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Understanding this generator - see schematic

Discussion in 'Power Electronics' started by Rascal, Mar 29, 2021.

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  1. Rascal


    Mar 29, 2021
    Hi all
    I recently got a bargain generator; It has a briggs I/C 8Hp engine. I'm not sure what the generator head model is. It is 220V output (here in South Africa)
    Assuming 90 - 95% efficiency and given that 8hp = 6KW, maybe 4.5KW output ??
    I had a closer look and traced the schematic. (see attached). The large square component with 4 terminals is a bridge rectifier; SKB 30/06A1 (And it's blown - see the picture. Anyone seen a schematic like this one? How does it regulate?
    I tested it - before noticing the blown rectifier, it gives about 220V under load but about 550V unloaded (probably due to the blown bridge). Keen to know what principle the regulation uses.

    Rascal schematic cropped.JPG

    Moderators note : cropped image

    Attached Files:

  2. Bluejets


    Oct 5, 2014
    More likely 3.5Kw.
    Some had 120v and 240v output.
    Numbers to recognise model numbers, year of manufacture etc. are usually stamped into the motor cowling at the top.

    Where did the schematic come from...??
  3. Rascal


    Mar 29, 2021
    Hi - I traced the schematic myself. The Engine type is a Briggs 195432-4035-01 - that number is visible on the engine. The year is 1990 according to the date code. I'm not sure about the generator head though.
  4. bertus

    bertus Moderator

    Nov 8, 2019
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Just my wild guess: Load current passes through the right rectifier (D5...D8) and stator 2. Thus when load current increases, the magnetization of stator 2 increases, too, thus more electrical power is generated by the rotor to satisfy the demand.
    Without load only stator 1 is supplied with power, thus reducing the electrical output of the rotor to a minimum. However, as there is no load current, that minimum may still result in a much higher voltage as the current is very small (only stator 1's current).
    Whcih rectifier? D1...D4 or D5...D8? I assume D5...D8 due to overcurrent as there doesn't seem to be any kind of overcurrent protection in the schematic.
  6. Rascal


    Mar 29, 2021
    Thanks for that. I made up a rectifier to replace the blown bridge using 4 high rated stud diodes. It works better now, with no overvoltage.
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