VS_2017

Technical Details – Components for Incandescent Lamps
Dimmer operation
VS safety transformers can be controlled using progressively adjustable phase-cutting leading-edge
dimmers for low-voltage halogen lamps.
Reliability and service life
VS safety transformers are designed for a long service life. Provided the specified maximum values for
the winding temperature are complied with during operation, a service life of 10 years can be expected.
Failure rate: < 0.025%/1,000 hrs
Conductor Contacts
Electrical installation
Conductors
Connections
Primary conductor cross-section: min. 0.75 m²,
secondary conductor cross-section: min. 0.75 m² for 50 W output
and a min. of 1 mm² for 100 W output
Terminal screws: max. torque of 0.5 Nm must not be exceeded
Parallel connection
Parallel connection is admissible on the primary side, but is inadmissible on
the secondary side
Conductors for low-voltage halogen installations
As the high temperatures associated with the operation of low-voltage halogen lamps place severe demands
on lampholder conductors, a skilful combination of conductor and insulation is essential. Tin-plated
copper conductors with silicone insulation are recommended for temperatures of up to 180 °C at the
cable's conductor; nickel-plated copper cables with polytetrafluoroethylene (PTFE) sheathing are recommended
for temperatures of up to 250 °C. Welded connections ensure the most effective heat discharge.
Control measurements should be carried out if other connection types are used, e.g. crimping or plug
connectors. To prevent the risk of additional heat generation, the maximum permissible current load must
be observed when dimensioning the conductor cross-section. When using electromagnetic transformers,
the conductor resistance causes a relatively large voltage drop. This drop in voltage is always associated
with a reduction of luminous flux. For instance, an 11% drop in voltage will lead to a 30% drop in luminous
flux. For this reason, care should be taken to ensure secondary conductors are kept as short as possible
and conductor cross-sections are adequately dimensioned when wiring luminaires. Nevertheless, transformers
should not be mounted too near the light source (> 25 cm clearance if possible) to prevent the heat
generated by the lamp from raising the ambient temperature above the critical level for a transformer.
As electronic converters operate at high frequencies, consideration must be taken of the skin effect,
i.e. the displacement of the electrons from the middle of the conductor to its surface. As a result, the full
cross-section of the conductor is no longer used, resistance increases and thus leads to a greater drop
in voltage. In addition, AC resistance, which is caused by feed line inductance, can result in an even
greater voltage drop. It is therefore recommended that lamp conductors be laid closely parallel or
twisted together.
Voltage losses (V) with a two-metre secondary conductor
Working frequency Load Cross-section/Voltage drop
W 0.75 mm² 1 mm² 1.5 mm²
50 Hz (electromagnetic transformers) 50 0,38 V 0.29 V 0.2 V
any wiring layout 100 0.74 V 0.56 V 0.39 V
40 kHz (electronic converters) 50 1.4 V 1.25 V 1.2 V
any wiring layout (loops) 100 3.3 V 3.1 V 3 V
40 kHz (electronic converters) 50 0.5 V 0.45 V 0.35 V
wires twisted together or closely parallel 100 1.2 V 1 V 0.85 V
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