What is CCR current control?
The feedback loop that measures the current leaving a constant current regulator and keeps correcting it until it matches the selected brightness step.
Most modern constant current regulators hold their output steady with a closed feedback loop. The selected intensity step provides the setpoint. A current transformer on the output supplies the measured current. The controller compares the two and adjusts the power stage, for example by changing when thyristors turn on in each AC cycle, until the difference is gone.
Because the loop keeps checking, the output current stays at the set value when the supply voltage or the circuit load changes, within the CCR’s rated range. Around the loop sit protection functions: overcurrent detection and open-circuit protection limit or stop the output if the current or voltage leaves safe limits.
- Set the target. The selected intensity step gives the controller its current setpoint.
- Measure. A current transformer on the output measures the actual current.
- Compare. The controller finds the difference between target and measured current.
- Correct. It adjusts the power stage to raise or lower the power delivered.
- Hold. Supply or load changes are corrected as they occur, so the current stays at the setpoint.
- Protect. Overcurrent and open-circuit limits stop the output if conditions become unsafe.
Frequently Asked Questions
Q1What is CCR current control in airfield lighting?
The closed feedback loop inside a constant current regulator that measures the output current, compares it with the selected step and adjusts the power stage until the circuit receives the required current.
Q2How does a CCR keep the current constant?
A current sensor on the output feeds the measured value to the controller. If it differs from the step setpoint, the controller changes the power stage, for example the firing angle of the thyristors, until the output matches again.
Q3What happens when the load or supply changes?
The current briefly drifts, the loop sees the difference and corrects it. This is why a CCR holds the set current when the input voltage varies or when the circuit load changes, within its rated range.
Q4What sets the target current?
The selected intensity step. Each step gives the controller a different setpoint, and the loop then drives the output to that value.
Q5Do all CCRs control current the same way?
The principle is the same: sense, compare and correct. The power stage differs, with thyristor phase control common and other designs using different power electronics. Ferroresonant CCRs regulate differently, by magnetic saturation of the core rather than an electronic feedback loop, so details depend on the CCR model.
Q6What stops the current going too high?
Protection built around the loop, such as overcurrent detection and open-circuit protection, which limit or shut down the output if the current or output voltage leaves safe limits.
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