OSG Standard Circuits - 3A lighting

Yes, inrush currents may well be a problem.


However, I think this is a vary valid question that requires a little more thought.


The distance of 68 m is limited by on 3 % volt-drop for a current of 5 A, roughly evenly distributed along the circuit. So, initially, you might think we could get away with a longer distance if we assume say a 3 A load current - and with an RCD protecting the circuit where Regulation 411.3.4 applies, the  circuit length for a 3 % volt drop could increase to over 100 m even with a 6 A protective device.


However, if a longer circuit is used, a designer would have to be careful that the impact of inrush currents does not cause a voltage drop which temporarily (for a couple of seconds) affects driver stability downstream of one or more drivers  being switched on ... and I've noticed occasionally this can be a problem with circuit lengths shorter than 68 m. There are ways round this, which could, perhaps very cheaply, be built into LED drivers themselves (e.g. MOV inrush current limiting and/or larger reservoir capacitor) - and there are probably drivers on the market that have this kind of approach built-in.


So,  LED lighting may well be more energy efficient, but unless inrush currents are managed, it doesn't necessarily translate to smaller cross-sectional area of cables, or longer circuit lengths.

Yes, inrush currents may well be a problem.


However, I think this is a vary valid question that requires a little more thought.


The distance of 68 m is limited by on 3 % volt-drop for a current of 5 A, roughly evenly distributed along the circuit. So, initially, you might think we could get away with a longer distance if we assume say a 3 A load current - and with an RCD protecting the circuit where Regulation 411.3.4 applies, the  circuit length for a 3 % volt drop could increase to over 100 m even with a 6 A protective device.


However, if a longer circuit is used, a designer would have to be careful that the impact of inrush currents does not cause a voltage drop which temporarily (for a couple of seconds) affects driver stability downstream of one or more drivers  being switched on ... and I've noticed occasionally this can be a problem with circuit lengths shorter than 68 m. There are ways round this, which could, perhaps very cheaply, be built into LED drivers themselves (e.g. MOV inrush current limiting and/or larger reservoir capacitor) - and there are probably drivers on the market that have this kind of approach built-in.


So,  LED lighting may well be more energy efficient, but unless inrush currents are managed, it doesn't necessarily translate to smaller cross-sectional area of cables, or longer circuit lengths.