Replacement AGL Isolating Transformer for Series-Circuit Maintenance
Identified from your existing transformer, not from its appearance
Replacement isolating transformers support maintenance teams when an installed transformer has failed, reached end of life or requires replacement. The Replacement AGL Isolating Transformer is intended for maintenance, repair and refurbishment of existing airport series-circuit lighting systems, as a replacement for compatible installed transformers used with runway, taxiway, approach and other airfield lighting fixtures.
Why Correct Identification Matters
Isolating transformers are selected according to the electrical characteristics of the existing series circuit and connected fixture. The original transformer information should be reviewed before selecting a replacement.
Where Replacement Transformers Are Used
Replacement isolating transformers are suitable for existing:
What the Replacement Provides
- Intended for replacement of compatible installed transformers
- Suitable for maintenance and refurbishment applications
- Supports replacement of failed or end-of-life transformers
- Selection based on existing transformer characteristics
- Compatible primary and secondary electrical interfaces
- Available for different fixture load requirements
- Suitable for existing series-circuit installations
- Supports planned lifecycle replacement
- Identified using existing transformer nameplate information
- Selection coordinated with existing connector arrangements
Replacement Selection
Selection should be based on the installed equipment rather than simply matching physical dimensions. Verify where available:
- Existing transformer model and rating
- Primary and secondary current
- Frequency
- Primary and secondary voltage characteristics
- Connected fixture load
- Connector arrangement
- Physical dimensions
- Installation location
- Environmental conditions
The existing nameplate is often the most useful starting point. A clear photograph of the nameplate and transformer assembly can help establish the required replacement characteristics.
Series-Circuit Application, Characteristics and Load
Series-Circuit Application
- Fixtures connect through isolating transformers in a series circuit
- The transformer is the electrical interface between series circuit and fixture
- The replacement must suit the circuit characteristics and fixture load
- Incorrect selection can result in unsuitable electrical operation
Primary & Secondary Characteristics
- Primary current
- Secondary current
- Primary voltage characteristics
- Secondary voltage characteristics
- Transformer power rating
- Primary insulation class (typically the 5 kV series-circuit class)
- Frequency
- Connected fixture load
Rating and Fixture Load
- Rating must suit the connected fixture load
- Establish fixture type and electrical load where possible
- Important where an older configuration was later modified
- For retrofit or upgraded fixtures, check against the current fixture configuration, not only original records
Primary and secondary parameters should correspond to the existing installation and applicable project requirements.
Connector Compatibility, Dimensions and Environment
Connector Compatibility
- Check primary and secondary connection arrangements before replacement
- The replacement should match the required connection arrangement
- Where connectors are damaged or unsuitable for reuse, the Primary Connector Kit or Secondary Connector Kit may also need replacement
Physical Dimensions
- Overall dimensions and mounting arrangement
- Cable entry and exit and connector position
- Available installation space
- Clearance from surrounding equipment
- Installation orientation
- Suitable electrical characteristics may still need review if the physical arrangement differs
Isolating transformers sit in underground or field locations. Consider moisture, water exposure, soil conditions, temperature variation, mechanical handling, cable connection conditions and the installation enclosure or pit arrangement, and install with the appropriate accessories and practices for the airfield environment.
Replacement of Failed Transformers
A failed transformer may be identified through fixture outage, electrical testing or maintenance inspection. Before replacement, verify the transformer identity and inspect the associated:
- Primary cable
- Primary connector
- Secondary lead
- Secondary connector
- Fixture
- Junction or base connection
- Surrounding installation
Replacing the transformer without checking associated connections may leave an underlying cable, connector or fixture fault unresolved.
Maintenance, Inspection and Rehabilitation
Maintenance and Inspection
- Physical condition and connector condition
- Cable connection integrity
- Evidence of moisture or environmental damage
- Fixture operation
- Transformer identification and correct circuit association
- Signs of overheating or abnormal operation where applicable
- Update records after replacement so installed transformer information matches maintenance documentation and asset records
Replacement and Rehabilitation
- Corrective maintenance and planned component replacement
- Fixture refurbishment and cable rehabilitation
- Connector replacement and airfield lighting upgrades
- Lifecycle maintenance programs
- Existing series circuits are often retained while individual components are renewed
- For multiple transformers, consistent identification and documentation simplifies future maintenance
Installation Considerations
Before installation, confirm:
- Existing transformer model
- Required electrical rating
- Primary and secondary characteristics
- Connected fixture type
- Connector arrangement
- Cable condition
- Installation location
- Physical dimensions
- Environmental conditions
Install using compatible connection components and according to the requirements of the applicable airfield lighting system.
Associated Cable and Connector Components
A transformer replacement may require inspection or replacement of associated cable accessories:
Reviewing these together can help prevent repeated excavation or access work caused by associated connection failures.
Identification from Existing Transformer
For replacement and spare-part enquiries, the existing nameplate or a clear photograph provides useful identification. Where possible, provide:
- Manufacturer
- Model or part number
- Transformer rating
- Primary current and secondary current
- Frequency
- Fixture type
- Connector information
- Overall dimensions
- Installation photographs
This supports a more accurate compatibility review and helps avoid selecting a transformer solely on appearance.
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. Confirm the current edition and the rating (watts and primary/secondary current) required by the circuit design on the manufacturer datasheet.
Match the Transformer to the Actual Load
Rating and Load
- Series isolating transformers are rated in watts at a fixed primary/secondary current, commonly 6.6 A / 6.6 A on a 6.6 A series circuit. Other circuit currents exist, so read the nameplate
- Choose a rating that carries the full fixture load at the highest brightness step, including any heaters or monitoring fitted
- Do not simply oversize. A lightly loaded transformer draws more reactive current, loads the regulator and can disturb some LED fixtures
- When a fixture has been upgraded (for example lamp to LED), size the transformer to the new load
Frequency and Failure Effect
- FAA AC 150/5345-47C covers the 60 Hz L-830 and the 50 Hz L-831, and many Indian circuits run at 50 Hz. Confirm the replacement is rated and tested for the actual frequency
- A secondary-side fault or lamp failure normally affects one fixture, because the transformer keeps the series loop closed
- A primary-side open circuit, such as a failed primary connector, can take down the whole circuit, so check the primary path first if several fixtures are out
Verify Before Returning the Circuit to Service
Checks
- Insulation resistance of the primary and secondary cables, per the airport test procedure, before re-energising
- Primary and secondary connections made up and sealed as for the original
- Regulator output current on each brightness step against the nominal circuit current
- Fixture operation on every brightness step, and no abnormal heating on first energisation
Records
Record the new transformer make, rating, serial number and location, and update the circuit and asset records so the installed equipment matches the documentation.
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
- Never open the secondary of a transformer on an energised series circuit: an open secondary can develop hazardous voltage and damage the transformer. Disconnect or reconnect secondary connectors only with the regulator de-energised and locked out
- 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
Standards and Project Requirements
Select and install replacement transformers according to the existing airfield lighting system, airport specifications and applicable project requirements. Where the original equipment documentation or airport authority specifies a transformer type or electrical characteristic, follow those requirements.
Evaluate the replacement as part of the complete series-circuit installation: regulator, primary cable, transformer, secondary connection and lighting fixture.
Reference documents may include FAA AC 150/5345-47C, IEC 61823 (AGL series transformers) and ICAO Doc 9157 Part 5 (Electrical Systems). Confirm the edition required by your project specification.
Replacement AGL Isolating Transformer — Frequently Asked Questions
When is a replacement isolating transformer needed?
A replacement is needed when an installed transformer has failed, reached end of life or otherwise requires replacement. Failure may be identified through a fixture outage, electrical testing or maintenance inspection. Replacement transformers serve existing runway, taxiway, approach and edge lighting, inset and elevated installations, and refurbishment projects on series circuits.
How is the correct replacement transformer selected?
Selection should be based on the installed equipment rather than on matching physical dimensions. Verify the existing transformer model and rating, primary and secondary current, frequency, primary and secondary voltage characteristics, connected fixture load, connector arrangement, physical dimensions, installation location and environmental conditions. The existing nameplate is often the most useful starting point, and a clear photograph of the nameplate and transformer assembly helps.
What ratings and currents do series isolating transformers have?
Series isolating transformers are rated in watts at a fixed primary and secondary current, commonly 6.6 A / 6.6 A on a 6.6 A series circuit. Other circuit currents exist, so read the nameplate. The primary insulation class is typically the 5 kV series-circuit class.
Should a replacement transformer be oversized?
No. Choose a rating that carries the full fixture load at the highest brightness step, including any heaters or monitoring fitted. A lightly loaded transformer draws more reactive current, loads the regulator and can disturb some LED fixtures. When a fixture has been upgraded, for example from lamp to LED, size the transformer to the new load.
Do I need a 50 Hz or a 60 Hz transformer?
FAA AC 150/5345-47C covers the 60 Hz L-830 and the 50 Hz L-831, and many Indian circuits run at 50 Hz. Confirm that the replacement is rated and tested for the actual frequency of the circuit.
Which standard covers series isolating transformers?
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. Other references may include IEC 61823 and ICAO Doc 9157 Part 5. Confirm the edition required by your project specification, and follow the airport authority and original equipment documentation where they specify a transformer type or electrical characteristic.
Do connectors also need replacing with a transformer?
Check the primary and secondary connection arrangements before replacement, as the replacement should match the required arrangement. Where connectors are damaged or unsuitable for reuse, the Primary Connector Kit or Secondary Connector Kit may also need replacement, and a Joint / Splice Kit may be needed for cable repairs. Reviewing these together can prevent repeated excavation or access work.
Does a failed transformer take down one fixture or the whole circuit?
A secondary-side fault or lamp failure normally affects one fixture, because the transformer keeps the series loop closed. A primary-side open circuit, such as a failed primary connector, can take down the whole circuit, so check the primary path first if several fixtures are out. Replacing the transformer without checking associated connections may leave an underlying cable, connector or fixture fault unresolved.
What should be checked after replacing a transformer?
Check the insulation resistance of the primary and secondary cables per the airport test procedure before re-energising, confirm the primary and secondary connections are made up and sealed as for the original, check the regulator output current on each brightness step against the nominal circuit current, and confirm fixture operation on every step with no abnormal heating on first energisation. Record the new transformer make, rating, serial number and location, and update the circuit and asset records.
Is it safe to change a transformer on an energised series circuit?
No. An open series circuit driven by a constant-current regulator can produce dangerously high voltage. Never open the secondary of a transformer on an energised series circuit, because an open secondary can develop hazardous voltage and damage the transformer. 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 send for a replacement transformer enquiry?
Where possible provide the manufacturer, model or part number, transformer rating, primary and secondary current, frequency, fixture type, connector information, overall dimensions and installation photographs. This supports an accurate compatibility review and helps avoid selecting a transformer solely on appearance.
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
Send Existing Transformer Nameplate / Photo for Identification
We can support identification and replacement selection using the information from your existing isolating transformer. Send the existing transformer nameplate or a clear photograph for identification and compatibility review.
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.