What does a CCR failure look like?
The regulator is the source of a series circuit’s current — when it fails, every light on that circuit goes dark, trips out or runs at the wrong brightness together.
A CCR failure is the loss or corruption of the regulated current that a whole series circuit depends on. Every fixture on the circuit is fed through its isolation transformer from the same loop, so when the CCR stops delivering output, every light on that circuit goes dark together. A single failed lamp normally leaves the rest of the circuit lit, and circuits fed by other CCRs are not affected.
A CCR can fail in three recognisable ways: it can lose its output so the circuit goes dark, trip on protection so it shuts down rather than drive a faulted or open circuit, or deliver the wrong current, leaving lights too dim or too bright. The last is the hidden one, because everything looks normal until the output is measured with an independent meter. The output side can carry hazardous voltage, so a dark circuit is isolated, locked out and proved dead before it is touched.
- Circuit reported dark. Every light on one circuit is out, or the control system shows the CCR off or in fault.
- Read the indication. The CCR display, alarms and ALCMS status show which protection or fault operated.
- Check the supply. Confirm the input supply and upstream protection before suspecting the CCR itself.
- Isolate. CCR off, locked out and tagged; prove the CCR and the loop dead.
- Separate CCR from loop. Test the CCR on its own and the loop by insulation and continuity tests to see which side holds the fault.
- Repair & prove. Fix or replace the failed part, then measure the output current at each step with an independent meter before restoring.
Whole circuit affected: every fixture is dark, dim or bright together. Look at the CCR, its supply and its display first.
One fixture affected: the isolation transformer lets the loop carry on, so the other lights stay lit. Look at that fixture and its transformer.
Frequently Asked Questions
Q1What is a CCR failure in airfield lighting?
The loss or corruption of the regulated current that a series lighting circuit depends on. The constant current regulator (CCR) may stop delivering output, trip on protection, or deliver the wrong current, and the whole circuit it feeds is affected.
Q2Why does a CCR failure darken a whole circuit when a lamp failure does not?
All the fixtures on a series circuit are fed from one loop supplied by one CCR. When the CCR stops producing output, no current flows in the loop and every fixture goes dark together. A single failed lamp normally leaves the rest of the circuit lit because its isolation transformer lets the loop current carry on, and circuits fed by other CCRs are not affected.
Q3What are the different ways a CCR failure shows up?
Three ways: no output, so the circuit goes dark; a protective trip, where the CCR shuts down rather than drive a faulted or open circuit; and wrong current, where lights are too dim or too bright. The wrong-current case can be hidden, because everything looks normal until the output is measured with an independent calibrated meter.
Q4Why does a CCR trip, and should the trip be reset?
A trip means protection operated for a reason, such as an open circuit, over-current, over-temperature or a fault inside the CCR. Resetting it repeatedly can stress the equipment and the circuit, so the cause should be found and cleared first, following the manufacturer's manual and the site procedure.
Q5How can a CCR fault be told apart from a cable or transformer fault?
Start with the CCR display, its alarms and its input supply. Then, with the circuit isolated and locked out, separate the CCR from the series loop as the procedure allows and test each side: the CCR on a suitable test load, and the loop by insulation resistance and continuity tests. A CCR that is healthy off the loop points to a cable, connector or transformer fault. See CCR Troubleshooting for the flow.
Q6Is a failed CCR dangerous?
It can be. The CCR output side can carry hazardous voltage, and a dark circuit is not a safe circuit. The CCR is switched off, locked out, tagged and proved dead before anyone works on it or on the loop it feeds.
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