1. What types of transformer are there and how do they differ?
2. How are transformers dimmed?
3. Can several transformers be connected together?
4. Why do transformers sometimes hum?
1. What types of transformer are there and how do they differ?
Toroidal transformers
Toroidal transformers are the most efficient magnetic transformers. Depending on the quality of the copper wire, the efficiency is 75-85 %. Due to the closed, air-gap-free toroidal core shape, the no-load losses are significantly lower than with iron-core transformers. If an inexpensive magnetic transformer is chosen, toroidal transformers can be used well in applications where low standby losses are important. By oversizing the transformer, losses can also be reduced under load: at 50 % partial load, they are only ¼ of those at nominal load.
BRUCK toroidal transformers have short-circuit protection by means of a fuse as well as overload and overtemperature protection. A current monitor in accordance with VdS / ENEC can be connected as an option. With BRUCK toroidal transformers, you are playing it safe.
Iron-core transformers
Iron-core transformers are also known as "block transformers". In this type of transformer, the primary and secondary windings are wound separately next to each other on the core. The losses are higher than with toroidal transformers due to the longer induction path through the air. The efficiency is 70-80 %. BRUCK iron-core transformers have short-circuit protection by means of a fuse as well as overload and overtemperature protection. A current monitor in accordance with VdS / ENEC can be connected as an option. This means you are on the safe side with BRUCK iron-core transformers.
Electronic transformers with AC secondary output
Electronic transformers (AC=alternating voltage) are characterised by a very compact design. Due to their small size, these transformers are preferably used in luminaires or for ceiling or wall installation. The primary voltage is converted into the secondary voltage using a combination of small coils and electronic components. These electronics enable the high efficiency of 95-98 %. The AC secondary voltage has a frequency of 40 kHz to 50 kHz. This means that the secondary power length is usually limited to 2 metres. Please also refer to the individual manufacturer's specifications.
Electronic AC transformers from BRUCK ensure maximum safety and convenience thanks to their short-circuit, overload and overtemperature protection. These transformers are fully functional again as soon as the fault has been rectified. The soft start increases lamp life and thus reduces maintenance costs.
Electronic transformers require a minimum load of around 20 %. If the minimum load is not reached, the connected lamps remain off or flicker. In most cases, the transformer also hums.
Electronic transformers with DC secondary output
The main difference between electronic DC transformers (DC=direct voltage) and AC transformers (AC=alternating voltage) is the rectified secondary voltage. This technology makes it possible to feed in longer low-voltage systems. Depending on the transformer type, 6 to 20 metres of secondary cable are possible. This makes it easy to install the transformers out of sight. The efficiency of the DC transformers is between 90 and 95 %.
The minimum load of around 20 % is just as necessary as for electronic AC transformers. If the minimum load is not reached, the connected lamps are off or flicker. In most cases, the transformer also hums.
Electronic DC transformers from BRUCK provide maximum safety and convenience thanks to their short-circuit, overload and overtemperature protection. Immediately after rectifying a fault, these transformers are fully functional again by switching the mains voltage off and on again. The soft start increases lamp life and thus reduces 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.