Description

The 3BHB002916R0101​ (module designation UFC721AE) is a scaling card / signal-conditioning PCB manufactured by ABB, belonging to the UFC (Unitrol Field Card) family that serves ABB UNITROL-series excitation systems — particularly UNITROL 6000 and the earlier UNITROL F/P generations controlling synchronous generators and large synchronous motors. Its core job is to receive raw analog feedbacks from the field (PT secondary, CT secondary, rotor shunt/milli-volt drop across the field breaker) or scaled references from the AVR logic, apply precision gain/offset (via onboard calibration elements or software-mapped range registers), and present a conditioned signal to the excitation controller (typically AC800PEC-based in UNITROL 6000) or onward to annunciation/limiter blocks.Mounted inside the UNITROL controller cubicle on the internal rack, drawing 24 V DC from the backplane, and hot-swappable in redundant controller configurations, the 3BHB002916R0101​ is one of those “invisible but consequential” spares: when its scaling elements drift after 15–20 years, the AVR still runs, but generator voltage reading, field-current reading, and consequently the OEL/UEL/P/Q limiter thresholds all drift — and that’s how a plant ends up with a “stronger than designed” overexcitation event or a nuisance V/Hz trip.

Application Scenarios

On a 220 MW thermal unit in Southern Europe running UNITROL 6000 (Medium, ~1200 A excitation), the protection engineer noticed a slow divergence: the DCS was logging stator voltage at 15.8 kV while the generator VT panel meter (calibrated) read 16.02 kV — a ~1.4 % spread that had widened from <0.3 % three years prior. The AVR’s own “Generator V” reading (visible on the ECT HMI) agreed with the DCS, not the VT meter. The unit had been through a 10-year mid-life inspection but the UFC-series scaling cards were left “if it ain’t broke.” The culprit turned out to be the 3BHB002916R0101​ (UFC721AE) on the PT-secondary input path — one gain-stage trim resistor had drifted ~1.8 % from thermal cycling, and because the card has no active temperature compensation on that legacy element, the AVR had been regulating to a slightly wrong Vref for months. Swapping the 3BHB002916R0101​ (genuine ABB, 3BHB002916R0101 traceable) and re-running the factory calibration routine in the ECT tool brought the spread back to <0.1 %. The engineer’s closure note: “Next 10-year outage, 3BHB002916R0101​ gets pulled and checked even if the AVR looks happy.” For any plant running UNITROL F/P or 6000 with >15-year cards, the scaling card is usually the quietest source of “why is my limiter hitting early/late.”

Parameter

Main Parameters	Value/Description
Product Model	3BHB002916R0101​ (UFC721AE)
Manufacturer	ABB
Product Category	Scaling Card / Signal Conditioning PCB (UFC series, UNITROL excitation)
Compatible Systems	UNITROL 6000 (Medium/X-power), UNITROL F/P legacy
Host Controller	AC800PEC (UNITROL 6000) / earlier UNITROL F/P processor
Supply Voltage	24 V DC (via UNITROL rack backplane)
Signal Path	PT secondary / CT secondary / rotor shunt mV → scaled ±10 V or 4–20 mA to AVR (path depends on slot assignment)
Calibration	Onboard scaling elements (legacy) + software range mapping via ECT/PSI tool
Isolation	Galvanic between field analog and backplane logic (typ. ≥ 1 kV functional, per UFC family)
Mounting	UNITROL controller rack slot (internal cubicle, guided rail + backplane header)
Operating Temp.	0 °C to +55 °C (control-room/cubicle spec)
Hot-Swap	Yes (in redundant controller config; single-controller swap requires AVR pause)
Dimensions (PCB)	~160 × 100 × 20 mm (UFC card format, consistent with UFC719/UFC722)
Weight	~0.2 kg

 

Technical Principles and Innovative Values

• Innovation Point 1: Precision Scaling Between Field Sensors and AVR Loop.​ The 3BHB002916R0101​ sits at the boundary where “real-world analog” (PT 110 V secondary, CT 5 A/1 A, rotor shunt 60 mV) meets “AVR math” (±10 V or 0–20 mA internal range on the AC800PEC I/O). Its gain/offset staging converts the field signal into the AVR’s expected window with <0.5 % class accuracy when new — and that accuracy is what the OEL (over excitation limiter), UEL (under excitation limiter), V/Hz limiter, and P/Q droop all implicitly trust. When the 3BHB002916R0101​ drifts, every limiter drifts with it.
• Innovation Point 2: Software-Calibrated Ranges + Legacy Trim Compatibility.​ The UFC721AE generation sits at the transition where ABB moved scaling from “all-hardware trim pots” toward “software range registers with hardware pre-scale.” The 3BHB002916R0101​ supports both paths: you can re-map the range in the ECT/PSI engineering tool (e.g., “Generator V: 0–20 kV → 0–10 V internal” or “Field I: 0–3000 A → 0–60 mV shunt”) without touching the PCB, but the hardware pre-scale elements still matter for noise floor. That hybrid approach is why a 3BHB002916R0101​ swap sometimes needs a 10-minute ECT re-calibration, not just a “plug and play.”
• Innovation Point 3: Rack-Backplane Integration with Redundant Controller A/B.​ In a dual-channel UNITROL 6000 (A and B controller racks), each rack carries its own 3BHB002916R0101​ — the AVR logic votes or hot-transfers between them. The card’s backplane header carries both the 24 V DC feed and the analog bus to the AC800PEC, so a failed 3BHB002916R0101​ in Channel A doesn’t take the excitation offline; Channel B carries the regulator while you swap. This is the difference between “night-shift card swap” and “trip-to-zero.”

 

Application Cases and Industry Value

A 400 MW combined-cycle plant in East Asia running UNITROL 6000 X-power (excitation ~4500 A) on the two 200 MW TG sets had a subtle problem: during a grid disturbance event, the OEL (over excitation limiter) on Unit 1 acted ~4 seconds earlier than Unit 2 under the same V/Hz trajectory. Post-event waveform review showed Unit 1’s field-current reading (derived from rotor shunt → 3BHB002916R0101​ → AVR) was reading ~3 % high versus the standalone DC millivolt logger they’d temporarily clamped across the shunt. The 3BHB002916R0101​ on Unit 1 was original (16 years), and the shunt-pre-scale element had drifted. They sourced a genuine 3BHB002916R0101​ (3BHB002916R0101, UFC721AE), swapped it during the next synchronization window (redundant Channel B carried the regulator), re-ran the ECT auto-cal on the field-current path, and the OEL timing matched Unit 2 within 0.2 s on the next disturbance. The plant’s protection lead’s note: “The scaling card isn’t sexy, but the OEL is only as honest as the shunt signal the 3BHB002916R0101​ feeds it.”In a second case, a hydro plant on a 125 MW Francis runner (UNITROL F/P vintage, later retrofitted with AC800PEC front-end but keeping the UFC-series analog front-end cards) had the “Generator V” on the ECT slowly climb 1.2 % over two years relative to the utility’s VT-check portable. The F/P-era 3BHB002916R0101​ (same 3BHB index, carried over into the retrofit) was the suspect; they’d been planning a full UFC-row refresh anyway, so they rotated all three UFC cards (including the 3BHB002916R0101) during the annual outage. Post-refresh, the VT-check delta stayed <0.15 % over the next 36 months.

Related Product Combination Solutions

Build a coherent UNITROL spare row around the 3BHB002916R0101​ with these companion ABB models:

• UFC719AE01 / UFC719AE101​ — Sibling UFC card (often the “measuring/IO” companion to the 3BHB002916R0101​ scaling role); in many UNITROL 6000 racks the two share the same row.
• PCD235A101 (3BHE032025R0101)​ — UNITROL excitation controller module (the “brain” that the 3BHB002916R0101​ feeds scaled analogs into); common in UNITROL 6000 Medium.
• GFD233A 3BHE022294R0101​ — Another UNITROL excitation control module; plants running mixed UFC + GFD rows often cross-reference.
• ABB AC800PEC​ — The high-performance controller platform that hosts the AVR/PSS logic in UNITROL 6000; the 3BHB002916R0101​ lands its scaled signals onto the AC800PEC I/O.
• KUC711AE101 3BHB004661R0101​ — Advanced voltage-regulation module in the broader UNITROL ecosystem; useful cross-reference when diagnosing whether a “wrong Vreg” fault is 3BHB002916R0101​ (scaling) vs. KUC711 (regulation).
• ABB 1KHL178012R0016A TRM01​ — The 24 V / 16 A DIN PSU (earlier in this series); the UNITROL cubicle’s 24 V backplane that feeds the 3BHB002916R0101​ often originates from a TRM01 or equivalent in the same relay room.