UFC 3-535-01
17 November 2005
CHAPTER 15: CHARACTERISTICS OF AIRFIELD GROUND LIGHTING
15-1
GENERAL
Airfield ground lighting (AGL) typically includes separate series-circuited lighting
systems that provide visual guidance to the pilot for aircraft operations. The systems
usually have brightness control for adapting to various visibility conditions. The types of
lighting systems installed for a particular runway are an important part in determining
the conditions under which aircraft operations are allowed (i.e., VFR, Category I or
Category II). The various lighting systems that may be installed for a runway are shown
in Figure 15-1. Not included in this figure are the several approach lighting systems
(ALS) which may also be installed. Details for lighted approach aids, runway lighting
systems, and taxiway lighting are provided in Chapters 3, 4 and 5, respectively.
15-1.1
Airfield ground lighting is characterized by constant current series
electrical circuits, which provide constant current for intensity control of lighting
components. This system allows for selectively changing the brightness of the lighting
components by increasing or decreasing the level of the constant current in the series
loop. While some older systems use constant voltage for shorter length series circuits,
most systems today are constant current type. The series circuit provides energy at
constant current to each device (such as a light or sign) on the circuit, supplied from a
CCR.
15-1.2
The major parts of a series circuit are: the CCR (power source), the
primary circuit cable, isolation transformers, and lighting components (such as lights
and signs). The isolation transformers are connected in series on the primary side, with
connected loads on the secondary side of each isolation transformer (Figure 15-2). The
system is characterized as follows:
15-1.2.1
A constant current is delivered along the entire loop on the primary side of
the isolation transformers, independent of the number of lighting loads. Power is
provided by the CCR.
15-1.2.2
The magnitude of the voltage along the series circuit primary depends on
the number and size of connected lighting loads. The voltage along the primary cable
will measure different at each point. (Calculating voltages for the constant current series
circuit is illustrated later in this chapter.)
15.1.2.3
The circuit is considered high voltage on the primary side, which typically
may be several thousand volts (5kV cable is used), and low voltage on the secondary
side or load side of the isolating transformers, which typically is less than 30V.
15-1.2.4
The isolation transformer provides an effective short for the primary circuit
in the event of a lamp filament failure, which opens the secondary circuit. This prevents
failure of a connected light from causing an open condition on the series primary circuit.
15-1.2.5
A constant current series circuit can also be used to power equipment with
specific voltage requirements. In this case a power adapter is used. The power adapter
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