Transformer dot notation

Discussion in 'Electronic Design' started by reggie, Jun 11, 2008.

  1. reggie

    reggie Guest

    Hi all,

    I have just been reviewing some magnetic stuff and come across some
    discrepancies in dot notation between different documents.

    I have sketched out a diagram as it is probably too hard to describe,
    it’s a small JPG file so don’t worry there are no virus issues in
    downloading this file.

    http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6e747d7fa93d0fcaf3c71e8dd.html

    Fig1 and fig 2 are the same electrically but I have just moved the
    secondary round the core to see it in my minds eye.

    What I am confused about is fig4s current direction in relation to the
    dots (I know its open circuit but assume it’s terminated) compared to
    the forward converter (fig5)

    I reckon the transformer is the same and connected in the same way, if
    this is the case then why when the current moves from 1 to 2 on both
    figures 4&5 primary’s, does the current in the forward converters
    secondary move in the opposite direction from that of the standard
    transformer?

    I know current can only flow from pin 4 to pin3 in the forward
    converter due to the top diode blocking current flow in the opposite
    direction. I also know that pin 3 will be positive and thus forward
    bias the top diode, what is really bothering me is the secondary
    current direction found in multiple textbooks describing transformers.

    I was wondering if there was some good information on the web about
    dot notation relating to transformer physical construction, or can
    someone please explain the discrepancies between current directions.
    (I am assuming conventional current flow from +ve to -ve).

    I know its basic, but its something I want to clear up,

    Thanks,

    Reggie.
     
    reggie, Jun 11, 2008
    #1
    1. Advertising

  2. reggie

    James Arthur Guest

    reggie wrote:
    > Hi all,
    >
    > I have just been reviewing some magnetic stuff and come across some
    > discrepancies in dot notation between different documents.
    >
    > I have sketched out a diagram as it is probably too hard to describe,
    > it’s a small JPG file so don’t worry there are no virus issues in
    > downloading this file.
    >
    > http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6e747d7fa93d0fcaf3c71e8dd.html
    >
    > Fig1 and fig 2 are the same electrically but I have just moved the
    > secondary round the core to see it in my minds eye.
    >
    > What I am confused about is fig4s current direction in relation to the
    > dots (I know its open circuit but assume it’s terminated) compared to
    > the forward converter (fig5)
    >
    > I reckon the transformer is the same and connected in the same way, if
    > this is the case then why when the current moves from 1 to 2 on both
    > figures 4&5 primary’s, does the current in the forward converters
    > secondary move in the opposite direction from that of the standard
    > transformer?
    >
    > I know current can only flow from pin 4 to pin3 in the forward
    > converter due to the top diode blocking current flow in the opposite
    > direction. I also know that pin 3 will be positive and thus forward
    > bias the top diode, what is really bothering me is the secondary
    > current direction found in multiple textbooks describing transformers.
    >
    > I was wondering if there was some good information on the web about
    > dot notation relating to transformer physical construction, or can
    > someone please explain the discrepancies between current directions.
    > (I am assuming conventional current flow from +ve to -ve).
    >
    > I know its basic, but its something I want to clear up,
    >
    > Thanks,
    >
    > Reggie.


    That's a lot of words, a splash ad site, and a mystery
    download.

    A simple question would get more replies. An ASCII
    drawing would be even better.

    Here's a diagram to help you along (fill in the details):

    T1 D1
    Vcc>--------. .----|>|---+----> Vout
    o ) || ( o |
    ) || ( C1
    ) || ( |
    ) || ( ===
    .---' '---. GND
    Q1 | |
    |/ ===
    ----| GND
    |>.
    |
    |
    ===
    GND

    Cheers,
    James Arthur
     
    James Arthur, Jun 11, 2008
    #2
    1. Advertising

  3. reggie

    Bob Eld Guest

    "reggie" <> wrote in message
    news:...
    Hi all,

    I have just been reviewing some magnetic stuff and come across some
    discrepancies in dot notation between different documents.

    I have sketched out a diagram as it is probably too hard to describe,
    it’s a small JPG file so don’t worry there are no virus issues in
    downloading this file.

    http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6e747d7f
    a93d0fcaf3c71e8dd.html

    Fig1 and fig 2 are the same electrically but I have just moved the
    secondary round the core to see it in my minds eye.

    What I am confused about is fig4s current direction in relation to the
    dots (I know its open circuit but assume it’s terminated) compared to
    the forward converter (fig5)

    I reckon the transformer is the same and connected in the same way, if
    this is the case then why when the current moves from 1 to 2 on both
    figures 4&5 primary’s, does the current in the forward converters
    secondary move in the opposite direction from that of the standard
    transformer?

    I know current can only flow from pin 4 to pin3 in the forward
    converter due to the top diode blocking current flow in the opposite
    direction. I also know that pin 3 will be positive and thus forward
    bias the top diode, what is really bothering me is the secondary
    current direction found in multiple textbooks describing transformers.

    I was wondering if there was some good information on the web about
    dot notation relating to transformer physical construction, or can
    someone please explain the discrepancies between current directions.
    (I am assuming conventional current flow from +ve to -ve).

    I know its basic, but its something I want to clear up,

    Thanks,

    Reggie.

    The dots on a transformer drawing usually indicate the start or beginnings
    of the windings. They could also indicate the end of the windings. The point
    is that all windings are dotted the same. All starts or all ends on a given
    transformer. They are not mixed.

    This means that the instantaneous polarity is the same on all dots. If the
    polarity of the primary dot is driven positive, all other winding dots are
    also positive in the same instant.

    If current is flowing into a primary dot it must flow out of all other dots
    (secondaries). Likewise if current is flowing out of a primary dot it must
    flow into all other dots. The primary is the sink of current and the
    secondaries are the source of current.
     
    Bob Eld, Jun 12, 2008
    #3
  4. reggie

    Tim Williams Guest

    "James Arthur" <> wrote in message
    news:GtW3k.46590$bs3.22826@trnddc07...
    >> http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6e747d7fa93d0fcaf3c71e8dd.html

    >
    > That's a lot of words, a splash ad site, and a mystery
    > download.


    Mystery? It's a JPG, like the man said. I'm viewing it in L-View Pro right
    now. I'm supposing you did too...

    > Here's a diagram to help you along (fill in the details):
    >
    > T1 D1
    > Vcc>--------. .----|>|---+----> Vout
    > o ) || ( o |
    > ) || ( C1
    > ) || ( |
    > ) || ( ===
    > .---' '---. GND
    > Q1 | |
    > |/ ===
    > ----| GND
    > |>.
    > |
    > |
    > ===
    > GND


    The transformer is backwards for such a flyback converter. But that doesn't
    matter, because he drew a forward converter, which uses two diodes and a
    choke (except for the cheapass / ignorant "engineers" that do them without
    chokes... eugh...).

    Tim

    --
    Deep Friar: a very philosophical monk.
    Website: http://webpages.charter.net/dawill/tmoranwms
     
    Tim Williams, Jun 12, 2008
    #4
  5. reggie

    reggie Guest

    On 12 Jun, 06:30, "Tim Williams" <> wrote:
    > "James Arthur" <> wrote in message
    >
    > news:GtW3k.46590$bs3.22826@trnddc07...
    >
    > >>http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6...

    >
    > > That's a lot of words, a splash ad site, and a mystery
    > > download.

    >
    > Mystery?  It's a JPG, like the man said.  I'm viewing it in L-View Proright
    > now.  I'm supposing you did too...
    >
    >
    >
    >
    >
    > > Here's a diagram to help you along (fill in the details):

    >
    > >                 T1       D1
    > >   Vcc>--------.     .----|>|---+----> Vout
    > >              o ) || ( o        |
    > >                ) || (         C1
    > >                ) || (          |
    > >                ) || (         ===
    > >           .---'      '---.    GND
    > >     Q1    |              |
    > >         |/              ===
    > >     ----|               GND
    > >         |>.
    > >           |
    > >           |
    > >          ===
    > >          GND

    >
    > The transformer is backwards for such a flyback converter.  But that doesn't
    > matter, because he drew a forward converter, which uses two diodes and a
    > choke (except for the cheapass / ignorant "engineers" that do them without
    > chokes... eugh...).
    >
    > Tim
    >
    > --
    > Deep Friar: a very philosophical monk.
    > Website:http://webpages.charter.net/dawill/tmoranwms- Hide quoted text -
    >
    > - Show quoted text -


    Guy, I think you have miss understood what I was asking, probably my
    long winded explanation… Sorry…

    Joel thanks,

    Your reply made sense to me. I hadn’t thought of the possibility of
    two drive circuits like a split primary mains transformer. I thought
    I’d always understood dot notation until I came across some lecture
    notes from MIT (Massachusetts institute of technology) where the
    current directions didn’t make sense when applied to forward or fly
    back circuits.

    I last studied magnetic’s back in the early 90s, so just wanted to be
    sure I wasn’t loosing my mind!!

    Your response was very helpful, thanks again!

    James,

    I take your point about downloading “mystery files” But as Tim said it
    was a JPG so no virus issues. Sorry for being critical but you looked
    at it and I have managed to get a good answer; so I shall not be
    restricting myself to ASCII drawings in the future!

    Engineers like diagrams! Why not move with technology, throw caution
    to the wind and give a video clip in future! Engineers communicate in
    diagrams so why not on line?

    Bob, I agree with what you have said, thanks!

    Thanks all again,

    Reggie.
     
    reggie, Jun 12, 2008
    #5
  6. reggie

    James Arthur Guest

    Tim Williams wrote:
    > "James Arthur" <> wrote in message
    > news:GtW3k.46590$bs3.22826@trnddc07...
    >>> http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6e747d7fa93d0fcaf3c71e8dd.html

    >> That's a lot of words, a splash ad site, and a mystery
    >> download.

    >
    > Mystery? It's a JPG, like the man said. I'm viewing it in L-View Pro right
    > now. I'm supposing you did too...


    Nope. I saw a bunch of ads & didn't care to click any further.

    A courteous stranger ought not require of us our trust and
    inconvenience in addition to our advice. Besides, ASCII art means
    these things get archived, for future seekers.


    >> Here's a diagram to help you along (fill in the details):
    >>
    >> T1 D1
    >> Vcc>--------. .----|>|---+----> Vout
    >> o ) || ( o |
    >> ) || ( C1
    >> ) || ( |
    >> ) || ( ===
    >> .---' '---. GND
    >> Q1 | |
    >> |/ ===
    >> ----| GND
    >> |>.
    >> |
    >> |
    >> ===
    >> GND

    >
    > The transformer is backwards for such a flyback converter. But that doesn't
    > matter, because he drew a forward converter, which uses two diodes and a
    > choke (except for the cheapass / ignorant "engineers" that do them without
    > chokes... eugh...).
    >
    > Tim


    Umm, that's a forward converter, which is what the OP meandered on about.

    True, it could use a catch diode and an extra inductor if the OP really
    meant "forward converter," but I wasn't sure.

    Since description was lacking, I offered a compromise meant as a
    starting point--one which would adapt easily to suit either case--and a
    gentle intro to ASCII art in the bargain. "Fill in the details" was
    supposed to encourage the OP to modify it to his purpose.

    Cheers,
    James Arthur
     
    James Arthur, Jun 12, 2008
    #6
  7. reggie

    James Arthur Guest

    reggie wrote:
    > On 12 Jun, 06:30, "Tim Williams" <> wrote:
    >> "James Arthur" <> wrote in message
    >>
    >> news:GtW3k.46590$bs3.22826@trnddc07...
    >>
    >>>> http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6...
    >>> That's a lot of words, a splash ad site, and a mystery
    >>> download.

    >> Mystery? It's a JPG, like the man said. I'm viewing it in L-View Pro right
    >> now. I'm supposing you did too...
    >>
    >>
    >>
    >>
    >>
    >>> Here's a diagram to help you along (fill in the details):
    >>> T1 D1
    >>> Vcc>--------. .----|>|---+----> Vout
    >>> o ) || ( o |
    >>> ) || ( C1
    >>> ) || ( |
    >>> ) || ( ===
    >>> .---' '---. GND
    >>> Q1 | |
    >>> |/ ===
    >>> ----| GND
    >>> |>.
    >>> |
    >>> |
    >>> ===
    >>> GND

    >> The transformer is backwards for such a flyback converter. But that doesn't
    >> matter, because he drew a forward converter, which uses two diodes and a
    >> choke (except for the cheapass / ignorant "engineers" that do them without
    >> chokes... eugh...).
    >>
    >> Tim
    >>
    >> --
    >> Deep Friar: a very philosophical monk.
    >> Website:http://webpages.charter.net/dawill/tmoranwms- Hide quoted text -
    >>
    >> - Show quoted text -

    >
    > Guy, I think you have miss understood what I was asking, probably my
    > long winded explanation… Sorry…
    >
    > Joel thanks,
    >
    > Your reply made sense to me. I hadn’t thought of the possibility of
    > two drive circuits like a split primary mains transformer. I thought
    > I’d always understood dot notation until I came across some lecture
    > notes from MIT (Massachusetts institute of technology) where the
    > current directions didn’t make sense when applied to forward or fly
    > back circuits.
    >
    > I last studied magnetic’s back in the early 90s, so just wanted to be
    > sure I wasn’t loosing my mind!!
    >
    > Your response was very helpful, thanks again!
    >
    > James,
    >
    > I take your point about downloading “mystery files” But as Tim said it
    > was a JPG so no virus issues. Sorry for being critical but you looked
    > at it and I have managed to get a good answer; so I shall not be
    > restricting myself to ASCII drawings in the future!


    Sure, we like diagrams, no question about that. I did not download or
    view yours, but I'm glad you got the answers you wanted from others who did.

    > Engineers like diagrams! Why not move with technology, throw caution
    > to the wind and give a video clip in future! Engineers communicate in
    > diagrams so why not on line?


    Personally, I prefer pencil and paper.

    Cheers,
    James Arthur
     
    James Arthur, Jun 12, 2008
    #7
  8. reggie

    reggie Guest

    On 12 Jun, 23:27, James Arthur <> wrote:
    > reggie wrote:
    > > On 12 Jun, 06:30, "Tim Williams" <> wrote:
    > >> "James Arthur" <> wrote in message

    >
    > >>news:GtW3k.46590$bs3.22826@trnddc07...

    >
    > >>>>http://www.adrive.com/public/5040381aef1a269de9465a441db0e5f92b0d4fc6....
    > >>> That's a lot of words, a splash ad site, and a mystery
    > >>> download.
    > >> Mystery?  It's a JPG, like the man said.  I'm viewing it in L-View Pro right
    > >> now.  I'm supposing you did too...

    >
    > >>> Here's a diagram to help you along (fill in the details):
    > >>>                 T1       D1
    > >>>   Vcc>--------.     .----|>|---+----> Vout
    > >>>              o ) || ( o        |
    > >>>                ) || (         C1
    > >>>                ) || (          |
    > >>>                ) || (         ===
    > >>>           .---'      '---.    GND
    > >>>     Q1    |              |
    > >>>         |/              ===
    > >>>     ----|               GND
    > >>>         |>.
    > >>>           |
    > >>>           |
    > >>>          ===
    > >>>          GND
    > >> The transformer is backwards for such a flyback converter.  But that doesn't
    > >> matter, because he drew a forward converter, which uses two diodes and a
    > >> choke (except for the cheapass / ignorant "engineers" that do them without
    > >> chokes... eugh...).

    >
    > >> Tim

    >
    > >> --
    > >> Deep Friar: a very philosophical monk.
    > >> Website:http://webpages.charter.net/dawill/tmoranwms-Hide quoted text -

    >
    > >> - Show quoted text -

    >
    > > Guy, I think you have miss understood what I was asking, probably my
    > > long winded explanation… Sorry…

    >
    > > Joel thanks,

    >
    > > Your reply made sense to me. I hadn’t thought of the possibility of
    > > two drive circuits like a split primary mains transformer.  I thought
    > > I’d always understood dot notation until I came across some lecture
    > > notes from MIT (Massachusetts institute of technology) where the
    > > current directions didn’t make sense when applied to forward or fly
    > > back circuits.

    >
    > > I last studied magnetic’s back in the early 90s, so just wanted to be
    > > sure I wasn’t loosing my mind!!

    >
    > > Your response was very helpful, thanks again!

    >
    > > James,

    >
    > > I take your point about downloading “mystery files” But as Tim said it
    > > was a JPG so no virus issues. Sorry for being critical but you looked
    > > at it and I have managed to get a good answer; so I shall not be
    > > restricting myself to ASCII drawings in the future!

    >
    > Sure, we like diagrams, no question about that.  I did not download or
    > view yours, but I'm glad you got the answers you wanted from others who did.
    >
    > > Engineers like diagrams! Why not move with technology, throw caution
    > > to the wind and give a video clip in future! Engineers communicate in
    > > diagrams so why not on line?

    >
    > Personally, I prefer pencil and paper.
    >
    > Cheers,
    > James Arthur- Hide quoted text -
    >
    > - Show quoted text -



    >Besides, ASCII art means
    >these things get archived, for future seekers.


    This it true, but that’s like saying one shouldn’t move from 3.5 inch
    floppy disk to DVD. I believe engineers should move with the times and
    try and always better the tools they use.

    We are in fact communicating via the internet with a VAST amount of
    people, something that is impractical with pencil and paper alone. I
    did in fact use pencil and paper to produce my drawing, I just scanned
    it so all you people could see it.

    I prefer forums that enable one to upload diagrams, but I cannot seem
    to find any with power supply engineers in.

    I apologise for the adverts on the file sharing site, but when I need
    a diagram in the future I will be using the same method.

    Each to their own and all that...
     
    reggie, Jun 13, 2008
    #8
  9. reggie

    James Arthur Guest

    reggie wrote:
    > On 12 Jun, 23:27, James Arthur <> wrote:
    >> reggie wrote:


    >>> James,
    >>> I take your point about downloading “mystery files” But as Tim said it
    >>> was a JPG so no virus issues. Sorry for being critical but you looked
    >>> at it and I have managed to get a good answer; so I shall not be
    >>> restricting myself to ASCII drawings in the future!

    >> Sure, we like diagrams, no question about that. I did not download or
    >> view yours, but I'm glad you got the answers you wanted from others who did.
    >>
    >>> Engineers like diagrams! Why not move with technology, throw caution
    >>> to the wind and give a video clip in future! Engineers communicate in
    >>> diagrams so why not on line?

    >>
    >> Personally, I prefer pencil and paper. ;-)
    >>
    >> Cheers,
    >> James Arthur
    >>

    >
    >
    >
    > This it true, but that’s like saying one shouldn’t move from 3.5 inch
    > floppy disk to DVD. I believe engineers should move with the times and
    > try and always better the tools they use.


    Since you don't know me, I've added a smiley face to my paper-and-pencil
    comment above. :)

    > We are in fact communicating via the internet with a VAST amount of
    > people, something that is impractical with pencil and paper alone. I
    > did in fact use pencil and paper to produce my drawing, I just scanned
    > it so all you people could see it.
    >
    > I prefer forums that enable one to upload diagrams, but I cannot seem
    > to find any with power supply engineers in.


    Here we post pictures to alt.binary.schematics.electronics, then alert
    folks to this in our posts to sci.electronics.design. That's not
    perfect though, since many people can't get binary newsgroups.

    > I apologise for the adverts on the file sharing site, but when I need
    > a diagram in the future I will be using the same method.
    >
    > Each to their own and all that...


    No need to apologize.

    That site you used was just a little pushy. It immediately pops up and
    prompts with a download window. That's actually convenient, but
    speaking of keeping up with the times, surely you understand that thanks
    to Bill Gates, following a link to a new site full of ads that
    immediately wants to download something--even a JPEG--to your computer
    is reason for pause?

    For example,
    http://www.secureworks.com/research/threats/jpegvirus/


    Anyway, it turns out you're a good guy, it's a decent website, etc., etc.

    I'll happily download your stuff in the future.

    Best wishes,
    James Arthur
     
    James Arthur, Jun 13, 2008
    #9
    1. Advertising

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