Series-Circuit Electrical Equipment
AGL Isolating Transformer (L-831)
Couples each airfield light fixture to the primary series circuit
AGL series-circuit isolating transformers for airfield lighting, with selection based on circuit current, fixture load, frequency and project requirements.
Supplied by Precision AGL Solutions
Product Overview
AGL Isolating Transformer (L-831)
What It Is
AGL Isolating Transformer (L-831) couples individual airfield light fixtures to the primary series circuit while providing the required electrical isolation between the primary circuit and the fixture circuit.
It transfers energy from the constant-current series circuit to the individual fixture, helping isolate the fixture and secondary circuit from the primary high-voltage series circuit. It also lets the series circuit stay closed if a fixture lamp or its secondary fails open, so one failed light does not interrupt the whole circuit.
What We Supply
Precision AGL Solutions supplies isolating transformers selected according to fixture wattage, series-circuit current, operating frequency, insulation requirements, cable interfaces and project specifications.
Each fixture is supplied through its associated transformer, so individual fixtures connect to the common series circuit without being directly exposed to the primary circuit voltage. The arrangement is widely used for runway, taxiway, approach and other airfield lighting.
L-831 is the 50 Hz version of the FAA L-830. FAA AC 150/5345-47C designates "type L-830 for 60 Hz operation and type L-831 for 50 Hz operation", so it is the designation to look for on series circuits fed from a 50 Hz supply, as in India.
CCRConstant Current Regulator
Primary CableSeries circuit
Primary ConnectorCircuit interface
L-831 TransformerIsolation & coupling
Secondary ConnectorFixture interface
AGL FixtureLight fixture
L-830 vs L-831
Same Family, Different Frequency
FAA AC 150/5345-47C covers both designations. They are paired one-to-one, and the numerical suffix gives the wattage and current rating.
| Item | L-830 | L-831 |
|---|---|---|
| Rated frequency | 60 Hz | 50 Hz |
| Type numbers | L-830-1 to L-830-19 | L-831-1 to L-831-19 (same suffix = same watt / current rating) |
| Example | L-830-1: 30/45 W, 6.6 A primary, 6.6 A secondary | L-831-1: 30/45 W, 6.6 A primary, 6.6 A secondary |
| Ratings covered | About 10/15 W up to 500 W; primary and secondary current 6.6 A or 20 A, by type | |
| Winding voltage class | Primary winding 5,000 V; secondary winding 600 V | |
| Typical use | 60 Hz supplies (for example North America) | 50 Hz supplies (for example India, Europe, most of Asia) |
See the L-830 isolating transformer page for the 60 Hz designation. Values are from AC 150/5345-47C; always confirm against the model datasheet and the project specification.
Applications
Where L-831 Isolating Transformers Are Used
Runway edge lightingSeries-circuit fixtures.
Threshold & runway endRunway threshold and end lighting.
Runway centrelineCentreline light circuits.
Touchdown zoneTouchdown zone lighting.
Taxiway edge & centrelineTaxiway series circuits.
Stop bar lightingControlled holding positions.
Approach lighting systemsThreshold and approach lighting.
Apron & associated lightingSeries-circuit apron lighting.
Replacement & rehabilitationReplacement of existing transformers, rehabilitation and new installations, plus maintenance spares.
The transformer rating should always be matched to the specific fixture and series-circuit design.
Electrical Isolation
Primary Series Circuit Separated From the Fixture
Purpose
The transformer separates the primary series-circuit electrical environment from the secondary connection to the light fixture while transferring the required power.
Exact insulation system and electrical characteristics depend on the selected model and project requirements.
This Arrangement Supports
- Individual fixture connection to the series circuit
- Electrical isolation between primary and secondary circuits
- Reliable operation of individual airfield lights
- Simplified series-circuit architecture
- Replacement and maintenance of individual fixtures
- Compatibility with constant-current airfield lighting systems
Rating Selection
Transformer Rating Selection
Correct selection is essential for reliable airfield lighting performance. Select against the complete electrical characteristics of the fixture and primary series circuit.
Fixture wattageRating must suit the connected load; evaluate LED and conventional fixtures against their specified electrical input. Avoid heavily under-loaded transformers (for example a high-wattage unit feeding a low-power LED fixture), which can distort circuit current and affect regulator loading. Check LED fixture and transformer pairing with the manufacturer.
Primary circuit currentMust be compatible with the series-circuit rated current; check against CCR operating current and the complete circuit.
Secondary requirementsCharacteristics must suit the connected fixture and its operating conditions.
FrequencyL-831 is the 50 Hz designation under FAA AC 150/5345-47C; the L-830 is the 60 Hz equivalent. Use L-831 for 50 Hz series circuits. A 60 Hz L-830 on a 50 Hz circuit is not an equivalent substitute, so confirm the nameplate frequency. IEC 61823 transformers are an alternative reference where the project specifies IEC.
Insulation requirementsInsulation system must suit the primary series-circuit environment and project requirements.
Installation environmentUnderground installation, pavement interfaces, moisture, temperature, mechanical protection, connector arrangement and maintenance.
System Compatibility
Part of the Complete AGL Series Circuit
The L-831 forms part of the complete series-circuit system rather than operating as an independent power supply.
CCR → Primary Cable → Primary Connector → Isolating Transformer → Secondary Connector → Fixture
The Selected Transformer Should Be Compatible With
- CCR rated current
- Primary series-circuit characteristics
- Fixture wattage
- Fixture electrical requirements
- Operating frequency
- Primary and secondary connector arrangement
- Insulation requirements
- Applicable airport specifications
Cable Interfaces
Primary and Secondary Cable Interfaces
Interfaces, Depending on Selected Configuration
- Primary lead arrangement
- Secondary lead arrangement
- Factory-fitted cable leads
- Connector-compatible leads
- Project-specific cable lengths
- Compatible primary connector systems
- Compatible secondary connector systems
Cable and connector selection should be coordinated with the complete AGL installation. See Primary Connector Kit and Secondary Connector Kit.
Insulation & Leakage
Insulation and Leakage Characteristics
Why It Matters
The transformer must maintain the required separation between primary and secondary circuits while reliably transferring power to the fixture.
Exact values should be taken from the applicable model datasheet and project specification.
Project Evaluation May Include
- Insulation system
- Dielectric withstand characteristics
- Insulation resistance
- Leakage characteristics
- Environmental sealing
- Cable insulation
- Transformer enclosure / protection
- Primary-to-secondary isolation
Construction
Construction and Environmental Protection
Isolating transformers operate in demanding airfield environments with long-term exposure.
Relevant Construction Considerations
- Robust transformer construction
- Suitable insulation system
- Moisture resistance
- Protection against environmental contamination
- Suitable cable insulation
- Mechanical protection
- Underground installation compatibility where specified
- Reliable primary and secondary connections
The required environmental protection level should be verified against the installation method and airport project requirements.
Technical Data
AGL Isolating Transformer Specification
| Parameter | Specification |
|---|---|
| Product Type | AGL Series-Circuit Isolating Transformer |
| Designation | L-831 (FAA series isolating transformer, 50 Hz); type numbers L-831-1 to L-831-19 under AC 150/5345-47C |
| Application | Airfield Ground Lighting series circuits |
| Transformer Rating / Wattage | Per type, from about 10/15 W to 500 W; project- and model-specific |
| Primary Current | 6.6 A or 20 A, by type, per selected model and series circuit |
| Secondary Current | According to selected model and fixture |
| Frequency | 50 Hz (the 60 Hz counterpart is the L-830) |
| Insulation System | Model-specific |
| Voltage Characteristics | Primary winding rated 5,000 V, secondary winding rated 600 V (AC 150/5345-47C); maximum secondary open-circuit voltage varies by type |
| Leakage Characteristics | Model-specific |
| Primary Cable Interface | Model/project-specific |
| Secondary Cable Interface | Model/project-specific |
| Cable Length | Configuration-specific |
| Environmental Protection | According to installation and project requirements |
| Dimensions | Model-specific |
| Weight | Model-specific |
| Installation | Airfield series-circuit installation |
| Compliance | Applicable FAA/project requirements |
Fixture Compatibility
Select According to the Connected Fixture
- Identify the fixture type
- Confirm the fixture wattage or electrical load
- Confirm the series-circuit operating current
- Confirm the operating frequency
- Select the appropriate transformer rating
- Confirm primary and secondary cable interfaces
- Verify insulation and environmental requirements
- Confirm compatibility with the airport/project specification
For replacement applications, check the existing transformer identification and fixture data before ordering.
Lighting Applications
Runway, Taxiway and Approach Lighting
L-831 isolating transformers can form part of series circuits serving many different airfield lighting fixtures.
Runway Lighting
- Runway edge lights
- Runway threshold lights
- Runway end lights
- Runway centreline lights
- Touchdown zone lights
Taxiway Lighting
- Taxiway edge lights
- Taxiway centreline lights
- Stop bars
- Runway guard lighting
- Intermediate holding position lighting
Approach Lighting
Selectable for suitable series-circuit approach lighting applications, subject to the electrical requirements of the individual fixture and project.
Installation
Installation Considerations
Installation should follow the approved airfield lighting design and applicable electrical procedures.
Carry Out in Accordance With the Approved Design
- Confirm the transformer rating before installation
- Verify the primary circuit current
- Confirm the connected fixture wattage
- Check primary and secondary cable identification
- Use compatible connectors and cable interfaces
- Maintain correct circuit polarity/connection arrangements where applicable
- Protect cable connections against moisture and contamination
- Follow approved airport electrical installation procedures
- Confirm transformer placement and accessibility
- Avoid mechanical damage to transformer leads
Where transformers are installed in transformer pits or other underground locations, also account for drainage, water exposure, cable routing and maintenance access.
Commissioning & Testing
Check the Transformer as Part of the Circuit
- Confirm transformer identification and rating
- Verify fixture wattage
- Confirm primary series-circuit current
- Check primary and secondary cable connections
- Inspect connector condition
- Verify insulation and electrical integrity as required
- Energize the circuit under controlled conditions
- Confirm fixture operation at the required intensity levels
- Check for abnormal heating, leakage or electrical faults
- Record commissioning results
Testing should follow the airport’s approved maintenance and commissioning procedures.
Maintenance
Inspect the Transformer and Its Connections
Recommended Checks May Include
- Transformer physical condition
- Cable insulation condition
- Primary connector condition
- Secondary connector condition
- Signs of moisture ingress
- Mechanical damage
- Corrosion or contamination
- Insulation condition
- Fixture operation
- Abnormal heating
- Circuit performance
For transformers installed in pits, also consider the condition of the pit, drainage and surrounding installation environment.
Troubleshooting
Symptoms and Areas to Investigate
Repeated failures should not automatically be treated as transformer-only problems.
Light Fixture Not Operating
- Open primary series circuit
- Damaged primary connector
- Transformer fault
- Damaged secondary lead
- Secondary connector problem
- Fixture fault
- Incorrect transformer rating
- CCR or circuit-control issue
Incorrect Fixture Performance
- Transformer rating
- Fixture wattage
- Series-circuit current
- Operating frequency
- Primary and secondary connections
- Fixture electrical characteristics
- CCR intensity setting
Repeated Transformer Failure
- Incorrect transformer selection
- Excessive fixture load
- Incorrect series-circuit current
- Moisture ingress
- Cable insulation damage
- Connector problems
- Installation damage
- Abnormal circuit conditions
- Fixture faults
A complete circuit assessment may be required before replacing the transformer again.
Replacement & Retrofit
Airport Rehabilitation and Replacement Programs
Before Replacing an Existing Transformer, Confirm
- Existing transformer designation
- Transformer rating
- Connected fixture wattage
- Series-circuit current
- Frequency
- Primary connector type
- Secondary connector type
- Cable requirements
- Physical installation constraints
- Current project specification
For modernization projects, evaluate the transformer together with the replacement fixture and existing CCR/series-circuit arrangement. See Replacement Isolating Transformer.
Procurement Checklist
When Requesting an AGL Isolating Transformer, Provide
Information Required
- Fixture type
- Fixture wattage
- Existing transformer rating, if replacing
- Series-circuit current
- Operating frequency
- Primary connector requirements
- Secondary connector requirements
- Required cable length
- Installation environment
- Airport/project specification
- Required quantity
- Existing transformer photographs or nameplate information
Providing these details allows the appropriate transformer configuration to be identified more efficiently.
Safety
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
- Work only under the airport's permit-to-work system, using qualified personnel and the manufacturer's instructions
- Do not disconnect a transformer secondary or fixture lead while the primary circuit is energised: with the secondary open the transformer can develop a high open-circuit voltage
- Follow the applicable national electrical safety regulations and site procedures
Specification
Transformer Specification
Series isolating transformers for airport lighting are covered by FAA AC 150/5345-47C — Specification for Series to Series Isolation Transformers for Airport Lighting Systems. The AC designates "type L-830 for 60 Hz operation and type L-831 for 50 Hz operation". Confirm the current edition and the rating (watts and primary/secondary current) required by the circuit design on the manufacturer datasheet. Nameplates are marked with the specification and the type, L-830 or L-831.
Standards & References
Associated Designation and Requirements
FAA L-831 Designation
The product is associated with the FAA L-831 designation, the 50 Hz version of the L-830 isolating transformer, both covered by AC 150/5345-47C.
Important: verify the applicable specification and revision for the specific airport project before procurement. Compliance requirements vary by authority, installation and project specification.
Depending on the Project
- FAA AC 150/5345-47C (series to series isolation transformers) and AC 150/5340-30J (installation details)
- IEC 61823 (AC series circuit isolating transformers for airfield lighting)
- ICAO Doc 9157 Aerodrome Design Manual, Part 5 (Electrical Systems) and Annex 14 Vol. I
- Airport authority specifications
- National electrical requirements
- Project-specific AGL specifications
- Approved airport electrical installation standards
Documentation
Technical Documentation
Depending on the Selected Model and Project
- Product datasheet
- Transformer rating information
- Dimensional drawing
- Cable and connector information
- Installation instructions
- Test documentation
- Inspection information
- Compliance documentation
- Packing and identification information
Project-specific documentation can be coordinated with the quotation or technical submittal.
FAQ
AGL Isolating Transformer (L-831) — Frequently Asked Questions
What is an L-831 isolating transformer?
An L-831 isolating transformer is the 50 Hz version of the FAA L-830. It couples an individual airfield light fixture to the primary series circuit with electrical isolation, and it lets the series circuit stay closed if a lamp or its secondary fails open. FAA AC 150/5345-47C designates type L-830 for 60 Hz operation and type L-831 for 50 Hz operation.
What is the difference between the L-830 and the L-831?
The rated frequency: 60 Hz for the L-830 and 50 Hz for the L-831. The two are paired one-to-one, with type numbers L-830-1 to L-830-19 and L-831-1 to L-831-19, and the same suffix means the same watt and current rating. For example, both the L-830-1 and the L-831-1 are 30/45 W with 6.6 A primary and 6.6 A secondary. See the L-830 isolating transformer page for the 60 Hz designation.
Which isolating transformer should I use on a 50 Hz series circuit?
Use the L-831 on series circuits fed from a 50 Hz supply, as in India, Europe and most of Asia. A 60 Hz L-830 on a 50 Hz circuit is not an equivalent substitute, so confirm the nameplate frequency. IEC 61823 transformers are an alternative reference where the project specifies IEC.
What ratings does the L-831 cover?
Under AC 150/5345-47C the types cover about 10/15 W up to 500 W, with primary and secondary current of 6.6 A or 20 A depending on the type. The primary winding is rated 5,000 V and the secondary winding 600 V, and the maximum secondary open-circuit voltage varies by type. Always confirm against the model datasheet and the project specification.
How do I select the right transformer rating?
Select against the fixture wattage, the series-circuit current, the operating frequency, the secondary requirements, the insulation requirements and the installation environment. Avoid heavily under-loaded transformers, for example a high-wattage unit feeding a low-power LED fixture, because this can distort circuit current and affect regulator loading. Check LED fixture and transformer pairing with the manufacturer.
Where are L-831 isolating transformers used?
They form part of series circuits for runway edge, threshold, end, centreline and touchdown zone lighting, taxiway edge and centreline lighting, stop bars, runway guard and intermediate holding position lighting, approach lighting and apron lighting, as well as replacement and rehabilitation work. Approach lighting use is subject to the electrical requirements of the individual fixture and project.
How is an L-831 installed and commissioned?
Install it to the approved design, confirming the rating, the primary circuit current and the connected fixture wattage, checking cable identification, using compatible connectors and protecting connections against moisture. At commissioning, verify insulation and electrical integrity as required, energise the circuit under controlled conditions, confirm fixture operation at the required intensity levels, check for abnormal heating or leakage and record the results.
What are common causes when a fixture does not operate?
Possible causes include an open primary series circuit, a damaged primary connector, a transformer fault, a damaged secondary lead or connector, a fixture fault, an incorrect transformer rating, or a CCR or circuit-control issue. A complete circuit assessment may be needed before replacing the transformer again, because repeated failures are not always transformer-only problems.
What should I confirm before replacing an existing transformer?
Confirm the existing transformer designation, rating, connected fixture wattage, series-circuit current, frequency, primary and secondary connector types, cable requirements, physical installation constraints and the current project specification. Check the nameplate, which is marked with the specification and the type, L-830 or L-831.
Which standards apply to the L-831?
FAA AC 150/5345-47C covers both the L-830 and the L-831, with installation details in AC 150/5340-30J. Depending on the project, IEC 61823, ICAO Doc 9157 Part 5, ICAO Annex 14 Volume I and airport authority specifications may also apply. Confirm the current edition and the rating required by the circuit design on the manufacturer datasheet.
Is it safe to disconnect a transformer secondary while the circuit is energised?
No. With the secondary open the transformer can develop a high open-circuit voltage, and opening, cutting or disconnecting any part of an energised series circuit can cause serious injury or death. De-energise the circuit at the regulator, apply the site lock-out / tag-out procedure, use the series circuit cut-out switch or an approved isolation device and work under the permit-to-work system. See the electrical safety warning on this page.
What information should I provide when requesting an L-831?
Provide the fixture type and wattage, the existing transformer rating if replacing, the series-circuit current, the operating frequency, primary and secondary connector requirements, the required cable length, the installation environment, the airport or project specification and the quantity. Photographs or nameplate information of the existing transformer help identify the correct configuration.
Why Precision AGL Solutions
The Transformer as Part of the Complete Series Circuit
Precision AGL Solutions focuses on components used throughout airport airfield ground lighting systems. For isolating transformers, our approach treats the transformer as part of the complete AGL series circuit rather than an isolated component. We can assist with:
Our Support
- Transformer rating selection
- Fixture compatibility review
- Series-circuit compatibility
- Primary and secondary interface selection
- Replacement transformer identification
- Airport lighting rehabilitation requirements
- Project-specific technical documentation
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 AGL Isolating Transformer Selection
Need the correct L-831 isolating transformer for an existing or new airfield lighting circuit? Send us the fixture wattage and series-circuit current for transformer selection. For replacement applications, you can also provide the existing transformer rating, fixture model, connector details or transformer nameplate information. Send your fixture wattage, circuit current, frequency and available transformer details to receive a project-specific transformer recommendation.
- Emailprecisionaglsolutions@gmail.com
- Websiterahulsharmaagl.in
- LinkedInPrecision AGL Solutions
- Phone+91 98214 96412
Engineering Note
Transformer rating, primary/secondary characteristics, insulation system, leakage characteristics, cable interfaces and dimensions are configuration-dependent. Final selection should be verified against the connected fixture, series-circuit design, CCR operating current, installation environment and applicable airport/FAA/project requirements 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.