Note: I am in the USA, so 120V 60Hz. Also this post is
really long so, sorry in advance, but if y'all can help that would be super great!
PREFACE:Normally if you are using an inductive choke ballast for any type of electric discharge lighting, the supply voltage has to be (approximately) at least twice the running voltage of the lamp. But, if you use the right capacitor in series with the right choke, this requirement is somehow bypassed(?). I hear this is called semi-resonant. I am sure many of you have heard of this, like in those cheap Lights Of America shop lights.
THE EXPERIMENT:I recently powered an F40T12 rapid start lamp with a .2H choke and 2.5uF capacitor in a standard preheat configuration with a manual starter switch. The lamp lit beautifully (with some initial striking problems), even though the arc voltage of one of these is supposed to be 100V (way more than half of 120V). The circuit drew .455A, which would suggest that the lamp was overdriven, but the lamp was still quite dim (we'll get to that later). I posted a picture of this lamp lit connected to this circuit in my gallery:
https://www.lighting-gallery.net/gallery/displayimage.php?album=8574&pos=0&pid=255553The following circuit was made (excluding the starting preheat circuit):
Hot--
(A)--{
.2H CHOKE}--
(B)--{
2.5uF CAP}--
(C)--{
F40T12 TUBE}--
(D)--
NeutralI also made a to-scale paper schematic drawing with physical distances representing voltage differences (also with voltage labels):
QUESTIONS:My questions are as follows:
1: Cap and choke voltage
How is the voltage across the inductor and capacitor so gosh darn high if the supply voltage isn't? I know the phase angle of them makes it all add up to 120V in the end but what is making it do that in the first place? Nothing about this makes sense.
2: Tube voltage:
How is the voltage across the tube only 37 volts? This calculates to around 17W, which explains the dimness of the tube. How is the tube being
overdriven by a few milliamps but still managing to output
less wattage?
3: HIDs?
Could this concept be used with HID lighting? I am thinking of trying it out but I am not sure if it is a good idea.
Thanks for reading this whole darn thing, I know this is a lot to ask, but maybe someone can help me out. I tried as best as I could to make this easy to understand, but let me know if you need any clarifications. I think this is an interesting thing for us to investigate, especially for the people like me who live in 120V countries. Thanks!
