Tony Rhodes writes:
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Message text written by jmwagner
>you to use the smaller modern type belt with a smaller pulley on the
generator.... hence less drag, and a faster running generator (red lig=
ht
is
less likely to come on!)...
<
Oh, stupid me. I missed the obvious and most likely correct alternative!=
The regulator sends a variable current to the field windings! Since I
doubt
that the reg. has a potentiometer, and I know it has a bunch of solenoids=
,
I bet that this is the essence of how it works. I hope Dam Masters sees
this
message and chimes in. Maybe you have experience with this....
There is a solenoid which pulls against a spring. The tension of the
spring is set so that when the voltage to the solenoid exceeds a certain
point then the solenoid has sufficient pull to open a switch and cut off
the
current to the field windings. The magnetic field of the field windings
drops
and then the power output of the generator drops which then
reduces the voltage to the solenoid and the field circuit is closed
which increases the generator output. =
You'd think that the solenoid would be buzzing like a door chime, but
I bet that the generator windings act like an inductor and the field
resists collapse, so the voltage takes on a somewhat smoother
waveform. I wonder how fast the regulator opens and closes?
I know that there are 2 or 3 solenoids in British regulators. I wonder =
what they are for. One is for regulator, the other is for "cut-out". I
do not know how those two functions are related. Dan, are you out
there?
I am about to refer myself to the VTR web site. If there is nothing
on the theory and repair of the voltage regulator, please
write a treatise for us, Dan! Or, If I gain enough expertise, I will do
it myself!
-Tony
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Tony, et al
Dave Massey, Electrical Engineer, stepping in for Dan Masters for a
moment. You are right that the voltage regulator controls the field
current. In the older generator models it did this by opening and
closing a set of contacts in the regulator. In the more modern,
alternator equiped cars there is a transistor that does the job. The
job of the regulator is to maintain the generator (alternator) output
at a constant voltage (14.2 - 14.5 volts). As the genertator slows
down the regulator will increase the voltage to the field windings
until the field voltage reaches system voltage. At this point the
generator can not "keep up" with the electrical load and the battery
makes up the difference (and begins to discharge).
So why not out a smaller pulley on the generator so it will spin
faster? Well, if you look at an alternator you will see that
they have done just that. So why not do it to a generator, too?
Because there is a rev limit that the generator can tolerate. If you
spin a generator too fast the centrifugal forces will pull the windings
off of the armature and the generator will self distruct. The same is
true of the alternator but since the windings in the rotor are the
field windings (see Dan Masters explanation of a few days ago) they
will tolerate much higher forces and, concequently, can turn much
faster.
I hope this answers your questions. If not, I'm sure Dan's explanation
will help.
Dave Massey
St. Louis, MO
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