Has anyone here done a stripdown of Ducati alternators?
I've been looking at them more closely, and I'm curious as to the principles of their design. They seem quite different from those on Japanese and British bikes I've seen. Namely, using 2 coils per pole piece? That's what's shown for the Mach1 schematic in the workshop manual. What's the theory there?
Jordan
Alternator forensics
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Jordan
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Alternator forensics
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ducwiz
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Re: Alternator forensics
Hi jordan,
you're right, modern japanese systems are based on different principles, equipped mostly with multi-pole 3-phase schemes. Also, they are equipped with so called shunt regulators, while Ducati uses the series regulators.
The Ducati circuit here is basically a 2-phase (or "2 branch") system with two alternating power output leads and a grounded center tap. This is accomplished by opposite winding sense of the coils on each pole piece. So, during the magnet wheel rotates and say, a North pole of a magnet is passing a pole piece, one output lead has positive polarity, while the other lead gives negative voltage against the chassis or ground reference.
This (AC) output voltage is then connected to a rectifier - 2 solid state diodes with their "cathodes" on a common terminal and acting as the system's positive power output. The diodes, and other stuff for voltage regulation, are mounted inside this notorious and heavy black box, which Ducati called a "static regulator".
Operational details: The particular diode which sees the positive voltage half cycle will conduct, while the other simultaneously blocks the negative going half cycle. By this, electric current flow occurs in only one branch of the winding, while the other branch is "idling". There is no current flow or power output from both output wires at the same time.
The wide case singles contain a system not very different. They are equipped with a 6-coil an pole piece stator, and a "dynamic" or electronic regulator. The wiring of the stator is kind of "upside down" here, with the center tap being the positive output of the system, while the branch wires are connected to ground through so called SCRs (silicon contolled rectifiers), which also provide voltage regulation due to their controllable switching characteristics.
By contrast to SCRs, diodes are simple check valves for electric current.
articulate, or too overblown?
cheers Hans
p.s. additional info might be found here: http://ducwiz.minus.com/uploads
you're right, modern japanese systems are based on different principles, equipped mostly with multi-pole 3-phase schemes. Also, they are equipped with so called shunt regulators, while Ducati uses the series regulators.
The Ducati circuit here is basically a 2-phase (or "2 branch") system with two alternating power output leads and a grounded center tap. This is accomplished by opposite winding sense of the coils on each pole piece. So, during the magnet wheel rotates and say, a North pole of a magnet is passing a pole piece, one output lead has positive polarity, while the other lead gives negative voltage against the chassis or ground reference.
This (AC) output voltage is then connected to a rectifier - 2 solid state diodes with their "cathodes" on a common terminal and acting as the system's positive power output. The diodes, and other stuff for voltage regulation, are mounted inside this notorious and heavy black box, which Ducati called a "static regulator".
Operational details: The particular diode which sees the positive voltage half cycle will conduct, while the other simultaneously blocks the negative going half cycle. By this, electric current flow occurs in only one branch of the winding, while the other branch is "idling". There is no current flow or power output from both output wires at the same time.
The wide case singles contain a system not very different. They are equipped with a 6-coil an pole piece stator, and a "dynamic" or electronic regulator. The wiring of the stator is kind of "upside down" here, with the center tap being the positive output of the system, while the branch wires are connected to ground through so called SCRs (silicon contolled rectifiers), which also provide voltage regulation due to their controllable switching characteristics.
By contrast to SCRs, diodes are simple check valves for electric current.
articulate, or too overblown?
cheers Hans
p.s. additional info might be found here: http://ducwiz.minus.com/uploads
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DewCatTea-Bob
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- Location: Near SE side of Lake Michigan
Re: Alternator forensics
By: Jordan...
" Has anyone here done a stripdown of Ducati alternators? "
____ Where were you when 'wcorey' started the never-ending thread concerning the subject ?
" I've been looking at them more closely, and I'm curious as to the principles of their design. They seem quite different from those on Japanese and British bikes I've seen. Namely, using 2 coils per pole piece? "
____ Indeed Ducati alt.stators are considerably different and employ a principle that's not commonly used !
__ Others who THINK that THEY know what's-what with Ducati-alternators may disagree with me, but I still stand-by everything I've ever claimed in the past as being fact (directly-concerning Ducati-alternators)... Such-as, that the type of charging-system they're intended to work with, as actually being 'dual half-wave', (rather than "full wave"), type of rectification-process,, and also that while they're alt.stator-windings may APPEAR to have what's termed to be a 'center-tap', THAT connection-point is really just merely a 'common' -(as in 'common-connection-point' or 'common-lead') and not actually a regular/standard-type of "center-tap", and that's because the two (separate!) stator-windings are actually two individual (semi independent) circuits which are wound in such a non-standard way so as to be able to take advantage of each-other's collapsing field effect, (and therefore can-NOT be a simple/standard single center-tapped winding !).
__ While a single-continuous (ONE winding-direction only) stator-winding that's been cut into two & spliced-together and then both connected to a third conductor, can certainly indeed be thought of as the same-thing as a 'center-tapped' single-winding, (rather than just merely two separate/individual windings with a 'common'),, the fair reason for WHY the term 'center-tap' ought not be applied with the pair of stator-windings (of the Ducati-alternator), is because it's two stator-windings are 'wound' in OPPOSING directions ! _ Thus quite obviously making them SEPARATE/independent winding-lengths from one another, and so-thus the so-called "center-tap" is then no-where near the center of either stator-winding., but rather, located at one END (of both windings), thus obviously the third connection-point can only be a 'common' !
Now if the term 'common' never existed, then I might have to accept in it's place the term 'center-tap' , as still fairly valid then,, but in THIS particularly peculiar non-usual arrangement/case, the term 'center-tap' can be fairly misleading, (just as it has been in the past, time & again !).
" What's the theory there? "
____ The particular theory supposedly allows attainment of higher max.power-output than that of an equally weight/sized alternator, but, measurements have proven that the increased maximum power-output is only available at higher RPMs which our Duke-engines rarely ever rev-up to, (so a full-wave rectification setup is actually more useful for lower-RPM running, [as Ducati finally realized with their 200w.alt beginning on 1986 860GT L-twins] ).
__ Getting further-into the 'theory' behind the purpose of the fairly unique stator-winding arrangement...
The reason that one (of either) of the two alt.windings is always (alternately) left to be non-(self)-productive -(basically meaning it's negative power-pulses are ignored), while the OTHER power-output happens to be allowed to go-ahead & convey/supply it's available positive-power, (due to the "dual half-wave" rectification setup),, is so that the two individual windings can then induce into one-another, each-others' built-up flux-field,, pretty-much through the same induction-process as how the primary-winding in an ignition-coil does with it's secondary-winding, except that the alt.stator's windings-ratio is merely 1:1 (and-so, when one winding happens to be as a 'primary', then the other is thus-then the 'secondary' ).
So when the alternator's power-load is drawing current through one of the stator-windings (and thus-then having produced an associated flux-field), then when that alt.stator-circuit begins to drop-down in power-production (as it's 'half-wave' falls-off to zero), the resulting collapse of it's established field then-next induces current-flow into the OTHER stator-winding, just before that other-winding itself begins to produce it's very-own power-output (and thus-then perform the very-same process for the first winding, and so-forth & so-on).
This special buddy-buddy like relationship allows the otherwise normally wasted collapsing flux-field energy (of both circuits) to be harnessed & freely made use of. _ I'm pretty-sure that there's a particular established term for this rather convenient process but, I don't know it's given-name and-so I've always logically referred to it as the "Pull/Pull" effect, (cuz the rotor-magnets clearly solely perform the 'pushing' [which gets the power flowing in the first-place], and when the individual stator-windings' fields collapse, the resulting induction-process is more like 'pulling' current-flow [rather more-so, than 'pushing' it] ).
__ So now, if you fairly-well comprehend this co-beneficial extra current-production process, then you could understand that a 50% increase in power-output can become available IF and only if there's a load that's drawing current,, and that the greater the current-draw by the load-system - directly-greater then becomes the power-output (that's produced by just the Pull/Pull-effect), AND...
and that's it's not directly dependent on the alt.rotor's RPM (so much as it is on the load's current-draw).
__ Doesn't it seem like some power/energy is getting had for free, with this somewhat strange alternator process ?
I assume that there has to be some limit to the Pull/Pull-effect (if the powered load were to become same as a complete short-circuit), as there must be some point when that effect runs-into a saturation-limit.
DUCATIly,
DCT-Bob
" Has anyone here done a stripdown of Ducati alternators? "
____ Where were you when 'wcorey' started the never-ending thread concerning the subject ?
" I've been looking at them more closely, and I'm curious as to the principles of their design. They seem quite different from those on Japanese and British bikes I've seen. Namely, using 2 coils per pole piece? "
____ Indeed Ducati alt.stators are considerably different and employ a principle that's not commonly used !
__ Others who THINK that THEY know what's-what with Ducati-alternators may disagree with me, but I still stand-by everything I've ever claimed in the past as being fact (directly-concerning Ducati-alternators)... Such-as, that the type of charging-system they're intended to work with, as actually being 'dual half-wave', (rather than "full wave"), type of rectification-process,, and also that while they're alt.stator-windings may APPEAR to have what's termed to be a 'center-tap', THAT connection-point is really just merely a 'common' -(as in 'common-connection-point' or 'common-lead') and not actually a regular/standard-type of "center-tap", and that's because the two (separate!) stator-windings are actually two individual (semi independent) circuits which are wound in such a non-standard way so as to be able to take advantage of each-other's collapsing field effect, (and therefore can-NOT be a simple/standard single center-tapped winding !).
__ While a single-continuous (ONE winding-direction only) stator-winding that's been cut into two & spliced-together and then both connected to a third conductor, can certainly indeed be thought of as the same-thing as a 'center-tapped' single-winding, (rather than just merely two separate/individual windings with a 'common'),, the fair reason for WHY the term 'center-tap' ought not be applied with the pair of stator-windings (of the Ducati-alternator), is because it's two stator-windings are 'wound' in OPPOSING directions ! _ Thus quite obviously making them SEPARATE/independent winding-lengths from one another, and so-thus the so-called "center-tap" is then no-where near the center of either stator-winding., but rather, located at one END (of both windings), thus obviously the third connection-point can only be a 'common' !
Now if the term 'common' never existed, then I might have to accept in it's place the term 'center-tap' , as still fairly valid then,, but in THIS particularly peculiar non-usual arrangement/case, the term 'center-tap' can be fairly misleading, (just as it has been in the past, time & again !).
" What's the theory there? "
____ The particular theory supposedly allows attainment of higher max.power-output than that of an equally weight/sized alternator, but, measurements have proven that the increased maximum power-output is only available at higher RPMs which our Duke-engines rarely ever rev-up to, (so a full-wave rectification setup is actually more useful for lower-RPM running, [as Ducati finally realized with their 200w.alt beginning on 1986 860GT L-twins] ).
__ Getting further-into the 'theory' behind the purpose of the fairly unique stator-winding arrangement...
The reason that one (of either) of the two alt.windings is always (alternately) left to be non-(self)-productive -(basically meaning it's negative power-pulses are ignored), while the OTHER power-output happens to be allowed to go-ahead & convey/supply it's available positive-power, (due to the "dual half-wave" rectification setup),, is so that the two individual windings can then induce into one-another, each-others' built-up flux-field,, pretty-much through the same induction-process as how the primary-winding in an ignition-coil does with it's secondary-winding, except that the alt.stator's windings-ratio is merely 1:1 (and-so, when one winding happens to be as a 'primary', then the other is thus-then the 'secondary' ).
So when the alternator's power-load is drawing current through one of the stator-windings (and thus-then having produced an associated flux-field), then when that alt.stator-circuit begins to drop-down in power-production (as it's 'half-wave' falls-off to zero), the resulting collapse of it's established field then-next induces current-flow into the OTHER stator-winding, just before that other-winding itself begins to produce it's very-own power-output (and thus-then perform the very-same process for the first winding, and so-forth & so-on).
This special buddy-buddy like relationship allows the otherwise normally wasted collapsing flux-field energy (of both circuits) to be harnessed & freely made use of. _ I'm pretty-sure that there's a particular established term for this rather convenient process but, I don't know it's given-name and-so I've always logically referred to it as the "Pull/Pull" effect, (cuz the rotor-magnets clearly solely perform the 'pushing' [which gets the power flowing in the first-place], and when the individual stator-windings' fields collapse, the resulting induction-process is more like 'pulling' current-flow [rather more-so, than 'pushing' it] ).
__ So now, if you fairly-well comprehend this co-beneficial extra current-production process, then you could understand that a 50% increase in power-output can become available IF and only if there's a load that's drawing current,, and that the greater the current-draw by the load-system - directly-greater then becomes the power-output (that's produced by just the Pull/Pull-effect), AND...
and that's it's not directly dependent on the alt.rotor's RPM (so much as it is on the load's current-draw).
__ Doesn't it seem like some power/energy is getting had for free, with this somewhat strange alternator process ?
I assume that there has to be some limit to the Pull/Pull-effect (if the powered load were to become same as a complete short-circuit), as there must be some point when that effect runs-into a saturation-limit.
DUCATIly,
DCT-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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Jordan
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Re: Alternator forensics
ducwiz wrote:Operational details: The particular diode which sees the positive voltage half cycle will conduct, while the other simultaneously blocks the negative going half cycle. By this, electric current flow occurs in only one branch of the winding, while the other branch is "idling". There is no current flow or power output from both output wires at the same time.
The wide case singles contain a system not very different. They are equipped with a 6-coil an pole piece stator, and a "dynamic" or electronic regulator. The wiring of the stator is kind of "upside down" here, with the center tap being the positive output of the system, while the branch wires are connected to ground through so called SCRs (silicon contolled rectifiers), which also provide voltage regulation due to their controllable switching characteristics.
By contrast to SCRs, diodes are simple check valves for electric current.
articulate, or too overblown?
cheers Hans
p.s. additional info might be found here: http://ducwiz.minus.com/uploads
Thank you, Hans.
I'm seeing now that the 2 windings on each pole piece is a method to allow centre-tap arrangement.
Jordan
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Jordan
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Re: Alternator forensics
DewCatTea-Bob wrote: the type of charging-system they're intended to work with, as actually being 'dual half-wave', (rather than "full wave"), type of rectification-process,, and also that while they're alt.stator-windings may APPEAR to have what's termed to be a 'center-tap', THAT connection-point is really just merely a 'common' -(as in 'common-connection-point' or 'common-lead'), because actually the two (separate!) stator-windings are of two individual (semi independent) circuits which are wound in such a non-standard way so as to be able to take advantage of each-other's collapsing field effect, (and therefore can-NOT be a simple/standard single center-tapped winding !).
__ While a single-continuous (one coil-direction) stator winding that's been cut into two & spliced-together and then both connected to a third conductor, can certainly indeed be thought of as the same-thing as a 'center-tapped' single-winding, (rather than just merely two separate/individual windings with a 'common'),, the fair reason for WHY the term 'center-tap' ought not be applied with the pair of stator-windings (of the Ducati-alternator), is because it's two stator-windings are 'wound' in OPPOSING directions !
Thanks, Bob.
I like your idea about the mutual inductive effect of the 2 windings on a common pole. I can't refute it, but I confess I'm just a wee bit sceptical! Sorry I didn't read the earlier thread you mentioned.
I looked up many diagrams of centre-tap circuits - Google Images is good for that. When I compared them to the Ducati alternator diagram, it showed a lot of similarity in a logical sense, although physical placement of wires and connections vary.
I'm inclined to try a bridge rectifier and non-standard regulator, instead of the standard centre-tap system, because some of the Googling links suggest that the wasted half of the windings could be put to full use! And, it seems easy to do.
The reason I'm thinking about Ducati electrics now, is that I want to get my 350 running, which has Motoplat CDI type alternator. Alas - no spark, and a resistance check of the sparks charger says "open circuit" - kaput. The Motoplat stator is buried in potting-resin, so getting at the charging coil wouldn't be fun. I have another, unpotted Ducati stator from a widecase though, with 6 poles. Perhaps I can use one of them, with a coil rewound to provide a few hundred volts, as per the Motoplat.
Or, anyone know the easiest way to remove the potting resin?
Jordan
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DewCatTea-Bob
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- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Alternator forensics
" I like your idea about the mutual inductive effect of the 2 windings on a common pole. I can't refute it, but I confess I'm just a wee bit sceptical! "
____ How could you possibly have any doubt (that such inductive-process must be REQUIRED [by established laws of physics] to occur) ? _ What other reason could there possibly be for Ducati to have produced their stator with it wound as they had particularly done it ?
Cuz not only would it have been easier for Ducati to only wind the stator-fingers with just ONE continuous winding, (that's coil-wound in only one direction per finger), and CONVENTIONALLY center-tap it,, but also, WITHOUT such effect being able to be occurring (within the stator), then other such related-things (like ign.coils & transformers) would not be able to similarly function EITHER !
__ And also, fellow-member (Bill / wcorey) ran a test of the power-output from just one stator-lead, and it's output was only about just 33% (I think) of the combined-output of BOTH stator-leads when used together (as normally).
" Sorry I didn't read the earlier thread you mentioned. "
____ So-then you did already-before know of that thread ?
" I looked up many diagrams of centre-tap circuits
When I compared them to the Ducati alternator diagram, it showed a lot of similarity in a logical sense, "
____ That's certainly understandable, because there's very little actual difference between the 'center-tap' and 'common' types of connection-points, however there in fact actually is SOME difference (which can become a SIGNIFICANT difference in some cases !).
Also, many of the related drawings to be found are not done 100% technically-correct !
For instance, that drawing you've posted...
It's been done (well enough) to indicate that the two stator-windings have been wound in OPPOSING directions, yet it does show a tech.error (of that proper indication) in the stator-finger that's located in the 7-o'clock position (precisely at the top-right of the upper-left coil). - (See added pic.)
" I'm inclined to try a bridge rectifier and non-standard regulator, instead of the standard centre-tap system, "
____ Well it seems that you too have now unfortunately been contaminated with that imprecise/general-term "center tap" , (even after I've clearly explained why it's not accurate).
__ Anyhow, the Ducati-stator is not properly wound to be 'full-wave' rectified.
" because some of the Googling links suggest that the wasted half of the windings could be put to full use! "
____ It's indeed true that the stock half-wave rectification system leaves all the negative power-pulses (of the available AC) ignored & unused, and full-wave rectification (with a bridge-rect) could turn (rectify) all AC-pulses into use for charging any polarized battery. _ And I agree that doing-so would make more power available at the lower-RPMs where it's more useful.
__ However, not only will the Pull/Pull-effect be cancelled-out then, but the two separate sets of flux-fields will then be butted-up head-to-head AGAINST one-another, and that circumstance can't be a positive/useful effect and may thus likely lead to high-RPM power-output reduction, (which has already proven to not be of much concern though).
" The reason I'm thinking about Ducati electrics now, is that I want to get my 350 running, which has Motoplat CDI type alternator. Alas - no spark, and a resistance check of the sparks charger says "open circuit" - kaput. "
____ That's unfortunate. _ Perhaps you should consider an aftermarket battery-powered electronic-ignition.
" I have another, unpotted Ducati stator from a widecase though, with 6 poles. Perhaps I can use one of them, with a coil rewound to provide a few hundred volts, as per the Motoplat. "
____ That could be an interesting project.
Dukaddy-DUKEs,
-Bob
PS. - I've edited my previous-post with hopes that my altered & added wording now makes my post easier to comprehend correctly.
____ How could you possibly have any doubt (that such inductive-process must be REQUIRED [by established laws of physics] to occur) ? _ What other reason could there possibly be for Ducati to have produced their stator with it wound as they had particularly done it ?
Cuz not only would it have been easier for Ducati to only wind the stator-fingers with just ONE continuous winding, (that's coil-wound in only one direction per finger), and CONVENTIONALLY center-tap it,, but also, WITHOUT such effect being able to be occurring (within the stator), then other such related-things (like ign.coils & transformers) would not be able to similarly function EITHER !
__ And also, fellow-member (Bill / wcorey) ran a test of the power-output from just one stator-lead, and it's output was only about just 33% (I think) of the combined-output of BOTH stator-leads when used together (as normally).
" Sorry I didn't read the earlier thread you mentioned. "
____ So-then you did already-before know of that thread ?
" I looked up many diagrams of centre-tap circuits
When I compared them to the Ducati alternator diagram, it showed a lot of similarity in a logical sense, "
____ That's certainly understandable, because there's very little actual difference between the 'center-tap' and 'common' types of connection-points, however there in fact actually is SOME difference (which can become a SIGNIFICANT difference in some cases !).
Also, many of the related drawings to be found are not done 100% technically-correct !
For instance, that drawing you've posted...
It's been done (well enough) to indicate that the two stator-windings have been wound in OPPOSING directions, yet it does show a tech.error (of that proper indication) in the stator-finger that's located in the 7-o'clock position (precisely at the top-right of the upper-left coil). - (See added pic.)
" I'm inclined to try a bridge rectifier and non-standard regulator, instead of the standard centre-tap system, "
____ Well it seems that you too have now unfortunately been contaminated with that imprecise/general-term "center tap" , (even after I've clearly explained why it's not accurate).
__ Anyhow, the Ducati-stator is not properly wound to be 'full-wave' rectified.
" because some of the Googling links suggest that the wasted half of the windings could be put to full use! "
____ It's indeed true that the stock half-wave rectification system leaves all the negative power-pulses (of the available AC) ignored & unused, and full-wave rectification (with a bridge-rect) could turn (rectify) all AC-pulses into use for charging any polarized battery. _ And I agree that doing-so would make more power available at the lower-RPMs where it's more useful.
__ However, not only will the Pull/Pull-effect be cancelled-out then, but the two separate sets of flux-fields will then be butted-up head-to-head AGAINST one-another, and that circumstance can't be a positive/useful effect and may thus likely lead to high-RPM power-output reduction, (which has already proven to not be of much concern though).
" The reason I'm thinking about Ducati electrics now, is that I want to get my 350 running, which has Motoplat CDI type alternator. Alas - no spark, and a resistance check of the sparks charger says "open circuit" - kaput. "
____ That's unfortunate. _ Perhaps you should consider an aftermarket battery-powered electronic-ignition.
" I have another, unpotted Ducati stator from a widecase though, with 6 poles. Perhaps I can use one of them, with a coil rewound to provide a few hundred volts, as per the Motoplat. "
____ That could be an interesting project.
Dukaddy-DUKEs,
-Bob
PS. - I've edited my previous-post with hopes that my altered & added wording now makes my post easier to comprehend correctly.
You do not have the required permissions to view the files attached to this post.
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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Jordan
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Re: Alternator forensics
from DewCatTea-Bob:
____ How could you possibly have any doubt (that such inductive-process must be REQUIRED [by established laws of physics] to occur) ?
J: I might be missing something, but by the time one winding is just starting to make a positive waveform excursion, the other one had just finished its own, and cannot contribute any power to the first. I don't think there's a storage effect?
_ What other reason could there possibly be for Ducati to have produced their stator with it wound as they had particularly done it ?
J: Good point - it threw me too. Maybe it allowed for maximum options, bringing out 4 ends on each of the windings? Maybe it's easier than conventional tapping? Just guessing. It's good news for us owners though, who might want to reconfigure it.
-- Cuz not only would it have been easier for Ducati to only wind the stator-fingers with just ONE continuous winding, (that's coil-wound in only one direction per finger), and CONVENTIONALLY center-tap it,, but also, WITHOUT such effect being able to be occurring (within the stator), then other such related-things (like ign.coils & transformers) would not be able to similarly function EITHER !
J: They would be in phase, whereas the Ducati windings are not, because of diode steering. The direction of the windings shouldn't matter - it can be adjusted externally, just by swapping over 2 of the 4 connections on each pole.
__ And also, fellow-member (Bill / wcorey) ran a test of the power-output from just one stator-lead, and it's output was only about just 33% (I think) of the combined-output of BOTH stator-leads when used together (as normally).
J: I can't account for that!
" Sorry I didn't read the earlier thread you mentioned. "
____ So-then you did already-before know of that thread?
J: I don't read all threads. That one seemed very involved, and I wasn't focussed on the topic at the time.
Jordan
____ How could you possibly have any doubt (that such inductive-process must be REQUIRED [by established laws of physics] to occur) ?
J: I might be missing something, but by the time one winding is just starting to make a positive waveform excursion, the other one had just finished its own, and cannot contribute any power to the first. I don't think there's a storage effect?
_ What other reason could there possibly be for Ducati to have produced their stator with it wound as they had particularly done it ?
J: Good point - it threw me too. Maybe it allowed for maximum options, bringing out 4 ends on each of the windings? Maybe it's easier than conventional tapping? Just guessing. It's good news for us owners though, who might want to reconfigure it.
-- Cuz not only would it have been easier for Ducati to only wind the stator-fingers with just ONE continuous winding, (that's coil-wound in only one direction per finger), and CONVENTIONALLY center-tap it,, but also, WITHOUT such effect being able to be occurring (within the stator), then other such related-things (like ign.coils & transformers) would not be able to similarly function EITHER !
J: They would be in phase, whereas the Ducati windings are not, because of diode steering. The direction of the windings shouldn't matter - it can be adjusted externally, just by swapping over 2 of the 4 connections on each pole.
__ And also, fellow-member (Bill / wcorey) ran a test of the power-output from just one stator-lead, and it's output was only about just 33% (I think) of the combined-output of BOTH stator-leads when used together (as normally).
J: I can't account for that!
" Sorry I didn't read the earlier thread you mentioned. "
____ So-then you did already-before know of that thread?
J: I don't read all threads. That one seemed very involved, and I wasn't focussed on the topic at the time.
Jordan
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DewCatTea-Bob
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- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Alternator forensics
" but by the time one winding is just starting to make a positive waveform excursion, the other one had just finished its own, and cannot contribute any power to the first. I don't think there's a storage effect? "
____ Of-course there's no "storage effect", and there's no actual raw power contribution from one circuit directly to the other ! _ But the winding which had just finished producing it's output of power also then just had it's directly-associated flux-field collapse, (providing of-course that it had also just been flowing current), which thus-then MUST have had to induce some potential-power into the other/neighboring coil-winding !
__ Now since the associated diodes are arranged & connected so that only the positive-half (of the AC) flows through the windings, then when that half-cycle falls-down towards zero, it's likewise collapsing-field must thus-then be that of a POSITIVE-type field, so-therefore that in-turn can only force a 'positive' current-flow into the other winding (which itself happens to then be current-dead at that moment because it's wound in the opposite direction [and-so could only itself offer neg.flow at the time, if allowed] ).
This positive-field's falling-flux causes a sort of 'kick' of POSITIVE current-flow into the other winding just before it itself begins to offer it's very-own pulse of (alt.rotor-driven) positive-current. _ (I use the word "kick" because that (relatively minor) pulse of positive-power is relentlessly-strong and provides a punch of current-flow immediately prior to the following normal-pulse of power.)
So, while the alt.rotor-driven pulses of power supplies each winding-output with only 180-degrees of pos.power-output (and 180-degrees without), the Pull/Pull-effect adds 90-degrees more pos.power-output (into whichever winding-output that happens to otherwise be dormant for 180-degrees).
So-thus these fairly unique Ducati-alternators will offer 270-degrees of power-output from EACH of their two stator-winding outputs, (rather than just-merely 180-degrees, as most would otherwise normally expect).
__ If you already understand how the induction-process works within an ign.coil, then it's pretty-much just as easy to understand how the related process can also work between Ducati's pair of stator-windings.
And it should now be fairly clear as to why the Pull/Pull-effect could not work if Ducati's stator-winding was a standard 'center-tapped' affair without it's two windings wound in opposite/opposing directions.
" Maybe it allowed for maximum options, bringing out 4 ends on each of the windings? "
____ But that still could've been achieved even with the stator's windings ALL 'turned' in the very-same direction, by simply cutting the entire length of wire into two pieces and turn-winding them both together at once, (which then would've been easier to do than having wound one length in one direction and the other in the opposite).
" Maybe it's easier than conventional tapping? "
____ Conventionally center-tapping is quite easy enough to accomplish on one continuous-winding,, but while it may be equally easy to wine two winding-lengths together at-once, that could not be the case when one length is wound oppositely.
__ And if the whole winding is to be either half-wave or full-wave rectified, then a center-tapped type affair would serve no useful purpose.
" It's good news for us owners though, who might want to reconfigure it. "
____ Reconfiguration of most-all of the individually-connected windings (of the stock stator) was well experimented with by Bill !! _ (And with some interesting results.)
__ The best reconfiguration would be to rewind all the coil-turns in one/same direction, and employ full-wave rectification.
" The direction of the windings shouldn't matter - it can be adjusted externally, just by swapping over 2 of the 4 connections on each pole. "
____ But simply doing that would then kill any possibility of Pull/Pull-effect from being able to occur, as both circuits would then both be live or dead at the same times. _ Thus when the two circuits are then in their dead-mode -(meaning when in their ignored negative-potential fully impeded-flow dormant-state), there's then no collapsing-field which can induce potential-power into either of them !
There does of-course remain one (larger) collapsing-field, but it would only serve to perform the standard flywheel-effect just to their very-own winding-circuits only (with nothing else left to take advantage of that flux-field, [just as in most other/regular-alternators] ) !
" I can't account for that! "
____ Ahh yes, but the Pull/Pull-effect can !
Cuz otherwise without that added enhancement-effect, each circuit would then each provide 50% of the total-output, (which would be about 50% less than is actually available with the P/P-effect).
Dukaddy-DUKEs,
DCT-Bob
____ Of-course there's no "storage effect", and there's no actual raw power contribution from one circuit directly to the other ! _ But the winding which had just finished producing it's output of power also then just had it's directly-associated flux-field collapse, (providing of-course that it had also just been flowing current), which thus-then MUST have had to induce some potential-power into the other/neighboring coil-winding !
__ Now since the associated diodes are arranged & connected so that only the positive-half (of the AC) flows through the windings, then when that half-cycle falls-down towards zero, it's likewise collapsing-field must thus-then be that of a POSITIVE-type field, so-therefore that in-turn can only force a 'positive' current-flow into the other winding (which itself happens to then be current-dead at that moment because it's wound in the opposite direction [and-so could only itself offer neg.flow at the time, if allowed] ).
This positive-field's falling-flux causes a sort of 'kick' of POSITIVE current-flow into the other winding just before it itself begins to offer it's very-own pulse of (alt.rotor-driven) positive-current. _ (I use the word "kick" because that (relatively minor) pulse of positive-power is relentlessly-strong and provides a punch of current-flow immediately prior to the following normal-pulse of power.)
So, while the alt.rotor-driven pulses of power supplies each winding-output with only 180-degrees of pos.power-output (and 180-degrees without), the Pull/Pull-effect adds 90-degrees more pos.power-output (into whichever winding-output that happens to otherwise be dormant for 180-degrees).
So-thus these fairly unique Ducati-alternators will offer 270-degrees of power-output from EACH of their two stator-winding outputs, (rather than just-merely 180-degrees, as most would otherwise normally expect).
__ If you already understand how the induction-process works within an ign.coil, then it's pretty-much just as easy to understand how the related process can also work between Ducati's pair of stator-windings.
And it should now be fairly clear as to why the Pull/Pull-effect could not work if Ducati's stator-winding was a standard 'center-tapped' affair without it's two windings wound in opposite/opposing directions.
" Maybe it allowed for maximum options, bringing out 4 ends on each of the windings? "
____ But that still could've been achieved even with the stator's windings ALL 'turned' in the very-same direction, by simply cutting the entire length of wire into two pieces and turn-winding them both together at once, (which then would've been easier to do than having wound one length in one direction and the other in the opposite).
" Maybe it's easier than conventional tapping? "
____ Conventionally center-tapping is quite easy enough to accomplish on one continuous-winding,, but while it may be equally easy to wine two winding-lengths together at-once, that could not be the case when one length is wound oppositely.
__ And if the whole winding is to be either half-wave or full-wave rectified, then a center-tapped type affair would serve no useful purpose.
" It's good news for us owners though, who might want to reconfigure it. "
____ Reconfiguration of most-all of the individually-connected windings (of the stock stator) was well experimented with by Bill !! _ (And with some interesting results.)
__ The best reconfiguration would be to rewind all the coil-turns in one/same direction, and employ full-wave rectification.
" The direction of the windings shouldn't matter - it can be adjusted externally, just by swapping over 2 of the 4 connections on each pole. "
____ But simply doing that would then kill any possibility of Pull/Pull-effect from being able to occur, as both circuits would then both be live or dead at the same times. _ Thus when the two circuits are then in their dead-mode -(meaning when in their ignored negative-potential fully impeded-flow dormant-state), there's then no collapsing-field which can induce potential-power into either of them !
There does of-course remain one (larger) collapsing-field, but it would only serve to perform the standard flywheel-effect just to their very-own winding-circuits only (with nothing else left to take advantage of that flux-field, [just as in most other/regular-alternators] ) !
" I can't account for that! "
____ Ahh yes, but the Pull/Pull-effect can !
Cuz otherwise without that added enhancement-effect, each circuit would then each provide 50% of the total-output, (which would be about 50% less than is actually available with the P/P-effect).
Dukaddy-DUKEs,
DCT-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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Jordan
- Posts: 1482
- Joined: Fri Dec 24, 2010 11:29 am
Re: Alternator forensics
DewCatTea-Bob wrote:" I looked up many diagrams of centre-tap circuits
When I compared them to the Ducati alternator diagram, it showed a lot of similarity in a logical sense, "
____ That's certainly understandable, because there's very little actual difference between the 'center-tap' and 'common' types of connection-points, however there in fact actually is SOME difference (which can become a SIGNIFICANT difference in some cases !).
Also, many of the related drawings to be found are not done 100% technically-correct !
For instance, that drawing you've posted...
It's been done (well enough) to indicate that the two stator-windings have been wound in OPPOSING directions, yet it does show a tech.error (of that proper indication) in the stator-finger that's located in the 7-o'clock position (precisely at the top-right of the upper-left coil). - (See added pic.)
Hi Bob,
I wouldn't necessarily take that drawing as meaningful, with regard to indicating the polarity of the windings. The convention is to show that with a dot at one end of the winding. I don't know why Ducati wouldn't do that too, being an electronics company, except that they weren't trying to indicate polarity in that drawing. Top marks for your eagle eye though!
Jordan
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DewCatTea-Bob
- Posts: 2897
- Joined: Sun Nov 01, 2009 10:53 am
- Location: Near SE side of Lake Michigan
Re: Alternator forensics
" I wouldn't necessarily take that drawing as meaningful, with regard to indicating the polarity of the windings. "
____ I agree that a great portion of such drawings are not to be FULLY trusted as being completely technically-accurate,, however I'm sure that the drawing in question was actually intended to indicate the fairly important particular-detail of the difference in the winding-directions of the two stator-windings, cuz an actual physical tear-down of this type of Ducati-stator has revealed the same opposing relationship.
__ I've now fixed the error in that picture, (now posted below).
____ I hope you've noticed that I've edited my previous posts (with "DCT-Bob") so as to provide a fuller explanation (of the same topic originally addressed), in hopes of being better understood.
Duke-Cheers,
-Bob
____ I agree that a great portion of such drawings are not to be FULLY trusted as being completely technically-accurate,, however I'm sure that the drawing in question was actually intended to indicate the fairly important particular-detail of the difference in the winding-directions of the two stator-windings, cuz an actual physical tear-down of this type of Ducati-stator has revealed the same opposing relationship.
__ I've now fixed the error in that picture, (now posted below).
____ I hope you've noticed that I've edited my previous posts (with "DCT-Bob") so as to provide a fuller explanation (of the same topic originally addressed), in hopes of being better understood.
Duke-Cheers,
-Bob
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PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob
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