Five Rapid-Start Ballast Questions!

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Topic: Five Rapid-Start Ballast Questions! (Read 193 times)

Multisubject
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I know how preheat works, I know how instant-start works, but rapid-start is sort of a mystery to me. Not that it really matters, but I would like to know what goes on in there. I have the following questions:

1: Filament Heating
I know that a rapid start ballast heats the filaments before striking, but what about after striking? Does it just constantly heat them during run-time, or does it reduce the heat after it strikes, or does it just not heat them at all after striking?

2: Lamp Voltage
Obviously an RS ballast presents a voltage across the length of the tube. Does it use a pulse along with preheating or is it just a sort of current-limited OCV kind of thing?

3: Lifespan
I have this image in my mind of complex electronics and transistors inside an RS ballast, but I have 2 very old RS ballasts that still work great. I would think that if it was filled with complicated electronic chips and stuff like that it wouldn’t have such a long lifespan, but maybe they aren’t as complex as they seem?

4: Two Tube RS Ballasts
Most RS ballasts power two tubes, but they won’t even light up one tube if the second tube isn’t present. Why isn’t it just 2 ballasts in one package? Does it have to be that complicated?

5: Trigger-Start
Is trigger-start just the same thing as RS but meant for smaller wattage preheat tubes? I assume that is the case but I may be wrong.

Thanks!

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dor123
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1. Rapid-start ballast ALWAYS heats the filaments using the same power, before, during and after lamp ignition compared to other ballast topologies.
2. In a rapid-start ballast, the lamp starts directly from the ballast OCV, which is usually 180-210V for each tube (Hence European energy saver T8 can't start on it).
3. Rapid-start is a magnetic ballast topology. It is an autoregulator ballast, that uses a capacitor as its ballasting element, and uses a transformer coil to supply filament heating. They tends to be very robust and last very long.
4. Two tubes in series with the ballast have less ballast losses and complexity than separate ballast for each tube.
5. Looks to me that trigger-start is very similar to rapid-start, but for low voltage tubes.
Keep in mind that instant start ballast uses their high OCV to start the lamps. They don't uses ignitors.

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I lives in Israel, which is a 220-240V, 50hz country.

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Quote from: dor123 on April 03, 2025, 08:08:54 AM

1. Rapid-start ballast ALWAYS heats the filaments using the same power, before, during and after lamp ignition compared to other ballast topologies.
2. In a rapid-start ballast, the lamp starts directly from the ballast OCV, which is usually 180-210V for each tube (Hence European energy saver T8 can't start on it).
3. Rapid-start is a magnetic ballast topology. It is an autoregulator ballast, that uses a capacitor as its ballasting element, and uses a transformer coil to supply filament heating. They tends to be very robust and last very long.
4. Two tubes in series with the ballast have less ballast losses and complexity than separate ballast for each tube.
5. Looks to me that trigger-start is very similar to rapid-start, but for low voltage tubes.
Keep in mind that instant start ballast uses their high OCV to start the lamps. They don't uses ignitors.

Wait a minute, so RS ballasts are just steel and copper (and a capacitor)? That’s crazy!

And with heated filaments, the striking voltage is only ~200V?! That is a lot lower than I thought it would be.

And by “autoregulator” do you mean it is similar to CWA HID ballasts? Or does it not have any leakage and just use the capacitor for current limiting?

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dor123
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Rapid start is the same as a CWA HID ballast.

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Multisubject
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Very very interesting, I will keep that in mind.

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WorldwideHIDCollectorUSA
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Quote from: dor123 on April 03, 2025, 09:16:37 AM

Rapid start is the same as a CWA HID ballast.

I have seen that in North America, there are also low power factor rapid start ballasts and those cannot function like CWA ballasts because a series capacitor in the ballast generally keeps the power factor high.

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DISCLAIMER: THE EXPERIMENTS THAT I CONDUCT INVOLVING UNUSUAL LAMP/BALLAST COMBINATIONS SHOULD NOT BE ATTEMPTED UNLESS YOU HAVE THE PROPER KNOWLEDGE. I AM NOT RESPONSIBLE FOR ANY INJURIES.

dor123
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Eltam Ein-Hashofet rapid-start ballasts, have a capacitor, but are still low power factor ballasts: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-65981

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WorldwideHIDCollectorUSA
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HID, LPS, and preheat fluorescents forever!!!!!!

As far as I understand, these ballasts can be low power factor if the capacitor is bypassed, but if the capacitor is connected to the circuit, the power factor is high.

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