Philips Electromagnetic Lamp manual Electrical wiring, 137

5

3.13 Effects of mains voltage fluctuations

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).

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 (Il ), lamp wattage (Pl ) and lamp voltage (Vl ).

Ambient temperature: 25 ºC, burning position: base up.

%

130 120 110 100 90

80 70

a)

				%
				130
			Il
				120
			Pl
			Φ	110
				100
			Vl
				90
				80
				70
90	100	110	120
	relative supply voltage (%)			b)

Il

Pl

Φ

Vl

90 100 110 120

relative supply voltage (%)

3 14 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.

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).

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).

137