMI board then communicates the data to the controller through the VME backplane.
4. The VAIC translates digital values to analog currents, which are then driven into the customer circuit via the terminal board.
5. The board supports both simplex and triple modular redundant (TMR) applications. When used in a TMR setup, the terminal board's input signals are fanned out to three VME board racks (R, S, and T), each containing a VAIC.

IS200VAICH1D Compatibility

The VAIC board comes in two generations, each with its own terminal board:

• The original VAIC generation includes versions up to and including VAICH1C, as well as VAICH1B.
• These boards can support up to 500 load resistance over 1000 feet of #18 wire while driving 20 mA outputs.
• For optimal operation, this generation requires terminal board TBAIH1B or earlier, and it is compatible with all DTAI terminal board revisions.

Compressor Stall Detection

The VAIC board performs gas turbine compressor stall detection at 200 Hz via firmware, with two available algorithms:

• The first algorithm is designed for small LM gas turbines and uses two pressure transducers.
• The second algorithm is for heavy-duty gas turbines and uses three pressure transducers.

The algorithm monitors the compressor discharge pressure (PS3) and detects drops in pressure (PS3 drop), which may indicate a compressor stall. The rate of change of discharge pressure (dPS3dt) is also calculated and compared with configured stall parameters (KPS3 constants). The parameter CompStalType selects the type of algorithm used (two or three transducers).

IS200VAICH1D Specifications

• Number of Channels: 24 channels per VAIC board (20 AI, 4 AO) with two-terminal boards.
• Input Span: 4-20 mA, ±1 mA, ±5 V dc, ±10 V dc.
• Input Converter Resolution: 16-bit A/D converter with 14-bit resolution.
• Power Consumption: Less than 31 MW.
• Compressor Stall Detection: Detection and relay operation are completed within 30 milliseconds.

Installation

1. Turn off the VME processor rack.
2. To seat the board's edge connectors, slide it in and push the top and bottom levers in with your hands.
3. Tighten the captive screws on the front panel's top and bottom.

Operation

1. Front Panel LEDs: The state of the VAIC front panel is shown by three LEDs at the top:
   • RUN state: Flashing green
   • FAIL condition: Solid red
   • STATUS LED: Normally off, flashes constant orange if a diagnostic alert is triggered.
2. Hardware Limit Testing: Each analog input undergoes hardware limit testing using predefined high and low levels near the operational range. If the limit is exceeded, the input is disabled and a composite diagnostic warning (L3DIAG VAIC) is generated. The individual diagnostic signals can be latched and reset using the RESET DIA signal.
3. System Limit Checking: System limit checking is performed on each input based on programmable high and low values. Alarms can be triggered if values fall outside these limits, and can be reset using the RESET SYS signal.
4. In TMR Systems: In Triple Modular Redundant (TMR) systems, one signal is identified and a defect is issued if it deviates from the median value by more than a predefined amount. This early warning can indicate potential problems in one channel.
5. Monitoring Outputs: The system monitors the D/A outputs, output currents, total current, suicide relays, and 20/200 mA scaling relays for reasonability and faults.
6. Terminal Board ID Check: The VAIC board checks the TBAI ID card, which contains a read-only chip with serial numbers, board type, revision number, and connector locations. A mismatch with this ID triggers a hardware incompatibility fault.