ABB 3BHB026281R0001 Special Circuit Board Card for Generator Excitation System

ABB 3BHB026281R0001 Special Circuit Board Card for Generator Excitation System
I. Basic Ownership Information
Brand: ABB (now Hitachi Energy)
Material Order Number: 3BHB026281R0001
Prefix Definition: 3BHB = ABB’s high-power power electronic, UNITROL generator excitation system dedicated circuit board series
Applicable System: UNITROL 5000 / UNITROL 6000 large-scale generator static excitation control system (mainstream AVR excitation platform for thermal power, hydropower, and gas turbine generators)
Category: Excitation System, Pulse Trigger / Power Interface Driver Board (Thyristor Gate Trigger Board)

Core Functional Usage
Generation of trigger pulses for thyristor SCR rectifier bridge and power drive
Receive regulation instructions issued by the excitation main control AVR board, generate multiple isolated high-frequency trigger pulses, directly send to the thyristor (SCR) gate of the power cabinet, precisely control the output voltage / current of the excitation rectifier bridge, and achieve generator terminal voltage and reactive power closed-loop regulation (core execution unit of AVR).
Loop status collection and feedback
Real-time collection of thyristor anode voltage, trigger circuit disconnection, power bridge fault signals, and upload to the main control board for fault diagnosis, overcurrent / overvoltage protection locking.
Power and weak current electrical isolation
Optical isolation between the high-voltage power circuit and the low-voltage control circuit, avoiding strong current interference damaging the main control unit and meeting the strict electromagnetic compatibility requirements of power stations.
Redundant system compatibility
Compatible with UNITROL dual-channel redundant excitation architecture, a single board card failure does not cause the entire excitation system to trip.

Key Hardware Electrical Parameters
Power Supply Specifications: Powered by the 24VDC DC power supply of the excitation machine frame backplane
Output Channels: 6 independent isolated thyristor trigger channels (compatible with three-phase fully controlled rectifier bridge)
Isolation Level: 2500VAC power and weak current insulation withstand voltage
Power Consumption: 8~12W
Environmental Conditions
Operating Temperature: -25℃ ~ +60℃
Storage Temperature: -40℃ ~ +85℃
Humidity: 5%~95% RH (no condensation)
Protection Grade: IP20 (plug-in installation inside the cabinet)
Structure: European-style box backplane plug-in, front panel status LED indicator, supports online plug-in and replacement of the cabinet
Weight: Approximately 0.75kg

Panel Indicator Light Meanings (Field Fault Troubleshooting)
PWR: Power indicator light (always on = normal power supply)
RUN: Operation indicator light (flashing = normal pulse output)
FAULT: Fault alarm red light (trigger circuit disconnection, thyristor breakdown, power abnormality will be lit)
CH1~CH6: Six trigger channel status lights

 Lifecycle Status (as of July 2026)
Original Factory Status: Old hardware version, already discontinued EOL
UNITROL5000 early hardware iteration product, has now upgraded to the new trigger board hardware; Hitachi Energy no longer batches produce original factory new machines, only accepts power station maintenance spare parts orders.
Supply Channel
New original factory inventory pieces: Low inventory, long procurement cycle, and high price;
Disassembly inspection refurbished pieces: The most commonly used replacement supply source for excitation power cabinets in domestic power plants and hydropower stations, all with load simulation tests before shipment;
Version Compatibility: The same as the 3BHB prefixed derivative boards with the same function, hardware pins, and program logic are intercommunicable, and the configuration can be adjusted directly for interchange.

Typical Application Scenarios
UNITROL5000 excitation power cabinet for large steam turbine generators and water turbine generators;
Excitation system for combined cycle gas power plants’ self-owned units;
Power plants of steel mills and refineries for synchronous generator AVR voltage regulation power unit.