Operating units
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.
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.
Three letters and a symbol

230V halogen lamps and incandescent lamps as well as 12V halogen lamps with electronic and magnetic transformers can be dimmed. However, during the installation it must be ensured that the correct dimmer for each load is installed. Different load types must not be actuated by one dimmer. In order to facilitate the allocation, dimmer and transformer manufacturers agreed on the following symbols.

The three letters `R`, `L` and `C` or a combination of these letters divide the dimmers into classes. `R` stands for resistive loads such as 230V halogen lamps or incandescent lamps. `L` stands for inductive loads such as magnetic transformers. `C` stands for capacitive loads such as electronic AC transformers for 12V halogen lamps. The wedge symbol indicates that it is possible to control the brightness.

In the future, transformers will also be provided with these symbols to facilitate the allocation to the correct dimmer.

By means of this identification you can proceed as follows:

Please check whether the same letter is to be found on the dimmer and on the transformer. If this is the case, it means that your combination is correct.

Make sure that downstream of a dimmer the L and C loads are not mixed. Even a universal dimmer that bears the letters L and C cannot operate mixed L /C loads. This requires particular diligence in the case of already existing installations.

Please note: this classification is not applied for fluorescent lamps as here the brightness is not controlled by means of a dimmer but with a 1-10V or a digital control system.

Dimming with magnetic transformers

Leading-edge dimmers are suitable for magnetic transformers (inductive = L). With this principle incandescent and 230V halogen lamps (R) can also be dimmed. During the dimming phase the sine wave of the 50 Hz alternating voltage is switched on with some delay – this is the so-called leading edge. The later it is switched on the darker is the light.

In exceptional cases, disturbing sounds can be issued during the dimming process. In most cases the noise emission in connection with iron-cored transformers is lower compared to toroidal transformers. These noises can be significantly reduced by means of targeted measures. If transformers are fitted on a soundboard such as, for instance, a metal or a wooden ceiling vibrations are transmitted and the humming sound is intensified. This can be remedied by loosening the screws or by inserting an isolating rubber mat between the transformer and the ceiling. Should this not have the desired effect it is recommended to interpose a noise limiter such as a choke and/or a filter between the dimmer and the transformer. Here, disturbing harmonics are filtered out of the voltage and the humming sound is reduced.

Dimming with electronic transformers (AC)

Trailing-edge dimmers are suitable for electronic AC transformers (capacitive = C). According to this principle, incandescent and 230V halogen lamps (R) can also be dimmed.

Joint dimming of multiple electronic transformers by means of one dimmer can lead to slightly different brightness levels of the illuminants since each electronic transformer has an individual dimming curve. An alternative for the use of multiple electronic dimmers with a reduced capacity is using an electronic transformer with a higher capacity of up to 300W. These are also available at BRUCK with an integrated touch dimmer function that is not controlled by means of a dimmer but with the aid of a standard switch. Further options are transformers with 1-10V or a DALI interface which requires a 2-pole control lead.

The minimum load of a transformer must not be underrun during the dimming process.

Electronic transformers produce almost no humming sound. In exceptional cases, a slight humming sound can be issued during the dimming process. These noises can be significantly reduced by means of targeted measures. If transformers are fitted on a soundboard such as, for instance, a metal or a wooden ceiling vibrations are transmitted and the humming sound is intensified. This can be remedied by loosening the screws or by inserting an isolating rubber mat between the transformer and the ceiling. In some cases it might be helpful to replace a universal dimmer by a leading-edge dimmer. Should this not have the desired effect, please refer to the operating instructions and check whether the specified installation instructions and the dimmer recommendations have been complied with.

Dimming with electronic transformers (DC)

In contrast to electronic AC transformers, DC transformers can generally be better controlled by means of a leading-edge dimmer (inductive = L) or a trailing-edge dimmer (capacitive = C). Universal dimmers, on the other hand, are not suitable for this purpose. Please observe the manufacturer specifications on the approved dimmers for the respective DC transformers. Dimmer recommendations regarding the BRUCK DC transformers can be found under „Light systems / Transformer / Transformers and accessories“.

Electronic transformers produce almost no humming sound. In exceptional cases, a slight humming sound can be issued during the dimming process. This noise can be significantly reduced by means of targeted measures. If transformers are fitted on a soundboard such as, for instance, a metal or a wooden ceiling vibrations are transmitted and the humming sound is intensified. This can be remedied by loosening the screws or by inserting an isolating rubber mat between the transformer and the ceiling. Should this not have the desired effect, please refer to the operating instructions and check whether the specified installation instructions and the dimmer recommendations have been complied with.

Dimming with universal dimmers

A universal dimmer itself recognises the connected electronic loads and adjust to them automatically. This is a comfortable solution, which is, however, more expensive. We therefore generally recommend using the leading-edge dimmer or the trailing-edge dimmer if the customer is familiar with the load.

Should there be problems with detecting the load in connection with universal dimmers, this is expressed by means of a humming sound, flickering or short flashing of the lamps. This is possible, for instance, when using DC transformers. In this case, please refer to the operating instructions of the transformer to find out which dimmer is approved.
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.
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.
The following dimmers by the specified manufacturers can be combined with the installed dimmable LED drivers from the Bruck luminaire range.

Manufacturer Model Leading edge Trailing edge Number of devices
Dimmer   per dimmer
CLIPSAL 32V500 X   20
HPM CAT300E x   15
HPM CAT400L x   15
JUNG 266 GDE x   30
KIWI electronics K 101L x   15
Legrand 573462 x   15
MK Electric DW480 x   20
North-West M 1500 x   15
Schneider SBD-SPL x   15
Schneider X3104-WH x   15
Berker 2874   x 30
Busch - Jäger 6513U-102   x 25
CLIPSAL 32E450UDM   x 25
CLIPSAL 32E450TM   x 25
HPM CAT400T   x 25
JUNG 225 TDE   x 30
Merten SBD315RC   x 15
Schneider CCTSE12011   x 20

The dimmer should be designed for a minimum load of 7.5 watts to ensure the optimum flow of light of the LED.
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