Appropriate xformer to repair fence charger

Discussion in 'General Electronics Chat' started by Talion, Sep 26, 2010.

  1. Talion

    Thread Starter New Member

    Sep 26, 2010
    2
    0
    I have a Gallagher S17 solar fence charger with, apparently, a bad output transformer, (a frequent problem with these models).

    Checking the output terminals, I find that the coil is open. No hint of a voltage during discharge. There is the crack of the magnetic field collapsing, but it's much, much quieter than it used to be.

    This transformer is proprietary, (part number googling turns up zilch), and costs $85 from Gallagher. Since the battery also needs to be replaced, unless I can find a cheaper substitute for the transformer I may as well pony up the extra for a new charger.

    The discharge capacitor is 2.0μf 250V and seems to charge to about 200V before discharging. The maximum output voltage is stated at 10,000V, so I'm guessing the transformer turns ratio is 50:1.

    The specs on the charger are as follows:

    If anyone can point me to an appropriate transformer somewhere on the net I would greatly appreciate it. I have searched and drawn a blank there, as well.

    I hope an automotive coil is not my only option.

    TIA
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Not going to be an easy find however the HV transformer (flyback) from an old TV set might prove to be useful.
     
  3. Talion

    Thread Starter New Member

    Sep 26, 2010
    2
    0
    As fate would have it, I threw away 2 old TVs just last month. :(

    I do have an old microwave, maybe 500-700 watts. Would the HV coil on that be suitable, I wonder.

    I'll be honest, In addition to trying to save $200+ I'm trying to get into better graces with the missus who doesn't understand my fascination with things electronic, nor my junk stash.
     
  4. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    Hi TIA, Sugest trying an old vehicle ignition coil as the electric fence units are basicly a Capacitor Discharge system as used in some CDI units on engines. Also make sure there is a spark gap on the output side( about 3mm) this should stop future coil failures. Daryl
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Debe's correct about needing the spark gap. Without a properly sized spark gap, the voltage on the output could go very high, indeed.

    It takes about 3 million volts to jump a 1 meter gap of air at sea level. So, a 3mm gap will ionize at about 9kV, which is right in the range that your original system was rated for. You could use a common engine spark plug with the gap widened to about 3mm or 0.118" and that would take care of it. It would be a good idea to seal it inside a glass vial using RTV silicone or something similar, so that you can see the spark occurring, but keep moisture and insects out of it.
     
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