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I want to know about this UPS transformer with 7 wires and how to get maximum power from it.

Discussion in 'Power Electronics' started by AhmedCJ1, Aug 28, 2018.

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  1. AhmedCJ1


    Aug 28, 2018
    Hi, my father bought an old UPS APC Back UPS 300 which did not provided any back up. Maybe the battery was dead, so I opened it and disconnected a transformer from it. Now it has seven wires on it. On one side it has Black and White wires and on the other side it has : White / Yellow ( I am not sure) ,Purple, White ( Another white ) ,Brown , Blue.
    Now I am not sure which is Primary or Secondary.
    Question 1 How to get maximum power from it by using 3 parallel 6 volts rechargeable battery?

    Note: I currently don't have access to a multimeter so its hard to calculate its electric flow.
    Sorry for my bad grammar I don't speak English IMG_20180828_230850.jpg IMG_20180828_230902.jpg IMG_20180828_230850.jpg IMG_20180828_230902.jpg IMG_20180828_230912.jpg IMG_20180828_230930.jpg IMG_20180828_230912.jpg
  2. kellys_eye


    Jun 25, 2010
    The transformer has a low voltage secondary and a primary with multiple taps at the local AC mains voltage. Simply measure the resistance of the primary and use the two wires that give the highest resistance reading - this will be the highest voltage tap (probably the 250V AC tap) and will give the LOWEST output on the secondary. Other taps will be lower AC volts (say 230V, 210V and 190V - these are typical primary tap voltages) and give increasingly HIGHER outputs on the secondary - always assuming the input voltage (local mains) remains the same i.e. 240V ????

    You can't apply DC volts (from a battery) to the transformer - you will burn it out almost immediately.
  3. dave9


    Mar 5, 2017
    I would put it back in the UPS and buy a battery since your father wanted an UPS, and make getting a multimeter a priority if you want to fiddle with electrical/electronics.

    However before buying a 12V battery you could hook two of your 6V in series to achieve 12V for testing the UPS, provided those batteries are capable of several amps output (I assume it used a 12V, roughly 3.5Ah battery? That size does in the US.) keeping in mind that the live circuits in an UPS are at a dangerously high voltage.
  4. AhmedCJ1


    Aug 28, 2018
    Thanks mate that was I was looking for. I used 3 6 volts batteries in parallel and it gave a great shock to me. ( probably it was high amps) I will put back in UPS and buy a new battery
  5. BobK


    Jan 5, 2010
    Don't know how you got a shock from 6V. Was this battery in the UPS with line voltage coming in as well? That could give you a shock, even a fatal one.

  6. davenn

    davenn Moderator

    Sep 5, 2009
    Thread is closed

    The OP obviously has no idea how to work with mains voltages
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