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Due to the constant-current characteristic of the capacitive circuit,the
influence of mains voltage deviations is less than with the inductive
circuit (see Fig.130).
Electrical wiring
The electrical wiring in a luminaire must be such as to ensure its
electrical safety.This necessitates great care both in the choice of wire
used and in its manner of installation.
There are a great many different types of wire available, in both
single-core (solid) and multi-core (stranded) versions (Fig. 131).There
is a wide variety in wire materials and diameters, as well as in thickness
and quality of insulating cladding material.
Whether the wire is single-core or stranded makes no difference as
far as its electrical characteristics are concerned.Mechanically, however,
things are quite different.
Single-core wire is much stiffer than stranded wire, which means that
fewer cable fasteners are needed to hold it in position. It is also easier
to strip, after which it can be pushed into self-clamping connector
blocks without further preparation. It is therefore more suitable than
stranded wire for the internal wiring in a luminaire (Fig. 132).
Single-core wire is, however,not suited for use in luminaires that are
subjected to vibrations and shock.The vibrations can be transmitted
along the wire, causing fixing screws to be loosened or the wire to
fracture and break. Here, stranded wire must be used. Being more
flexible, it is able to absorb vibrations harmlessly.Stranded wire is also
necessary in those situations where the wire must be able to bend in
use - as in a spotlight, for example (Fig. 133).
314
5
137
Fig. 130. Influence of variation of the supply
voltage on a PL-L 18 or 24 W lamp operated
in a lagging (inductive) circuit (Fig. 130a) and
in a leading (capacitive) circuit (Fig. 130b).
Relative values of luminous flux (
Φ
), lamp
current (I
l
), lamp wattage (P
l
) and lamp
voltage (V
l
).
Ambient temperature: 25 ºC, burning position:
base up.
Fig. 131.Types of wire used in luminaires.
From left to right: solid core (3), stranded (3),
with heat-resistant insulation (3) and high-
voltage ignition cable (1).
3.13 Effects of mains voltage fluctuations
130
120
110
100
90
80
70
90
100
110
120
%
relative supply voltage (%)
I
l
P
l
V
l
Φ
130
120
110
100
90
80
70
90
100
110
120
%
b)
a)
relative supply voltage (%)
I
l
P
l
V
l
Φ