The dedicated Constant Current Regulator failure-intelligence section of the AGL Failure Database — covering output regulation, power electronics, cooling, controls, protection, communication, indications, auxiliary supply and load-related problems across 22 failure categories.
Key principle — A CCR failure should be recorded by the actual failure mode, operating symptom, evidence, root cause and effect on the series circuit — not simply as "CCR failed." Capture three separate levels for every event: Failure Event (what happened), Failure Mode (how it happened) and Root Cause (why it happened).
Diagnostic principle — Events like "CCR shutdown" or "protection trip" are symptoms, not root causes. Always trace the failure chain back to its initiating condition, and establish whether the CCR itself is the source of the problem or whether it is correctly responding to an abnormal connected series-circuit load.
CCR output is not stable at the commanded operating condition.
Determine whether instability originates from the CCR itself or the connected series-circuit load.
Failure of the CCR power-control thyristor or associated thyristor circuit.
Failure of the CCR cooling fan resulting in inadequate heat removal.
Failure of the CCR control electronics responsible for regulating or controlling CCR operation.
CCR protective function operates and removes or limits output.
Do not treat the protection trip itself as the final root cause. Determine: why did the protection operate?
Loss of communication between the CCR and its external control/monitoring system.
If the underlying problem is in the wider ALCMS/control network, cross-reference Division 07 — Control System Failures.
CCR indication or output progressively deviates from its calibrated/reference condition.
Compare:
Actual CCR output current differs from the required/commanded value.
Record current at each applicable intensity level: commanded step, expected current (reference), actual current (measured), deviation (calculated), load/circuit condition, CCR status (normal/fault) and corrective action.
CCR is unable to maintain the required constant-current output.
Output-current deviation = measured output differs from expected. Current regulation failure = CCR cannot maintain the required regulated output.
CCR fails to correctly produce one or more commanded intensity levels.
Test each available intensity level systematically and record commanded step, expected current, actual current, deviation, transition response and alarm status. This should be linked to CCR testing and commissioning records.
CCR alarm function fails to correctly detect, generate, display or transmit a fault condition.
An alarm failure can become a latent safety/maintenance problem, because the CCR may have a developing fault without providing the expected warning.
CCR display/interface fails to correctly present operating or fault information.
CCR cannot be correctly controlled through the remote-control interface.
CCR fails to respond correctly to commands from its local control interface.
Abnormally high temperature at a CCR electrical terminal or connection.
Loss or degradation of the auxiliary electrical supply required for CCR control, monitoring, cooling or associated functions.
A CCR may appear to have a controller failure when the actual cause is an auxiliary-supply failure.
Failure of the CCR's overall cooling arrangement. This is broader than Cooling-Fan Failure.
Cooling-fan failure = specific failure mode. Cooling-system failure = wider system-level condition.
CCR internal temperature exceeds the allowable operating condition.
Unintended or fault-induced cessation of CCR operation.
"CCR shutdown" is the event/symptom. The investigation must identify the actual initiating failure. For example:
or:
CCR repeatedly starts, stops or behaves abnormally without remaining continuously failed.
This failure requires particularly strong evidence: event logs, alarm history, operating time, temperature, output current, load condition, and the number/timing of occurrences.
CCR abnormal behaviour caused by the connected AGL series-circuit load rather than an isolated CCR component failure.
Before replacing a CCR component, establish whether the CCR is actually the source of the problem. A CCR can correctly respond to an abnormal series-circuit condition.
Diagnostic matrix, failure chains, structured failure record and RCA linkage that apply across all 22 Division 03 CCR failure topics.
Quick-reference mapping of main symptom to first investigation focus for every Division 03 failure category:
| Failure | Main Symptom | First Investigation Focus |
|---|---|---|
| Output instability | Fluctuating output | Regulation/load |
| Thyristor failure | Incorrect/no output | Power section |
| Cooling-fan failure | Temperature rise | Fan/airflow |
| Controller failure | Control abnormality | Controller/auxiliary supply |
| Protection trip | CCR trips | Determine initiating fault |
| Communication failure | Remote status/control lost | Interface/network |
| Calibration drift | Measurement deviation | Calibration |
| Output-current deviation | Wrong current | Measurement/regulation |
| Current regulation failure | Cannot maintain current | Feedback/power/load |
| Intensity-step failure | Wrong step output | Step-control system |
| Alarm failure | Fault not indicated | Alarm logic/interface |
| Display failure | Wrong/no display | Display/auxiliary supply |
| Remote-control failure | Remote command fails | Control interface |
| Local-control failure | Local command fails | Local interface |
| Internal wiring failure | Intermittent/control fault | Internal connections |
| Terminal overheating | Hot terminal | Connection/current |
| Auxiliary-supply failure | Multiple control functions lost | Auxiliary supply |
| Cooling-system failure | Thermal problems | Complete cooling path |
| Over-temperature | High temperature | Cooling/load |
| CCR shutdown | CCR stops | Identify initiating fault |
| Intermittent operation | Random fault | Logs/thermal/connections |
| Load-related failure | CCR reacts abnormally to circuit | Series-circuit condition |
Record the failure chain, not just the final symptom.
Here, CCR shutdown is not the root cause. The initiating failure is the electrical fault in the series circuit.
For every CCR event, capture three separate levels:
Failure Event: What happened? — CCR shutdown
Failure Mode: How did it happen? — Over-temperature condition
Root Cause: Why did it happen? — Cooling-fan failure / blocked airflow / maintenance deficiency
This separation prevents the CCR database from becoming a simple list of symptoms and allows it to connect properly with Electrical Failures, Control System Failures, Testing & Commissioning, Maintenance-Induced Failures, RCA, Criticality and Reliability Trend divisions.
Every CCR failure should have a structured record containing at minimum:
Identification
Failure Information
Investigation
RCA
Restoration
Reliability
Every failure receives a severity classification, plus operational-impact tagging:
Critical / Safety-Critical — immediate operational or safety risk
Major / Operationally Critical — significant availability impact
Moderate — reduced performance, not yet critical
Minor / Non-Critical — limited or no operational effect
Degradation / Intermittent / Latent — developing or hidden fault
Of the source's 18 root-cause categories, the most important for Division 03 are:
Division 02 captures failures in the electrical path feeding the circuit — cable, connector, termination, insulation, protection. Division 03 captures failures within the CCR itself — power electronics, cooling, controls, calibration, indication and auxiliary supply. Where a CCR trips or shuts down, always confirm whether the initiating failure is internal to the CCR (Division 03) or an abnormal series-circuit condition upstream (Division 02) before replacing any CCR component.
Quick answers about Constant Current Regulator (CCR) failures, as covered in Division 03 of the AGL Failure Database.
Division 03 covers failures within the Constant Current Regulator itself. It contains 22 published topics (CCR-01 to CCR-22) spanning output regulation, power electronics, cooling, controls, protection, communication, indications, auxiliary supply and load-related problems.
Output instability, thyristor failure, cooling-fan failure, controller failure, protection trip, communication failure, calibration drift, output-current deviation, current regulation failure, intensity-step failure, alarm failure, display failure, remote-control failure, local-control failure, internal wiring failure, terminal overheating, auxiliary-supply failure, cooling-system failure, over-temperature condition, CCR shutdown, intermittent CCR operation and load-related failure.
They are grouped into five sets: CCR Output & Power-Control Failures (6 topics), CCR Regulation & Performance Failures (4), CCR Indication & Control Failures (4), Internal Electrical & Thermal Failures (5) and CCR Operational & Load Failures (3).
Every CCR event should record a failure event (what happened, for example a CCR shutdown), a failure mode (how it happened, for example an over-temperature condition) and a root cause (why it happened, for example cooling-fan failure, blocked airflow or a maintenance deficiency). This keeps the database from becoming a simple list of symptoms.
No. A CCR shutdown is often a consequence. In one recorded chain, a cable insulation problem causes an earth fault, which causes a CCR protection trip, a CCR shutdown and a lighting outage. Here the initiating failure is the electrical fault in the series circuit, not the CCR.
Division 02 covers failures in the electrical path feeding the circuit, such as cable, connector, termination, insulation and protection. Division 03 covers failures within the CCR itself: power electronics, cooling, controls, calibration, indication and auxiliary supply. When a CCR trips or shuts down, confirm whether the initiating failure is internal to the CCR or an abnormal series-circuit condition upstream before replacing any CCR component.
The diagnostic matrix maps each symptom to a first investigation focus. For example, output instability points to regulation and load, thyristor failure to the power section, cooling-fan failure to fan and airflow, controller failure to the controller and auxiliary supply, communication failure to the interface and network, and a protection trip to determining the initiating fault.
Each record should include identification (failure ID, airport/project, CCR identification, manufacturer, model, rating, circuit served, installation date), failure information (date/time, category, mode, symptoms, intensity step, output current, CCR temperature, load condition, alarm and event-log information), investigation results, evidence and photographs, RCA (immediate cause, root cause, contributing factor, failure mechanism) and restoration details.
Every failure receives a severity classification, plus operational-impact tagging. The classes are Critical / Safety-Critical (immediate operational or safety risk), Major / Operationally Critical (significant availability impact), Moderate (reduced performance, not yet critical), Minor / Non-Critical (limited or no operational effect), and Degradation / Intermittent / Latent (a developing or hidden fault).
A CCR fault can come from a thyristor failure, a current-transformer error, a control-logic fault or a downstream circuit problem — real troubleshooting means understanding CCR architecture well enough to trace the alarm back to its actual source.
Take that knowledge further with Precision AGL Academy.
Learn how to connect:
Develop structured knowledge across AGL fundamentals, components, electrical systems, testing, photometry, troubleshooting, maintenance and commissioning.
Find the failure. Understand the cause. Build the engineering skill.
Please read before relying on any content on this page or on any record downloaded from it.