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F13T5 running on 120V via resonance

F13T5 running on 120V via resonance

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With an arc voltage of 100V, the F13T5 can't run on a standard 120V choke ballast. However, by connecting a capacitor in series with a choke, a partially resonant circuit can be created that multiplies the voltage seen by the lamp to a level that allows it to run. This is how those crappy LOA shoplights work.

In this picture I have a 1.5 uF capacitor in series with a 13-22W choke. It runs the lamp great - current is a perfect 0.14A. Different capacitances were tested to yield the proper current. The sum of the voltages across the lamp, capacitor, and choke is 355V.

Because the open-circuit voltage is still only 120V, an FS-4 starter can't be used. However, a Pulsestarter EFS120 does the trick.

One caveat is that the lamp does shimmer very slightly. I would guess this is due to the open-circuit voltage reverting to 120V following zero-crossings. In this particular setup, the capacitor is the dominant ballasting element, and I'm not sure how healthy for the lamp that would be.

I'm going to try this again with an F32T8 lamp soon.

youtube_3DgSaysFxnk.jpg IMG_20190113_214412999[1].jpg IMG_4605.JPG IMG_2694.JPG

Light Information

Light Information

Lamp
Lamp Type:F13T5
Fixture
Ballast Type:13-22W choke + 1.5 uF capacitor
Electrical
Voltage:120V

File information

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Album name:themaritimegirl / Experiments, Projects, & Mods
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Date added:Jan 13, 2019
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dor123
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Jan 14, 2019 at 12:11 AM Author: dor123
I think you essentially made a 120V SRS ballast if the capacitor is used for the OCV and the cathode heating, similar to Eltam "Rapidstart" ballast for F40T12 , which have a 230V series choke and a capacitor.

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.

themaritimegirl
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Jan 14, 2019 at 12:21 AM Author: themaritimegirl
It is not; this is a preheat circuit.

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dor123
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Jan 14, 2019 at 12:31 AM Author: dor123
But you said that the circuit is partially resonant after adding the capacitor, which is similar to the British SRS circuits.

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.

themaritimegirl
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Jan 14, 2019 at 12:35 AM Author: themaritimegirl
Right, but in this circuit the capacitor is in series with the choke as a ballasting element. In an SRS circuit the capacitor and a secondary inductor form the starting circuitry, and are essentially out-of-circuit once the lamp has started.

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funkybulb
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Jan 14, 2019 at 01:02 AM Author: funkybulb
it called Leading preheat circuit. this circuit is very common in 125 watt 8 footer in UK
and it also bring voltage up for 125 watt tube
to start. one thing your doing wrong is using
a 15-20 watt type of choke as cap reducing
it current. try using a 4 to 8 watt ballast with cap

No LED gadgets, spins too slowly.  Gotta  love preheat and MV. let the lights keep my meter spinning.

dor123
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Jan 14, 2019 at 01:45 AM Author: dor123

Right, but in this circuit the capacitor is in series with the choke as a ballasting element. In an SRS circuit the capacitor and a secondary inductor form the starting circuitry, and are essentially out-of-circuit once the lamp has started.

I thought that in SRS, the capacitor is also connected in series to the choke and acts as a ballasting element, which is why the topology is close to the resonance electronic ballasts.

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.

Men of God
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jiachao.wei.71 chao_813975447 UChyTpXvlQ8ZCfBPP_lJjubg chao990613
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Jan 14, 2019 at 02:05 AM Author: Men of God
我试过用100V 30W 0.62A的扼流圈式镇流器启动T5 12W,通电后灯管瞬间烧毁,是什么原因?

那我还可以用100V 20W 0.375A,100V 15W 0.3A或110V 10W 0.23A的镇流器做这个实验吗?

我不会英文,所以我用中文,请你们用翻译网站翻译我打的字!

I can't in English, so I in Chinese, please use the translation website to translate my words!

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Jan 14, 2019 at 02:05 AM Author: Medved

But you said that the circuit is partially resonant after adding the capacitor, which is similar to the British SRS circuits.


SRS does not operate in resonance from the lamp arc perspective, it is an inductive ballast circuit, with the PF capacitor connected using auxiliary winding so, it provides cathode heating for start.
It is called "semi", because it is not a resonant, but contains components which may form a resonant circuit. But ion a different arrangements.

Although there is inductor and capacitor, the ballast windings are connected so the inductance cancels out in the capacitor circuit. Since there is no inductance, no resonance happens. When disregarding resistive drop across the wires and lamp filaments, the capacitor sees essentially the mains voltage, in any mode of operation. Just its current is preheating the lamp electrodes.
For the arc circuit both filaments could be seen as (parallel) one inductor. Because the same number of turns, it is like there were single winding with such number of turns, forming the arc ballasting impedance. With the arc burning the capacitor just forms the power factor compensation phase shift.
Plus because of the phase conditions (when you sum up the heating plus arc currents) the currents into the lamp terminals become lower than the total arc current, which is rather neat feature, so it allows the filaments to be designed thinner for better heating berfore the lamp ignites, at the same time they are not that much loaded when the arc burns, so when the electrode dissipation is providing enough heat.


The ballast here is a lead ballast, using resonance to boost the voltage available for the zero cross. It works, because at the zero cross the capacitor is charged to way higher voltage than would correspond to the 120V mains.
For lamp life the most important thing is, how well the lamp filaments are preheated before the ignition attempt. Knowing these electronic starters (2s preheat before any ignition attempt), it should be perfectly fine, provided the preheat current is within the range of 0.13..0.2A (1x .. 1.5x the lamp current rating). The shimmering would be more related to the lamp atmosphere stabilizing, I don't think it signals any wear problem. You may check the current shape (via a current transformer - a 120V/6V transformer do the job, connected with the 6V winding in series with the tested current, the 120V winding connected to some 180Ohm resistor and an oscilloscope; you get about 1V/100mA conversion factor by that, but do not rely on it for absolute values, just for the shape)

No more selfballasted c***

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Jan 14, 2019 at 04:45 PM Author: themaritimegirl

The ballast here is a lead ballast, using resonance to boost the voltage available for the zero cross. It works, because at the zero cross the capacitor is charged to way higher voltage than would correspond to the 120V mains.
For lamp life the most important thing is, how well the lamp filaments are preheated before the ignition attempt. Knowing these electronic starters (2s preheat before any ignition attempt), it should be perfectly fine, provided the preheat current is within the range of 0.13..0.2A (1x .. 1.5x the lamp current rating). The shimmering would be more related to the lamp atmosphere stabilizing, I don't think it signals any wear problem.


Thanks for the info! The lamp never stops shimmering, and doesn't shimmer when run on an ordinary autotransformer ballast, so I'm not sure what's going on there.

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Jan 17, 2019 at 10:13 PM Author: themaritimegirl
I wasn't able to replicate this using an F32T8. I assume I need more inductance.

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^homebuilt fixture


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Jan 17, 2019 at 11:01 PM Author: xmaslightguy
Interesting test themaritimegirl!

I'd love to see you make it go with a F32 too!

Colored Fluorescent's such as F40T12 Red or  Green or Blue are awesome...

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Jan 18, 2019 at 10:44 PM Author: Medved

I wasn't able to replicate this using an F32T8. I assume I need more inductance.


Although a combination of an L and C, at the end it is still just a series impedance, so you still need the lamp arc voltage to be lower than the mains for any current to flow. Because the F32T8 has about 140V drop, there is no way it may ever work on 120V.

A standard L only usually requires the mains voltage to be at least double to the arc (to have enough instantenous voltage available for zero cross reignitions), the LC allows to overcome that by replacing the mains voltage be the capacitor one. But the fundamental voltages have to still be so the current could flow.

No more selfballasted c***

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Jan 19, 2019 at 04:49 PM Author: themaritimegirl
Ah, okay, now I get it. Thanks.

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