Guide to cascading LED luminaires: What do you need to consider?
Do you want to illuminate a large work area but have few power connections or simply want to minimise cabling costs? Cascaded LED luminaires are probably the best solution for this situation.
But how exactly does cascading work, and what benefits does it offer? What questions need to be answered when planning the lighting? Everything you need to know is explained in this guide.
What exactly does it mean to cascade LED luminaires?
Cascading involves stringing several LED luminaires together and supplying them with the same voltage source. Cascading requires special luminaires that have both a connection for their own power supply and one for connecting to the next luminaire.
When purchasing luminaires, you therefore have to specifically purchase cascadable models (the last luminaire in the cascade does not have to be cascadable).
One typical application example would be a large workspace that is to be illuminated with three long luminaires. In this case, you would simply connect the second light to the first and the third to the second instead of laying an extra cable for each light. Cascading is also ideal in larger installations, machines or at several workstations next to each other if a single luminaire is not sufficient for the area requiring illumination.
Cascading is a parallel connection, not a series connection
While cascaded luminaires may appear to be connected in series, a cascade is not a series connection, but a parallel connection. The difference is seen in how the luminaires are set up.
With a series connection, the light sources (from the second in the series) are only connected to the voltage source via the previous light sources. In colloquial terms, it can be said that the current flows directly through all the interconnected light sources. This graphic illustrates the principle:
When cascading, each light is connected directly to the voltage source (positive and negative poles). The light sources are supplied with voltage individually, completely independently of the others. The structure appears as follows:
Benefits of cascading LED luminaires
Why is cascading LED luminaires recommended?
Illuminating longer distances without high effort and costs
Where several luminaires are cascaded, you can illuminate longer distances or larger areas without major installation effort. There is no need to lay long supply cables and cable ducts through the room, and less material is required. Instead, you simply connect the lights together using short connecting cables.
In addition, the entire cascaded lighting system only requires one connection in the control cabinet instead of one per light. Your control cabinet lasts longer – and looks tidier too.
Control several luminaires with greater ease
Another advantage of cascading is the simplified control. For example, you can switch five cascaded lights in a system on and off synchronously via just one control output. Without cascading, however, five separate outputs would have to be programmed and controlled.
Higher reliability compared to series connection of individual LEDs
Unlike when connecting individual LEDs in series, cascading complete luminaires offers significantly greater reliability. With series connections, the failure of a single LED light source causes an interruption in the power supply and all subsequent LEDs remain dark.
With cascaded luminaires, however, the individual luminaires are connected in parallel to the supply voltage. If one luminaire fails, this has no effect on the subsequent luminaires. These are still supplied with power and continue to light up normally.
Disadvantages of cascading
Two disadvantages offset the many advantages, and come into play in certain situations. It is not yet possible to control individual luminaires within the cascade. If you want to switch luminaires on and off individually, adjust their brightness and the like, you must not cascade them.
The number of luminaires or the length of the entire connecting section in a cascade is physically limited. If you are planning larger installations, you therefore need to calculate the technical feasibility of your lighting system in advance.
Planning and sizing a cascaded LED installation
The limiting factors for cascading are the number of luminaires and the total cable length in relation to the cable cross-section. The longer the cable runs and the more luminaires, the higher the voltage loss. The larger the cable cross-section (cable thickness), the lower the voltage loss.
The installation must be dimensioned in such a way that the last light in the cascade still receives sufficient supply voltage. According to the standard DIN VDE 100 Part 520, voltage losses of a maximum of 6% should occur in lighting circuits.
Our LED2WORK luminaires are somewhat more tolerant: they have a voltage stabilisation range of +/- 10% and can process voltages between 21.6 and 26.4 V (with a 24 V supply voltage).
If the voltage at one or more luminaires in the cascade is below the tolerance, they will no longer light up at full power. They will also break down much more quickly due to the undersupply.
You can use the following formula to calculate the voltage loss of your planned installation:
Voltage loss ΔU = ρ * (L * 2) * I / A
ρ = specific resistance of the conductor material
(L * 2) = length of the entire cable route to the last luminaire and back
I = total amperage of all cascaded luminaires
A = cable cross-section
If the calculated voltage loss is too high, you will either need to use thicker cables or distribute the number of luminaires over several cascades. Alternatively, you can use an adjustable power supply unit and increase the output voltage sufficiently (within the tolerance of 10%) to supply all luminaires with sufficient voltage.
Consult a specialist
Cascading LEDs simplifies many aspects of workplace and system lighting: it is practical, inexpensive and fast. The technical limitations described may seem daunting at first. However, a specialist can easily calculate the correct dimensions for your installation: simply contact our customer service team and our advisors will be happy to help you.
