The IS220PSVOH1B is a high-performance servo control I/O module belonging to the PSVO (Servo Control I/O Pack) series within the GE (General Electric) Mark VIe control system. This module is specifically designed to provide a precise electrical interface and control function for servo valves in gas turbines, compressors, and other industrial rotating machinery. The IS220PSVOH1B communicates with the TSVC servo terminal board via one or two I/O Ethernet networks and cooperates with the adjacent WSVO servo driver assembly to achieve closed-loop control of two independent servo valve position loops.
The IS220PSVOH1B adopts a modular design, incorporating a common distributed I/O processor board and a dedicated servo function I/O board. The module supports five selectable servo valve output currents ranging from 10 mA to 120 mA, accommodating servo valves of different specifications. The module also provides LVDT (Linear Variable Differential Transformer) excitation signals and can receive up to eight LVDT feedback signals and two pulse rate inputs from fuel flow meters.
The IS220PSVOH1B can be applied in simplex and TMR (Triple Modular Redundant) systems, meeting the high reliability and high availability requirements of industrial control applications. The module connects directly to the TSVCH1A terminal board via a DC-62 pin connector and accesses the IONet network through RJ-45 Ethernet interfaces for real‑time data exchange with the controller.
II. Hardware Structure and Interfaces
2.1 Physical Dimensions and Mounting
The IS220PSVOH1B is designed with compact surface‑mount technology. Its physical dimensions are as follows:
Parameter | Value |
Height | 8.26 cm (3.25 inches) |
Width | 4.19 cm (1.65 inches) |
Depth | 12.1 cm (4.78 inches) |
Mounting Method | Direct plug‑in to TSVCH1A terminal board connector, mechanically secured via threaded inserts next to Ethernet ports and mounting bracket |
2.2 Main Connectors
The IS220PSVOH1B is equipped with the following connectors:
DC‑62 pin connector : Located on the underside of the module, mates directly with the corresponding connector on the TSVC terminal board, carrying all I/O signals including LVDT signals, servo current commands, and excitation outputs.
ENET1 (RJ‑45) : Primary system Ethernet interface for connection to the IONet network.
ENET2 (RJ‑45) : Redundant/secondary system Ethernet interface supporting dual‑network configurations for improved communication reliability.
Infrared port : Located on the front panel but not used in this product.
2.3 Status LEDs
Multiple LED indicators on the front panel provide visual diagnostics, including power status, Ethernet link status, and module health status.
III. Functional Description
3.1 Servo Control Function
The IS220PSVOH1B works together with the WSVO servo driver assembly. The WSVO contains a power supply that converts the P28 voltage input to ±15 V for the servo current regulator circuits, two servo current regulators operating from the current references provided by the I/O pack, a selection of five configurable gains, and the servo suicide relays and excitation output driver circuits.
Inside the module, the BSVO servo board multiplexes 24 analog channels into a 16‑bit A/D converter (100 kHz sampling rate, ±10 V dc range). This A/D handles servo current regulator signals, LVDT inputs, and power supply monitoring. The current references for the analog current regulators on the WSVO are generated on the BSVO by a 14‑bit D/A converter. LVDT excitation uses a digital‑to‑analog converter that outputs a 3.2 kHz sine wave, which is filtered and passed to the WSVO.
3.2 LVDT Interface
The module supports up to eight LVDT feedback inputs for precise position measurement of valves or actuators. Each LVDT input features low‑pass filtering and high common‑mode rejection to ensure stable position signals even in harsh electromagnetic environments. Users can perform automatic calibration of each LVDT using the ToolboxST software, recording the Vrms values corresponding to the fully closed and fully open valve positions (MnLVDTx_Vrms and MxLVDTx_Vrms), thereby converting voltage signals into 0%–100% position percentages.
3.3 Pulse Rate Inputs
The IS220PSVOH1B provides two pulse rate input channels, configurable for:
Magnetic (passive) : Suitable for fuel flow meters and similar devices. The signal conditioning circuit is optimized for flow divider sensors.
TTL active sensor : Suitable for 5–27 V active output sensors.
Pulse rate inputs also support several application types:
Flow type : Used for flow divider fuel flow measurements.
Speed type : Used for conventional single‑shaft turbine speed measurement.
Speed High type : Extends speed measurement range.
Speed LM : Designed specifically for LM series turbines.
Speed_HSNG : Used to compensate for inconsistent tooth spacing on the speed wheel. This mode maps tooth spacing to remove periodic speed variations, providing mapping lock status bits (HSNGn_Stat).
If lock cannot be achieved due to excessive tooth‑to‑tooth variation, the Lock_Limit parameter can be adjusted in 1% increments to allow more variation per revolution. Reasons for adjustment may include: magnetized speed wheel, two‑piece speed wheel, external electromagnetic interference, or improper wiring/shielding practices. However, increasing Lock_Limit allows more speed variation; the root cause should be addressed whenever possible.
3.4 Servo Valve Calibration
The IS220PSVOH1B supports valve actuator stroking tests. Servo performance can be verified in three ways:
Manual mode : Enter desired value numerically and monitor performance using the trend recorder.
Position ramping (Verify Position) – applies a ramp to the actuator.
Step current (Verify Current) – applies a step input to the actuator.
When a new terminal board is used on a system, recalibration of the IS220PSVOH1B servo loops is required. The controller saves the barcode of the terminal board and compares it to the current terminal board during reconfiguration load time. Each time a calibration is saved, the barcode name is updated to the current board.
Calibration steps (in ToolboxST):
In the Component Editor, select the Hardware tab.
In the Tree View, select the desired IS220PSVOH1B module.
In the Summary View, select the Variables tab, then click Go On/Offline.
Scroll to CalibEnab1 or CalibEnab2 and double‑click to enable calibration (only enabled regulators can be calibrated).
Switch to the Regulators tab, select the desired regulator from the drop‑down list, and check the Enable box.
Click the Calibrate button to open the Calibrate Valve dialog.
Click Calibration Mode to enter calibration mode.
Click Minimum End (stroke actuator to minimum end), Fix Minimum End (read voltage), Maximum End (stroke to maximum end), Fix Maximum End (read voltage).
Click Calibrate to use the calculated values, then Save to store them in the I/O module and the current ToolboxST configuration.
Verification commands (no sequence requirement) include: Position (step and monitor), Current (step and monitor), Manual (manual movement, used with Send button), Send (send setpoint value), OFF (exit verification mode).
3.5 Regulator Algorithm Types
The IS220PSVOH1B supports multiple servo regulator algorithm types selectable via the Reg_Type parameter:
Reg_Type Value | Description |
Unused | Not used |
no_fbk | No feedback regulator |
1_LVposition | Single LVDT position regulator |
1_PulseRate | Single pulse rate (fuel flow) regulator |
2_LVpilotCyl | Dual LVDT pilot cylinder regulator (main + pilot) |
2_LVposMAX | Position regulator using maximum of two LVDTs |
2_LVposMIN | Position regulator using minimum of two LVDTs |
2_PIsRateMAX | Fuel flow regulator using maximum of two pulse rates |
3_LV_LMX | Median of three LVDTs (for LMX100 turbine) |
3_LVposMID | Median of three LVDTs (for heavy‑duty gas turbines) |
4_LV_LM | Ratio‑metric dual LVDT pair selection (for LM1600/2500/6000) |
4_LV_LMX | Four‑LVDT regulator (LMX extended) |
4_LVP/cylMAX | Four LVDT main/pilot maximum regulator |
Each regulator type has dedicated configuration parameters such as gain (RegGain), null bias (RegNullBias), position limits (MaxPOSvalue/MinPOSvalue), and LVDT voltage correspondence values (MnLVDTx_Vrms/MxLVDTx_Vrms).
3.6 Dither Function
To prevent the servo valve from sticking due to prolonged static operation, the IS220PSVOH1B provides an adjustable‑amplitude dither function. Dither frequency options: 12.5 Hz, 25 Hz, 33.33 Hz, 50 Hz, 100 Hz, or Unused. Dither amplitude (DitherAmpl) is specified in % current, range 0–10%. Note: When shorted coil detection is enabled, dither amplitudes greater than 2% are not recommended as they may interfere with coil resistance calculation. If dither amplitude is critical, disable the coil resistance calculation.
3.7 Suicide Protection
The IS220PSVOH1B provides multiple suicide protection mechanisms for servo outputs to ensure safe drive of the servo valve to a safe position (typically closed) upon detection of a fault. Configurable suicide conditions include:
Current suicide (EnablCurSuic) : Triggered when the error between commanded current and actual feedback current exceeds the set Curr_Suicide threshold (0–100%).
Position feedback suicide (EnablFbkSuic) : Triggered when position feedback exceeds (100% + Fdbk_Suicide) range.
Open coil suicide (OpenCoilSuic) : Triggered upon detection of an open servo coil; use OpenCoildiag to obtain specific diagnostic information.
Short coil suicide (ShrtCoilSuic) : Triggered upon detection of a shorted servo coil; use ShrtCoildiag for diagnostic details.
Open and short circuit detection is based on coil resistance calculation: after calibration, RcoilOpen = 2 × (Servo Compliance Voltage / Servo Current), RcoilShort = 0.5 × (Servo Compliance Voltage / Servo Current). Users can set RopenTimeLim and RShrtTimeLim (seconds) as fault confirmation delays.
VI. Configuration Parameters Summary
The IS220PSVOH1B is configured via ToolboxST software. Main configuration items include:
4.1 Servo Tab
Parameter | Description | Options / Default |
Servo_MA_Out | Nominal servo current rating (mA) | 10, 20, 40, 80, 120 (default 10) |
EnablCurSuic | Enable Current Suicide | Enable/Disable (default Disable) |
EnablFbkSuic | Enable Position Feedback Suicide | Enable/Disable (default Disable) |
EnblAutoGain | Enable Auto Gain (for 4_LV_LM, 3_LVLMX, 4_LVLMX) | Enable/Disable (default Disable) |
Coil_RS_Only | 2‑coil servo configuration (no load on S terminal) | Enable/Disable (default Disable) |
Curr_Suicide | Current error suicide threshold (%) | 0–100 (default 5) |
Fdbk_Suicide | Position feedback suicide margin (%) | 0–10 (default 5) |
OpenCoilSuic | Enable open coil suicide | Enable/Disable (default Disable) |
ShrtCoilSuic | Enable short coil suicide | Enable/Disable (default Disable) |
AttentionTBmAJmpPos | TSVC mA jumper position match | 10/20/40/80/120 mA_A/120 mA_B (default 10) |
RopenTimeLim | Open circuit detection delay (seconds) | 0–100 (default 1) |
RShrtTimeLim | Short circuit detection delay (seconds) | 0–100 (default 1) |
TMR_DiffLimit | TMR vote difference diagnostic limit (%) | 0–110 (default 25) |
4.2 Pulse Rates Tab
Parameter | Description | Options / Default |
SysLim2Latch | System Limit 2 latch enable | Latch/NotLatch (default Latch) |
SysLim2Type | Limit comparison type | ≤ or ≥ (default ≥) |
SysLimit2 | Flow rate upper limit | 0–20000 (default 0) |
TMR_DiffLimit | TMR vote difference limit (%) | 0–20000 (default 5) |
4.3 Regulators Tab
Parameter | Description | Range / Default |
Reg_Type | Regulator algorithm type | See list above (default Unused) |
Dither_Freq | Dither frequency (Hz) | 12.5, 25, 33.33, 50, 100, Unused (default Unused) |
DitherAmpl | Dither amplitude (% current) | 0–10 (default 2) |
LVDT_Margin | LVDT over‑range diagnostic margin (%) | 1–100 (default 2) |
RegGain | Position loop gain (% current / Eng. unit) | -200 to 200 (default 1) |
RegNullBias | Null bias compensation (% current) | -100 to 100 (default 0) |
MaxPOSvalue | Position at full open (usually %) | -15 to 150 (default 100) |
MinPOSvalue | Position at full closed (usually %) | -15 to 150 (default 0) |
MnLVDT1_Vrms | LVDT voltage at full closed (Vrms, simplex/TMR) | 0–7.1 (default 1 / 1,1,1) |
MxLVDT1_Vrms | LVDT voltage at full open (Vrms, simplex/TMR) | 0–7.1 (default 5 / 5,5,5) |
V. Diagnostics and Alarms
The IS220PSVOH1B performs the following self‑diagnostic tests:
Power‑up self‑test: checks RAM, flash memory, Ethernet ports, and most processor board hardware.
Continuous monitoring of internal power supplies.
Electronic ID check: verifies that the terminal board, acquisition board, and processor board hardware set matches, and that the application code in flash is correct for the hardware.
Each analog input has hardware limit checks based on preset (non‑configurable) high and low levels near the operating range. If exceeded, a logic signal is set and the input is no longer scanned.
Each input also has system limit checks based on configurable high/low levels, which can generate alarms, enable/disable functions, and be latching/non‑latching. RSTSYS resets out‑of‑limit conditions.
The analog input hardware includes precision reference voltages in each scan; measured values are compared against expected values to confirm A/D converter health.
Analog output current is sensed on the terminal board using a small burden resistor; the I/O pack conditions this signal and compares it to the commanded current to confirm D/A converter health.
The analog output suicide relay is continuously monitored for agreement between commanded state and feedback indication.
Detailed diagnostic information is available through the ToolboxST application. Diagnostic signals can be individually latched and reset via the RSTDIAG signal when they return to healthy.
VI. Installation Notes
Securely mount the TSVCH1A terminal board.
Plug one (simplex) or three (TMR) IS220PSVOH1B modules directly into the terminal board connectors.
Mechanically secure the modules using the threaded inserts next to the Ethernet ports and the terminal‑board‑specific mounting bracket. Adjust the bracket position so that no right‑angle force is applied to the DC‑62 pin connector.
Plug the WSVO servo driver assemblies into the J2 48‑pin connectors and secure with the four screws.
Plug in one or two Ethernet cables depending on system configuration. When a single IONet connection is used, the module works over either port. If dual connections are used, standard practice is to connect ENET1 to the network associated with the R controller.
Apply power to the I/O packs and drivers using the power switches on TSVC. Use SW3 for R, SW2 for S, and SW1 for T, and check the indicator lights. For simplex applications that use the TSVC JDI/JD2 (K1 relay), verify that SW1 is ON and the green DS1 LED is lit; otherwise the K1 trip override relay will not provide intended protection.
Use the ToolboxST application to configure the I/O packs as necessary. Note: If the downloaded configuration contains I/O packs with different module IDs than the currently running configuration, incorrect firmware may be installed to some I/O packs. In that case, ensure the controller is running the new configuration, restart the entire system, and then restart the ToolboxST Download Wizard.
