Re: nighthawk 550 electrical problem
- From: "krusty kritter" <kriyamanna@xxxxxxx>
- Date: 23 Sep 2005 17:16:13 -0700
jlpridge wrote:
> It appears that the only time there is a drain on the battery is when
> the key is turned on (running or not).
Well, that suggests that none of the six diodes in the three phase full
wave rectifier are leaking to ground, anyway. If you have a diode that
continually leaks 500 milliamps to ground and you have a 14 ampere hour
battery, it will go dead in 28 hours...
> I am charging the battery now
> and will check in the morning to see if the voltage goes up once I
> start it up.
Yes, do the charging circuit test I mentioned in a previous post and
tell us what you get.
> If it does not go up but stays the same or drops does this
> indicate an alternator problem or could it also be the rectifier?
It could be an open or shorted stator winding, a bad connection, or a
blown diode in the rectifier.
The stator is Y-wound. Imagine a Mercedes Benz emblem. A three-pointed
star. Each point of the star represents one phase of the three phase
stator. Imagine that "A" phase is the top point of the star and go
around clockwise. "B" phase is pointing down and to the right. "C"
phase is pointing down and to the left. All three phases meet at
neutral in the center.
The permanent magnet rotor is turned by the engine. As a north pole of
the magnet passes "A" phase, it induces and electrical current into
that phase. But the other side of the magnet has a south pole. It is
inducing a voltage with the opposite polarity into "B" phase.
As each phase generates AC voltage, that voltage has to return to a
different phase winding. In other words, what goes out of "A" phase has
to come back to "B" phase.
Suppose "A" phase is capable of generating 60 volts all by itself.
Remember the phases are connected in the center. "B" phase is helping
"A" phase. The combined output of "A" phase and "B" phase is 60 X 1.73
= 104 volts...
But, what if one of those phase windings has a broken wire, or is
shorted out? Right there, half the power of the alternator is missing,
there's no circuit. You don't even get the 60 volts that each phase can
generate, because the electricity has no way to get out of the stator
and back. You get nada, zilch, zip, squat out of the stator in that
case, for at least half the time with only ONE bad connection!
Even if the stator is OK, if only one of the three AC output pins in
the connector that hooks up to the rectifier regulator is dirty, loose,
or corroded, the alternator output is cut in half.
Then there are the six diodes. If only one of the six diodes is blown
out, the rectifier is toast, some of the AC doesn't get turned into DC,
since it has no way to get back to the stator...
So, if your voltage doesn't rise up when you start the engine and rev
it up you can suspect the stator, the electrical connectors or the
diodes.
If the battery is in good condition, but the voltages goes DOWN when
you rev up the engine, you can suspect a shorted out zener diode in the
voltage regulating part of the rectifier regulator. It's a shunt type
regulator. When voltage reaches a certain level, the zener diode is
supposed to suddenly conduct current to the gate of a solicon control
rectifier and the silicon control rectifier is supposed to ground out
one phase of the stator. It can ground out one phase without blowing
itself up because there is enough resistance in the silicon control
rectifier to burn up excess electricity and turn it into heat.
But, if the zener diode is shorted out, or the silicon control
rectifier is shorted out, one phase of the stator will be grounded out
all the time, and in that case, the stator can only put out half the
power it's supposed to put out.
.
- References:
- nighthawk 550 electrical problem
- From: jlpridge
- nighthawk 550 electrical problem
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