My lights/transformer hum when I perform dimming – what’s causing this?
Dimmers function as fast electronic switches. This means that a dimmer switches the light off for short periods. The switching on and off processes cause abrupt changes in the magnetic field in conventional transformers. These changes in the magnetic field cause the transformer windings to vibrate, and this vibration is amplified particularly strongly on wooden ceilings. Loosening the screws might help. If necessary, you can place a rubber strip (foam rubber) between the transformer and the ceiling. This reduces the vibrations.
Are transformers dimmable?
It’s not a one-size-fits-all situation. Whether a transformer is dimmable depends on the type of transformer and the light bulb connected to it. As a general rule, both the transformer and the light bulb must be explicitly labelled as ‘dimmable’.
Depending on the transformer technology, the following rules apply:
1. Transformers for 12V AC (AC)
Here, the dimmer is installed on the 230V primary side (before the transformer):
Electronic transformers (EVG): Require a phase-cut dimmer (capacitive load – marked C or R,C).
Conventional transformers (block / toroidal transformers): Require a leading-edge dimmer (inductive load – marked L or R,L).
2. Transformers / power supplies for 12V / 24V / 48V direct current (DC)
Standard DC power supplies: These are usually not dimmable on the primary side via a wall-mounted dimmer. Dimming takes place on the secondary side (after the transformer) via an intermediate controller (e.g. Zigbee, BLE or wireless dimmer via PWM).
Primary-side dimmable DC transformers: Only specialised DC power supplies explicitly labelled as ‘dimmable’ can be controlled directly via a phase-cut wall dimmer. We do not stock such products.
Should transformers be loaded with more or fewer components (load factor)?
A higher load causes the transformer to overheat; the maximum load must not be exceeded. This may cause the thermal switch or thermal fuse to trip. Transformers with thermal fuses are then permanently faulty. If the required minimum load is not reached, the light will not come on or will flicker. Here, the transformer must be replaced with a different model.
When is a transformer needed?
A transformer or power supply unit is used to step down the voltage, for example from 230V AC to 12/24V AC or DC. In addition, there are transformers/power supplies that convert alternating voltage into a constant current (constant current), e.g. 350 mA or 700 mA.
Why is the transformer humming? How can this be prevented?
With conventional transformers, a minimal amount of noise is unavoidable. This can be dampened, for example, by placing a small piece of foam rubber under the mounting plate. If the noise level is higher than this, there is likely to be a fault. The device will need to be replaced.
Why are there two 230V primary connection terminals?
The two primary terminals are connected in parallel on the transformer. If, for example, two transformers are to be connected to a single supply line, one transformer can be connected directly, whilst the second transformer can be connected to the second primary terminal.
Why is the cable length limited to 2 metres for electronic transformers operating on alternating current?
This is required by law, as otherwise other devices could be interfered with due to the antenna effect. The following problems arise with longer cable lengths:
Radio interference can increase significantly, as the low-voltage cables act as transmitting antennas (the transformer operates in the high-frequency range).
At high operating frequencies (in the kilohertz range), the so-called skin effect occurs. This means that the full conductor cross section is no longer available for the transmission of current. The current is forced more towards the outer regions of the conductor. Less current flows in the centre of the cable. As a result, with longer cable lengths, the voltage drop increases disproportionately and the light becomes extremely dimmer. With star-shaped wiring (transformer in the centre), a length of 4 metres can be supplied (2 metres from the transformer in each direction). If this is not sufficient, a conventional AC transformer must be used instead.
Why does the electronic transformer take a while to switch on?
The transformer performs a soft start. The converter detects a high inrush current and counteracts this using short-circuit current limiting, i.e. the inrush current is limited. This protects the LEDs from damage.
An excessive delay may also be caused by an overload of the electronic converter (transformer).
The soft start is completed within a maximum of 1.5 seconds.
What type of fuse is required for conventional transformers?
The fuse rating is always indicated next to the fuse. The inrush current may cause the fuse to blow if the wrong type of fuse is used. There must be none of the following fuses marked M, MT or F used for this application: slow-blow (e.g. T 1.6A) or extra-slow-blow (e.g. TT 1.6A).
What is a converter?
A term used to describe a ballast that converts the voltage level and frequency of the input voltage.
What happens if the output falls below the minimum power rating of an electronic transformer?
The light starts to flicker or does not light at all. Reason: a safety mechanism that switches off the transformer when it is not in use.
Which transformer should be used for LED lights?
Here are various types of ballasts for operating LED light sources:
LED transformer
These are conventional metal-core transformers that output a 12V alternating current (AC). These transformers are suitable for all 12V retrofit light bulbs (replaceable light bulbs that feature standard sockets and are modelled on 12V halogen light bulbs in terms of design).
DC LED power supply
These ballasts output 12V direct current (DC) and are suitable for lights without replaceable light bulbs, which are clearly marked on the type plate for operation with 12V direct current (DC).
LED Driver
These ballasts supply a constant current of 350/700/1000 milliamps (mA) (depending on the model) at a varying voltage (V). LED drivers are suitable for lights without replaceable light bulbs that are clearly marked on the type plate as being designed for operation with a constant current. The voltage is always direct current (DC).
How do you find a suitable replacement transformer?
There is a Paulmann sticker on or underneath the transformer, on which you can find the product’s item number (usually a 5-digit number separated by a full stop, e.g. 123.45).If there is none of this information on our website, please contact our customer service team with the number.
How can lights be converted to LED?
It is important to note here whether the light is high-voltage or low-voltage. With high-voltage light bulbs (gu10, E27, E14), the light bulb can simply be replaced. With low-voltage light bulbs (gu5.3, G4), the minimum load/power rating of the transformer must be taken into account.
How warm or hot do the ballasts in Paulmann products get?
Depending on the power supply unit’s output, the connected components and the ambient temperatures (ta – ambient temperature), different temperatures are to be expected on the surface of the power supply unit (tc – case temperature). This value can usually be read directly from the power supply unit. A maximum temperature of 60–85°C is not unusual in this context.
