The ABB UNITROL 1020 (Part No. 3BHE030579R0003) is an indirect excitation Automatic Voltage Regulator (AVR) of the BASIC variant under the UNITROL 1000 series. Equipped with a dedicated communication processor and dual control processors, it adopts an IGBT power topology. It delivers a continuous rated excitation output of 20A at 40°C and 15A under 55°C operating conditions, with a 10-second short-time overload capacity up to 40A. It is designed for excitation control of medium and small synchronous generators and synchronous motors.
This unit integrates a complete set of basic excitation control logics, supporting islanded reactive power sharing, dual-channel redundancy, rotating diode monitoring, and Modbus TCP Ethernet communication. It complies with global grid codes for fault ride-through requirements. Featuring a compact aluminum baseplate construction, the device can be directly mounted on the motor body. It withstands harsh operating conditions across multiple application scenarios including onshore power stations, marine vessels, locomotives, and wind turbine direct-drive synchronous machines. The supporting CMT1000 commissioning software enables parameter tuning, fault waveform recording and remote monitoring.
Model Decoding
Complete Model Designation: UNITROL 1020-0003Material Part Number: 3BHE030579R0003
UNITROL: The general product designation for ABB’s full range of static excitation systems1000: Product line category for compact low-voltage excitation controllers1020: Hardware model, representing a maximum continuous excitation output of 20A, equipped with a local LCD operator panel-0003: Software version identifier; 0003 corresponds to the BASIC feature package3BHE030579R0003: Global unified ordering part number for procurement and spare part matching
BASIC: Mid-tier software feature level, positioned between entry-level LIGHT and full-feature FULL versions. It supports expandable functions including grid synchronization, dual-channel redundancy, fieldbus communication and rotating diode monitoring.
Core Technical Features
Dual-processor separated architecture enables independent operation of communication and control tasks without mutual interference. Non-volatile flash memory stores time-stamped event logs and fault oscillographs for convenient fault tracing.
Wide-range AC/DC auxiliary power compatibility:
- Auxiliary control power supply: 9~300V three-phase AC / 18~420V DC
- Main power circuit input: 0~300V AC / 0~420V DC
- Steady-state voltage regulation accuracy: 0.2% at 25°C
- Three-phase measurement response time: ＜20ms; Single-phase measurement response time: ＜50ms
- PWM adjustment range: 0.5%~99%
Fully configurable I/O resources:3 analog inputs, 2 analog outputs, 12 digital channels (4 dedicated digital inputs + 8 bidirectional I/O). Built-in ±10V analog reference and integrated 24V/600mA relay power supply.
Multi-hardware communication interfaces:USB (offline commissioning without external power supply), Ethernet Modbus TCP, RS485 Modbus RTU, CAN bus (dual-channel interconnection with PM40 power modules).
Comprehensive limiting and protection logic:Multi-layer limit functions including upper/lower excitation current limits, Volts/Hertz ratio limit, P-Q reactive power limit, stator voltage limit and stator current limit. Integrated voltage boost and zero-voltage soft-start functions.
Environmental durability specifications:Operating ambient temperature: -40℃ ~ 70℃. Complies with DNV Marine Class B vibration standard and Level 2 shock resistance requirements, meets industrial EMC immunity standards, with IP20 ingress protection rating.
Local 4-line LCD human-machine interface supports local start/stop, parameter modification, and real-time display of terminal voltage and excitation current. Basic commissioning can be completed without upper monitoring software.
Exclusive Functional Features of BASIC Version
Disturbance-free switching of operating modes: Seamless transition between four regulation modes — constant voltage AVR, constant field current FCR, constant power factor PF, and constant reactive power VAR.
VDC Islanded Reactive Power Load Sharing:Up to 31 generating units realize synchronous reactive power equalization via RS485 bus to stabilize bus voltage, supporting both bus and ring network topologies.
Dual-channel Redundant Control:CAN bus enables setpoint tracking between master and standby channels, with automatic seamless switchover upon channel faults. The unit provides 23 equipment monitoring alarms and trip relay outputs.
On-line Rotating Diode Monitoring:Real-time detection of open-circuit and short-circuit faults on exciter rectifier diodes, with dedicated alarm contact outputs.
Modbus TCP Remote Control:Multi-terminal parallel monitoring, parameter reading and writing via Ethernet, supporting remote operation and maintenance through upper computer networking.
Voltage Matching Pre-synchronization:Automatically matches the amplitude of generator terminal voltage and grid voltage before grid connection; automatic grid synchronization can be realized when matched with an external synchronizing module.
Fast Fault Detection & Fault Ride-Through (FRT):Millisecond-level identification of grid voltage dips; dry contact outputs transmit signals to the governor for active power derating, complying with global grid fault ride-through standards.
Integrated logic for soft start, zero-voltage boosting and loss-of-excitation voltage boosting, optimized for small synchronous units with low residual voltage.
Application Fields
Onshore Power Generation
Small diesel, gas and hydroelectric generator sets, distributed self-consumption power plants, and synchronous generators for industrial waste heat recovery.
Marine Sector
Excitation control for marine main generators, marine propulsion synchronous motors and marine auxiliary power supplies, with DNV marine classification certification.
Rail Transit
Excitation regulation for main synchronous motors of diesel-electric locomotives.
Wind Power Generation
Excitation control for direct-drive synchronous wind turbines.
Industrial Motors
Voltage stabilization control for large synchronous drive motors and synchronous condensers in steel mills and chemical plants.
Working Principle
The device adopts closed-loop regulation with a DSP digital PID core. It collects feedback signals including generator terminal voltage from PTs, stator current from CTs and excitation current. It calculates the deviation between the collected signals and setpoints from the local panel or remote terminals, then outputs PWM pulses to drive the internal IGBT power unit. By adjusting the DC excitation output current, the magnetic field strength of the synchronous machine rotor is modified to stabilize the generator terminal output voltage.
The hardware adopts a layered architecture consisting of a measurement & acquisition layer, dual-core control layer, power output layer and communication & I/O layer:
- Measurement LayerIsolated acquisition of three-phase generator voltage, single-phase grid voltage, stator current and excitation current signals; analog-to-digital conversion is performed before data is transmitted to the DSP.
- Control LayerThe DSP executes voltage regulation algorithms, various limiting logics and synchronization judgment. A separate MCU processes the human-machine interface, fieldbus communication and fault data storage. Data exchange between the two chips is realized via an internal bus.
- Power LayerIt adopts an IGBT single-phase full-bridge rectifier topology, converting wide-range AC and DC input into controllable DC excitation output, with built-in short-circuit current limiting protection.
- Communication & I/O LayerDigital and analog I/Os receive external switch signals and analog setpoints. Multiple buses enable data exchange between upper monitoring systems, redundant control channels and power expansion modules.
Product Comparison (Within the UNITROL 1000 Series)
UNITROL 1010 (LIGHT/BASIC): Maximum excitation output of 10A, no local display panel. It only provides basic voltage regulation and does not support dual-channel redundancy or rotating diode monitoring. Suitable for ultra-low-power generator sets with cost constraints.
UNITROL 1020-0002 LIGHT (3BHE030579R0002): 20A excitation output. Only equipped with basic voltage regulation and limiting functions, without Modbus communication, dual-channel redundancy or VDC reactive power load sharing.
UNITROL 1020-0003 BASIC (3BHE030579R0003, This Product): Complete BASIC function package. Supports fieldbus communication, dual-channel redundancy, rotating diode monitoring, islanded reactive power sharing and voltage matching pre-synchronization. It excludes event logging, data waveform recording and built-in automatic grid synchronization.
UNITROL 1020-0006 FULL: Built upon the BASIC version, it adds 500 event records, 12-channel data oscillography, an integrated automatic synchronizer and a real-time clock.
UNITROL 1020-0007 FULL+PSS: Retains all functions of the FULL version with an additional built-in Power System Stabilizer (PSS) to suppress low-frequency oscillations. Designed for large-capacity grid-connected generating units.
UNITROL 1000-PM40 Power Expansion Module: Matched for use with UNITROL 1020. It boosts the maximum continuous excitation output to 40A with a short-time overload capacity of 80A, and achieves coordinated control via CAN bus.
FAQ
Q1: What are the core differences between 3BHE030579R0003 and 3BHE030579R0006?
A1: The former features the BASIC software package with dual-channel redundancy, Modbus communication, VDC reactive power sharing and rotating diode monitoring. The latter is the FULL version, additionally equipped with an event recorder, data waveform recording, built-in fully automatic synchronizer and hardware real-time clock. It is ideal for power stations requiring fault tracing and frequent grid connection operations.
Q2: How to handle cases where the excitation current of a single unit exceeds 20A?
A2: Deploy the UNITROL 1000-PM40 power expansion module, which connects to the UNITROL 1020 main controller via CAN bus. The continuous excitation output is increased to 40A with a 10-second short-time overload rating of 80A, meeting the requirements of high-power exciters.
Q3: Can this model be directly selected for marine projects?
A3: Yes. The product holds DNV Marine Class B certification and adopts a wide-temperature, vibration-resistant design. Only marine-specific shielded cables are required, along with moisture-proof protection for the control cabinet.
Q4: Is equipment commissioning possible without an external 220V auxiliary power supply?
A4: Yes. Connect a laptop via USB to power the core controller. Parameter reading, modification and firmware upgrades can be completed, while no output will be generated from the power excitation circuit.
Q5: What are the key wiring points for a dual-channel redundant control system?
A5: Link two UNITROL 1020 controllers via CAN bus and install a termination jumper on terminal X1302. Parallel the PT and CT measurement signals to both controllers. Digital I/O ports transmit fault switchover signals between the two units, and setpoints of the master and standby channels track each other in real time.
Q6: What faults typically cause the red alarm light to stay illuminated?
A6: Three common fault types: open circuit of generator terminal voltage PT, short/open circuit of excitation output, and startup parameter verification failure. Connect the CMT1000 commissioning software to read event logs for accurate fault localization.
Q7: How to resolve uneven reactive power distribution when multiple diesel generator sets operate in parallel?
A7: Enable the VDC voltage droop compensation function. Daisy-chain all AVR units via RS485 bus, assign a unique unit ID to each controller, set a unified droop coefficient Kq = -5%, and restart the reactive power sharing function to balance the load.
Q8: Can spare parts be matched by only providing the model UNITROL 1020 during procurement?
A8: No. The complete material part number 3BHE030579R0003 must be provided. The same UNITROL 1020 hardware supports multiple software versions including LIGHT, BASIC and FULL, and each part number uniquely corresponds to a specific functional configuration.
Recommended Models of the Same Brand
UNITROL 1005 Compact Low-Voltage AVRUNITROL 1010-0002 LIGHT Excitation RegulatorUNITROL 1020-0003 BASIC (3BHE030579R0003)UNITROL 1020-0007 FULL+PSS Excitation ControllerUNITROL 1000-PM40 40A Power Expansion ModuleUNITROL 6080 Thyristor Static Excitation EquipmentUNITROL 6000 Medium Excitation System for Medium-Sized UnitsUNITROL 8000 High-Capacity Static Excitation SystemUNL 13300 High-Power Static Excitation CabinetUNL 14300 Turbo-Generator Excitation SystemSYNCHROTACT 5 Automatic Synchronizing DeviceSYNCHROTACT 6 Advanced Grid Synchronizing Equipment
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