Circuit Breaker Suggestion For MEAN WELL LED Drivers

Different types of circuit breakers have different characteristics. Firstly, the absolute trip level is specified and within the range of 10 to 20 Amp for commonly used models. Secondly, a circuit breaker can have different trip characteristics (the well-known A, B, C or D type) with respect to the time that a current exceeds the absolute trip level. Predicting the amount of LED drivers connected to a specific circuit breaker can be calculated if the maximum inrush current (Imax, figure 1) and the time it takes until the inrush current drops to fifty percent (T50, figure 1) is known.

Figure 1: Typical inrush current measurement

The typical values of T50 and the Imax parameters of nearly all of MEAN WELL’s LED drivers can be found in Table 1. Different voltage ratings are similar for the same type of driver. 

A so called proof factor (K) is required in order to calculate the amount of drivers that can be connected to a specific circuit breaker. The K factor can graphically be found by looking at the pulse tripping curve (Figure 2), according to EN 60898.

The typical inrush currents (Table 1) were used to calculate the maximum amount of LED drivers that can be connected to a circuit breaker. 

The results of the calculation that are shown in Table 2 are based on worst-case conditions;
– lowest specified value for circuit breakers trigger level is used *
– values are rounded off down

* for B type the tripping current is  3 times rated tripping current for t<10ms
   for C type the tripping current is  5 times rated tripping current for t<10ms
   for D type the tripping current is 10 times rated tripping current for t<10ms

Example: A 16B type circuit breaker will not get triggered for a current pulse of 240A, with t<520uSec. Proof factor is 5, and thus 5 x 3 x 16 =240Amp

Figure 2: Graphical circuit breaker response that was used to calculate Table 2 [source: ABB]

Table 1: Typical input current (Iin), inrush current (Imax) and T50 of MEAN WELL LED driver

Table 2:  Suggested maximum amount of LED driver for a specific circuit breaker

*B10 stands for B type circuit breaker with 10A tripping current