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15-20w series choke on 18W LPS

15-20w series choke on 18W LPS

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Even after warming the SOX lamp by running it for an hour on its own L69 magnetic ballast, it could not remain lit with a simple magnetic choke for a 15-20W fluorescent. The 18w SOX lamp & the starter would alternate on off. Caught together only because I used a half of a second exposure. See the uneven sodium plasma in the SOX?

SOX-35w-on-magnetic-ballast.jpg IMG_2966.jpg IMG_2461_SOX18w_15-20w-chok.jpg IMG_2444_ICF-2S42-M2-LD-on-LPS.jpg

Light Information

Light Information

Lamp
Lamp Type:LPS
Fixture
Ballast Type:15w-20w magnetic choke (attempted)
Electrical
Wattage:18W

File information

File information

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Filename:IMG_2461_SOX18w_15-20w-chok.jpg
Album name:lights*plus / SOX or LPS testing
Keywords:Gear
File Size:675 KB
Date added:Feb 18, 2016
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dor123
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Feb 18, 2016 at 04:51 AM Author: dor123
If the lamp can't maintains the discharge, so the lamp voltage is higher than 120V, so an autotransformer is needed anyway.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

rjluna2
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Feb 18, 2016 at 06:21 AM Author: rjluna2
Nice experiment, light*plus

Pretty, please no more Chinese failure.

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Feb 18, 2016 at 08:24 PM Author: themaritimegirl
Wow, interesting! I do recall being told that an 18 watt LPS lamp has a 55V arc voltage, so it's odd that it won't stay running. Since the choke is likely underdriving it, maybe the arc voltage is higher than normal, which is triggering the starter. Who knows. Thanks for trying this, anyway!

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Feb 19, 2016 at 01:24 AM Author: lights*plus
I think the arc current just wasn't enough. And I also didn't use the Philips SOX-E lamp (but need to double check my pics as I attempted to get both lamp & starter lit, so I can see which one I actually used). The 18W SOX-E needs 0.2A while normal SOX needs 0.35A, not sure.

But I have a 32-40w fluorescent fixture in an extremely cold cool-room that I'll dig out..I'll see if I can light it with that magnetic ballast (which can't remember the specs for it as well).
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Feb 19, 2016 at 04:26 AM Author: FrontSideBus
Could try a different rated starter to stop it cutting in. 330ma @ 57v springs to mind for 18w SOX. That is a really small ballast, ours are much bigger!

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Mar 26, 2016 at 01:32 AM Author: Globe Collector
Replace the starter with a pair of wires with bared ends, "splat" the wires together until the lamp starts, then leave the ends apart.....i.e a manual starter. If it still extinguishes, the arc voltage is too close to 120v to maintain a high enough arc current through the choke. (And you will need some sort of step-up transformer to get the mains voltage up a bit.
Actually, an even simpler solution than the two bared wires....wait till the lamp strikes then, quickly remove the starter before the glowbottle can act and extinguish the SOX. Or, just "fiddle" the starter in the socket...i.e., have it loose in the socket with the pins just touching and just turn it a back and fourth little to make and break contact till the SOX starts, then remove it entirely....after all it is just a STARTER, and once the lamp had started it has served its purpose and is no longer required in the circuit!

Manufactured articles should be made to be used, not made to be sold!

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Mar 26, 2016 at 06:54 AM Author: Cal
I do like the bared wire idea. Have seen this done and been thinking of trying it. I have some T12 tubes that are very stubborn on startup because they're new.
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Mar 26, 2016 at 07:21 AM Author: sol
Or you could use a stuck starter and then remove it.
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Mar 26, 2016 at 07:08 PM Author: Globe Collector
Something else I "forgot" to mention, but Trent says as much above.....discharge lamps have a STRONG NEGATIVE RESISTANCE COEFFICIENT....so increasing the current by decreasing the inductance of the choke, (or placing two on parallel) will also DECREASE the arc voltage (not increase it, like would happen with an incandescent lamp). So the 55v is at 330mA as Mark states, but at 600mA the arc voltage should be less.

Another solution would be to adjust the mains voltage a bit by using a (60Hz) transformer cabbaged from a C.D. player or the like to "boost" it up a bit. This will raise the lamp current and have the consequence of decreasing the arc voltage, but the choke may end up getting a bit too much across it, with the mains going up at one end and the lamp going down at the other...so one will need to keep a finger on the choke to check it does not get too hot.

Manufactured articles should be made to be used, not made to be sold!

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Mar 26, 2016 at 07:15 PM Author: HIDSarge12
I have seen several examples of someone running an LPS lamp on a Fulham Workhorse electronic ballast. Is this safe for the lamp? How is it supposedly better-working than running it off of a magnetic ballast?

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Mar 26, 2016 at 09:38 PM Author: Globe Collector
Again, the arc current is paramount...if it is around the 350mA designed for the lamp, then it is O.K. Short durations at up to 900mA won't hurt it...but over time the electrodes will sputter badly.
Use this set up to measure arc current at over 1KHz....

At high frequency, capacitive effects between the cathode glow and the electrodes passes some arc current directly into the plasma column and bypasses the electrodes...so at 60Hz, about 100% of the 350mA arc current is borne by the electrodes. At 50Kz a few percent of the arc current is coupled capacitively because capactitve reactance decreases as the frequency rises.

Manufactured articles should be made to be used, not made to be sold!

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Nov 30, 2020 at 04:38 AM Author: WorldwideHIDCollectorUSA
What about trying a European 4-22w Electronic starters designed for 240v series and 120v single circuits using this exact setup. Examples include the Philips S2-E starter and the Arlen EFS120 starter.

Say NO to ballast and bulb bans. MV, MH, HPS, and SOX forever!!!! Magnetic preheat fluorescent forever!!!!!

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Nov 30, 2020 at 06:07 AM Author: Globe Collector
As you know, I am not "bogged down" by specific makes and models...I solve problems by going back to first principles.

RUNNING

For most discharge lamps to run in a stable manner with a choke in series, the magnitude of the voltage drop across the lamp and the magnitude of the voltage drop across the choke have to be approximately equal, (although the drop across the choke can be more than the drop across the lamp, but it is a bit inefficient). Note I say magnitude because these are scalar quantities...but on adding them, "directional" vector addition has to be used...i.e Pythgoras' Thorem.

The SOX 18 is rated at 350mA @ 57v arc drop at this current.


Let's set the choke drop to 50v at the same 350mA, (as it is in series with the lamp and the same current flows through both.)


Now we vector add these two to get the supply voltage we will need to keep it all going.

So, the lamp voltage drop is one side of as right-angled triangle and the choke drop is the other side at 90*, the hypotenuse is the "mains" or supply voltage that will be required. So, applying Pythgoras' Thorem to this triangle of voltages:-

(57) Squared + (50) squared = (supply) squared

3249 + 2500 = 5749

Root 5749 = 75.8v

So a supply of 75.8v will run the setup stably, but we need to know the value of the choke in mH that will drop 50v @ 350mA @ 60Hz.

Choke drops 50v @ 350mA....Using Ohm's Law we can find the Inductive Reactance...


V = I x R (Choke V = Lamp Current x Choke Reactance)

50 = 0.35 x Xl

Xl = 143 iOhms

Now use the inductive reactance equation to find the inductance of the choke required at 50Hz.

Xl = 2pi f L

143 = 3.14159 x 2 x 60 x L

143 = 6.2918 x 60 x L

143 = 377.5 x L

143/377.5 = L

L = 379mH

If you place a SOX 18 in series with a 379mH choke and run it off 75.8 volts R.M.S. @ 60Hz...once started, it should run up normally.


Now you can furnish the 76 volts using a buck/boost transformer arrangment, you need to buck 44 volts off 120v.


Alternatively, you can recalculate the choke value that would be needed in series at the full 120v supply and then no transformer will be required. This will increase the drop across the choke to more than the drop across the lamp so it will be a bit inefficient, but it will work O.K.

Again, back to the triangle, one side is still 57v long (same lamp), but the hypotenuse has now been increased to 120v long (from 76v)...new higher supply voltage...how does this effect the third side, the drop across the choke? Again, Pythgoras' Thorem:-

(120) Squared = (57) Squared + (Unknown Choke Drop) Squared

14400 = 3249 + (Unknown Choke Drop) Squared

11151 = (Unknown Choke Drop) Squared

Root (11151) = Unknown Choke Drop

105.6v = Unknown Choke Drop


So use Ohm's Law again to find the new reactance of this choke...it will be a little more than twice that of the choke above (which was 143 iOhms).

V = I x R

106v = 0.35 x Xl

Xl = 301.7 iOhms

Now for the inductance:-

Xl - 2 x pi x f x L

302 = 377 x L (f = 60)

L = 801mH


So, you have two choices now, 76v supply with 380mH in series...OR:-

120v supply with 800mH in series

Or any other combination you might care to calculate using the same techniques as above. (E,G. running a SOX-18 off 240v @ 50Hz if you came here to visit me!).

STARTING

The 380mH in series off 76v will mean the open circuit voltage across the lamp will be 76v and the E.M.F. generated from the 380mH choke when the lamp is shorted and the short is then removed will be smaller than an 800mH choke will generate.

The chokes must be able to carry that current that will flow through them of they are placed directly across their respective supplies...So, Using Ohm's Law again:-

76v across 143 iOhms ------> 531mA

120v across 302 iOhms ------> 397mA



You can measure the inductances of fluoro chokes by three methods:-

1, Measure it in its original circuit with its original T12 or T8 lamp, i.e, its drop and the current flowing through it and calculate its inductive reactance using Ohm's Law and Inductance from that. This would be the easiest method as it only needs a multimeter.

2, Use an L,R,C, impedance bridge to measure that choke passively out of circuit. Next easiest method, requires access to an L,R,C, bridge.

3. Use the resonant method. Place known capacitor, (1uF say) in parallel with choke to be measured, place a 1K resistor in series with this parallel LC network. Feed the whole network from an audio signal generator and sweep from 10Hz to 1KHz. Measure voltage across choke with oscilloscope and note where peak occurs. Take frequency of peak and value of capacitor and plug back into parallel resonance equation to solve for unknown L.


As for those specific starters you mention, you will have to acquire them, measure their properties in circuit, i.e, how their impedance changes with applied voltage from a high source impedance, draw their circuits and analyse those circuits to extract their mode of operation...to "get back inside the head" of the bloke who designed them and work out what his intentions were and whether or not they match your intentions.

Any starter would need to be activated by the open circuit voltage..i.e. 76 or 120 for the two cases above and would need to stop acting below about 65v.

Measuring the voltage drop of the lamp right after startup (when it was still on the neon) would be helpful in designing a starter circuit that would not keep re-triggering. At starting the arc drop is slightly greater, by about 18% and the arc current is slightly less. As the lamp comes up the arc voltage rises a bit, by another 9%, then falls to the operating value of 57v. So, at the highest point the arc drop is about 73v....very close to the supply in the first case gear scenario and difficult for a starter to distinguish between the lamp in this state of half-run up (73v) and an extinguished lamp (76v). So, based on this, the 800mH/120v supply option is more advantageous from an automated starting perspective and the starter would be required to act in the 80-120v range but cease to act below 80v.

Manufactured articles should be made to be used, not made to be sold!

Fee, Fye, Fow, Fum, A dead man's eye and a parrot's BUM!

WorldwideHIDCollectorUSA
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Dec 04, 2020 at 06:52 PM Author: WorldwideHIDCollectorUSA
I was trying this same experiment with better results using a special 2 wire HPS ignitor.

Say NO to ballast and bulb bans. MV, MH, HPS, and SOX forever!!!! Magnetic preheat fluorescent forever!!!!!

Desire to collect various light bulbs (especially HID), ballasts, and fixtures from around the world.

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