Transformers are electronic components used to convert currents, voltages or frequencies. In the field of lighting engineering they are mostly used as voltage transformers to supply low voltage halogen capsule lamps with the appropriate voltage (6V, 12V, 24V).

Transformers generate this low voltage either via induction with two separate windings (conventional transformers) or electronically (electronic transformers).

In both cases it is essential to ensure that no voltage can pass into the low-voltage system (safety transformers pursuant to VDE 0551). Transformer fuse protection is provided in the primary circuit.

As a transformer delivers electric power at relatively low voltages, the system has to carry high currents, and this must be borne in mind with regard to the correct rating for conducting parts. The transformer itself must also have the appropriate rating for the system on the secondary circuit.

Overheating protection for the transformer is not a luxury; it is essential for the safe operation of the system. In the case of overloading (too many lamps at too much power, or a short circuit) the transformer can quickly become too hot, and that is a serious fire hazard.

If the load is too low (too few lamps at too little power), on the other hand, secondary voltage in the lamps rises, and that can burn out the filament causing premature lamp failure. This process can then "snowball".