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Alternator Exciter Wire Light

Discussion in 'Automotive Electronics' started by MCE Mike, Jun 17, 2016.

  1. RODALCO

    RODALCO Well-Known Member

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    The rotor draws between 0.5 and 4 Amps. Depends upon what the output load of the alternator is.
    DC resistance is around 3 Ohms.
    For 10 Amp load my guess is around 1 Amp value.
     
  2. RODALCO

    RODALCO Well-Known Member

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    I have a circuit somewhere in my archives in which I used in an Australian made Ford Falcon for 12 years with no problems at all.
    The Email alternator died which had an external electro-mechanical regulator, and I used an old Renault Paris-Rhone alternator
    It uses a 2N3055 transistor, Zener and a few other parts.
    Excitation is via a 3 Watt lamp.
    I look for it and will post it.
     
  3. spec

    spec Well-Known Member Most Helpful Member

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    Thx- you obviously know about alternators. I would like to see your regulator circuit.

    spec
     
  4. dave

    Dave New Member

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  5. RODALCO

    RODALCO Well-Known Member

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    Hi spec, I have worked a lot with alternators, generators and starter motors before I ventured in the High Voltage power industry in the late 1988's .

    I did find the old schematic which I found in an old Electronics Australia magazine from the early 1980's.
    also redrawn it on a clean piece of paper as the glue has printed through the edges.

    Some alternators give clean external access to the brushes which is perfect for this circuit as a simple 2N3055 transistor can be used which is cheap and reliable.

    I also fitted this circuit in a V8 Rover P5B with a Lucas alternator which is still running fine, WIN_20160622_155222.JPG WIN_20160622_155156.JPG and must have been in service for over 20 years.
     
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  6. spec

    spec Well-Known Member Most Helpful Member

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    Thx RODALCO: interesting, informative and useful.:cool:

    spec
     
  7. debe

    debe Active Member

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    BOSCH RE55 REG CIRC.jpg ADJ REG.6.JPG ADJ REG.5.JPG ADJ REG.4.JPG ADJ REG.3, 5mv-1ms.JPG ADJ REG.2.JPG This is a Voltage regulator & circuit for an 80Amp Bosch altenator.
     
  8. debe

    debe Active Member

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    This is a Bosch altenator circuit to suit the above regulator. The CRO waveform is the voltage across the Rotor. BOSCH ALTENATOR.jpg
     
  9. spec

    spec Well-Known Member Most Helpful Member

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    Thx to you too debe- very informative.

    spec
     
  10. RODALCO

    RODALCO Well-Known Member

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    Thanks for that schematic too, great for alternators where the negative of the rotor is direct on the ground. Brilliant work in unpotting that Bosh regulator.
     
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  11. spec

    spec Well-Known Member Most Helpful Member

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    Hy debe,

    I know it is probably obvious to most of you, but you couldn't describe what the scope trace is showing: where it is connected and also what current the alternator is supplying.

    spec
     
  12. debe

    debe Active Member

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    The scope trace is the voltage a cross the field. In the circuit above the .047uf cap & 1k resistor provide a feed back circuit to make the circuit oscillate to reduce the heating of the output transistor.
     
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  13. debe

    debe Active Member

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    This is the current draw on the Field circuit of a 60A altenator with very little load & then about 45Amps. BOSCH ALT. D+ current Min.JPG BOSCH ALT. D+ current Max.JPG BOSCH ALT.2.JPG
     
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  14. debe

    debe Active Member

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    This is the circuit of a Lucas altenator, the field on these is fed voltage straight from the field feed diodes. Ive added the circuit values when I dismantled one of these regulators. LUCAS ALTENATOR.jpg
     
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  15. spec

    spec Well-Known Member Most Helpful Member

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    Hell debe,

    You know your alternators. :cool:

    spec
     
  16. debe

    debe Active Member

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    This is the wave form across the Field windings. One is a load of about 5A & the other about 20A. What changes is the frequency & the Duty cycle. ALT ROTOR.5A.JPG ALT ROTOR. 20A.JPG
     
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  17. RODALCO

    RODALCO Well-Known Member

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    Thanks debe for your excellent photo's and scope images.
    It proves also my data re the rotor current varying between 0.5 and 4 Amps.
     

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