[TheForge] Re: Generators

[Paul Sperbeck]

The newer gas driven 'generators' use a blushless design. The stator
windings are, as in the case of an automobile alternator, fixed and are used
to drive the load. The rotating field is on the armature, and is supplied
with DC power by a diode rectifier located on the armature that is powered
by a rotor coil, generating AC, that also resides on the armature that is
excited by an fixed field coil that is excited by DC, ala old style
automotive 'generator'.

I agree that back flashing the 'generator' with a drill or any power source
certainly would not magnetize the field winding in a modern 'generator' nor
do I suspect that it would be necessary in any generator of the blushless
design.

The reference to field winding was not meant to describe a location as much
as a function. Whether the field is fixed or rotating it's function remains
the same, it provides a magnetic field that may be controlled in intensity
if the design requires it, but mainly it is the winding that provides
magnetic excitation to the driven coils and their associated iron cores. The
armature is the rotating mechanical part. In the case of the automotive
'alternator' the field rotates and the armature has the field windings on
it. The stator coils, typically three phase are located in the housing of
the power generation unit.

In closing I would say that any generating plant that I have obtained to
provide heat and light to my family that required me to zap the field
windings would find it self unceremoniously dumped on the curb for trash
pickup or cannibalized fro any remaining GOOD parts before it was consigned
to be scrapped


Paul C. Sperbeck

My Grandfather was a blacksmith,
and It didn't do me one damn bit of good...
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-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net]On Behalf Of Charle B Vincent
Sent: Wednesday, September 01, 2004 6:58 PM
To: Sponsored by ABANA
Subject: Re: [TheForge] Re: Generators


In autos alternators and generators are reversed.   Generator operates
as you describe,  field windings on outside of case creat a magnetic
field that  induce a current in the armature/rotor windings that then
drives the load.  In an alternator, the rotating component creates the
magnetic field that induces a current in the windings in the case.
Additionally, a generator rectifies the current through the use of
individual segements and brushes on the armature or rotating element.
An automotive alternator creates three pahse AC and uses diodes to
rectify the voltage to create DC.     The primary reason manufacturers
went to alternators was that they can operate at higher rpm, due to the
fact that the rotating assembly is simpler (no individual segments) and
lighter.    This allowed it to be geared high enough to generate current
at idle and not explode at full rpm.    All of the old home generators
that I have worked on work as you describe ala auto generators, but they
are all old.   I was not sure that newer home generators didn't work
like an auto alternator.  Basically the concern that I had with the
drill motor approach was that if you induced a current using the 110
tap, that in either configuration ( rotating field or rotating load)  it
would be energizing the wrong coil.   Old generators used relays that
could stand a lot of experimentation like that maybe, but I would expect
new units to be using solid state components with an SCR or something
like it, that might not respond well to the wrong thing.   Who knows,
maybe nothing has changed.

Charles


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