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jluckey(at)pacbell.net
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 Posted: Thu Apr 23, 2020 5:16 pm Post subject: Crowbar_B-Lead Drawing |
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Bob,
The alternator in this drawing may not start.
Most of the internal reg machines I've looked at use battery energy at the B terminal to power the internal reg and excite the field. With the diode blocking B+ to that terminal, the alternator may not be able to self-start. Unless of course the CTRL lead actually provides power to the regulator. But on single-wire alternators this circuit may be problematic.
[img]cid:4ad7eec2-6a79-25fa-2127-e4d676ea80a8(at)yahoo.com[/img]">
-Jeff
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nuckolls.bob(at)aeroelect
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| Posted: Thu Apr 23, 2020 7:21 pm Post subject: Crowbar_B-Lead Drawing |
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At 08:12 PM 4/23/2020, you wrote:
| Quote: | Bob,
The alternator in this drawing may not start.
Most of the internal reg machines I've looked at use battery energy at the B terminal to power the internal reg and excite the field. With the diode blocking B+ to that terminal, the alternator may not be able to self-start. Unless of course the CTRL lead actually provides power to the regulator. But on single-wire alternators this circuit may be problematic.
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That's something to be explored for sure . . .
If that's a problem, then a resistor across
the diode might get it. It doesn't take much
to wake 'em up. I'm thinking something on
the order of 10 ohms, 25w would surely do
it and maybe not even that much priming
current.
Of course that same resistor would become
a parasitic load on the crowbar FET during
a shut down . . .
I've not been able to acquire schematics
of any modern alternators. Back about 2004
I did a study on the Motorola MC33099
https://tinyurl.com/ybot24z5
which is a pretty sophisticated piece of
silicon. I don't think it's made any more.
The block diagram doesn't suggest a substantial
power path from the control/ign terminals
to the field winding. Field power source is
indeed the B terminal.
Bob . . .
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