Transformers and converters for low-voltage halogen lamps

Operating low-voltage halogen lamps depends on operating devices that transform the usual mains voltage of 230 V to approx. 11.5 V. Safety transformers, of either electromagnetic or electronic (converter) design, have been in almost exclusive use for several years now. The type plate of electromagnetic transformers bears the symbol for safety transformers in accordance with VDE 0570, corresponding to EN 61558. Electronic converters are marked with the sign for Safety Extra Low Voltage (SELV), which indicates that the product is an isolating converter whose secondary out put is safe to touch even during no-load operation.
Transformers and converters fall into one of two protection classes. Operating devices of protection class I are base-insulated and must always be connected to a protective conductor. Isolating transformers and converters of protection class II are equipped with double or reinforced insulation that protects against dangerous casing currents.

Operating devices can also be differentiated according to the way they are used. Built-in transformers have to be installed in a permanent casing, e.g. aluminaire. In contrast, so-called independent transformers and converters can be operated independently of a luminaire. These are often found in ceiling installations; in order to prevent possible noise development, isolation transformers must be mounted in such a way as to avoid vibration transmission.
Transformers or converters bearing the MM mark can be mounted on surfaces of unknown flammability, which can be the case when mounting these devices on wooden furniture elements. Such devices comply with the temperature requirements of VDE 0710, part 14, of < 95 °C during normal and < 115 °C during abnormal operation