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 VOLTAGE LOSS 

Avoiding voltage loss when installing LED-flex stripes

Voltage loss in a nutshell:

The ideal voltage loss when supplying flex stripes should be less than 3%, which can sometimes only be achieved by increasing the cable cross-section of the voltage supply. Some DIN rail transformers offer the option of increasing the output voltage by up to 10% in order to ensure sufficient voltage at the feed-in point even with long supply cables, e.g. from the distribution cabinet to the living room. Wherever possible, additional feed points are advisable to avoid voltage and light losses across the entire light line.

Ideally, the voltage loss when supplying flex stripes should be less than 3%. In practice, this can often  only be achieved with large cable cross-sections. Some transformers, e.g. all grid transformers in the ISOLED® range, offer the option of adjusting their output voltage upwards by up to 10% to ensure 12 V or 24 V at the first power feed point even with long supply cables. The following table shows the voltage losses to be expected:

LENGTH OF SUPPLY CABLE VOLTAGE DROP/LOSS ON THE COPPER SUPPLY CABLE LOAD: 5 M ROLL OF 24 V LED FLEX STRIPE WITH 14.4 W/M
0,50 MM² 0,75 MM² 1,00 MM² 1,50 MM²
VOLTAGE LOSS VOLTAGE LOSS VOLTAGE LOSS VOLTAGE LOSS
1,0 m 23,79 V 0,21 V 23,86 V 0,14 V 23,89 V 0,11 V 23,93 V 0,07 V
3,0 m 23,36 V 0,64 V 23,57 V 0,43 V 23,68 V 0,32 V 23,79 V 0,21 V
5,0 m 22,93 V 1,07 V 23,29 V 0,71 V 23,46 V 0,54 V 23,64 V 0,36 V
7,5 m 22,39 V 1,61 V 22,93 V 1,07 V 23,20 V 0,80 V 23,46 V 0,54 V
10,0 m 21,86 V 2,14 V 22,57 V 1,43 V 22,93 V 1,07 V 23,29 V 0,71 V
15,0 m 20,79 V 3,21 V 21,86 V 2,14 V 22,39 V 1,61 V 22,93 V 1,07 V
20,0 m 19,71 V 4,29 V 21,14 V 2,86 V 21,86 V 2,14 V 22,57 V 1,43 V
30,0 m  17,57 V 6,43 V 19,71 V 4,29 V 20,79 V 3,21 V 21,86 V 2,14 V

Formula for calculating the
voltage drop with DC voltage

2 · length  (l) · current  (I)
Voltage  (U)  = Conductivity copper  (56) · Cable cross-section    
(A in mm2)

Copper conductivity(σ in S/m): 56 - 106 (the value depends on the purity of the material)

In order to avoid excessive heat generation, we recommend the following for the power supply of
LED-flex stripes should remain below 3 amps per feed contact!

Current per feed contact in  A (I) 

=

Flex strip power in  W/m (P) · length in m (served by one feed contact)
Operating voltage in V (U) 

Power
Flex stripe		 AFTER 5 M LENGTH
VOLTAGE VOLTAGE
4,8 W/m ca. 23,3 V ca. 0,7 V
9,6 W/m ca. 22,6 V ca. 1,4 V
12,0 W/m ca. 22,2 V ca. 1,8 V
14,4 W/m ca. 21,9 V ca. 2,1 V
14,4 W/m ca. 20,7 V ca. 3,3 V
14,4 W/m ca. 19,8 V ca. 4,2 V

The voltage loss in the supply cable and on the flex stripe board is halved or reduced

  • when using a flex stripe with 7.2 W/m instead of 14.2 W/m i.e. with lower LED power;
  • when operating at a higher voltage, i.e. using 24 V DC instead of  12 V DC LED-flex stripes.

The voltage loss of the supply cable and on the flex stripe board is doubled or elevated 

  • when using a flex stripe with double or higher power W/m;
  • when operating at a lower voltage, e.g. when using a 12 V LED-flex stripe.

APPLICATION TIP - ADDITIONAL INFEED

Even if the transformer in complex installations such as escalators does not have to be positioned centrally as in the ideal case, but further away, the following sketches describe options for efficiently infeeding the current and thus avoiding different levels of light emission over the entire length of the light strip:

Beispiel: 24 V LED Flexband mit 14,4 W/m (Gesamt 216 W auf 15 m)

3 rolls each 5 m long (light line therefore 15 m in total) Supply cable: copper cable heads 5 m long

With additional feed points, which are realized by a sufficiently in size cable, one avoids

  • Voltage losses,

  • Light losses and

  • overheating of the LED boards (maintaining the intended service life!).

Single-sided infeed - NOT RECOMMENDED!

 Tip 1 Parallel feed points at 5 m and 10 m along the light line

Tip 2 Additional infeed at the end of the Light path

Notice

If the LED flex strip is properly mounted on heat-dissipating substrates (e.g. aluminum profile), the surface temperature never rises above 50°C! 
Excessive temperatures mean a rapid reduction in the the service life.

The thermal conductivity of various substrates must be taken into account: the heat absorption of e.g. stainless steel and coated sheet metal is far lower than that of aluminum.

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