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triac based 50v to 110v battery charger

Discussion in 'Power Electronics' started by n1tromad, Feb 28, 2017.

  1. n1tromad

    n1tromad

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    Nov 30, 2014
    Hello all

    to best understand this i think some background is needed :)

    i work at a heritage railway. we have some locos "class 08 shunters " that run on a 90volt system. we also have 110volts loco's and 48volts locos. an passed away member built a triac based circuit using a 230v to 110v ac transformer.

    i have never worked with triac's before and looking on advice how to go about this.i could just copy the current and only charger but it not very user friendly you got use a POT to set voltage needed and well lets just say some users more than once tried charging 48v loco with POT cranked upto 110v !

    i was thinking more in line of a three way selector for the three voltages but i not sure if that would work with triac circuit.

    also there is next to no failsafes just MCB on pri and sec sides
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    You can replace the pot by 4 resistors and a three way switch like this:
    upload_2017-2-28_20-4-45.png
    The values of the resistors need to be determined such that the voltages at the 3 taps are equivalent to the voltages you select by the respective potentiometer setting.

    A selector switch will not prevent a user selecting the wrong voltage. A fail-safe method I can imagine is by using three different, incompatibe plug/socket combinations for the charger cable and using a double-pole three-way switch which not only sets the correct output voltage as shown above but also switches the output of the converter to the respective socket. This way only one socket will be powered at a time, namley the one which corresponds to the set voltage.
     
  3. duke37

    duke37

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    Jan 9, 2011
    You could measure the loco battery voltage and only connect the charger when it senses one of the three voltages. This would mean that no charging would occur if the battery was badly out of charge.

    There are car battery chargers which need some battery voltage with the right polarity before working.

    Are you working at Butterley?
     
  4. n1tromad

    n1tromad

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    Nov 30, 2014
    Hi
    no i work at Chinnor railway
    also it never crossed my mind to use three connector setup.
    my problem is i no master electronic guru. i know the basic with some advance ish stuff.the more "smarter" i make this charger the more chances i get it wrong lol.
    btw what a good live simulator program these days ? my livewire no longer works.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Just be aware that in most countries your heritage railway workshop may come under the scrutiny of gov safety officers and as such, equipment used therein may require certification by qualified personel.
     
  6. n1tromad

    n1tromad

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    Nov 30, 2014
    yeah i am the railways PAT tester wouldn't be first time gov come sticking there nose in hell it takes a full week worth of testing if i was to do it all in one go, plus this will be "portable/mobile" as sometimes we need to charge in the yard
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    :)...yep...know what you mean.

    Mob here closed down a restoration workshop for 3 months because a puffing billy ( which was in a million pieces at the time) didn't have a danger tag displaying "Danger-do not start"
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    This is how my setup would look like:
    upload_2017-3-1_7-13-18.png
    Note that for the input side (resistor tap selector) a small switch would suffice. On the output side you will need a power switch to be able to control the current from charger to battery. Since I'm not aware of switches with low-power and high power contacts operating in parallel, you wil have to resort to a high power switch for the input side, too.
    Alternatively you can use a low power switch and replace the output side by three relays which can be controlled by the second set of contacts from the low power switch,
    In any case the threee outlets should have different, incompatible sockets to ensure the right combination of charger setting/loco voltage.
     
  9. n1tromad

    n1tromad

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    Nov 30, 2014
    thank you for all the help . hope you all don't mind if i come back if i run into anymore problems :)
     
  10. n1tromad

    n1tromad

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    Nov 30, 2014
    hi again

    just want second pair of eyes to view this circuit :)

    ignore the switches they just there for testing in program

    [​IMG]
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    9,413
    1,925
    Nov 17, 2011
    What has this circuit got to do with your initial post?
    • I don't see a triac.
    • The potentiometer as shown has such a high resistance that you will not be able to realistically charge a battery through it (assuming the circle at the top with the green + and - signs is supposed to be the battery).
    • The transistor and zener dide at the bottom work as a shunt regulator to provide (roughly) 129 V (DC) to the potentiometer. From your first post I understodd that the potentiometer is used as a control to set the output voltage of the charger.
    Help me understand your circuit and the relevance to your initial post.
     
  12. n1tromad

    n1tromad

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    Nov 30, 2014
    yeah..... i messed that circuit i was using a online program to draw it out the circle thing is infact just a in program measuring point. yes there no triac i was just trying other options . i forgot to say in my last post.

    i think at this point i might just put project on hold and do some research into triacs.

    you also right the POT on current charger does control output via Phase angle hybrid triac firing circuit (pcfc)
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Is there a link where I can see these locos?

    Chris
     
  14. n1tromad

    n1tromad

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    Nov 30, 2014
    just google chinnor railway then go to "stock"
     
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