Operating units

1. What kind of transformers do exist and what are the differences?

2. How can you dim transformers?

3. Can several transformers be interconnected?

4. Why do transformers sometimes make a humming sound?

1. What kind of transformers do exist and what are the differences?

Toroidal transformers

Toroidal transformers are the most efficient magnetic transformers. Depending on the quality of the copper wire an efficiency rate of 75-85% is achieved. Due to the closed, air-gap free toroidal-core form, the no-load losses are significantly lower compared to iron-cored transformers. If you decide to choose a lower priced magnetic transformer, toroidal transformers can be easily be integrated into applications, in which low standby losses are of great importance. By overdimensioning the transformer the losses can also be reduced under load: at 50 % partial load they amount to only ¼ of the respective one at nominal load.

BRUCK toroidal transformers are provided with a short-circuit protection by means of a fuse as well as with an overload and overtemperature protection. A current relay according to VdS / ENEC can optionally be connected. This means you play it safe with BRUCK toroidal transformers.

Iron-cored transformers

In the case of iron-cored transformers the primary and secondary windings are wound around the core separately but next to each other. Here, due to the longer induction period the losses are greater compared to toroidal transformers. The efficiency rate amounts to 70-80 %. BRUCK iron-cored transformers are provided with a short-circuit protection by means of a fuse as well as with an overload and overtemperature protection. A current relay according to VdS / ENEC can optionally be connected. This means you play it safe with BRUCK iron-cored transformers.

Electronic transformers with secondary AC output

Electronic transformers (AC = alternating current) distinguish themselves through a very compact design. Due to their small size these transformers are preferably used for luminaires or for ceiling or wall mounting fixtures. The primary voltage is transformed to the secondary voltage by means of a combination of small coils and electronic components. These electronic components enable the high efficiency rate of 95-98%. The AC secondary voltage has a frequency of 40 kHz to 50 kHz. Thus, the secondary consumption length is mostly restricted to 2 metres. For this purpose, please also observe the individual manufacturer specifications.

Electronic AT transformers by BRUCK ensure a maximum level of safety and convenience thanks to the short-circuit, overload and overtemperature protection. Right after the fault was remedied these transformers are in full working order again. The soft start increases the service life of the luminaire and reduces the maintenance costs.

Electronic transformers require a minimum load of about 20 %. If the minimum load is not reached the connected illuminants cannot be switched on at all or the light flickers. In most cases the transformer makes a humming sound.

Electronic transformers with secondary DC output

Electronic DC transformers (DC = direct current) significantly differ from AC transformers (AC = alternating current) due to a constant secondary voltage. Thanks to this technology, longer low-voltage systems can be fed. Depending on the type of the transformer, 6 to 20 metre long secondary lines are possible. Thus, the transformers easily can be mounted out of sight. The efficiency rate of DC transformers is between 90 and 95%.

Just as for electronic AC transformers a minimum load of about 20% is required. If the minimum load is not reached the connected illuminants cannot be switched on at all or the light flickers. In most cases the transformer makes a humming sound.

Electronic AT transformers by BRUCK ensure a maximum level of safety and convenience thanks to the short-circuit, overload and overtemperature protection. Right after the fault was remedied these transformers are in full working order again after switching the mains voltage off and then on again. The soft start increases the service life of the luminaire and reduces the maintenance costs.

2. How can you dim transformers?

Dimming halogen or incandescent lamps probably significantly increases the service life and reduces the energy consumption. The brightness is reduced more significantly than the energy consumption. Thus, this leads to a decline in the energy efficiency. If a lamp is dimmed very often, a large part of the energy can be saved by means of a lamp with a lower capacity. Dimming the light also changes the luminous colour and increases the red component.

3. Can several transformers be interconnected?

Interconnection of magnetic transformers

When switching on magnetic transformers it is possible that the upstream circuit breakers are triggered due to the higher inrush current. In the case of magnetic transformers, the inrush current can be up to 10 times the nominal current. For a 300 VA transformer with a nominal current of 1.3 A, this would temporarily be 13 A. When safeguarding a light power circuit with an automatic circuit breaker of 16 A, this might mean that the fuse will respond too sensitively. This tripping is prevented by the inrush current limiter. Magnetic transformers by BRUCK with a power of 300 and 400 VA are therefore, as standard, equipped with an inrush current limiter. Thus, several transformers can be interconnected.

Interconnection of electronic transformers

A joint control of multiple electronic transformers by means of one switch is possible without a problem since the inrush currents are relatively low. Please observe the switching capacity of the switch. High-quality electronic transformers by BRUCK do not show any inrush current peaks as known from magnetic transformers without an inrush current limiter.

On the secondary side electronic transformers must not be interconnected.

4. Why do transformers sometimes make a humming sound?

Transformers consist of two coils that are wound around an iron core. The iron core is manufactured from thin metal sheets that are isolated against one another. A humming sound is created within the transformer whenever magnetic forces set the sheet metal parts in motion.

Electronic transformers are operating according to another principle and thus do not make any humming sound. Here you can find solutions to achieve a humming-free operation of your transformers.