How transformers work in the lighting system

Conventional transformers

In short there are two types of transformers. On the one hand, the conventional transformers, which consist of an iron core which has two coils, which are electrically separated from one another and usually wound from copper wire. One coil has more windings, the other less. The ratio of the voltages corresponds to the ratio of the number of windings.

However, this principle only works with alternating current. In order to achieve a voltage of 12 V, the coil, which is supposed to have a voltage of 12 V, must have approximately 10 times less windings than the coil at which the input voltage of 230/240 V is applied. If, on the other hand, a low voltage is to be transformed into a higher one, the principle works exactly the opposite way. In lighting technology the conversion into a smaller voltage is usual. One factor always remains the same: and this is the electrical power.

Among the conventional transformers, there are two types: the block core transformers and ring core transformers. Both are the same as with their heavy relatively large dimension.

An important advantage is the larger cable length, which can be realized with conventional transformers (the cable cross section, however, also plays a role). A conventional transformer has an external fuse in the housing, which can be protected and replaced before the transformer is overloaded. Common conventional transformers in lighting technology were 60VA to 300VA transformers. However, the conventional transformers have been on the decline for many years.

Electronic transformers

The correct term for the electronic variants of transformers would be “primary switched switching power supply”, but the term “electronic transformer” is often used in the lighting industry. So we stick with it. In contrast to conventional power supplies, the electronic transformer operates at a higher frequency and can thus be more efficient. This is because, at higher frequencies, transformers need less magnet core volume for the same power. For this purpose, the main voltage has to be rectified and “screened”, then chopped into a higher frequency voltage and after the transformation in a high frequency base, re-aligned to the desired alternating voltage 11.5 -12V. This happens in fractions of seconds and time and time again.

The electronic switching devices, which are smaller, lighter, cheaper and more versatile, are very popular. They are indispensable especially for recessed lighting, as they pass through a hole cut through the small flat design and do not have to be hidden anywhere in the ceiling. Also for table lamps electronic switching power supplies are popular, then as a rule as a plug transformer.

Further advantages of the electronic transformers are the integrated overvoltage protection, which means that the transformer switches off when too much voltage is generated in the power supply. The cable length should not exceed approx. 2m, in order to avoid problems with voltage loss and EMC (electromagnetic compatibility). Electronic transformers are usually available with max. 250 VA, since for larger versions, a much higher level of protection would have to be used.

Also a lot of LED-based lamps (via an LED driver) work with a transformer or switch to reduce the voltage of the power line.

Advantages of lighting systems with transformers

• The flexibility with which flat installation options for downlights can be created. Or even with filigree, fine rail systems which allow simple distribution of many light sources in a large room with only one power connection.
• Low-voltage halogen technology also offers 2-5 times longer lifetime of the lamps and a brilliant light with very good color reproduction properties. Transformers, whether conventional or electronic, can be easily dimmed using 230V halogen or 12V halogen.
• A conventional transformer should be charged up to 80% in order not to permanently damage the lamps. So, as soon as possible exchange defective bulbs! This is different for electronic switching devices. They always maintain the level of the output voltage constant up to the maximum load. If the consumption drops below the minimum load, the transformer switches off.
• Since transformers always produce a heat of their own, it is advisable not to “pack” them somewhere, E.g. in a ceiling insulation or similar. There should be sufficient space to allow the heat to escape from the transformer. This also increases the life of transformers.