The IS200EMCSG1A is a 100mm Exciter Conduction Sensor Board designed by General Electric (GE) for its EX2100™ Excitation Control System. This board is the standard version within the EMCS series, primarily used to detect current flow through bus lines in the power converter, providing critical conduction feedback information to the excitation control system.
The core function of the IS200EMCSG1A board is to detect current in the bus lines using Hall Effect sensors. Each EMCS board uses two unidirectional Hall Effect sensors facing in opposite directions to detect bidirectional current. When a sensor detects a magnetic field above its operating threshold (indicating current flow), the circuit produces a logic low output. The sensor maintains this low output state until the field drops below the release point. This design allows the EMCS board to accurately detect the conduction status of SCRs, providing real-time conduction feedback to the voltage regulator.
The IS200EMCSG1A board is powered by the IS200EHPA Exciter Gate Pulse Amplifier board. The EHPA board also filters the output signals from the EMCS board before sending the processed information to the IS200EMIO Exciter Main Input/Output board. In the EX2100 excitation system, one EMCS board is used in each of the six SCR bridge legs for each Power Converter Module (PCM). For example, in a bridge with four PCMs, up to 24 EMCS boards can be present.
The board designs safety in high-voltage environments:
The bus is insulated with tubing to prevent accidental contact of the rings with the energized bus.
The EMCS board is mounted adjacent to the bus line using a Glastic® mounting bracket, which also holds the steel rings in place.
All inputs and outputs are through the 6-pin P1A connector to the EHPA board.
The IS200EMCSG1A board includes the following main components and features:
Two 6-pin connectors: P1A and P1B (redundant, providing backup outputs)
Gapped steel rings: Concentrate the magnetic flux produced by the bus, enhancing detection sensitivity
Two Hall Effect sensors: Mounted in opposite directions to detect bidirectional current
Redundant logic outputs: Two identical logic output signals for enhanced reliability
Passive design: Board has no fuses, test points, LED indicators, or adjustable hardware
II. Main Functions
The primary functions of the IS200EMCSG1A include, but are not limited to, the following:
1. Current Conduction Detection
The IS200EMCSG1A board detects current flowing through the bus line using Hall Effect sensors. When current flows through the bus, it generates a magnetic field around it. The gapped steel rings on the EMCS board concentrate the magnetic flux, enabling reliable detection by the Hall Effect sensors. When a sensor detects a magnetic field exceeding the operating threshold (corresponding to a typical current of approximately 80 A), the circuit outputs a logic low level (< 1.2 V dc). When the field drops below the release point (corresponding to a typical current of approximately 10 A), the output returns to a logic high level (> 11 V dc).
2. Bidirectional Detection
By using two unidirectional Hall Effect sensors mounted in opposite directions, the IS200EMCSG1A board can detect current flowing in either direction through the bus. Regardless of the current direction, at least one sensor will respond, ensuring complete conduction detection.
3. Redundant Outputs
Each IS200EMCSG1A board provides two identical logic output signals via the P1A and P1B connectors. The corresponding pins on these two connectors carry identical signals, acting as backups for each other. This redundant design enhances system reliability; even if one connector or cable fails, the other remains functional.
4. Interface with EHPA
The IS200EMCSG1A board is powered and communicates with the EHPA board via 4-pin shielded cables:
Power Supply: EHPA provides +12 V dc (±10%) power, maximum power consumption 0.3 W.
Signal Transmission: Conduction detection signals are sent back to EHPA through the same cable.
Daisy Chain Connection: One cable connects EHPA to the first EMCS for a given phase. Another 4-pin shielded cable daisy chains from that EMCS to the EMCS for the other SCR leg of the same phase.
5. Status Indication on EHPA
Although the EMCS board itself has no LED indicators, the EHPA board features three LEDs per phase to indicate the working status of the EMCS boards for that phase. When current is detected in a phase, the corresponding LED lights up, allowing field personnel to quickly assess conduction status.
6. Flux Concentration
The gapped steel rings attached to the board concentrate the magnetic flux produced by the bus, enabling the Hall Effect sensors to detect current more sensitively. The gap in the rings ensures effective flux concentration while preventing the formation of a closed magnetic circuit.
III. System Applications
1. Application in EX2100 Excitation Control System
The IS200EMCSG1A is a critical sensor board for detecting SCR conduction status within the EX2100 Excitation Control System. Its roles within the system include:
Conduction Status Detection: Real-time detection of current conduction in each SCR bridge leg, determining whether the SCR is firing correctly.
Fault Diagnosis: Conduction information is transmitted via EHPA and EMIO to the control system for SCR fault diagnosis and protection.
Redundant Feedback: Each EMCS provides two identical output signals, ensuring reliable transmission of conduction information even if one signal path fails.
System Monitoring: LED indicators on the EHPA board provide conduction status indication for field personnel.
2. Coordination with EHPA and EMIO
The IS200EMCSG1A board works closely with EHPA and EMIO within the system:
EHPA Power and Signal Conditioning: EHPA provides power to the EMCS and filters the output signals from the EMCS before sending the processed information to EMIO.
EHPA Status Indication: EHPA features LEDs per phase; when current is detected in that phase, the LED lights up, facilitating quick on-site assessment.
EMIO Signal Acquisition: EMIO receives the conduction information from EHPA for use by the control system.
3. Daisy Chain Connection Method
EMCS boards for each phase are connected in a daisy chain configuration:
EHPA connects via one 4-pin shielded cable to the EMCS for the first SCR leg of a phase (e.g., the EMCS for positive leg SCR1 of phase A).
That EMCS connects via its P1B connector and another 4-pin shielded cable to the EMCS for the other SCR leg of the same phase (e.g., the EMCS for negative leg SCR4 of phase A).
Thus, EHPA obtains conduction information for both SCR legs of that phase using two cables.
4. Typical Application Scenarios
SCR conduction monitoring for large synchronous generator excitation systems
Fault diagnosis for steam turbine generator excitation power units
Protection for hydro turbine generator excitation systems
Monitoring for gas turbine excitation systems
Upgrades and retrofits for industrial excitation systems
IV. Detailed Interface Description
1. P1A and P1B Connectors
The IS200EMCSG1A board features two 6-pin connectors, P1A and P1B. These connectors have identical pin assignments, providing redundant outputs. Pin assignments are as follows:
| Pin | Signal Name | Description |
| 1 | P12 | +12 V dc power input |
| 2 | CONSENO | Logic output (Low = 0 V indicates Conduction, High = +12 V indicates No Conduction) |
| 3 | Shield | Connects to ground |
| 4 | PCOM | 0 V dc power common |
| 5 | CONSENO | Logic output (same as pin 2) |
| 6 | NC | Not Connected |
Note:
P1A is typically used for connection to EHPA or the previous EMCS.
P1B is typically used for connection to the next EMCS (daisy chain).
Both pins 2 and 5 on each connector provide the same logic output; either can be used, or both can be used for redundancy.
2. Steel Rings and Hall Effect Sensors
The IS200EMCSG1A board has gapped steel rings attached. The bus line passes through these rings. When current flows through the bus, the rings concentrate the magnetic flux, enabling the Hall Effect sensors mounted in the ring gaps to detect it reliably. The two sensors are mounted in opposite directions, ensuring that regardless of the current direction, at least one sensor can detect it.
3. Power and Signal Flow
V. Installation and Replacement
1. Mounting Location
The IS200EMCSG1A board is mounted inside the Power Converter Module (PCM) cabinet. The EMCS for each SCR is located above its associated SCR heat sink, near the front of the cabinet. Positions for each phase are as follows:
Phase A positive leg (SCR #1): Upper left
Phase A negative leg (SCR #4): Upper right
Other phases follow similarly.
2. Replacement Procedure
Important Safety Warnings:
The EMCS board is located in a high-voltage circuit. Power to the excitation system must be turned off before replacement (for online repair, ensure the affected PCM is de-energized according to online repair procedures).
Follow the complete de-energizing procedures outlined in the Installation and Startup Guide (GEH-6631). Adhere to all local Lock-out/Tag-out practices. Allow time for capacitors to discharge.
Use safety test equipment designed for high voltages to confirm circuits are de-energized before touching them.
Adhere to ESD (Electrostatic Discharge) precautions when handling the board. Wear a grounding strap and store the board in anti-static bags.
Replacement Steps:
Verify Power Off: Ensure the excitation system or the affected PCM is completely de-energized.
Open Cabinet Door: Open the PCM cabinet door. Using high-voltage test equipment, verify that circuits are de-energized.
Remove Protective Covers: Remove the Glastic strip and LEXAN® shield to access the EMCS board to be replaced.
Remove Bus Section:
Disconnect Cables:
Remove EMCS Assembly:
Separate Board:
Install New Board:
Orient the new EMCS board the same as the original and secure it with the magnetic rings to the plastic mounting bracket using the four screws.
Be careful not to damage the sensor devices on the EMCS.
Before tightening the screws, hold the magnetic rings so as to minimize the gap at the sensors.
Install Assembly:
Slide the assembly back into the cabinet and mount it in place.
Ensure the magnetic rings are not touching any exposed bus, and that the insulating tubing over the bus is properly positioned to protect the rings.
Reconnect Cables: Reconnect the P1A and P1B cables disconnected in step 5.
Install Bus Section:
Restore Protective Covers: Install the LEXAN and Glastic pieces removed in step 3.
Restore Power: Close the PCM cabinet door, restore power following procedures, and test operation.
