Author Topic: Wanted: 230V 50Hz (magnetic)Rapid start ballast  (Read 1446 times)
Roi_hartmann
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Wanted: 230V 50Hz (magnetic)Rapid start ballast « on: April 27, 2009, 01:04:26 PM » Author: Roi_hartmann
I dont know how rare they are, but local "lampshop" owner told me that 230V models do exist too, you know the old-fashioned magnetic one not the new electronic one. If somebody has these and would like to sell one or two to me please PM me or post here or directly email me at roihartmann@arktikprospekt.com

It would be so nice to have one. Even thought I like preheat blinking, rapid start would be something differend. New or used it doesnt really matter main thing is that its working.

Im searching ballast for 1or2 X20W or 1or2 X40W T12 and only for 230V 50Hz mains.

Thanks for your effort.
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Medved
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Re: Wanted: 230V 50Hz (magnetic)Rapid start ballast « Reply #1 on: April 27, 2009, 03:01:42 PM » Author: Medved
Somebody described to me, he has them, for 120W lamps. They have two coils, each differring with turns. One was connected in series with the lamp (as preheat), second coil (most likely with less turns) was in series with specified capacitor connected "instead of the starter".
I tried to calculate such concept some time ago and i got:
Start with "preheat" ballast design (core type, number of turns, wire diameter, gap)
Use wire of 70% diameter and wind full number of turns, this would be the coil in series with the lamp.
Then wind 70% of turns for the starting winding.
The capacitor use the same, as originally specified for PF compensation (for single lamp).
Such ballast would have OCV ~300..350Vrms, current mode filament, it might work for single 40W lamp. For 2*20W series, split the "starting" winding into two and use two capacitors (each twice the value for half the voltage).

But for 20W (as 230V would be enough for lamp ignition) i think it might be quite easy to build other concept:

Use regular F18WT8 choke and transformer 230V to 2*9V/0.5A. Wire the lamp as follow:
Line input to one end of ballast.
Second end of the ballast choke to one pin of the lamp and to one primary end of the transformer.
One pin of the lamp's second end to mains neutral and to the primary's second end.
Each transformer's secondary wire to one lamp filament.
So you will get:
Ballast with OCV=230V, what at the same time power the filament by 9V.
When the lamp ignite, the voltage on the lamp will fall to ~56..60V, so voltage on the filament to ~2.3V.
This would work for the single 20W lamp, the 40W you might try, but i think the 230V would not suffice to start it, the same for 2*20W series (there you would need a transformer 2*6V/0.5A + or 6V/1A or 12V/0.5A).
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Roi_hartmann
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Re: Wanted: 230V 50Hz (magnetic)Rapid start ballast « Reply #2 on: April 27, 2009, 03:45:56 PM » Author: Roi_hartmann
Well. building/modifying your own ballast(and ofcourse all electrical DIY) is nice thing to do, But i'm searching factory made this time. I'm not any expert in electronics so I dont have so big need to build it myself. even thought I have education in  electrician(I graduate last summer)I have not do that work so long(ecxept my own project etc.) I have mostly worked in telecommunication industry since my graduation.

So summa summarum Im searching factory made thing. But thanks anyway. I copy your advice and if I somewhere in the future find an inspiration maybe I build that.
« Last Edit: April 27, 2009, 03:48:59 PM by Roi_hartmann » Logged

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Roi_hartmann
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Re: Wanted: 230V 50Hz (magnetic)Rapid start ballast « Reply #3 on: April 28, 2009, 02:29:36 PM » Author: Roi_hartmann
After sleeping over night I gived a another thought about that transformer thing. I could build one because if I remember right I have one 2X9V transformer I just need to find where it is. Is the current of the transformer critical thing. I mean does it have to be exactly 0,5A or could it be little bigger?

 I found old installation guide to Helvar fluorescent lamp dimmer. they mentioned something called starting transformer, is this 2x9V transformer something like that?

But still, If there is ready to instal product Im  ready to buy one!
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Medved
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Re: Wanted: 230V 50Hz (magnetic)Rapid start ballast « Reply #4 on: April 28, 2009, 03:19:13 PM » Author: Medved
Yes, it does something like it: It takes care of filament preheat, so 230V OCV would be enough to strike the lamp.
The transformer secondary should be able to supply the filament and /or the lamp current (as on RS you do not know upfront, how the arc current would divide to both electrodes), so you need at least the lamp current rating, what is 0.37A for the 20W lamp. I stated 0.5A, as it is the closest higher rating for transformers you might buy (at least in the shop with electronic components here). The voltage rating is not critical either, it should be somewhere between 4.5..9V for 20W lamp, as the filament is designed typically for 3V: So when the arc is not present, the voltage should be higher (to ensure it will be able to reach required temperature) and when the arc strikes and lamp volt fall, there should not be more then these 3V to avoid filament overheating in run. And higher the voltage, sooner the filament reach emission temperature, so sooner the lamp start. And if you phase windings so, the winding keep the direction, you will get 9V more OCV between filament centers...
I would not oversize the transformer too much, as large transformers tend to have higher magnetizing current, what make with the ballast choke an inductive divider, lowering the OCV. If the transformer has a 115V center-tap, you might connect 1uF capacitor there and to neutral, by this you might gain about 11V in OCV. Such capacitor cannot be directly in parallel with the lamp, as it will shorten it's life a lot, transformer's leakage inductance and wire resistance make an efficient ballast to avoid electrode overstress by such capacitor.

I tried to "draw" it as an "ASCII ART" (copy it into some fixed-width editor...):

                                -------O --------
                               |                 |
                  F18T8       o)|                |
                    or         )|                |
                  F20T12    9V )|                |
                  Ballast      )|                |
                  -------      ||                |
  Line  O---------^^^^^^^------*-------O -----   |
                               ||             |  |
                              o)|            ------
                               )|           |      |
                               )|           |      |
                               )|           |      |
                          115V )|           |      |
                               )|           |   L  |
                               )|           |   A  |
  230V                         ||           |   M  |
  50Hz                  -------*|           |   P  |
                       |       ||           |      |
                       |      o)|           |      |
                       |  115V )|           |      |
                       |       )|           |      |
                      ---      )|           |      |
                      ---      )|           |      |
               1uF/250 |       )|           |      |
                       |       )|            ------
                       |       ||             |  |
Neutral O--------------*-------*-------O -----   |
                               ||                |
                              o)|                |
                            9V )|                |
                               )|                |
                               )|                |
                               ||                |
                                -------O --------
                        Transformer 2*115V/2*9V

« Last Edit: April 28, 2009, 03:21:53 PM by Medved » Logged

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