Briggs & Stratton 86262GS, Руководство по ознакомлению и устранению неисправностей

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Section 2 • Generator Components & Systems
Portable Generator Familiarization & Troubleshooting Guide
Revolving Field Excitation Methods
Up to this point, we have observed the following:
• The strength of the revolving magnetic field is directly
proportional to the current flow (in amperes) through
the rotor windings.
• The electromotive force, or voltage, induced into the
stator windings is directly proportional to the strength
of the revolving field.
With these observations in mind, it is then possible to
regulate voltage induced into the stator windings by
regulating current flow through the rotor windings. Several
methods are available to accomplish such voltage regulation
including the following:
• Direct Excitation
• Reactor Method
• Electronic Voltage Method (Solid State Voltage
Regulation)
• Brushless Excitation Method.
Direct Excitation
Figure 2.64 is an operating diagram of a revolving field
alternator that has the direct excitation feature.
Its operation may be described as follows:
• The rotor is rotated at a pre-determined speed.
• Residual or “stored” magnetism in the rotor creates
magnetic lines of flux which cut through stator windings
“A” and “B”, to induce an EMF into both windings.
• Winding “B” is the Direct Excitation Winding.The EMF
induced into this winding produces an alternating
current flow, which is applied to a Bridge Rectifier.
• The Bridge Rectifier changes alternating current (AC)
back into direct current (DC).
• Direct current (DC) from the bridge rectifier is applied
to the Rotor windings via the slip ring and brush
assembly, to create a magnetic field that is stronger than
that created by the residual magnetism of the rotor.
• This stronger magnetic field induces a greater EMF (and
resultant current flow) into both stator windings “A”
and “B.” The cycle then repeats itself until a pre-
determined (AC) output is reached. Any loads
connected across the (AC) output wires from winding
“A” (called the power winding) completes the winding
“A” circuit.
Reactor Excitation (Early Production Units)
Figure 2.65 illustrates a very simple reactor (also known as a
transformer).
It consists of a primary and secondary coil of wire wound
around a laminated iron core.The core concentrates the
magnetic lines of force created by current flow through the
coils.
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Figure 2.64 — Operation Of Direct Excited Alternator
Figure 2.65 — A Simple Reactor