The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by ghost307
Today at 06:25 AM
International Wire Colour Codes
by Tjia1981
Yesterday at 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 229 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#37099 - 04/21/04 12:54 PM AC vs. DC
jerrytyler Offline
Junior Member

Registered: 04/21/04
Posts: 2
Loc: Atlanta,GA, USA
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!


Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#37100 - 04/22/04 04:21 AM Re: AC vs. DC
C-H Offline


Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
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.

#37101 - 04/22/04 06:25 AM Re: AC vs. DC
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
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!!!

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#37102 - 04/23/04 07:42 PM Re: AC vs. DC
cpalm1 Offline

Registered: 01/06/04
Posts: 62
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


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals