The IS200EMCSG1AAB is a conduction sensor board manufactured by GE Energy as part of the EX2100™ excitation control series. This board is specifically designed for use in 100 mm (multibridge) EX2100 excitation systems. Its primary function is to detect current flow through the bus lines in the power converter. The IS200EMCSG1AAB is a critical component that provides real‑time feedback to the excitation control system, indicating whether current is flowing in each leg of the three‑phase power bridge.
The board is powered by the IS200EHPA Exciter Gate Pulse Amplifier (EHPA) board, which also filters the output signals from the EMCS board before sending them to the IS200EMIO Exciter Main Input/Output (EMIO) board. One IS200EMCSG1AAB board is used in each of the six Silicon Controlled Rectifier (SCR) bridge legs for every Power Converter Module (PCM) in the exciter. For example, in a bridge with four PCMs, up to 24 EMCS boards can be present in a single application.
The IS200EMCSG1AAB uses two unidirectional Hall Effect sensors facing in opposite directions to detect current. When either sensor detects a magnetic field above its operating threshold (indicating current flow), the board produces a logical low output. This output is sent to the EHPA board, which then conditions the signal and forwards it to the control system. The board is designed for high reliability and is built to withstand the harsh electrical environment of the power converter cabinet.
The suffix AAB indicates a specific revision and factory configuration that maintains full backward compatibility with all EX2100 excitation systems while incorporating the latest design enhancements. This board is intended for use by trained personnel familiar with GE excitation products.
Functional Description
The IS200EMCSG1AAB is a passive sensing board that detects the presence of current in a bus conductor. It does not measure the magnitude of the current but rather provides a logical indication of whether the current is above a certain threshold. This on/off information is essential for the control system to verify proper commutation of the SCRs and to detect faults such as a missing firing pulse or a failed SCR.
The board operates on the principle of magnetic flux concentration. Gapped steel rings are attached to the IS200EMCSG1AAB, and the bus line (the conductor whose current is to be sensed) passes through these rings. Two Hall Effect sensors, placed in opposition, measure the concentrated magnetic flux produced within the rings when current flows through the bus. The sensors are unidirectional, meaning each sensor responds to current in one direction only. By using two opposite‑facing sensors, the board can detect current flow in either direction (though in a typical bridge application, current flows in only one direction through each leg).
When either sensor detects a magnetic field above the operating threshold, the board’s output circuit pulls the logical output signal low (less than 1.2 V dc). If no current is present (magnetic field below the release point), the output remains high (above 11 V dc). The typical operating current that causes switching is 80 A, and the typical release current is 10 A. These values are based on the designed flux concentration and the sensor’s characteristics.
The board provides two identical logical output signals (CONSENO and CONSENO on separate pins) for redundancy. Both outputs are available on the same 6‑pin connector (P1A). The board also includes a shield connection for noise immunity. Power is supplied by the EHPA board: +12 V dc ±10% at a maximum of 0.3 W, plus a 0 V dc return (PCOM).
Multiple IS200EMCSG1AAB boards are connected in a daisy‑chain configuration. The EHPA board powers six EMCS boards via three 4‑pin shielded cables, one per phase. Each cable connects to the first EMCS board of that phase (e.g., the positive leg), and from that board a second cable daisy‑chains to the other EMCS board of the same phase (the negative leg). The EHPA filters the output signals from each EMCS board and transfers the information to the EMIO controller board.
Visual indication of conduction is provided by LEDs on the EHPA board (not on the EMCS itself). For each phase, a yellow LED (PHA, PHB, PHC) illuminates when the EMCS board for that phase detects current.
Hardware Characteristics
The IS200EMCSG1AAB is a small printed wiring board designed for mounting inside the Power Converter Module (PCM) cabinet of the EX2100 exciter. It is mounted using a Glastic® (fiberglass‑reinforced plastic) mounting bracket that also holds the steel magnetic rings in place. The board is positioned above its associated SCR heat sink, near the front of the cabinet. The bus conductor (insulated with tubing) passes through the steel rings attached to the board.
Connectors and Interface
The board has a single 6‑pin connector (P1A) for all power and signal connections. Some revisions may have a second connector (P1B) for daisy‑chain purposes, but the primary interface is through P1A.
Pin Number | Signal Name | Description |
1 | P12 | +12 V dc power supply input |
2 | CONSENO | Logical output (low = current detected, high = no current) – first output |
3 | Shield | Connects to ground (cable shield) |
4 | PCOM | 0 V dc power supply return |
5 | CONSENO | Logical output (low = current detected, high = no current) – second output (redundant) |
6 | NC | Not connected |
Both output signals are identical and active low. A low output (≤1.2 V) indicates that current is flowing through the bus. A high output (≥11 V) indicates no current or current below the release threshold.
Steel Rings and Flux Concentrator
The board is supplied with gapped steel rings that are attached to the board via screws. These rings concentrate the magnetic field generated by the bus current, allowing the Hall Effect sensors to reliably detect currents as low as the release point (10 A typical). The rings must not touch the bus conductor; insulating tubing over the bus prevents accidental contact.
LED Indicators
The IS200EMCSG1AAB itself has no on‑board LEDs. Status is indicated by LEDs on the associated EHPA board. For each phase (A, B, C), a yellow LED (PHA, PHB, PHC) on the EHPA illuminates when the corresponding EMCS board detects current. This provides a quick visual check of conduction in each bridge leg.
Installation and Replacement Procedures
Handling Precautions
Static sensitivity – The IS200EMCSG1AAB contains static‑sensitive components (Hall Effect sensors). Always wear a grounding wrist strap and handle the board only at a grounded workstation. Store the board in its antistatic bag when not in use.
De‑energise before handling – To prevent electric shock, turn off power to the exciter (or to the affected Power Converter Module for online repair) and verify zero voltage on all circuits before touching the board or any connected cables. Follow all local lock‑out/tag‑out procedures. Refer to GEH‑6631 (EX2100 Installation and Startup Guide) for complete de‑energising procedures.
Do not remove or insert with power applied – Doing so may cause equipment damage or personal injury.
Avoid dropping hardware – Mounting screws or other small parts dropped into the cabinet can cause short circuits or damage when power is restored.
Replacement Procedure (Offline or Online with PCM De‑energised)
The EMCS board is located in the PCM cabinet. In 100 mm exciters that include the online repair option, it is possible to de‑energise only the affected PCM while other PCMs remain online.
De‑energise the exciter (or the specific PCM) following the EX2100 Installation and Startup Guide and local lock‑out/tag‑out procedures.
Open the PCM cabinet door and test all electrical circuits for zero voltage using high‑voltage testing equipment.
Locate the EMCS board above its associated SCR heat sink. The phase A positive leg (SCR #1) is in the upper left, phase A negative leg (SCR #4) is in the upper right, etc. Remove the Glastic strip and LEXAN® shield to access the board.
Remove the small L‑shaped bus piece in front of the EMCS by removing the three 5/16‑inch bolts connecting it to the heat sink and the three 5/16‑inch bolts connecting it to the bus piece that passes through the magnetic rings.
Carefully disconnect the P1A cable (and P1B if present) from the EMCS board by squeezing and pulling the cable connectors. Label the cables if not already marked, to ensure correct reconnection.
Remove the screws that hold the EMCS assembly to the PCM sidewall and carefully slide the assembly forward and out of the cabinet.
Remove the four screws that secure the EMCS board and the magnetic rings to the plastic mounting bracket. Remove the board.
Orient the new IS200EMCSG1AAB board exactly as the original. Secure it to the mounting bracket with the four screws, together with the magnetic rings. Before tightening the screws, hold the magnetic rings to minimise the gap at the sensors – this ensures proper flux concentration.
Slide the assembly back into the cabinet and mount it in place. Verify that the magnetic rings are not touching any exposed bus and that the insulating tubing over the bus is correctly positioned to prevent contact.
Reconnect the P1A and P1B cables to the new board.
Reinstall any LEXAN baffles that were removed (these are essential for proper air flow cooling of the PCM).
Reinstall the L‑shaped bus piece removed in step 4. Torque the six 5/16‑inch bolts to 115 inch‑pounds.
Reinstall the Glastic strip and LEXAN shield removed in step 3.
Close the PCM cabinet door and follow re‑energisation procedures.
After power is restored, verify that the appropriate conduction LED (PHA, PHB, or PHC) on the associated EHPA board illuminates when the corresponding SCR is gated. Absence of the LED may indicate improper sensor alignment, a missing cable connection, or a faulty EMCS board.
When ordering the IS200EMCSG1AAB, use the complete part number exactly as shown. The part number follows GE’s convention:
IS200 – Innovation Series, 200‑class.
EMCS – Functional acronym: Exciter Conduction Sensor.
G1 – Generation/version.
A – Base designator.
A – Modifier (e.g., coating or component variation).
B – Revision B.
Warranty and Order Placement
Warranty replacements (within the warranty period): Contact GE Energy Product Service Engineering:
GE Energy
Product Service Engineering
1501 Roanoke Blvd.
Salem, VA 24153‑6492 USA
Phone (US): +1 888 GE4 SERV (888 434 7378)
Phone (International): +1 540 378 3280
Fax: +1 540 387 8606
Spare parts or non‑warranty orders: Contact your nearest GE Sales or Service Office. Provide:
Note: All digits and letters in the part number are significant. GE may substitute later compatible revisions, but backward compatibility is assured.
Diagnostics and Maintenance
The IS200EMCSG1AAB requires no routine calibration or adjustment. However, periodic inspection of the mounting, the magnetic rings, and the bus insulation is recommended. The board’s health is primarily indicated by the EHPA’s LED status and by the control system’s diagnostic messages.
Troubleshooting:
Symptom | Possible Cause | Corrective Action |
EHPA phase LED (PHA/B/C) off when SCR is firing | EMCS board not detecting current; misaligned rings; open cable; faulty sensor | Check cable connections; verify rings are properly gapped; replace EMCS board. |
EHPA phase LED on when SCR is not firing | False detection; magnetic interference; sensor stuck low | Check for stray magnetic fields; remove and re‑seat board; replace EMCS. |
Control system reports conduction fault for one leg | EMCS output missing or incorrect | Verify power supply (+12 V) at EMCS; check output signal with oscilloscope; replace board if necessary. |
Physical damage to steel rings or bus insulation | Arcing or mechanical interference | De‑energise, repair or replace insulation, ensure rings are centred on bus. |
