LED - Energy savers with a bright future and some little quirks
LEDs have made a career for themselves in recent years. Thanks to advances in efficiency and colour rendering index, there is hardly an area of lighting technology where they are not present: As retrofit LED light sources, they are a welcome alternative to the unloved energy-saving lamps. As luminous strips and surfaces, they nestle up to any surface, opening up completely new lighting design possibilities. Even high-performance devices such as stage and studio spotlights or floodlights are available as LED versions.
But not every incandescent lamp can simply be replaced by an LED retrofit lamp. This can cause massive disruptions to the installation - surprisingly, even when simply switching. The reason is the short but also extremely high inrush currents. They can be a thousand times or more the rated power. Contacts can burn or weld as a result.
The LED challenge and how to deal with it
The difficulties associated with such everyday tasks as switching or dimming are surprising. The problem is that there is still no standard specifically for LED light sources. It is true that the general regulations for luminaires apply to LED lamps, from the design of the lamp holder to the measurement setup for luminous intensity. What happens in between, however, is not covered. In contrast to a classic lamp with a simple filament, LED lamps contain a lot of electronics for control. Every manufacturer worldwide can decide for themself how this is constructed. Manufacturers of switching and dimming devices therefore have no clues as to which electronics are controlled and how the LED lamp behaves. The corresponding standards currently exist only as drafts.
No standard at hand? Then let's test it ourselves!
If special switching loads for LED lamps and discharge lamps are not specified on a product, one can assume that the product has not been approved for these. However, the specifications for LED loads are not always helpful. Which switching currents does the device manufacturer assume? These may differ from lamp to lamp. You should also be careful when adding several LEDs with a low rated output together on one circuit they may have a higher combined switching current than one single LED with the respective total output. In order to be able to specify the load specifications for switching devices and dimmers, Theben conduct ongoing measurements on all conventional retrofit lamps. During these tests, the switching devices run through at least 40,000 switching cycles. This allows us to make reliable statements for the switchable loads.
LED - Economical in consumption
Wasteful when switched on
Hard work for the contacts: Capacitive switching loads
How can an LED lamp that only has a few Watts rated output destroy a switching contact that is rated for a higher wattage? Upon closer inspection, the answer is found in the switching currents: in light bulbs, the typical switching currents of the cold spiral coil cause a tenfold increase of the respective rated current. With LED lamps and energysaving lamps with their capacitive characteristics, one finds switching current pulses in the µs range that could be a thousand-fold and more of the rated current.
A measurement in our test laboratory authorised by the VDE has shown, that in a most unfavourable case, a 1.8 W LED lamp had a switching current of 19 A. That is 1.706 times the rated output!
Optimum switching of LED lamps: With the right contact at the right time
Two contacts for all switching cases: Tungsten pre-contact
High currents require special contacts. Next to silver tin oxide (AgSnO2), Theben uses a combination of two contacts that close one after another: the tungsten pre-contact. The leading contact comprises< of high-Ohm and highly-resistant tungsten. It captures the starting current and limits it at the same time. The low-Ohm main contact remains unloaded from the switching peaks in such a manner. Theben uses these relays for the KNX switching actuators, KNX dimming actuators and KNX blind actuators.
Switching precisely at a point: zero-cross switching
Switching devices that are designed for a C load generally deal with the switching currents in a better manner. In doing so, Theben uses a particularly efficient solution, so-called zero-cross switching. This calculates the zero crossing of the sine curve of the alternating voltage. At this moment, the switch-on current is minimum when switching. This protects the relay contact and extends its service life, even at nominally high switching loads. The C-Load KNX switching actuators with current detection are equipped with this.
KNX dimming actuators:
More resiliant, more reliable, stronger
To cover all applications: An overview of switching values
Quality has a price. But it pays for itself: Due to the high testing requirements in our company laboratory, e.g. 40,000 switching cycles, we are above the standard. This demand in quality is also confirmed by an external VDE test. This also applies to switching loads, from which the same is expected.
| KNX switching actuators | Execution | Item no. | Switching capacity | LED switching capacity |
| RMG 4 U KNX | Basic module | 4930223 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600 W (>2W) |
| RME 4 U KNX | Extension module | 4930228 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600 W (>2W) |
| RM 4 U KNX | Module FIX1 | 4940223 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600 W (>2W) |
| RMG 4 I KNX, C-Last | Basic module | 4930210 | 16 A | max. 1.500 A/200 μs 40.000 Schaltzyklen bei 200 μF* |
850 W (>2W) |
| RME 4 I KNX, C-Last | Extension module | 4930215 | 16 A | max. 1.500 A/200 μs 40.000 Schaltzyklen bei 200 μF* |
850 W (>2W) |
| RM 4 I KNX, C-Last | Module FIX1 | 4940210 | 16 A | max. 1.500 A/200 μs 40.000 Schaltzyklen bei 200 μF* |
850 W (>2W) |
| RM 8 I KNX, C-Last | Module FIX2 | 4940215 | 16 A | max. 1.500 A/200 μs 40.000 Schaltzyklen bei 200 μF* |
850 W (>2W) |
| RM 4 H KNX | Module FIX1 | 4940212 | 25 A | max. 1.200 A/200 μs | 850 W (>2W) |
| RM 8 H KNX | Module FIX2 | 4940217 | 25 A | max. 1.200 A/200 μs | 850 W (>2W) |
| RMG 8 S KNX | Basic module | 4930220 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RME 8 S KNX | Extension module | 4930225 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RM 8 S KNX | Module FIX1 | 4940220 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RM 16 S KNX | Module FIX2 | 4940225 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| KNX switching- & blind actuators | Execution | Item no. | Switching capacity | LED switching capacity |
| RMG 8 T KNX | Basic module | 8-way switching or 4-way blind actuator | 4930200 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RME 8 T KNX | Extension module | 8-way switching or 4-way blind actuator | 4930205 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RM 8 T KNX | Module FIX1 | 8-way switching or 4-way blind actuator | 4940200 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| RM 16 T KNX | Module FIX2 | 16-way switching or 8-way blind actuator | 4940205 | 16 A | max. 800 A/200 μs 40.000 Schaltzyklen bei 140 μF |
600W (>2W) |
| KNX Flush mounted actuators | Execution | Item no. | Switching capacity | LED switching capacity |
| SU 1 KNX | Flush mounted switching actuator | 4942520 | 16 A | max. 740 A/200 μs* | 600W (>2W) |
| SU 1 RF KNX | Flush mounted wireless switching actuator | 4941620 | 10 A | max. 740 A/200 μs* | 600W (>2W) |
*Thanks to optimised zero-cross switching
Dimming LEDs precisely: Today and in the future
Whether you opt for the FIX series or the MIX series, with KNX universal dimming actuators from Theben you can steplessly dim LED, halogen and energy-saving lamps without any flickering. The only prerequisite is that the selected lamp is dimmable. In view of the increasing number of connected LED lamps with small wattages, multiple channels provide greater freedom of design.
Up to date with KNX: Adaptable dimming curves
KNX universal dimmer actuators from Theben go one step further: in the KNX programming software ETS, various dimming curves are stored, which correct the dimming response depending on the lamp used, thus ensuring stepless transitional dimming. Theben is currently the only manufacturer to offer you the possibility to adapt dimming curves individually to your lamps, to create a harmonius dimming response. Another advantage is the high dimming output with up to 400 watts LED per channel. This output can even be increased to 800 watts by connecting 2 channels in parallel.
Continuous, flicker-free, harmonious:
KNX dimming actuators for small LED wattages
MIX2 actuators KNX
To the product
FIX1 / FIX2 actuators KNX
To the product
KNX Flush mounted actuators
To the productThe times of high wattages are over. Today, the art is in dimming LEDs with small wattages. Theben is keeping abreast of this trend and offers dimming actuators with a minimum load of just 2 watts.
In the KNX programming software ETS, various dimming curves are stored, which correct the dimming response appropriately depending on the lamp used, thus ensuring stepless dimming.
Quick function tests for start-up are possible via 4 buttons (25 %, 50 %, 75 %, and 100 %) even without bus connection. With the MIX2 series of KNX actuators, the bus module can also be retrofitted.
The DMG 2 T KNX – similar to the RMG 8 S KNX switching actuator – can be used to save different scene functions.