Quick Sizing & Sourcing Snapshot

• Manufacturer:​ GE (General Electric)
• Part Number:​ IS200EACFG1B
• System Platform:​ EX2100 / EX2100e Excitation Control (Mark VI/VIe)
• Hardware Type:​ Exciter AC Feedback Board (EACF)
• Architectural Role:​ Conditions and fans out Generator PPT (Voltage) and Air Core CT (Current) signals to the M1, M2, and C controllers via DB9 links.
• Key Specifications:​ 480V RMS​ Input Rating (G1), 3x DB9​ Outputs, 2​ Flux Coil Terminals.

 

System Architecture & Operational Principle

The is a passive signal-conditioning hub located in the Exciter Auxiliary Cabinet. It is the “G1” variant in the EACF family, designed for systems with lower PPT secondary voltages (rated 480V RMS​ nominal, +20% transient).

Physically, it mounts to the cabinet framework (chassis mount). Upstream, it receives raw 3-phase AC from Generator Potential Transformers (PPTs)​ and signals from Air Core Current Transformers (CTs)​ at its screw terminals (TB1-TB3 for PPT, TB4 for CT). The board uses internal step-down transformers (T2, T3)​ to isolate and scale these signals. Downstream, it has no active processing; it “fans out” the conditioned signals via three 9-pin D-Sub (DB9) connectors​ (J504 to M1, J409 to M2, J514 to C). This allows the three TMR (Triple Modular Redundant) controllers on the EBKP​ backplane to independently vote on AC feedback for the AVR (Automatic Voltage Regulator) loop. It operates at Level 1/2, providing the sensory interface required to regulate generator terminal voltage.

 

Core Technical Specifications

• Voltage Rating (G1):​ 480V RMS​ (Nominal +20% Transient Tolerance)
• Current Inputs:​ Air Core CT (0 to 0.8V RMS), 2 Terminals (TB4)
• Voltage Inputs:​ 3-Phase PPT (L1, L2, L3), Terminals TB1, TB2, TB3
• Output Interfaces:​ 3x DB9 (D-Sub)​ -> J504 (M1), J409 (M2), J514 (C)
• Transformers:​ T2, T3 (Active Signal Conditioning), T1/T4 (Omitted/Spare)
• Test Points:​ TP1-TP4 (Phase-to-Phase: AB, BC, CA @ Scaled ~1.6V)
• Power:​ Passive (No Active Consumption; Signal Sourced from PT/CT)
• Indicators:​ None​ (Blind Board; Diagnostics via Controller/EBKP)
• Coating:​ Conformal Coated (Revision B)
• Mounting:​ Chassis Mount (Exciter Aux Cabinet Framework)
• Max Cable Length:​ Up to 90m (300ft) to EBKP

 

Customer Value & Operational Benefits

Voltage Rating Specificity (G1)

The “G1” (480V) rating is critical for smaller gen-sets or units with lower PPT ratios. Using a G2 (1000V) or G3 (1400V) here works electrically at low volts, but the transformer turns ratio​ is optimized for higher voltages. The G1 ensures the best signal-to-noise ratio (SNR)​ when your PPT secondaries are in the 70-120V AC range, preventing AVR “hunting” (VAR oscillation) caused by under-scaled signals.

TMR Signal Isolation

By fanning out via dedicated DB9s to M1, M2, and C, the board ensures galvanic separation​ of the redundant paths at the sensor level. If a fault (e.g., lightning surge) spikes the PPT wiring and cooks the T2 transformer on thisboard, it won’t propagate to the M1 processor’s ADC. The M2 and C paths remain viable for the 2oo3 vote.

Centralized Calibration Access

The TP1-TP4​ test points provide scaled AC voltage (approx 1.6V AC for 120V PT secondary). You can verify PPT phasing and scaling with a DMM right at the board while synchronized at 100% load, without probing live high-voltage bushings or pulling EBKP cards. This speeds up AVR tuning​ and “Volts Mismatch” diagnostics.

 

Field Engineer’s Notes (From the Trenches)

This board is “Blind”—zero LEDs. When the AVR goes unstable (VAR hunting), don’t just swap the M1 processor. Grab a Fluke 115.

Check TP1 to TP2 (Phase A-B). You should see the scaled PPT voltage (~1.6V AC for 120V secondary). If TP1-2 reads 0V but your PPT secondary panel reads 120V AC, the T2 transformer​ on the EACFG1B is open (likely cooked by a past surge on the grid).

Shield Drains: The DB9 cables (J504 etc.) have shield drains. The grounding screw is on the EACF metal chassis, within 3 inches of TB1. Land the shield drain there, not at a distant cabinet ground bar. Running the shield 10 feet to a remote bus creates a ground loop; 60Hz hum injects into your AC feedback, causing the generator to hunt under load swings.

Torque TB1-TB3. These are PPT inputs. A loose L2 connection causes “Phase Imbalance” or “Volts Loss” in the TMR vote. Use a 0.5-0.6 Nm driver; exciter fan vibration loosens standard screws over a year.

 

Real-World Applications

• 50MW Gas Turbine Generator (13.8kV:120V PPT):​ The EACFG1B handles PPT secondaries (~120V AC nominal). It scales and isolates these for the M1, M2, C controllers managing the static exciter’s AVR loop. The 480V rating is perfect for this PPT ratio.
• Industrial Steam Turbine (4160V Drive):​ Terminating Air Core CT​ signals (representing DC Field Current as AC). The G1 rating handles electrical noise from the 6-pulse thyristor bridge adequately for mid-size units, preventing spurious “Field Over Current” trips.

 

High-Frequency Troubleshooting FAQ

Q: ToolboxST shows “Voltage Feedback Loss” or “PPT Signal Invalid” on M1 only. EACFG1B looks fine. Where’s the fault?

A: The EACF fans out to all three. If only M1 complains, the issue is the DB9 Cable (J504)​ or the M1’s EBKP receiver, not the EACF board itself. Wiggle the thumbscrews on J504; vibration loosens these. If tight, ohm the 9-pin cable (Pin 2-3, 4-5, 6-7 for phases). A broken pin 3 kills the A-B voltage signal to M1.

A: Electrically functional, but suboptimal for control quality.​ Pinouts are identical, and it will “work” at 120V nominal. However, the G2’s T2/T3 transformers​ are wound for higher voltages. At 120V input, the output to the DB9 (scaled signal) is proportionally lower, reducing your signal resolution​ at the ADC. This can make the AVR loop “jittery” or slow to respond to small grid disturbances. Use G1 for G1-rated systems.

Q: TP1-TP2 reads 0V AC, but PPT secondaries are live at the terminal block. Is the board trash?

A: Likely, yes. Check for a blown fuse​ (if equipped on specific sub-revs) near T2. If the fuse is good, the T2 transformer​ winding is open (cooked from a past surge). The EACF is passive; if input power is verified at TB1/TB2 but test points are dead, the board took the hit. Verify no shorts on the PPT field wiring (L1-L2 short) before installing the replacement, or you’ll blow the new T2 in seconds.

Please note:​ The listed price is not the actual final price. It is for reference only and is subject to appropriate negotiation based on current market conditions, quantity, and availability.