[quote= Harvey ...
" I don’t think I have overlooked anything, just that you have an inaccurate understanding of the capacitor’s (condenser’s) role in the points circuit. "
____ Harvey, just because I hadn't bothered to explain the condenser's COMPLETE role which it performs within the ign.system, does-not mean that MY understanding of it is "inaccurate" !
Furthermore, what I do understand (about points-type ign.systems) is-not JUST merely my-OWN understanding, but ALSO that of '
Ignition-systems 101' ! - (Of-which you-yourself have now made fairly apparent that you've partially forgotten some-of, [if you had EVER known of it all].)
So I think it will make it easier to understand the facts if I go through, what the cap does, in the DC circuit.
When the points close, the current flows through the Primary winding creating a magnetic field that rises up from the iron core passing through the windings, this produces an opposite potential against the primary flow to slow the rise. This is the reason we have a Dwell period, to charge the coil.
When the points start to open the resistance across them increases to reduce the current flowing, this reduction causes the magnetic field to start to collapse, inducing a current in the primary that will flow in the same direction, to try to put the field up again. If this current does flow it will slow the collapsing field, and the secondary voltage will be reduce, due to the slow magnetic movement. Remembering that it is the speed of the field going through the windings, that produces the voltage.
So the main function is to have the primary current completely stop when the points open, but as the points open slowly, the resistance across them slowly increases, till they are far enough apart to prevent, the induced voltage of about 250Volts, from jumping across them. As a compromise we can allow a small amount of the voltage to flow into the, low resistance capacitor, till the points are far enough apart to prevent any flow across them. If the capacity of the capacitor is too small, it will fill before the points are far enough apart, and will jump across (spark), and the induced current will flow in the primary killing the HT. If the capacitor is too big, too much current will flow into it also killing the HT. So the capacitor is chosen to JUST do the job, and no more.
____ All fairly-good related-info, most-all pretty-much right out of 'Ignition-systems 101' ! - (Anyone who has never been taught this basic ign.system-info, has been deprived by their High School , [either in Science-class or Auto-shop] !)
" If the capacity of the capacitor is too small, it will fill before the points are far enough apart, and will jump across (spark), and the induced current will flow in the primary "
____ Right, cuz the HT.coil's collapsing-field will force the primary-circuit's established current-flow to convert to whatever voltage is required to jump the point-gap (if the condenser doesn't have enough room to hold the pulse-charge) !
" If the capacitor is too big, too much current will flow into it also killing the HT. "
____ RIGHT, that's quite correct ! ... Exactly-because, if it really is TOO-big, then it will never get enough of it's time-constants fulfilled enough to stop acting like a short-circuit in-time, and then would cause the ign.system to behave as-if the contact-points had-not opened at the very-time when they actually had !
" Ok now to look at you’re theory, that the secondary current will flow through the capacitor, back through the primary windings to get to the other end of the secondary winding. "
____ Yes, RIGHT,, as it MUST-do in DC.powered ign.systems, (especially where there's NO battery-circuit) !
__ (And, it's not 'MY' "theory" ! ... It's merely well-known fact !, [although it's of-course not really fair to suggest that "current will
flow though" the condenser, as it only does-so in a virtual-manor].)
" As I have said the capacitor is only big enough to take a small amount of the 250Volts in the primary, "
____ There is no such
specific voltage (as "250Volts") that's much higher than that of the battery's voltage, within the primary-circuit,, so-long as the condenser-size is up-to absorbing all the 'flux-induced' current-flow after the points open ! _ (Although that 'flywheel-effect' may-possibly momentarily shove electrons into the condenser at a faster rate than they can become fully disbursed throughout the condenser's entire holding-room,, and-so THEN (in such case), briefly possibly slightly spike-up the voltage felt at the condenser [by an amount that's well-less than the condenser is rated to handle].)
__ I tend to wonder how the supposed "250Volts" could be expected to particularly exist anywhere within the primary-circuit,, cuz even-if the condenser wasn't large enough to fully absorb & prevent all of any such voltage build-up, then WHATEVER the possible built-up voltage-AMOUNT could be, it would specifically depend-on the relative sizes of the condenser & primary-coil/flux-field, (both of which vary somewhat, between the various ign.systems employed by different manufacturers),, so-thus to expect "250Volts", is fairly unlikely in any case.
" and its dielectric break down voltage is about 400Volts. So it hasn’t the capacity for the large amount of energy, that the secondary flow produces. Faced with this resistance the secondary voltage will rise, to blow a hole through the dielectric insulation of the capacitor, and flow back to the secondary, the way you say, "
____ That statement of yours is worded so clearly,, that it's now fairly quite-clear to me that not-only does it seem that you do-not fully-understand the evolved physics, you also didn't-even learn-of & correctly comprehend any of it from my previous-post, (so I guess I had overestimated your ability to grasp that which I had thought would be relatively-easy for the likes of anyone [with at-least a BASIC-understanding], such-as like yourself).
__ The involved condenser indeed DOES have the capacity to cope with ANY current-flow which the ign.coil passes, (either in the primary OR the secondary) ! ...
The HT/ign.coil does-NOT 'step-up' "energy" -(wattage), rather it merely alters the ratio of voltage to current ! _ So there is NO "
large amount of energy" for the condenser to have to handle & deal-with ! ...
__ It should already be understood that the amount of energy -(power/wattage) coming-out of the HT.coil is actually NO-greater than that which goes into it !
And if what you had actually-meant by "energy", was really meant to be the large-amount of '
voltage' or 'tension',, then THAT is most-entirely DROPPED-across the plug-gap, so-therefore the condenser-itself is never subjected to any such HT.voltage, (rather, only-just the HT.secondary-circuit's MINISCULE current) !
" its dielectric break down voltage is about 400Volts.
Faced with this resistance the secondary voltage will rise, to blow a hole through the dielectric insulation of the capacitor, and flow back to the secondary, the way you say, "
____ That stated-wording is certainly
WRONG, for two reasons ! ...
(You really should've learned from what I had STATED in my previous-post, [as most-anyone who already has a fairly-good grasp of this-stuff, should've understood] !) ...
__ FIRSTLY,, (directly concerning the condenser), there is NO "resistance" to the secondary-circuit's current-flow, (other than at the plug-gap),, because a
discharged condenser is virtually the very-same as a SHORT-circuit, (as it can then pass-on an equal amount of electrons as it takes-in ! , [thus virtually completing the secondary-circuit !] ) _ Anyone who understands the workings of a condenser, knows this to be FACT !
And when such a circuit-component has no significant resistance (compared-to any other circuit-component), then IT will-NOT be subjected to any significant voltage-drop !
__ SECONDLY, (even-if the plug-gap were to-be reduced to zer0, thus-then making the condenser-itself a MAJOR circuit-load [instead of the plug-gap] ),, the relatively very-small
amount of electrons within a secondary-pulse of current is
insufficient to charge-up the condenser ! ... Anyone who has learned about how condensers -(& capacitors) become charged-up, knows that they need to be exposed to the DC.charging-source's voltage-level for 5 'time-constants' before they finally become fully charged-up to the same voltage-level as that of the voltage-source ! _ And considering the relatively large 'size' of the condenser in relation to the very-short length of time that the miniscule secondary-pulse -(spark) current-flow actually so briefly lasts,
it's most-likely that not-even the very
1st.time-constant is ever achieved ! _ So-therefore (even-THEN), the condenser could NEVER* become exposed to ANY voltage-level which it cannot handle ! - (* Since the condenser is always repeatedly bled back-down to it's discharged-state, until each time the contact-points reopen & un-ground it.)
(Although IF the duration-time of the secondary's current-pulse ever happened to last long-enough,, THEN yes, the resulted extreme HT.voltage-pressure would have had the chance to adequately build-up and-THEN indeed punch a hole through the dielectric/separator-wall within the condenser, [quite-likely well-before ever reaching a significant-fraction of the full HT.secondary voltage-level] !
Such a (fairly remote!) possibility is a reason why the condenser needs to be of a minimal-size, so that the VAST-majority of the HT.voltage is then always instead dropped-across the plug-gap, rather than getting any chance to build-up at the condenser, (in such event when there's no storage-battery circuit available to bleed-through} !) " remembering that the battery circuit is parallel to the capacitor, and has a very low resistance, so wish as you may, that is the path that it will take, and the capacitor will survive to work again. "
____ Clearly Harvey, YOU need to bone-up on this stuff ! _ Cuz there's NO-need for the secondary's current-flow to pass-through the battery-circuit when the condenser is MORE
like a short-circuit !
So it is-not
I who should "wish", as the fact is ALREADY
fact (without any wishing-help from myself) !
__ And by-the-way, the battery is-not exactly in parallel with the condenser, (as the condenser is in 'series' with the ign.coil, [and only part-of-the-time, at that] ).
" If the capacitor was big enough to pass all the energy from the secondary, it would also pass all the energy induced in the primary. "
____ I believe that what YOU are possibly meaning to make main-point of (with that [rather questionable] summation), is:
is that the prospect of the condenser possibly passing all-of the primary's power-juice, would thus-then make the condenser pretty-much worthless to it's expected-purpose,, and-so thus-THEN, it therefore also can't be true that the condenser could pass the secondary's power-juice, either). ... __ Well, your use of the term "energy", is fairly misleading on this speculated-issue...
Rather than proclaiming that condensers absorb & contain or "pass" mere "energy", they actually deal with quantities of 'electrons' ! _ And while the secondary-circuit flows a VERY-
FEW electrons, (which is a relatively very-easy task for a condenser to deal-with),, conversely however, the primary-circuit flows a
vastly-LARGER quantity of electrons, which tends-to fill-up the condenser at a much greater rate !
So-therefore it's not fair to indicate that the condenser handles both circuits rather equally !
____ Harvey, if you wish to continue-on arguing-out any of THIS (above) DC.ignition-matter any further (with me), then I'll have-to move it out of this-thread and into another of it's very-own,, cuz THIS-matter (on
DC.ign.systems) has already gotten too-far off-topic for the original-topic (concerning a 160-type ign.system), and-so may otherwise further confuse-up anyone who's merely concerned with just such AC.powered-type ign.systems.
____
Now-NEXT onward-to a RELATED-matter of THIS-original thread-topic. .......
" This one is based on a false premise.

That the stator winding has an increased energy, from the magnetic field collapsing around it. "
____ I'm thinking that rather your-own interpretation of my posted-wording is more-likely that which is at fault for your apparent disagreement. _ Cuz I never meant to indicate that there was any "
increased energy" !
__ After you've read & understood THIS post, then try re-reading my previous-post on this particular aspect, and-see if you don't then correctly understand exactly-what I had (fairly clearly) ACTUALLY-meant to convey.
" At the time of Ignition, the stator winding has the flywheel magnet, directly above it, "
____ While that's not unfair to say,, actually, you must really mean that the North & South poles of all the rotor-magnets are MEANT to be aligned with the stator-poles (as near as possible) for max.generated-power near when the ignition is set to fire-off.
" and the magnetic flux is passing through the stator’s winding producing energy in it. It does not stop, or collapse, it keeps producing energy, "
____ Yes, but of-course THAT's certainly quite-true Harvey ! _ BUT my posted-point was not bothering to include any of such of those BASIC working-details,, rather than the permanently-established mag.field of the flywheel-rotor, I was RATHER in reference-to the temporary mag.field which becomes established due-TO the
flowing current passing-through the stator-winding ITSELF, all on it's OWN ! ...
__ Most-everyone who understands this stuff correctly, realizes that ALL wires which are passing flowing-current through them, are then also surrounded with a resulting magnetic-field of their very-own (regardless of whether or not ANOTHER separate magnetic-field originally directly-induced the current-flow within) ! _ So-then it should be understood that the collapsing-mag.field which
I-myself was particularly in actual reference-to, is actually that of the flowing-current within the stator-winding itself, (and NOT that of the rotor-magnets, [which of-course never collapses] ) !
__ Now the aspect which seems to-be like magic, is that even when the current-flow itself is stopped (or even merely 'impeded'), that SAME-amount of current/power-flow will-NOT seize UNTIL it's very-OWN established flux-field finally collapses ! _ So-therefore as THAT flux-field, (minor as it may relatively be), collapses,, it's established current-power MUST continue-on even if it has to auto-convert up-to whatever high-voltage is needed to fully-satisfy that collapsing-field's induced current-flow ! -
THUS the 'flywheel-effect' ! (Note that it's 'power', rather than current or voltage alone, which builds the strength of a flux-field.)
" so there can be no “flywheel effect” or “the voltage being increased” due to a collapsing magnetic field, "
____ By NOW Harvey, you should finally understand why that statement of yours is NOT correct ! _ Cuz (as for one thing), ALL established flux-fields must induce that flywheel-effect into the current-flow (as the flowing is ended) !
And the short-circuited stator-winding's very-OWN (briefly)- established full-strength flux-field MUST-not be ignored ! _ Cuz when it's rather high established current-flow becomes impeded (by being diverted, [from the short-circuit through the contact-points], over-to the HT.coil primary-winding*), there's then NO-choice other-than for the established full-strength current-flow to auto-convert to whatever higher voltage is required to maintain the very-same flow of power (against the opposing reactance of the primary-coil) ! _ (* While the primary-coil may have a relatively low 'resistance', it's still rather quite a substantial resistance-change (compared-to the short-circuit !),, and also, the reactive-impedance of the primary-coil considerably compounds the total-resistance/impedance that the stator-winding's established current/power is pressure-forced against,, and all that opposition, FORCES the flowing-power's voltage to spike-upward !)
And that forced voltage-increase by-the-way, is of-course pretty-much just-what the-doctor-ordered to help build-up the spike-voltage for the HT.coil !
__ Harvey, you simply CAN'T deny this FACT !
" as the field remains the same through the whole ignition phase. "
____ Yeah, right, (more-or-less),, that-is, as far as the ALT.ROTOR's mag.field itself is concerned, however. _ (But I guess we're supposed to have been in room-202 now, not merely '101' any longer.)
__ (Anyone with your knowledge-level Harvey, shouldn't be remaining stuck back on 1st.base, when we've so obviously moved-onward to the more advanced details.)
" It is only the points opening, and the high impendence caused by the inductive reactance of the primary windings that causes the energy to change from high current to high voltage. "
____ Your included word "only", merely makes your statement fairly-true for a CD.type ign.system,, but by now, you really ought-to understand how the reactive-impedance -(reactance) effect (of the primary-winding) actually does-NOT work-alone all by itself to spike-up the primary-voltage in an ET.system like Ducati's !
__ So Harvey,, if you STILL fail to give-in & follow that which I've been trying to convey to your sense of reasoning, then I suggest that you get your grandson's science-teacher to submit a confirming-explanation.
Hopeful-Cheers,
DCT-Bob