Rewiring variable autotransfomer *tap confusion*

Discussion in 'General Electronics Chat' started by jprokos, Apr 24, 2012.

  1. jprokos

    Thread Starter New Member

    Apr 23, 2012
    3
    0
    Because of my location, middle of Nepal, I have to resort to this forum for answers to a problem.

    I have a Chinese made SVC 3000VA (servo voltage controlled auto transformer) and the wires coming off the winding aren't marked in any way (no board or connectors). This auto transformer takes power in the 160v-240v range and outputs 120v and 220v.

    There are a group of wires (taps) that come from the 'front' of the coil, one is yellow and one is blue - I assume those must be the corrected 120v and 220v taps. Then there is the uncorrected black wire that runs through the fused switch to the servo mechanism at the top of the coil and makes contact with the coil via a graphite brush. The wire that's confusing me is a red wire that's connected to the winding on the outside edge of the coil (it's physically isolated from the rest of the wires with a piece of paperboard - I don't know if this is neutral/common or hot/line?? or where to connect it?

    On the exterior of the case there are two sets of terminals. The first set are for 120v and the second set are for 220v.

    If anyone requests I can snap and post a photo to help clarify.

    I would appreciate any help from this boards gurus.

    Thank you
     
  2. alim

    Senior Member

    Dec 27, 2005
    113
    1
    Hi can you say why you want to rewire it, what do you want to achieve?
     
  3. jprokos

    Thread Starter New Member

    Apr 23, 2012
    3
    0
    alim, The wires are no longer connected to the terminals at the back of the unit, they have all been disconnected and I am trying to discern how they were originally connected. There are no labels on the wires and there is no internal connection board with information. The wires coming out of the winding are soldered and clamped to covered stranded wire - where they join has protective white tubing. I could take a picture of the transformer with the wires, etc. if that's needed.
     
  4. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    The first thing to do is to use an ohmmeter to draw a crude schematic and take a photo or two. Another method would be to use a step down transformer to give two wires maybe 12 volts AC and see what happens on the other wires with a voltmeter.
     
  5. jprokos

    Thread Starter New Member

    Apr 23, 2012
    3
    0
    #12,

    I don't know the first thing about using an ohm meter to draw a schematic. Unfortunately, I tend to think in terms of images - right brained. I realize this is a shortcoming in this situation.

    I thought with the clues I provided someone who knows transformers could give me a suggestion. I think I will add a photo or two to help in a separate post.

    Thank you.
     
  6. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    Photos will give you the best chance that somebody will recognize your transformer. A major part of my day job is to open a box of spaghetti looking wires and know what they're doing by looking at them. Other people have that skill, too.
     
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