[SML] Source 4 Power and LED Cabling

[billn at peak.org]

> Alf asks a good question that I would like to answer. The short answer is
> because Inrush is different than max draw.
>
> Lemme explain:
> Unlike a traditional incandescent source, when you first power any driver or
> ballasted fixture ( like an  LED) there is a spike in power consumption that
> exceeds normal operating power consumption. This can be significantly higher
> than normal use. In some fixtures the first few cycles is significantly more
> than normal operating voltage. Think a factor of 6-10 times higher.

Normal incandescent lamps also have an inrush current, it is just not as
significant as devices using a power supply with no "soft start" circuitry.

For an incandescent lamp, you can determine what the maximum inrush can be by
measuring the cold lamp resistance using an accurate ohmmeter.

For example, if the cold resistance is 6 ohms and the power is 120 VAC, then
the maximum possible inrush is 20 Amps. This will decrease rapidly as the
filament heats.

As a side note, the instantaneous wattage would be 2400 watts.

Bill