e27 lampholders - Spotled

TECHNICAL INFORMATION
Metal alloys are highly appreciated because of the outstanding
mechanical strength of the bodies and the connections, but often
the determining factor in choosing metal is aesthetics.
The unmistakable smooth and polished finish gives the lampholder a
solid appearance and, at the same time, a sophisticated look:
appearance and finish that match well with those of other materials
commonly used in a decorative lighting fixture, such as wood, fabrics,
painted or enamelled metals and glass.
Given the good electrical conductivity of metals, it is obvious that in
this type of lampholder, other insulating materials must be used, such
as phenolic resins or polyester, to guarantee efficient operation and
safety.
All the insulating materials must pass specific tests to determine:
• heat resistance;
• self-extinguishing power;
• electric strength against surface currents.
One of the tests most frequently performed is the incandescent wire
test. An incandescent metal wire is applied to the surface of the piece
for 30 seconds. If a flame appears it must be extinguished within 30
seconds from the moment the wire is removed
CONNECTION CABLES
The main elements of a connection cable are:
• conductor material;
• conductor cross-section;
• material of the insulating sheath(es) (main insulation and/or double
insulation);
• rated voltage;
• temperature resistance (see following table).
The choice of the lampholder connection cables inside a lighting fixture
will vary greatly depending on the type of fixture, its normal operating
conditions and the light source installed. Therefore, the basic
parameters to be considered when choosing the cable are:
• temperature resistance, mainly related to the material of the
insulating sheath and the conductor material;
• maximum current load permitted, mainly correlated to the conductor
cross-section;
• rated voltage, mainly correlated to the thickness and material of the
insulating sheath.
It has been demonstrated that the presence of high temperatures
reduces cable conductivity and thus the sustainable current load. In
addition, with cross-section being equal, the greater the current load,
i.e. the power absorbed by the fixture, the hotter the cable
will get.
A fundamental factor in reducing the voltage and dissipating the heat
is the way the cable is connected to the lampholder terminals/contacts.
Soldering produces less heat than a clip.
Lampholders for incandescent light sources (E14, E27, B15) normally
are wired inside the luminaires using a cable made of:
• copper core whose cross-section is no less than 0.5 mm 2 ;
• sheath/insulations that can withstand a temperature of:
90°C for ordinary PVC (e.g. H03VV-F);
105°C for heat-resisting PVC (e.g. H03V2V2-F).
For both cables temperatures are reduced by 15°C where the insulation
is stressed, e.g. clamped or flexed.
BEWARE: The above mentioned temperatures are the maximum
permitted under the artificial test conditions given in table 12.2 of
luminaire standard IEC/EN60598-1.
The situation is different for low-voltage halogen lamps that require
lampholders that normally are supplied already wired with cable ends
(see page 144). For temperatures of 180 °C it is recommended to use
a cable with a tin-plated copper core and a fluorocarbon resin-fep
(TF20) insulating sheath. For temperatures of 250 °C it is
recommended to use a cable with a nickel-plated copper core and a
fluorocarbon resin-ptfe (PT18) insulating sheath.
For mains voltage halogen lamps, it is possible to use wired
lampholders (see page 121) whose cables have double insulation and
can withstand a temperature of 180 °C and 250 °C (see following
table). By combining this type of cable with the appropriate
lampholders, it is easy to make class II lighting fixtures.
ARDITI S.p.A. 24012 BREMBILLA (BERGAMO) ITALY - Via Caberardi, 3 - Tel. +39 0345 52111- Fax +39 0345 52355 - Internet: http://www.arditi.com - E-mail: arditi@arditi.com 217