The IS200SCNVG1A is an SCR-Diode Converter Interface Board designed by General Electric (GE) for its Innovation Series™ SCR-Diode Converters. This board is the standard version within the SCNV series, primarily used for 6-pulse sources in 1800 amp and 1000 amp stand-alone units. Each board drives three SCRs (66 mm or smaller). This board is not used for driving paralleled SCRs from the same board.
The IS200SCNVG1A board is located between the control rack and the power bridge, serving as a critical signal interface and driver stage. It receives control signals from the IS200BIC Bridge Interface Board, isolates and amplifies them, and drives the SCRs and the optional Dynamic Braking (DB) IGBT. The board integrates various feedback circuits, including input current sensing, line-to-line voltage feedback, DC link voltage feedback, and DB IGBT VCE feedback, providing comprehensive operational status information to the control system.
Key features of the IS200SCNVG1A include:
6-Pulse Drive: Suitable for 6-pulse SCR-diode converters, driving three SCRs per board.
Multiple Feedbacks: Provides three-phase input current sensing, two line-to-line voltage feedbacks, DC link voltage feedback, and DB IGBT VCE feedback.
Dynamic Braking Support: Optional DB IGBT gate drive circuit and temperature fault detection.
Electrical Isolation: Driver and feedback circuits utilize galvanic and optical isolation for safety.
Gate Enable Control: DRVP5 and NDRPC signals control gate enabling/disabling.
Onboard ID Memory: Serial read-only memory stores board identification and revision information.
Multiple Power Supply Generation: Nine isolated power supplies are generated from an 18.4 V ac input via onboard transformers.
No User-Adjustable Components: The board has no LED indicators, fuses, user test points, or adjustable hardware.
The board mounts in slot 6 of the Innovation Series board rack and connects to the IS200CABP Control Assembly Backplane via the P1 connector. It features six plug connectors for interfacing with gate drivers, the DC link, and current shunts.
Important Safety Warning: The board has four test points (TP1-TP4) for engineering test use only. Users must not access these test points! High voltage (575 V ac or 900 V dc) is present on these test points.
II. Main Functions
The primary functions of the IS200SCNVG1A include, but are not limited to, the following:
1. SCR Gate Drivers
The IS200SCNVG1A board provides three individually isolated SCR gate drive circuits for phases A, B, and C. Each circuit uses the same hybrid module as the DB gate drive circuit but in a different configuration. The SCR gate driver circuit switches between VCC (22 V) and VEE (0 V) to deliver gate current. No SCR gate driver faults are reported on this board.
2. Dynamic Braking (DB) IGBT Gate Driver
The optional DB IGBT gate drive circuit is used for dynamic braking. The circuit is composed of an optically isolated hybrid gate driver module and a few discrete components. The module switches the IGBT gate-to-emitter voltage between VCC (+15 V) and VEE (-7.5 V).
Two types of faults can be generated by this circuit:
Desaturation Fault: Generated when the IGBT is commanded to turn on and VCE exceeds 10 V for 4 microseconds or longer. When a desaturation fault occurs, the module will slowly decrease VGE until the IGBT is OFF (soft shutdown).
Driver Supply Undervoltage Fault: Generated when the voltage between VCC and VEE drops below 16 V.
These faults are ORed together and optically coupled back to the control logic. These faults are transient and must be latched by the fault handling circuit monitoring the faults through P1 (this is done on the BIC board).
3. Gate Enable Control
The DRVP5 and NDRPC signals from the BIC board are used to disable/enable gating. DRVP5 should be high (+5 V) and NDRPC should be low (DCOM) to enable gating. The gate drive is disabled when either DRVP5 goes low or NDPRC goes high.
4. Shunt Current Feedback
Output phase current is monitored by deriving a Voltage Controlled Oscillator (VCO) output signal from the voltage dropped across the phase shunt. This voltage is amplified and then passed on to the VCO circuitry. The VCO has a range of 0-2 MHz, and the circuit is biased so that at zero current the nominal output is 1 MHz. A ±400 mV shunt voltage is converted into a ±800 kHz change in the VCO output frequency. The output of the VCO is optically coupled to a differential driver interface to the control logic.
5. Line-to-Line Voltage Feedback
The board provides two isolated line-to-line voltage feedback circuits for VAB and VBC. Input line-to-line voltage is monitored by deriving two VCO signals, VAB and VBC, from the input phase shunt connections. These circuits share power supplies and clock oscillators with the phase B and C shunt feedback circuits. The VCOs have a range of 0-2 MHz, and the circuit is biased so that zero line-to-line voltage produces a nominal output of 976.8 kHz. A ±1 V change in line-to-line voltage translates into a ±959.58 Hz change in output frequency. The outputs of the VCOs are optically coupled to the control logic. The line-to-line voltage feedback circuits have an input filter with a break frequency of 17.46 kHz.
6. DC Link Voltage Feedback
The board provides one isolated DC link voltage feedback circuit. This circuit shares its power supply with the DB IGBT VCE feedback circuit and is referenced to the negative DC link (same as the DB IGBT emitter). The positive DC link input is fed to the VCO circuit through a resistive attenuator. The VCO has an output range of 0-2 MHz. The input is scaled so that 0-1197.5 V link volts corresponds to 0-2 MHz. The output of the VCO is optically coupled to the control logic. The DC link voltage feedback circuit has an input filter with a break frequency of 10.03 kHz.
7. DB IGBT VCE Feedback
If equipped with the DB option, the board provides one isolated DB IGBT VCE feedback circuit. It shares its power supply with the DC link voltage feedback circuit and is referenced to the DB IGBT emitter (same as the negative DC link). The DB IGBT collector input is fed to the VCO circuit through a resistive attenuator. The VCO has an output range of 0-2 MHz. The input is scaled so that 0-1197.5 V corresponds to 0-2 MHz. The output of the VCO is optically coupled to the control logic. This circuit has an input filter with a break frequency of 10.03 kHz.
8. DB Temperature Fault Detection
If equipped with the DB option, the board provides a DB temperature fault detection circuit. An isolated 15 V supply (P15T) is used as a power supply. The signal DBTF is used to enunciate DB temperature faults to the BIC board. Under normal conditions (no faults), the externally supplied thermostat contact is closed, and 12 mA flows into the optocoupler, causing DBTF to be low. When a fault occurs (DB heatsink temp ≥ thermostat threshold), the thermostat contact opens, and no input current flows into the optocoupler, causing DBTF to be high.
9. Power Supply Generation
The board receives +5 V dc regulated power (P5) and DCOM, plus an 18.4 V ac, 25 kHz square wave input (VAC1 and VAC2) via the P1 connector from the backplane. Nine isolated power supplies are derived from the secondaries of four transformers:
| Transformer | Power Supply Purpose | Specification |
| T1 | Phase A SCR Gate Drive | Isolated +22.5 V, half-wave, referenced to positive DC bus, unregulated ±10%, max 1 A |
| T1 | Phase A Shunt Feedback | Isolated +12/-12/+5 V, full-wave, referenced to bridge side of shunt A, unregulated (except 5V), ±10%, max 100 mA |
| T2 | Phase B SCR Gate Drive | Isolated +22.5 V, half-wave, referenced to positive DC bus, unregulated ±10%, max 1 A |
| T2 | Phase B Shunt Feedback/VAB Feedback | Isolated +12/-12/+5 V, full-wave, referenced to bridge side of shunt B, unregulated (except 5V), ±10%, max 100 mA |
| T3 | Phase C SCR Gate Drive | Isolated +22.5 V, half-wave, referenced to positive DC bus, unregulated ±10%, max 1 A |
| T3 | Phase C Shunt Feedback/VBC Feedback | Isolated +12/-12/+5 V, full-wave, referenced to bridge side of shunt C, unregulated (except 5V), ±10%, max 100 mA |
| T4 | DB IGBT Gate Drive | Isolated +15/-7.5 V, half-wave, referenced to DB IGBT emitter (= negative DC bus), unregulated ±5%, max 1 A |
| T4 | DC Link Voltage/DB VCE Feedback | Isolated +12/-12/+5 V, full-wave, referenced to negative DC bus (= DB IGBT emitter), unregulated (except 5V), ±10%, max 100 mA |
| T4 | DB Temperature Fault | Isolated +15 V, half-wave, unregulated ±10% |
10. Onboard ID Memory
The IS200SCNVG1A board features a serial read-only memory device pre-programmed with board identification and revision information. This information is accessible via the BRDID data line on the P1 connector, facilitating automatic board type and revision identification by the system.
III. System Applications
1. Application in Innovation Series SCR-Diode Converters
The IS200SCNVG1A is a critical interface board connecting the control and power circuits within Innovation Series SCR-Diode Converters. Its roles within the system include:
SCR Gate Driving: Isolates and amplifies gate control signals from the BIC board to drive the three-phase SCRs.
Dynamic Braking Control: Optional DB IGBT drive for dissipating regenerative energy.
Status Feedback: Provides comprehensive operational status information (current, voltage, VCE, temperature) to the control system via multiple feedback circuits.
Fault Protection: Detects DB IGBT desaturation, supply undervoltage, and over-temperature faults, reporting them promptly to the control system.
2. Typical Application Scenarios
High-Power Rectifiers: Used in industrial high-power rectifier power supplies.
AC Variable Frequency Drives: Serves as the control interface in 6-pulse SCR converters.
DC Motor Drives: Used for speed control of DC motors.
Renewable Energy Systems: Applied in converters for wind power and photovoltaic generation.
Rail Transit Traction Systems: Controls SCRs in traction converters.
IV. Detailed Interface Description
1. SAPL Connector (Phase A Shunt)
| Pin | Nomenclature | Description |
| 1 | ASHL | AC Line Side of Shunt (A-) |
| 2 | ACOM | Bridge Side of Shunt (A+) |
2. SBPL Connector (Phase B Shunt)
| Pin | Nomenclature | Description |
| 1 | BSHL | AC Line Side of Shunt (B-) |
| 2 | BCOM | Bridge Side of Shunt (B+) |
| 3 | NC | Not Connected |
3. SCPL Connector (Phase C Shunt)
| Pin | Nomenclature | Description |
| 1 | CSHL | AC Line Side of Shunt (C-) |
| 2 | CCOM | Bridge Side of Shunt (C+) |
| 3 | NC | Not Connected |
| 4 | NC | Not Connected |
4. SPL Connector (SCR Gate Drive)
| Pin | Nomenclature | Description |
| 1 | GC | Phase C SCR Gate |
| 2 | CDCOM | Phase C SCR Cathode |
| 3 | NC | Not Connected |
| 4 | GB | Phase B SCR Gate |
| 5 | BDCOM | Phase B SCR Cathode |
| 6 | NC | Not Connected |
| 7 | NC | Not Connected |
| 8 | GA | Phase A SCR Gate |
| 9 | ADCOM | Phase A SCR Cathode |
5. DPL Connector (DB Gate Drive, Optional)
| Pin | Nomenclature | Description |
| 1 | DBTP | DB Temperature Positive |
| 2 | DBTN | DB Temperature Negative |
| 3 | NC | Not Connected |
| 4 | NC | Not Connected |
| 5 | DBP15 | +15 V PS for DB Gate Drive |
| 6 | DBN7 | -7.5 V PS for DB Gate Drive |
| 7 | NC | Not Connected |
| 8 | DBE | DB IGBT Emitter |
| 9 | DBG | DB IGBT Gate |
| 10 | NC | Not Connected |
| 11 | NC | Not Connected |
| 12 | DBC | DB IGBT Collector |
6. DCPL Connector (DC Link Voltage, not used if no DB option)
| Pin | Nomenclature | Description |
| 1 | DCP | DC Link Positive |
| 2 | NC | Not Connected |
| 3 | NC | Not Connected |
| 4 | NC | Not Connected |
| 5 | NC | Not Connected |
| 6 | DBCOM | DC Link Negative |
7. P1 Backplane Connector Key Signals
| Signal | Description |
| VAC1/VAC2 | 18.4 V ac, 25 kHz square wave power input |
| P5 | +5 V dc digital power source |
| DCOM | +5 V dc digital power return (common) |
| DRVP5 | Gate enable (active high) |
| NDRPC | Gate enable (active low) |
| NVDC | DC link voltage feedback |
| NVDBCE | Dynamic braking VCE feedback |
| DBF | Dynamic braking fault |
| DBTF | Dynamic braking temperature fault |
| NAD | Phase A SCR gate drive |
| NBD | Phase B SCR gate drive |
| NCD | Phase C SCR gate drive |
| NASFB | Phase A shunt feedback (current) |
| NBSFB | Phase B shunt feedback (current) |
| NCSFB | Phase C shunt feedback (current) |
| NVAB | VAB line-to-line voltage feedback |
| NVBC | VBC line-to-line voltage feedback |
| BRD_ID | Serial board identification line |
| I24/I24_COM | Isolated 24 V dc power source (for customer relays) |
V. Installation and Replacement
1. Mounting Location
The IS200SCNVG1A board inserts into slot 6 of the Innovation Series board rack and connects to the CABP backplane's J15 connector via P1.
2. Replacement Procedure
Safety Warnings:
WARNING: To prevent electric shock, turn off power to the drive system and follow all local Lock-Out/Tag-Out procedures.
CAUTION: Use safety test equipment designed for high voltages to confirm circuits are de-energized before touching.
WARNING: High voltage (575 V ac or 900 V dc) is present on this board. Extreme caution is required.
CAUTION: To prevent component damage caused by static electricity, treat all boards with static sensitive handling techniques. Wear a grounding strap and store boards in anti-static bags.
Removal Steps:
Verify Power Off: Ensure the drive system is completely de-energized.
Open Cabinet Door: Open the drive cabinet door. Use high-voltage test equipment to verify circuits are de-energized.
Remove Old Board:
Loosen the screws at the top and bottom of the board near the ejector tabs (screws are captive, do not remove).
Unseat the board by raising the ejector tabs.
Gently pull the board straight out of the rack using both hands.
Installing the New Board:
Insert Board: Slide the new board into the correct slot (slot 6) along the guides.
Seat Board: Using thumbs, firmly press the top and bottom of the board simultaneously to initially seat it.
Tighten Screws: Alternately tighten the top and bottom screws evenly to ensure the board is squarely seated.
Restore Power: Close the cabinet door and restore power to the system.
