This original ABB control and signal interface board with commercial part number UFC921A101 is also named INT-2 board. It is designed for UNITROL5000 static excitation system of synchronous generators and ACS2000 medium voltage converters under AC800PEC control platform. The whole PCB is covered with three-proof conformal coating to resist moisture, dust and corrosive gas inside control cabinets. It adopts standard rack plug-in structure connected with backplane bus as core intermediate signal conversion component. Original mass production has been discontinued, and the product is only supplied as aftermarket spare parts for maintenance and renovation of power plant excitation cabinets and medium voltage converter equipment.

3BHE is the unified fixed spare part prefix for ABB printed circuit boards of excitation and medium voltage drive products.024855 is the exclusive internal hardware development serial number defined by ABB R&D department for UFC921A101 hardware platform.R0101 represents the first official mass-production hardware revision without subsequent circuit modification.UFC921A101 is the standardized commercial ordering code of this complete module.

Rated auxiliary operating power is DC24V±10%, typical power consumption is less than or equal to 7W. Operating ambient temperature ranges from -20℃ to +65℃, storage temperature ranges from -40℃ to +85℃, relative humidity keeps between 5%RH and 95%RH under non-condensing condition. Optocoupler isolation is arranged between low voltage control circuit and high voltage sampling circuit with isolation withstand voltage of 2000VAC, complying with IEC61000 EMC anti-interference standard. The overall dimension is 257mm×125mm×30mm, net weight is approximately 0.34kg with IP20 protection grade for cabinet built-in installation. The refresh cycle of multi-channel analog signal sampling is controlled within 60μs.

Rear gold-finger connector inserts into rack backplane bus to exchange internal data with main control CPU via ABB proprietary internal bus protocol. Front terminal blocks are used for external wiring of PT/CT sampling signals, thyristor trigger feedback signals and field digital input & output circuits. Multiple LED indicators on panel display power supply status, running state and channel fault alarm information. Only factory dedicated test pads are reserved on PCB for offline calibration, no independent external fieldbus communication port is configured.

The board collects stator voltage, field current and grid synchronization analog signals from external instrument transformers, implements filtering and signal conditioning before uploading processed data to upper master control board. It receives excitation regulation commands from main controller and distributes control pulses to each thyristor trigger drive board of rectifier bridge. Integrated protection logics including overvoltage, overcurrent, loss of synchronization and over-excitation interlock will lock excitation output immediately and upload fault codes once abnormal working conditions are detected to protect generator set and rectifier power components.

It is installed inside UNITROL5000 excitation cabinets for synchronous generator units of thermal power plants and hydropower stations, and also matched with control cabinets of ACS2000 medium voltage converters. Typical application fields include generator excitation system of power plants, medium voltage main fan drive for mining industry, heavy-load main transmission of cement rotary kilns and variable frequency drive equipment of large compressors in petrochemical industry.

Cut off cabinet main AC power and DC24V auxiliary control power completely before disassembly or regular maintenance, and keep power disconnected more than 30 minutes to release residual capacitor energy and avoid static damage to precision onboard chips. Complete annual maintenance by cleaning dust and oxide on PCB surface and gold-finger contacts with dry soft brush, and check wiring tightness and cable aging condition of all external terminals regularly. When excitation system or medium voltage converter triggers sampling or channel failure alarms, inspect external sensor wiring preferentially before module replacement. Unauthorized disassembly of original components and arbitrary circuit modification are strictly forbidden; replace with brand-new complete module after permanent hardware damage is verified via professional inspection.