GE Mark VIe Series IS200VSVOH1B VME Servo Control Panel

The IS200VSVOH1B is a VME servo control board manufactured by General Electric as part of the Mark VI series used in gas turbine control systems. The four electrohydraulic servo valves that operate the steam/fuel valves are under the direction of the servo control (VSVO) board. Typically, two servo terminal boards are used to separate these four channels (TSVO or DSVO). The valve position (LVDT) is determined using a linear variable differential transformer.

The VSVO performs a cyclic control algorithm. Three cables are connected to the VSVO at the J5 plug on the front panel and at the J3/J4 connectors on the VME rack. the JR1 connector is used for the

TSVO to provide simplex signals, while the JR1. JS1 and JT1 connectors are used to fan out TMR signals. The external trip of the protection module is inserted into JD1 or JD2.

IS200VSVOH1B Installation

Close the VME's processor rack.

Place the board in place, then hand press the top and bottom ties into the base of the edge connector.

Tighten the plus screws at the top and bottom of the front panel.

The cable connections to the TSVO terminal board are made at the lower J3 and J4 connectors of the VME rack. They are locking the connections in order to secure the cables. Start the VME rack and check the diagnostic indicators on the front panel.

IS200VSVOH1B Operation

LVDT position feedback, LVDT excitation, bi-directional servo current outputs, and pulse rate flow inputs are contained within the four channels of the VSVO.

The TSVO can provide excitation for up to six LVDT valve position inputs, and the TSVO accepts inputs from them as well. For each servo control loop, one, two, three or four LVDTs can be selected.

For applications measuring gas turbine flow, three inputs are provided. These signals are routed through the TSVO and sent directly to J5 on the front of the VSVO board. when power is lost, each servo output has a dedicated suicide relay which, when controlled by firmware, short-circuits the VSVO output signals to common and then returns to normal operation after a manual reset command.

Each servo's output voltage, current, and suicide relay are monitored through the diagnostic function.

Diagnostics

Three LEDs at the top of the VSVO front panel display status data. The regular RUN status is flashing green, while FAIL is normally lit in red. The third LED is STATUS, which is normally off, but will flash a constant orange color if the board has an alarm condition. The following diagnostic tests are included:

Output servo current is too high or unresponsive, causing a fault.

The regulator feedback (LVDT) signal has exceeded its limits. When a problem occurs, remove the bad sensor from the associated regulator from the feedback calculation and use a good sensor.

Servo suicide. This can cause a defect.

The A/D converter calibration voltage is out of range and is being used as the default.

The excitation voltage for the LVDT is out of range. A defect was created.

The difference between the input signal and the selected value exceeds the TMR differential limit. This causes a fault to be generated indicating a problem with this sensor input.

If any of the above signals become abnormal, the composite diagnostic alarm L#DIAG VSVO is triggered This toolbox contains information about the individual diagnostics. If the individual diagnostic signals return to normal, they can be latched and reset along with the RESET DIA signal.

The terminal board connectors JR1. JS1. and JT1 each have their own ID device that is queried by the I/O board.The ID device is a read-only chip that contains the serial number of the terminal board, the board type, the revision number, and the plug location. When VSVO reads the chip and detects a mismatch, a hardware incompatibility fault is generated.

Digital Servo Regulators

Digital Servo Regulator n = 1-4 divides the servo regulator into the software and hardware portions of the control loop. The user can select servo feedback from the LVDT and pulse rate inputs.

The LVDT input is a 3.2KHz sinusoidal signal whose amplitude is proportional to the position of the electromechanical valve controlled by the servo output. The pulse rate input is a TTL-type signal or some other periodic signal that activates the comparator input.The FPGA on the VSVO counts the comparator output transitions and converts them to flow. For LVDT feedback. the LVDT1 - 12 is scaled and adjusted in the position feedback function of the digital regulator or can be independently adjusted by a separate monitoring function. If an asterisk appears after the block name, it indicates that a more detailed graphic exists to better define the block function.