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My previous thread got off track (I apologize), so perhaps if I rephrase the question we can stay on track. Referring to figure 42 in the attached UTC catalog sheet, observe the 'hum bucking' coil and associated 1 uFd cap. Notice that the rectifier feeds pin 2 and that the cap connects to pin 1. What is the theory behind this configuration? How does it work/sound? It must not have been a huge commercial success, since only a few UTC chokes offered this configuration.
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For the informative replies. I have a UTC LS-980 choke and will do some experimenting. I would also like to try some simulations, but don't think that PSUD2 will hack it since this is a non standard configuration.
That's a page from Ghirardi's Radio Physics Course published in the early 30's (a FUN book!) He calls the circuit the Miessner tapped-choke system. Below is a link to Miessner's patent. It does not appear to be a tuned circuit by Miessner's description, but I might be missing something. The patents that reference Miessner's might be interesting, I don't know; the legalese of modern patents is nearly impenetrable by me. :(Meaningful interpretations are welcome. :)
-- Dave
I have never understood ghirardi's explanation of the meissner approach since the drawing doesn't match the description. The diagrams in the patent are crystal clear and all have one common factor in that the signal is input from a tap on the choke and various advantages are taken from the relationships at hand. The version where he offsets both AC and DC in a single choke still has me drooling and scratching my head how he got there in 1929.dave
"This arrangement reduces the ripple in the current by a factor of five to ten over that obtained with the same choke and condensers connected in the usual manner of (A)."Does this mean simply that winding two identical coils on a single core more than doubles their total inductance? In other words (common knowledge today), the inductance wound on a single core increases as the square of the turns? Folks knew that back then, right?
"The increased filter action is due to a neutralizing effect between the induced a-c components of the two portions of the choke. that is, a rather strong induced a-c component flows through the portion marked L1, the coupling of which to L2 neutralizes, to a large degree, the induced a-c voltage component therein, so that the output pulsations are reduced."
Well, this sounds like much the same thing. Mutual coupling between the turns increases the inductance beyond the two same coils uncoupled.
I haven't read through the entire patent yet, but a quick skim didn't reveal anything materially different. What a shame there are no values for the caps; it would be nice to see if this might have been resonant. Maybe further study of the doc will show more. You're right, it's not an easy read.
Based on the schematic, it appears that the hum-bucking connection allows resonating the first section of the choke at the ripple frequency. It would then act as a tuned trap to ground. I don't konw why it wasn't commercially successful, but it does look as though it might be more expensive to produce than standard chokes. It would also probably be limited to a rather narrow range of current draw. Current draw changes inductance, so there's a finite window over which the LC would be resonant at 120 Hz. This would obviously also rule out the possibility of manufacturing a swinging choke in this configuration, and those were very popular back then for many applications.
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