CONSTANT CURRENT REGULATORS COMPLETE NOTES

WHAT IS A CCR?

The Constant Current Regulator (CCR) is one of the most important electrical components in an AGL system. In a conventional series circuit it supplies a controlled current through the complete primary loop, and maintains that current despite changes in circuit load, within the regulator's operating range. It is the main power-control device for an AGL series circuit.

A CCR converts the available supply into a controlled output suitable for an AGL series circuit. Unlike an ordinary voltage-regulated supply, it is primarily concerned with controlling output current.

AC INPUT
   │
   ▼
┌──────────────────────┐
│ Constant Current     │
│ Regulator (CCR)      │
└──────────────────────┘
   │  controlled AGL current
   ▼
PRIMARY SERIES CABLE (one continuous loop, same current everywhere)
   │
   ├─▶ [Primary of Isolation Tr. 1] ─▶ (Secondary → Light 1)
   │
   ├─▶ [Primary of Isolation Tr. 2] ─▶ (Secondary → Light 2)
   │
   ├─▶ [Primary of Isolation Tr. 3] ─▶ (Secondary → Light 3)
   │
   └─▶ [Primary of Isolation Tr. n] ─▶ (Secondary → Light n)
   │
   ▼
return to CCR output terminal

Primaries are in SERIES (one current path).
Only the secondary side feeds each lamp separately.

WHY A CCR IS REQUIRED

A lighting circuit may contain many fittings, isolation transformers, cables and other loads, and its electrical characteristics change with operating conditions. The CCR compensates by controlling the circuit current.

The basic electrical chain

HOW A CCR WORKS

A CCR continuously senses its output current and adjusts its internal power-control system to keep the current near the selected setpoint. The internal technology varies by manufacturer; the principle does not.

Desired current
      ↓
Current reference
      ↓
Controller
      ↓
Power switching / regulation
      ↓
Output transformer / reactor
      ↓
AGL series circuit
      ↑
Current feedback ──────┘

Why it is called a series circuit

The primary sides of the isolation transformers are connected in series, so the same current passes through every one. A CCR output of 6.6 A means the designed operating current of the loop is approximately 6.6 A RMS, subject to the applicable regulator specification and operating conditions.

CURRENT IS CONTROLLED, VOLTAGE VARIES

This is one of the most important concepts for an AGL engineer. An ordinary supply is described as, say, 230 V constant. A CCR is operated as 6.6 A constant; the output voltage is whatever the regulator must produce, within its capability, to drive that current through the connected circuit.

Current = controlled
Voltage = varies according to circuit requirement

V ≈ I × Z
  V = circuit voltage   I = regulated current   Z = effective circuit impedance

Real AGL circuits contain transformers, cables and reactive effects, so design calculations must use the actual equipment and circuit characteristics.

BRIGHTNESS CONTROL AND CURRENT STEPS

As the selected current changes, the light output of compatible AGL fixtures changes. For FAA Class 1 CCRs, AC 150/5345-10H defines:

LOW intensity    → lower current
MEDIUM intensity → medium current
HIGH intensity   → higher current

CLASSIFICATION: L-827, L-828, L-829

FAA AC 150/5345-10H defines three CCR-related types and two class/style dimensions.

Class 2 (20 A) five-step currents are given in Section 7. For a Class 2, 3-step arrangement, take the step currents from the table in AC 150/5345-10H and the project specification; do not assume them from Class 1.

6.6 A AND 20 A CIRCUITS

MAIN PARTS OF A CCR

INPUT, OUTPUT AND VOLTAGE

Input: receives utility or airport power. AC 150/5345-10H lists standard input ratings of 208, 220, 240 and 480 V at a standard frequency of 60 Hz. Other voltages, frequencies or sizes may be supplied for local conditions when all the requirements of the specification are met. On 50 Hz systems, as in India, the CCR, isolation transformers (FAA L-831 is the 50 Hz type; L-830 is 60 Hz) and fittings must be specified and tested for 50 Hz operation (see Note 08); confirm supply voltage and frequency in the project specification and do not assume a 60 Hz FAA catalogue item is suitable.

Output: feeds the AGL series circuit at the selected regulated current. The output voltage is not a fixed value; it depends on the connected series load.

Environment: the specification defines temperature, humidity, altitude and continuous-operation requirements, for example an equipment range of approximately −40 °C to +55 °C for covered equipment. Project specifications may add requirements.

CCR LOAD, SIZING AND POWER RATING

CCR sizing is not simply number of lights × lamp wattage. A proper load assessment considers transformer ratings, fixture power, number of fittings, cable and transformer losses, control components, power factor, expected maximum and minimum load, circuit configuration and spare capacity. FAA visual-aid guidance warns that changing loads can affect CCR efficiency and stability, so design for both the lowest and highest possible loading.

Selection sequence

1. Identify the AGL circuit.
2. Determine the series current.
3. Count fittings and transformers.
4. Determine transformer ratings.
5. Calculate the circuit load.
6. Determine the required CCR kW / kVA capacity.
7. Check voltage capability.
8. Check brightness steps.
9. Check control and monitoring.
10. Check the standard and project specification.

CCR capacity is commonly expressed as output power in kW. AC 150/5345-10H lists standard sizes of 1, 2, 4, 7.5, 10, 15, 20, 25 and 30 kW, with larger legacy sizes also identified; some manufacturers also offer intermediate sizes (e.g. 5 kW), so confirm the size table of the edition in force. The selected size must come from the project design and manufacturer's calculations.

Total requirement = Load + system losses + required operating margin

Losses: isolation transformers · cables · equipment · control components · other connected loads

Worked outline: 100 fittings on a 6.6 A circuit

EFFICIENCY AND POWER FACTOR

MONITORING, LOCAL AND REMOTE CONTROL

A monitored CCR does more than regulate. It detects abnormal circuit conditions and reports faults to the airport control system. The FAA specification identifies monitoring of:

• Loss of AC input power
• Regulator shutdown by protection
• Significant reduction in delivered circuit VA
• Failure to deliver the selected output current
• Failure of a specified number of lamps

CCR and ALCMS

The CCR is the bridge between the control system and the high-power series circuit. AC 150/5345-10H references AC 150/5345-56 for the airport lighting control and monitoring system.

CCR COMPARED WITH OTHER EQUIPMENT

CCR vs isolation transformer

CCR vs ordinary power supply

FAILURES: PRIMARY VS SECONDARY

A secondary-side open circuit may stop one fitting while the primary series circuit stays continuous through the isolation transformer. That is why a single failed fixture does not take down the CCR circuit.

A break in the primary series circuit interrupts the only current path, so every fitting on that circuit goes out, not only those beyond the break. The CCR sees an open circuit and its open-circuit protection normally shuts it down; the break must be located and repaired before re-energising. Fault finding must always separate primary faults from secondary / fixture faults.

Protection functions

• Overcurrent
• Overvoltage
• Open-circuit protection (output opened or primary loop broken)
• Short-circuit conditions
• Thermal overload
• Input abnormalities
• Internal component faults
• Surge conditions

Protection philosophy and settings vary by manufacturer and specification. Do not treat the CCR as an ordinary industrial motor controller or generic power supply.

WAVEFORM, ENCLOSURE AND LOCATION

CCR, PHOTOMETRY AND LED FIXTURES

An incorrectly adjusted CCR can change the light intensity of compatible fittings. LED fixtures do not remove the CCR requirement: the CCR, isolation transformer, LED fixture, secondary arrangement and control system must all be compatible, and the fitting must operate correctly from the selected current-control arrangement.

CCR SELECTION CHECKLIST

TESTING: FAT, SAT AND CURRENT CHECK

CCR testing is part of Factory Acceptance Testing, Site Acceptance Testing, commissioning and periodic maintenance, following the applicable specification, approved procedure and manufacturer instructions.

FAT outline

• Document verification: datasheet, GA drawing, wiring diagram, test and calibration certificates, compliance documents
• Electrical: input, output current, steps, voltage, efficiency, power factor
• Functional: local and remote control, alarms, monitoring, interlocks
• Safety: insulation, dielectric withstand, earthing, protection

SAT / commissioning

Test the complete chain (CCR, primary cable, isolation transformers, secondary cable, fixtures) under actual installed conditions. Verify correct circuit, current, brightness levels, loading, transformer configuration, fixture operation, remote indication and fault monitoring.

Output current check

For a nominal 6.6 A setting, measured RMS current must fall within the equipment tolerance. AC 150/5345-10H specifies 6.50–6.70 A RMS for the applicable Class 1 steps, with similar tolerances for other steps. Use an appropriate calibrated true-RMS method and the approved procedure. Measure with a correctly rated clamp or CT around the insulated primary conductor; never break the series loop to insert a meter while energised.

FAULT-FINDING

CCR OFF?
  ↓ Check input supply
  ↓ Check control command
  ↓ Check protection / fault indication
  ↓ Check CCR output
  ↓ Check primary circuit
  ↓ Check transformers
  ↓ Check secondary circuit
  ↓ Check individual fitting

By symptom

CCR PREVENTIVE MAINTENANCE

Include thermal inspection (hot terminals, loose connections, overheating components, ventilation problems) and functional checks of local and remote ON/OFF, brightness selection, monitoring, alarms and the control-system interface.

COMMON CCR MISTAKES

IMPORTANT CCR TERMS

QUICK REVISION

Master flow

                 CONSTANT CURRENT REGULATOR
        ┌───────────────────┼───────────────────┐
      INPUT              CONTROL            OUTPUT
   AC supply          Local / remote      Series current
                      Brightness steps    Primary AGL cable
                      Monitoring          Isolation transformer
                      Protection          AGL fixture

EXAM / INTERVIEW QUESTIONS

FINAL STUDY TAKEAWAY

The CCR is the heart of the electrical side of a conventional AGL series circuit. Remember five things: current is the controlled parameter; it supplies the series circuit; current settings give brightness levels; a monitored CCR provides monitoring; and it must be considered as part of the whole system of cable, isolation transformer, connector, fixture, control system and photometry.

ENGINEERING & EXPERT NOTES

REFERENCES & FURTHER READING

These notes are a study aid. Verify details against the primary sources below.

EXPLORE ALL AGL STUDY NOTES