Thyristor Constant Current Regulator for Airfield Ground Lighting
Controlled series-circuit current, sized to the circuit it actually serves
A Constant Current Regulator (CCR) is a key power-control component in a series-circuit Airfield Ground Lighting system. It supplies controlled current to runway, taxiway, approach and other series-connected lighting circuits, allowing connected fixtures to operate at defined intensity levels. Precision AGL Solutions supplies and supports thyristor constant current regulators for airport lighting projects, replacement programs, system upgrades and new AGL installations.
Constant Current Regulator
A CCR maintains the required circuit current despite changes in the connected series-circuit load within its specified operating range. In an AGL series circuit, fixtures are connected through isolating transformers and associated primary circuit components; the CCR is the controlled source for that circuit and plays an important role in consistent lighting performance.
A thyristor-based regulator uses controlled semiconductor switching to regulate output power, supporting controlled current levels and, depending on configuration, multiple brilliance settings. Typical CCR systems may include:
- Thyristor power-control assembly
- Input power section
- Output series-circuit section
- Control electronics
- Current regulation and sensing
- Protection functions
- Alarm and monitoring interfaces
- Local controls and indications
- Remote control interface where specified
- Enclosure and internal switching/protection equipment
The exact configuration depends on the selected CCR rating and project requirements.
Where Thyristor CCRs Are Used
The CCR rating and configuration should be selected after determining the complete connected series-circuit load and the electrical characteristics of the installed lighting system.
Thyristor Control and Current Regulation
Thyristor-Controlled Operation
- Controlled constant-current output
- Multiple selectable brilliance steps
- Local and remote control
- Current monitoring
- Fault, alarm and status indication
- Interface with an airfield lighting control system
Constant Current Regulation
- Regulates to the specified current rather than a fixed voltage
- Accommodates changes in series-circuit characteristics within its designed range
- Sizing considers total load, fixture count and type, isolating transformer ratings
- Also considers circuit resistance and impedance, cable characteristics, maximum circuit voltage
- Starting and operating conditions must be included
CCR sizing should be completed as part of the overall series-circuit design, not as an isolated equipment selection. The control arrangement should follow the airport's AGL control philosophy and existing infrastructure.
Multi-Step Brilliance Control
Airfield lighting commonly requires different intensities depending on operational conditions, visibility and circuit type. Where applicable, the CCR provides multiple predefined current settings so the connected circuit can operate at different brilliance levels. The number and value of the steps should be established from the project specification.
- Number of required intensity steps
- Rated series-circuit current
- Minimum and maximum operating current
- Lighting fixture characteristics
- Circuit load
- Control system interface
- Local/remote operation requirements
- Airport operational procedures
The CCR should be coordinated with the connected lighting equipment so that each selected current level produces the intended system performance.
Input, Output, Control and Protection
Input & Output
- Input supply voltage
- Number of phases
- Input frequency
- Rated output current
- Maximum output voltage
- Output power rating
- Series-circuit load range
- Control and auxiliary supply
Control & Monitoring
- Local control
- Remote brilliance selection
- Run/stop command
- Circuit status
- Regulator fault indication
- Remote status contacts
- Control-system interface
- Communication interface where specified
Protection
- Input protection
- Output overcurrent protection
- Open-circuit protection (output de-energised if the series circuit opens)
- Overvoltage and surge protection
- Thermal and semiconductor protection
- Internal fault and control circuit protection
- Earth/insulation fault monitoring where specified
- Alarm indication
Confirm the electrical arrangement against the project single-line diagram and equipment schedule. Interface requirements should be set at design stage, and protection settings coordinated with the upstream distribution and the connected series circuit.
Typical Specification / Selection Requirement
| Parameter | Typical Specification / Selection Requirement |
|---|---|
| Regulator Type | Thyristor-controlled constant current regulator |
| Rated Current | Project-specific |
| Input Voltage | Project-specific |
| Input Frequency | 50 Hz or 60 Hz, by project. India (50 Hz): L-829 designation; 60 Hz: L-828 (FAA AC 150/5345-10H). Confirm the model rating. |
| Output Voltage | Determined by circuit load and regulator rating |
| Output Power | Selected according to connected series-circuit load |
| Brilliance Steps | Project-specific; multi-step operation where applicable |
| Current Regulation | Constant-current controlled output |
| Control Interface | Local and/or remote, according to project |
| Monitoring | Status and alarm functions according to configuration |
| Protection | Electrical, thermal and control protection as applicable |
| Efficiency | Model- and load-dependent |
| Cooling | Equipment-specific |
| Enclosure | Indoor/outdoor arrangement according to installation |
| Dimensions | Model-specific |
| Weight | Model-specific |
| Installation | Electrical equipment room, CCR shelter or designated installation location |
India (50 Hz): specify the 50 Hz (L-829) regulator and IEC 61822 where the project follows IEC, and confirm input frequency and series-circuit current on the datasheet. Final technical values should always be confirmed against the selected CCR model and project datasheet.
CCR Sizing and Selection
Correct sizing is one of the most important steps in designing an AGL series circuit. Precision AGL Solutions supports selection from the available project information:
This avoids selecting a regulator on nominal current alone while overlooking the complete circuit load and operating conditions. Allow for isolating-transformer and cable losses and for planned future expansion. Do not oversize either: a regulator that is lightly loaded gives a poorer power factor and waveform, and this matters after halogen-to-LED conversion, where the connected load drops sharply. Re-check the regulator against the new load.
Integration with AGL Series Circuits
Each component must be electrically compatible with the selected regulator. The design should consider CCR output current, cable length and impedance, transformer ratings, fixture load, circuit insulation and continuity, expected operating voltage and required brilliance settings.
Incorrect matching between the CCR and series circuit can result in unsuitable current regulation, excessive circuit voltage, nuisance alarms or reduced system performance.
Installing and Commissioning the CCR
Installation Considerations
- Suitable equipment-room or enclosure location
- Adequate ventilation and heat dissipation
- Electrical clearances and incoming supply protection
- Series-circuit output connection
- Control and monitoring wiring
- Earthing arrangements and cable routing
- Accessibility for inspection and maintenance
- Coordination with airport electrical distribution
Commissioning Activities
- Verification of input supply and electrical connections
- Earthing verification
- Series-circuit continuity and insulation resistance checks
- Output-current verification with a true-RMS instrument (phase-controlled output is not a pure sine wave)
- Verification of brilliance steps
- Control-interface, alarm and remote-control testing
- Circuit operation at required intensity levels
- Documentation of commissioning measurements
For replacement projects, check the existing feeder, series circuit, control interface and protection arrangement before installing a new regulator. Commissioning should follow the manufacturer's instructions and the approved testing and commissioning plan.
Maintenance and Common CCR Problems
Routine maintenance supports reliable CCR operation. Activities may include visual inspection, cleaning of equipment and ventilation areas, inspection of connections, cooling and protection systems, verification of indications, alarms, output current and brilliance-step operation, functional testing of control interfaces, checking for overheating or abnormal noise, and review of recorded faults. Intervals should follow the manufacturer's recommendations and the airport's maintenance program.
Replacing Ageing or Obsolete Regulators
Thyristor CCRs can replace ageing or obsolete regulator equipment where the existing AGL infrastructure remains suitable. Before replacement, review:
- Existing CCR rating
- Existing series-circuit current
- Circuit load
- Input supply
- Existing control interface
- Remote-control arrangement
- Alarm requirements
- Existing cabinet dimensions
- Cable termination arrangement
- Available spare capacity
A replacement should not be selected solely from the rating of the existing unit. The actual installed circuit should be evaluated to confirm compatibility.
Quotation Checklist
When requesting a CCR quotation, provide as much of the following as possible:
- AGL application
- Runway, taxiway or approach circuit
- Required rated current
- Input supply voltage and frequency
- Existing CCR rating, if replacement
- Number of brilliance steps
- Series-circuit load
- Existing control system
- Required remote interface
- Alarm requirements
- Installation environment
- Existing cabinet or mounting dimensions
- Project standards/specification
- Required quantity
- Existing equipment make/model
This lets the CCR be selected against the actual project requirements.
Electrical Safety — Isolation and Lock-Out
WARNING — never open a live series circuit. An open series circuit driven by a constant-current regulator can produce dangerously high voltage. Opening, cutting or disconnecting any part of an energised circuit can cause serious injury or death and damage equipment.
- De-energise the circuit at the regulator and apply the site lock-out / tag-out (LOTO) procedure before any work
- Where the circuit must be isolated or shorted, use the series circuit cut-out switch or approved isolation device — not an improvised bypass
- Verify the circuit is de-energised and the output is isolated before touching conductors, connectors, splices or transformers
- Open-circuit protection in the regulator is a protective function, not a method of isolation — always isolate and lock out first
- Work only under the airport's permit-to-work system, using qualified personnel and the manufacturer's instructions
- Follow the applicable national electrical safety regulations and site procedures
CCR Specification and Ratings
FAA Specification
Constant current regulators and regulator monitors for airport lighting series circuits are covered by FAA AC 150/5345-10H — Specification for Constant Current Regulators and Regulator Monitors. The specification defines the L-827 regulator monitor, the L-828 regulator (without monitoring) and the L-829 regulator (with monitoring). Class 1 is a 6.6 A output and Class 2 a 20 A output. Style 1 has three brightness steps and Style 2 has five. The AC covers other regulator designs as well as thyristor types. Confirm the current edition and the applicable class/style designation with the manufacturer datasheet.
Also review IEC 61822 (constant current regulators for aerodrome lighting), ICAO Annex 14 Vol. I Chapter 8, the ICAO Aerodrome Design Manual (Doc 9157) Part 5 — Electrical Systems, and applicable national electrical requirements.
Ratings to Specify
- Regulator rating (kVA) matched to the connected circuit load
- Rated output current and available current steps (for example 3-step or 5-step brightness control; on a 6.6 A circuit the FAA steps are typically 4.8 / 5.5 / 6.6 A for 3-step and 2.8 / 3.4 / 4.1 / 5.2 / 6.6 A for 5-step; on a 20 A circuit the 5-step values are typically 8.5 / 10.3 / 12.4 / 15.8 / 20 A — confirm against the project specification)
- Input supply voltage and frequency
- Regulator class/style per the applicable specification
- Monitoring and remote-control interface
Exact kVA and current ranges offered are supplied on the manufacturer datasheet for the project.
Harmonics, Power Factor and EMI
Thyristor (phase-controlled) regulators draw non-sinusoidal current and can introduce harmonic distortion, a reduced input power factor at low brightness steps, and electromagnetic interference. These matter when sizing standby generators and UPS supplies and when routing sensitive control or communication cables.
- Request total harmonic distortion (THD) and power-factor figures at each brightness step from the datasheet
- Size generators and UPS with harmonic loading and power factor in mind
- Check EMI/EMC compliance and filtering requirements with the manufacturer
- Separate regulator output cabling from low-level signal and communication cables
- ICAO Annex 14 Chapter 8 sets maximum switch-over times to the secondary power supply by runway type, so check how quickly the regulator restarts and restores output after a supply change
Standards, References and Documents
Standards and References
- FAA AC 150/5345-10H — Constant Current Regulators and Regulator Monitors (L-828 / L-829)
- FAA AC 150/5345-47C — Series to Series Isolation Transformers for Airport Lighting Systems
- FAA AC 150/5345-7F — L-824 Underground Electrical Cable for Airport Lighting Circuits
- FAA AC 150/5345-53D — Airport Lighting Equipment Certification Program
- IEC 61822 (constant current regulators) and IEC 61821 (maintenance of series circuits)
- ICAO Annex 14 Vol. I Chapter 8 and Aerodrome Design Manual (Doc 9157) Part 5 — Electrical Systems
- Airport authority, DGCA and project specifications, and applicable national electrical regulations
- Manufacturer installation and testing requirements
Typical Documentation
- CCR datasheet and technical specifications
- Rated-current and input/output electrical data
- Control-interface, protection and alarm information
- General arrangement drawings and wiring diagrams
- Installation instructions and commissioning procedures
- Test documentation
- Operation and maintenance information
- Spare-parts information
The applicable edition and equipment-specific requirements should be verified during project design and procurement. Documentation requirements should be agreed in the procurement specification.
Support Matched to Your Circuit
We support airport lighting projects with equipment selection based on the actual requirements of the airfield lighting system. The objective is a regulator appropriately matched to the connected series circuit and the airport's operational control requirements.
Thyristor Constant Current Regulator — Frequently Asked Questions
What is a thyristor constant current regulator?
A thyristor CCR uses controlled semiconductor switching to regulate output power, giving a controlled constant-current supply to runway, taxiway, approach and other series-connected lighting circuits, with multiple brilliance settings depending on configuration.
What does a CCR do in an AGL series circuit?
It maintains the required circuit current despite changes in the connected series-circuit load within its specified operating range. Fixtures connect through isolating transformers and primary circuit components, and the CCR is the controlled source for the circuit.
Which designation applies for 50 Hz systems such as India?
For India (50 Hz), specify the 50 Hz regulator, designated L-829, and IEC 61822 where the project follows IEC. The 60 Hz designation is L-828 under FAA AC 150/5345-10H. Confirm the input frequency and series-circuit current on the datasheet. See also the ferroresonant CCR page.
How is a thyristor CCR sized?
Sizing considers the series-circuit type, the number and type of fixtures and isolating transformers, the required circuit current and brilliance settings, circuit resistance and impedance, cable characteristics, maximum circuit voltage, control and monitoring requirements and environmental conditions. Allow for transformer and cable losses and planned future expansion, but do not oversize, because a lightly loaded regulator gives a poorer power factor and waveform.
Does LED conversion affect the regulator?
Yes. After halogen-to-LED conversion the connected load drops sharply, and a lightly loaded regulator gives a poorer power factor and waveform, so re-check the regulator against the new load.
What brilliance steps are provided?
Where applicable the CCR provides multiple predefined current settings so the circuit can operate at different brilliance levels. The number and values of steps should be established from the project specification, the rated series-circuit current, the fixture characteristics and the control system interface.
What protection and monitoring functions does it include?
Depending on configuration: input protection, output overcurrent protection, open-circuit protection (output de-energised if the series circuit opens), overvoltage and surge protection, thermal and semiconductor protection, internal fault and control circuit protection, earth or insulation fault monitoring where specified, and alarm and status indication, with local and remote control interfaces.
How is the output current verified at commissioning?
Use a true-RMS instrument, because phase-controlled output is not a pure sine wave. Commissioning also covers input supply and connections, earthing, series-circuit continuity and insulation resistance, brilliance steps, control, alarm and remote-control testing, circuit operation at the required intensity levels and documentation of the measurements.
What should I check when the current is unstable or a step does not work?
For incorrect or unstable current, check the configuration, whether the circuit load is outside range, series-circuit faults, control-system issues or an internal regulator fault. For a brilliance step not operating, check the control input, step-selection configuration, CCR settings, control-system command and regulator fault status. Do not simply reset repeated alarms; assess the regulator, series circuit, transformers and control system together.
What should be reviewed before replacing an ageing regulator?
Review the existing CCR rating, series-circuit current, circuit load, input supply, control interface, remote-control arrangement, alarm requirements, cabinet dimensions, cable termination arrangement and available spare capacity. A replacement should not be selected solely from the rating of the existing unit.
Is it safe to open a series circuit while the regulator is running?
No. An open series circuit driven by a constant-current regulator can produce dangerously high voltage. De-energise the circuit at the regulator, apply lock-out / tag-out, use the series circuit cut-out switch or approved isolation device and work under the permit-to-work system. See the electrical safety warning on this page.
What information should I provide for a CCR quotation?
Provide the AGL application and circuit, required rated current, input supply voltage and frequency, existing CCR rating for replacements, number of brilliance steps, series-circuit load, existing control system, remote interface and alarm requirements, installation environment, existing cabinet dimensions, project standards, quantity and existing equipment make and model.
Procurement Information for Indian Projects
Indian public tenders commonly ask for the documents below. State which ones your tender requires when you send the enquiry, so they are covered in the quotation.
- Manufacturer / OEM authorisation
- Country of origin and local-content declaration (for Make in India purchase preference)
- Type-test and routine-test certificates, and the FAA / ICAO / IEC compliance documents named in the specification
- Datasheets, drawings and installation instructions
- Warranty, delivery period and spares support
- GeM catalogue or tender-portal requirements, where applicable
Request CCR Sizing and Selection
Need a Constant Current Regulator for a new airport lighting circuit or replacement project? Provide the available circuit information, existing CCR details, required current, input supply and control requirements. Our team can help identify the appropriate regulator configuration and associated series-circuit equipment.
Engineering Note
CCR selection is project-specific. Rated current, input supply, output characteristics, circuit load, brilliance settings, control interfaces and protection requirements should be verified against the complete AGL series-circuit design and the applicable current airport lighting standards before procurement.
Product Disclaimer
Product availability, configuration, dimensions, electrical characteristics, photometric performance, certifications and compliance status depend on the selected manufacturer and project specification. The technical values published on this page should not be treated as a substitute for the manufacturer's current approved Technical Data Sheet.
Final selection shall be based on the approved project specification, applicable aviation standards, authority requirements, manufacturer documentation and site conditions. Use of this page is also subject to the Legal Notice, Disclaimer & Terms of Use.
Standards and editions referenced on this site are listed on the Standards Reference page.