Portable generator head scratcher.

Discussion in 'General Electronics Chat' started by tcmtech, Sep 4, 2015.

  1. tcmtech

    Thread Starter Well-Known Member

    Nov 4, 2013
    I recently fixed up a old Generac 3500xl generator that had a bad AVR and exciter winding on it.

    After removing the 12 volt charging winding and the exciter winding and doing a bit of redesign of the wiring in general to work with a aftermarket AVR (About $2o ) I got it up and running. It works great but it runs hot.

    When I redid it I reconfigured it from its original 120/240 output to 120 only by putting all four windings in parallel. Independently they all high potted good between each other and the stator core plus their resistances all showed the same to within a few milliohms and their inductances all came in identical too.
    As it looks all four were wound in together at the same time so thats why I suspected they could be paralleled without problems.

    After that I started it up with a 15 volt DC feed to the rotor and all four windings showed 108 volts with less than a .2 volt difference between them and there were no visible sparks between any of the four when I wired them in parallel live.

    So heres the thing . Its output is 122 VAC, runs loads just fine up to about 3000 watts with no issues then fall on its face above that , the original peak rating was something like 4250 watts, (engine powers out and the 3 amp rotor breaker trips) despite having a Honda 6.5 HP engine and the generator end runs hot even with no load on it.

    I have a pretty good idea whats causing it but I thought I would run this little puzzle past you guys and see what theories you come up with. ;)
  2. crutschow


    Mar 14, 2008
    Is there any phase difference between the windings?
  3. tcmtech

    Thread Starter Well-Known Member

    Nov 4, 2013
    No phase differences. They are all wound together in the same core slots as basically one winding made up of four parallel 16 ga wires.