ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
VDE 0100 to introduce AFCIs
by LongRunner. 01/17/18 10:32 AM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
Air Compressor feeder conductor sizing
by Potseal. 01/15/18 09:08 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 26 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
DIMMER CIRCUITS #44736
11/10/04 04:38 PM
11/10/04 04:38 PM
J
james S  Offline OP
Member
Joined: May 2003
Posts: 107
West England
Has anyone ever worked with fluorescent light fittings(less than 100w lamps, two lamps in each fitting)that are dimmed via a 10v dc control to the ballast with a 230v mains supply to power the fitting?

What i would like to know is how do these special ballasts work, what is the dimming process?
ps never came across such fittings before.

Work Gear for Electricians and the Trades
Re: DIMMER CIRCUITS #44737
11/10/04 05:17 PM
11/10/04 05:17 PM
M
marcspages  Offline
Member
Joined: Oct 2004
Posts: 48
London, UK
James,

Just confirm there are two ballasts (one per lamp) but the 10V is taken through both? (or are you unsure of the number of ballasts?

Marc.

Re: DIMMER CIRCUITS #44738
11/10/04 05:53 PM
11/10/04 05:53 PM
J
james S  Offline OP
Member
Joined: May 2003
Posts: 107
West England
i think there is only one ballast for what i can see, if it helps each lamp can work independently they are not in any series circuit set up, what makes it that bit intresting is that the particular light i have access to is an emergency fitting.

Re: DIMMER CIRCUITS #44739
11/11/04 04:53 AM
11/11/04 04:53 AM
M
marcspages  Offline
Member
Joined: Oct 2004
Posts: 48
London, UK
James,

This is going to be complete conjecture on my part - especially as this may be a new, fandangled ballast with DMX control or the like - but if it's old, then the following may just be the trick (you did not say whether the dimming was achieved with a 0-10VDC, or the 10V was modulated in some other way).

The principle applied is called a "magenetic amplifier". It was used extensively in 3-phase voltage regulation systems (for professional VCRs etc.) where the natural tendency of 3-phase is to cancel out.

[Linked Image]

But the same can be very successfully done with single phase. You need two identical transformers at least about twice the rating of the load. The primaries are wired in series, and this then in series with the load (see pic below - hope the link works!).

[Linked Image]

The secondaries, however, are wired 'back-to-back' so as to CANCEL each other out. If a DC current is injected (with the aid of a voltage, of course - note, you're only working against the DC resistance of the two secondaries in series), the primaries become a lower impedance. The more the current, the lower the impedance.

You can try this at home if you wish, it is perfectly safe (well, should be as all of you play with at least mains on a daily basis! so simply carry on respecting the mains as you always do and it won't bite!). I like to go down in voltage on the secondary (say about 50V), but not too far (else the controlling current goes up).

Now, putting this in to principle with the dimmable tubes.

It may just be possible the fittings are adjusting the arc current in the fluoro tube with the same principle? There is likely to be a "max" you can reach where the core becomes saturated thus controlling the maximum arc current (else you destroy the tube), but it might just be possible to get a reasonable brightness range out of the tube. Hmm, you've got me thinking! I must dig through my scrap and see what I can find and see how much I can change the brilliance.

M.


[This message has been edited by marcspages (edited 11-11-2004).]


Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Bill Addiss
Bill Addiss
NY, USA
Posts: 3,890
Joined: October 2000
Show All Member Profiles 
Top Posters(30 Days)
sparky 20
Admin 20
Potseal 13
Popular Topics(Views)
243,539 Are you busy
180,341 Re: Forum
170,830 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.130s Queries: 14 (0.112s) Memory: 0.9595 MB (Peak: 1.0915 MB) Zlib enabled. Server Time: 2018-01-18 19:54:08 UTC