Controlling light intensity

controlling light intensity

Hi,
I need to control light intesity of sodium street lights. There are 40 such sodium bulbs conneted in parallel (& can be more) & i think each rates 250W. should i use TRIAC method to control the intensity? I think either i'll need heavy current rating Triac (which one can i use?) or else i'll need to put Triacs in parallel????? which one is possible?? & is better? I refered to

Thanks in advance,

ragards,
Garg

This is not simple task and triac will not do. Find company that makes dimmable ballasts and buy it. If you are still into making something yourself, you should research how HPS lamp works, electronic balasts and what is involved in designing one. Buying one will save you awfully lot of time and headache.

fan dimmer will work .

250w : if 230v then i ~ 1.X amp

so I total = i x 40 = 40~60 amp

you can get it , such current ratting triacs !

or make a group of 10 , 10 , 10 & 10 it will also work , keep firing ckt common or cascaded.

garg29 said:

Hi,
I need to control light intesity of sodium street lights. There are 40 such sodium bulbs conneted in parallel (& can be more) & i think each rates 250W. should i use TRIAC method to control the intensity? I think either i'll need heavy current rating Triac (which one can i use?) or else i'll need to put Triacs in parallel????? which one is possible?? & is better? I refered to

Thanks in advance,

ragards,
Garg

Click to expand...

u can simply use a fan dimmer

u can simply use a fan dimmer

Click to expand...

How do you know? Did you try?

garg29 said:

Hi,
I need to control light intesity of sodium street lights. There are 40 such sodium bulbs conneted in parallel (& can be more) & i think each rates 250W. should i use TRIAC method to control the intensity? I think either i'll need heavy current rating Triac (which one can i use?) or else i'll need to put Triacs in parallel????? which one is possible?? & is better? I refered to

Thanks in advance,

ragards,
Garg

Click to expand...

The electronic ballast of a theatrical lighting system is possibly what you need to look at, it provides a current controlled continuous square wave to the lamp. It is used for HMI lamps but the idea itself can be applied to the sodium lamp. I do not think you will get adequate results from triac phase triggering with discharge lamps. See the ballast section in the web page below:

https://en.wikipedia.org/wiki/Hydrargyrum_medium-arc_iodide

:!: I think it is not possible to use Triac based designs Since the Sodium vapour lamps have complex electrical characteristics. You can probabely do it by using Switch mode technology based Ballast.

hi
u can use tis link to find required icswww.semicon.toshiba.co.jp

Simple Auto-transformer supply control will serve your purpose.

You can easily reduce power of an HPS Fittings and measure the Lumen output / Lux value at a particular point for different voltage rating (Use a variac). Then just use a transformer to reduce 20 to Maximum 40 voltage drop and use.

If further steppings are required, you may use solid state thyristor switching (For automatizing ) in full voltage coil to avoid high current switching.

For your help, I am giving you some considerations:
1.EM Ballasts consume 1/5th of Lamp power. So, your complete luminaire must consume 300 watt.

2. Capacitors are to be checked, otherwise, line PF will be low and voltage drop will be occured at the furthest end.

3. You may use timer and contactor for switching to low intensity during low traffic periode (11PM to 1 PM) and extra low intensity at extra low traffic (1 PM to 4 PM). Of course, for this timming, consider your traffic Dept.

4. For current calculation, please check the light feding cable, three or single phase. If three phase, then per phase loading only will be considered for the calculation of Transformer low voltage side.

Hope you will be helped with this feedback.

Thanks

manish12 said:

fan dimmer will work . 250w : if 230v then i ~ 1.X amp
so I total = i x 40 = 40~60 amp. you can get it , such current ratting triacs !
or make a group of 10 , 10 , 10 & 10 it will also work , keep firing ckt common or cascaded.

Click to expand...

Manish..You are very calculative...thanks for the efforts. Keep it up. But the subject here is the Sodium vapour lamp and its not an easy task to dimm it with a triac. There are some ballasts specifically designed for dimming such lamps. For flourescent lamps Dali works fine. But i am not sure with HPSV..

rokibulalam said:

u can simply use a fan dimmer

Click to expand...

Thanks for a simple answer...Curious to know...did you ever dimmed one on your side? with a fan dimmer?

Thanks a lot all of you.