Automotive alternator windings & rectifier

Discussion in 'Electronic Equipment' started by Mike Cook, Aug 19, 2013.

  1. Mike Cook

    Mike Cook Guest

    http://www.autoshop101.com/forms/alt_bwoh.pdf

    has photos of an alternator with 4 connections for windings (each of 3 phases
    + common), and the 8 diode rectifier. But wiring diagrams show only 3
    connections and 6 diodes.

    Where does the common winding terminal connect (there is a connection on the
    rectifier plate)? Where do the other 2 diodes connect?

    I handled one of these disassembled units but didn't have time to ohm out the
    connections.

    Thanks.
     
    Mike Cook, Aug 19, 2013
    #1
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  2. Mike Cook

    amdx Guest

    On 8/19/2013 11:49 AM, Mike Cook wrote:
    > http://www.autoshop101.com/forms/alt_bwoh.pdf
    >
    > has photos of an alternator with 4 connections for windings (each of 3 phases
    > + common),


    Not one of the pages shows four connections brought out from the
    windings.


    >and the 8 diode rectifier.


    I don't see any 8 diode rectifier.

    >But wiring diagrams show only 3
    > connections and 6 diodes.



    Yup.

    > Where does the common winding terminal connect (there is a connection on the
    > rectifier plate)? Where do the other 2 diodes connect?


    Common is created by the way the diodes are connected. >THAT< common is
    connected to the auto frame.


    > I handled one of these disassembled units but didn't have time to ohm out the
    > connections.


    Hmm.


    > Thanks.
    >


    Wo uld you ask your question again and maybe clarify the situation?
     
    amdx, Aug 19, 2013
    #2
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  3. On Mon, 19 Aug 2013 09:49:18 -0700, Mike Cook <>
    wrote:

    >http://www.autoshop101.com/forms/alt_bwoh.pdf
    >
    >has photos of an alternator with 4 connections for windings (each of 3 phases
    >+ common), and the 8 diode rectifier. But wiring diagrams show only 3
    >connections and 6 diodes.
    >
    >Where does the common winding terminal connect (there is a connection on the
    >rectifier plate)? Where do the other 2 diodes connect?


    The common in the Wye connection (called "Neutral Junction" in the
    photo on page 18) goes to the 4th pair of diodes (and typically the
    regulator). The other three pairs of winding ends ("Stator Lead Ends")
    go to the other three pairs of diodes.

    >I handled one of these disassembled units but didn't have time to ohm out the
    >connections.
    >
    >Thanks.
     
    Spehro Pefhany, Aug 19, 2013
    #3
  4. In sci.electronics.basics Jim Thompson <> wrote:
    > On Mon, 19 Aug 2013 09:49:18 -0700, Mike Cook <>
    > wrote:
    >
    >>http://www.autoshop101.com/forms/alt_bwoh.pdf
    >>
    >>has photos of an alternator with 4 connections for windings (each of 3 phases
    >>+ common), and the 8 diode rectifier. But wiring diagrams show only 3
    >>connections and 6 diodes.
    >>
    >>Where does the common winding terminal connect (there is a connection on the
    >>rectifier plate)? Where do the other 2 diodes connect?
    >>
    >>I handled one of these disassembled units but didn't have time to ohm out the
    >>connections.
    >>
    >>Thanks.

    >
    > The common point is sometimes used for fault detection.
    >
    > When I was at Motorola SPD in the '60's I developed a circuit that
    > could detect just about any fault, shorted or open diodes and shorted
    > or open windings, by viewing that node. That node, BTW, is often
    > labeled "S". Old GM alternators brought that out as a post on the
    > back of the alternator (before regulators were internal... that's what
    > some of my patents are all about... integrating the regulator).
    >
    > That was before CAD ;-) If I can find my hand drawing, I'll post it.
    >
    > ...Jim Thompson


    dumb question.

    what EXACTLY does the charge lamp indicate?

    what triggers it to go on and off?

    can it simply be removed and ignored?
     
    Cydrome Leader, Aug 20, 2013
    #4
  5. Mike Cook

    tm Guest

    "Cydrome Leader" <> wrote in message
    news:kuu98f$jtp$...
    > In sci.electronics.basics Jim Thompson
    > <> wrote:
    >> On Mon, 19 Aug 2013 09:49:18 -0700, Mike Cook <>
    >> wrote:
    >>
    >>>http://www.autoshop101.com/forms/alt_bwoh.pdf
    >>>
    >>>has photos of an alternator with 4 connections for windings (each of 3
    >>>phases
    >>>+ common), and the 8 diode rectifier. But wiring diagrams show only 3
    >>>connections and 6 diodes.
    >>>
    >>>Where does the common winding terminal connect (there is a connection on
    >>>the
    >>>rectifier plate)? Where do the other 2 diodes connect?
    >>>
    >>>I handled one of these disassembled units but didn't have time to ohm out
    >>>the
    >>>connections.
    >>>
    >>>Thanks.

    >>
    >> The common point is sometimes used for fault detection.
    >>
    >> When I was at Motorola SPD in the '60's I developed a circuit that
    >> could detect just about any fault, shorted or open diodes and shorted
    >> or open windings, by viewing that node. That node, BTW, is often
    >> labeled "S". Old GM alternators brought that out as a post on the
    >> back of the alternator (before regulators were internal... that's what
    >> some of my patents are all about... integrating the regulator).
    >>
    >> That was before CAD ;-) If I can find my hand drawing, I'll post it.
    >>
    >> ...Jim Thompson

    >
    > dumb question.
    >
    > what EXACTLY does the charge lamp indicate?
    >
    > what triggers it to go on and off?
    >
    > can it simply be removed and ignored?
    >
    >


    One cause that can light the lamp is a broken belt. You would like to know
    as soon as that happens.
     
    tm, Aug 20, 2013
    #5
  6. Mike Cook

    David Lesher Guest

    Mike Perkins <> writes:

    >>> Where does the common winding terminal connect (there is a
    >>> connection on the rectifier plate)? Where do the other 2 diodes
    >>> connect?



    That pictured alternator is one used on Hondas. ISTM it's a
    Nippon-Densi or such.

    I have too much experience with same. I went through 3-4
    boneyard ones before I bought a rebuilt one from Retarded Auto
    Parts. That brand/model alternator is nice because the diode
    array unscrews easily. No unsoldering needed.

    That particular alternator has 4 pairs of power diodes; the
    center point of the wye has a pair from there as well.... and I
    have no idea why... Jim??

    That said, all recent alternators also have a diode trio of tiny
    diodes. Their function is to rectify enough power to excite the
    rotor. It takes a few amps to drive it. Until it's up to speed,
    that excitation comes from the battery, through the red idiot
    light. When the alternator is up to speed, there is 12V on the
    battery side of the lamp, and 12v on the load side....and it
    goes out.



    --
    A host is a host from coast to
    & no one will talk to a host that's close........[v].(301) 56-LINUX
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433
     
    David Lesher, Aug 20, 2013
    #6
  7. On Mon, 19 Aug 2013 22:32:24 +0100, the renowned Mike Perkins
    <> wrote:

    >On 19/08/2013 18:42, Spehro Pefhany wrote:
    >> On Mon, 19 Aug 2013 09:49:18 -0700, Mike Cook <>
    >> wrote:
    >>
    >>> http://www.autoshop101.com/forms/alt_bwoh.pdf
    >>>
    >>> has photos of an alternator with 4 connections for windings (each
    >>> of 3 phases + common), and the 8 diode rectifier. But wiring
    >>> diagrams show only 3 connections and 6 diodes.
    >>>
    >>> Where does the common winding terminal connect (there is a
    >>> connection on the rectifier plate)? Where do the other 2 diodes
    >>> connect?

    >>
    >> The common in the Wye connection (called "Neutral Junction" in the
    >> photo on page 18) goes to the 4th pair of diodes (and typically the
    >> regulator). The other three pairs of winding ends ("Stator Lead
    >> Ends") go to the other three pairs of diodes.
    >>

    >
    >Not the alternators I've taken apart. The star point is typically a
    >crimp, and serves no other useful purpose.


    Those were alternators with only six power rectifiers, right?

    >The field, and regulator power, are normally taken from an additional set of
    >diodes, usually 3, ie one per phase, such that the regulator is
    >effectively isolated from the battery when the engine is not turning.


    The power rectifiers connected to the Wye common are used to extract
    3rd harmonic power- yielding up to 10% additional current capacity-
    when operating at high speed.



    Best regards,
    Spehro Pefhany
    --
    "it's the network..." "The Journey is the reward"
    Info for manufacturers: http://www.trexon.com
    Embedded software/hardware/analog Info for designers: http://www.speff.com
     
    Spehro Pefhany, Aug 20, 2013
    #7
  8. Mike Cook

    Mike Cook Guest

    > Not the alternators I've taken apart. The star point is typically a
    > crimp, and serves no other useful purpose.
    >
    > The field, and regulator power, are normally taken from an additional set of
    > diodes, usually 3, ie one per phase, such that the regulator is
    > effectively isolated from the battery when the engine is not turning.


    But THAT'S why I'm asking here: this Denso alternator (used in MANY Hondas,
    Toyotas, and myriad other makes) does have a common terminal connection to
    the rectifier. The rectifier has EIGHT diodes.

    Yes I agree that common configuration is 6 diodes. That's why I'm confused.
    The system is quite populous and apparently functions. I just don't
    understand how.
     
    Mike Cook, Aug 20, 2013
    #8
  9. > One problem with this arrangement... if the red idiot light burns out
    > or a wiring fault opens the circuit, the alternator won't "bootstrap"
    > the next time you start the car, and you won't (of course) get any
    > red-light warning. Dead battery, here we come.
    >
    > Ask me how I know :-(


    That's why you LOOK at the Idiot Light when you turn the ignition switch on,
    just before you start the engine. A lit ALT bulb means it is present and
    functioning.
     
    Fester Bestertester, Aug 20, 2013
    #9
  10. Mike Cook

    Jasen Betts Guest

    On 2013-08-19, Cydrome Leader <> wrote:

    > dumb question.
    >
    > what EXACTLY does the charge lamp indicate?


    current into the regulator not supplied by the altenator.

    > what triggers it to go on and off?


    basically a working altenator.

    > can it simply be removed and ignored?


    you could replace it with a short circuit

    --
    ⚂⚃ 100% natural

    --- news://freenews.netfront.net/ - complaints: ---
     
    Jasen Betts, Aug 20, 2013
    #10
  11. In sci.electronics.equipment Mike Perkins <> wrote:
    > On 20/08/2013 08:04, Mike Cook wrote:
    >>> Not the alternators I've taken apart. The star point is typically
    >>> a crimp, and serves no other useful purpose.
    >>>
    >>> The field, and regulator power, are normally taken from an
    >>> additional set of diodes, usually 3, ie one per phase, such that
    >>> the regulator is effectively isolated from the battery when the
    >>> engine is not turning.

    >>
    >> But THAT'S why I'm asking here: this Denso alternator (used in MANY
    >> Hondas, Toyotas, and myriad other makes) does have a common terminal
    >> connection to the rectifier. The rectifier has EIGHT diodes.
    >>
    >> Yes I agree that common configuration is 6 diodes. That's why I'm
    >> confused. The system is quite populous and apparently functions. I
    >> just don't understand how.

    >
    > I can find very little on the web regarding neutral point rectification
    > for car (Lundell) alternators, but there is a lot about 3rd harmonic
    > neutral currents. An example how these manifest in electrical systems
    > for non-linear loads.
    >
    > http://static.schneider-electric.us...ormers/Harmonic Mitigating/0104ED9501R896.pdf
    >
    > A conventional automotive alternator uses six diodes to rectify
    > three-phase AC (Alternating Current) into DC (Direct Current). The
    > average voltage of the neutral point is 1/2 of the output DC voltage.
    > While a low output current flows, the voltage at the neutral point is
    > mostly DC, but it also includes an AC portion. As current output
    > increases, the AC portion increases.
    >
    > When the alternator speed exceeds 2,000 to 3,000 rpm, the peak value of
    > this AC portion exceeds the DC output voltage.
    >
    > This means that, compared with the output characteristics of the
    > alternator without neutral-point diodes, the output gradually increases
    > from midway by 10 to 15% at a normal rated alternator speed of approx.
    > 5,000 rpm.
    >
    > http://youronlinemechanic.com/alternator-with-neutral-point-voltage/


    Here's a diagram of what the above link failed to clearly explain

    http://autonopedia.org/renewable-energy/generators/alternator-secrets/

    so somehow tapping neutral is good. I guess those two diodes bypass
    current flowing int coils the wrong way or something? As to how speed
    matters, I'm not following that.
     
    Cydrome Leader, Aug 21, 2013
    #11
  12. Mike Cook

    Don Kelly Guest

    On 19/08/2013 10:33 PM, Spehro Pefhany wrote:
    > The power rectifiers connected to the Wye common are used to extract
    > 3rd harmonic power- yielding up to 10% additional current capacity-
    > when operating at high speed.

    That doesn't make sense to me. One advantage of 3 phase is the
    elimination of triplen harmonics. Now, with a 3 phase bridge-will there
    be a significant 3rd harmonic voltage? Certainly,if the wye neutral is
    not connected to the DC ground, there is no 3rd harmonic current and
    power. Generally this is a good thing.
    Somehow, I appear to be missing something-could you elucidate? A circuit
    diagram and analysis would help.

    --
    Don Kelly
    remove the cross to reply
     
    Don Kelly, Aug 21, 2013
    #12
  13. On Wed, 21 Aug 2013 02:15:27 +0100, the renowned Mike Perkins
    <> wrote:

    >On 21/08/2013 00:47, Cydrome Leader wrote:
    >> In sci.electronics.equipment Mike Perkins <> wrote:
    >>> On 20/08/2013 08:04, Mike Cook wrote:
    >>>>> Not the alternators I've taken apart. The star point is typically
    >>>>> a crimp, and serves no other useful purpose.
    >>>>>
    >>>>> The field, and regulator power, are normally taken from an
    >>>>> additional set of diodes, usually 3, ie one per phase, such that
    >>>>> the regulator is effectively isolated from the battery when the
    >>>>> engine is not turning.
    >>>>
    >>>> But THAT'S why I'm asking here: this Denso alternator (used in MANY
    >>>> Hondas, Toyotas, and myriad other makes) does have a common terminal
    >>>> connection to the rectifier. The rectifier has EIGHT diodes.
    >>>>
    >>>> Yes I agree that common configuration is 6 diodes. That's why I'm
    >>>> confused. The system is quite populous and apparently functions. I
    >>>> just don't understand how.
    >>>
    >>> I can find very little on the web regarding neutral point rectification
    >>> for car (Lundell) alternators, but there is a lot about 3rd harmonic
    >>> neutral currents. An example how these manifest in electrical systems
    >>> for non-linear loads.
    >>>
    >>> http://static.schneider-electric.us...ormers/Harmonic Mitigating/0104ED9501R896.pdf
    >>>
    >>> A conventional automotive alternator uses six diodes to rectify
    >>> three-phase AC (Alternating Current) into DC (Direct Current). The
    >>> average voltage of the neutral point is 1/2 of the output DC voltage.
    >>> While a low output current flows, the voltage at the neutral point is
    >>> mostly DC, but it also includes an AC portion. As current output
    >>> increases, the AC portion increases.
    >>>
    >>> When the alternator speed exceeds 2,000 to 3,000 rpm, the peak value of
    >>> this AC portion exceeds the DC output voltage.
    >>>
    >>> This means that, compared with the output characteristics of the
    >>> alternator without neutral-point diodes, the output gradually increases
    >>> from midway by 10 to 15% at a normal rated alternator speed of approx.
    >>> 5,000 rpm.
    >>>
    >>> http://youronlinemechanic.com/alternator-with-neutral-point-voltage/

    >>
    >> Here's a diagram of what the above link failed to clearly explain
    >>
    >> http://autonopedia.org/renewable-energy/generators/alternator-secrets/
    >>
    >> so somehow tapping neutral is good. I guess those two diodes bypass
    >> current flowing int coils the wrong way or something? As to how speed
    >> matters, I'm not following that.
    >>

    >
    >If you consider that at any time 2 windings will be supplying one
    >polarity of current and the remaining winding the other polarity, you
    >can see the neutral point is going to move in the direction dictated by
    >the two windings. At higher currents, and higher frequencies, the
    >inductance of the winding causes an increasing voltage to appear at the
    >neutral point.


    Some more info:-

    http://tinyurl.com/kdcsayk

    http://ece.ubm.ro/cjece/web/CJECE_VOL5_2012/3_Barz.pdf



    Best regards,
    Spehro Pefhany
    --
    "it's the network..." "The Journey is the reward"
    Info for manufacturers: http://www.trexon.com
    Embedded software/hardware/analog Info for designers: http://www.speff.com
     
    Spehro Pefhany, Aug 21, 2013
    #13
  14. Mike Cook

    Don Kelly Guest

    On 20/08/2013 8:33 PM, Spehro Pefhany wrote:
    > On Wed, 21 Aug 2013 02:15:27 +0100, the renowned Mike Perkins
    > <> wrote:
    >
    >> On 21/08/2013 00:47, Cydrome Leader wrote:
    >>> In sci.electronics.equipment Mike Perkins <> wrote:
    >>>> On 20/08/2013 08:04, Mike Cook wrote:
    >>>>>> Not the alternators I've taken apart. The star point is typically
    >>>>>> a crimp, and serves no other useful purpose.
    >>>>>>
    >>>>>> The field, and regulator power, are normally taken from an
    >>>>>> additional set of diodes, usually 3, ie one per phase, such that
    >>>>>> the regulator is effectively isolated from the battery when the
    >>>>>> engine is not turning.
    >>>>>
    >>>>> But THAT'S why I'm asking here: this Denso alternator (used in MANY
    >>>>> Hondas, Toyotas, and myriad other makes) does have a common terminal
    >>>>> connection to the rectifier. The rectifier has EIGHT diodes.
    >>>>>
    >>>>> Yes I agree that common configuration is 6 diodes. That's why I'm
    >>>>> confused. The system is quite populous and apparently functions. I
    >>>>> just don't understand how.
    >>>>
    >>>> I can find very little on the web regarding neutral point rectification
    >>>> for car (Lundell) alternators, but there is a lot about 3rd harmonic
    >>>> neutral currents. An example how these manifest in electrical systems
    >>>> for non-linear loads.
    >>>>
    >>>> http://static.schneider-electric.us...ormers/Harmonic Mitigating/0104ED9501R896.pdf
    >>>>
    >>>> A conventional automotive alternator uses six diodes to rectify
    >>>> three-phase AC (Alternating Current) into DC (Direct Current). The
    >>>> average voltage of the neutral point is 1/2 of the output DC voltage.
    >>>> While a low output current flows, the voltage at the neutral point is
    >>>> mostly DC, but it also includes an AC portion. As current output
    >>>> increases, the AC portion increases.
    >>>>
    >>>> When the alternator speed exceeds 2,000 to 3,000 rpm, the peak value of
    >>>> this AC portion exceeds the DC output voltage.
    >>>>
    >>>> This means that, compared with the output characteristics of the
    >>>> alternator without neutral-point diodes, the output gradually increases
    >>>> from midway by 10 to 15% at a normal rated alternator speed of approx.
    >>>> 5,000 rpm.
    >>>>
    >>>> http://youronlinemechanic.com/alternator-with-neutral-point-voltage/
    >>>
    >>> Here's a diagram of what the above link failed to clearly explain
    >>>
    >>> http://autonopedia.org/renewable-energy/generators/alternator-secrets/
    >>>
    >>> so somehow tapping neutral is good. I guess those two diodes bypass
    >>> current flowing int coils the wrong way or something? As to how speed
    >>> matters, I'm not following that.
    >>>

    >>
    >> If you consider that at any time 2 windings will be supplying one
    >> polarity of current and the remaining winding the other polarity, you
    >> can see the neutral point is going to move in the direction dictated by
    >> the two windings. At higher currents, and higher frequencies, the
    >> inductance of the winding causes an increasing voltage to appear at the
    >> neutral point.

    >
    > Some more info:-
    >
    > http://tinyurl.com/kdcsayk
    >
    > http://ece.ubm.ro/cjece/web/CJECE_VOL5_2012/3_Barz.pdf
    >
    >
    >
    > Best regards,
    > Spehro Pefhany
    >

    Thank you for the information- also thanks to Mike Perkins-The
    references were useful my background is in power systems so I have a
    different view on 3rd harmonics.

    Don Kelly
    remove the cross to reply
     
    Don Kelly, Aug 23, 2013
    #14
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