ECN Forum Forums General Topics of the Trade General Discussion Area AC vs. DC

Hi y'all. I've really enjoyed reading the stuff on this site, and now I have a question.
I am a lighting distributor, and we sell quite a bit of low voltage lighting. Most of the transformers that come with the fixtures are AC, but certain systems come with DC transformers, and I can't seem to get a straight answer about why, or what the difference would be. The only clue I have is that the DC transformers come with these cable lighting systems you might have seen, so I think this may be a voltage drop issue?

Thanks for any help!

Jerry

Modern electronic transformers (switching mode power supply) output high frequency AC. This means that long cables will cause radio/TV/etc. interference.

Adding a rectifier circuit means greater cost to the manufacturer, lower efficiency and less power.

The Low Voltage Incandescent Lamps "May" run a little better using DC instead of AC (well filtered DC as opposed to AC), but the most apparent reason would be to drive LED type Lamp arrays.

Wish I had a definite answer for you, but not knowing the specifics per installation / usage / equipment types, I can only "Ass-U-Me" these two things!

on the 'Ass-U-Me" word usage!!!

Scott35

some high quality low voltage light fixtures use DC to improve bulb life. incandescent bulbs last longer on filtered DC than AC. this is because filtered DC is a smooth current while AC has a 60 Hz frequency which causes the filiment of the bulb to vibrate. the vibration shortens the bulb's life