Briggs & Stratton 86262GS, Familiarization & Troubleshooting Manual

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Section 2 • Generator Components & Systems
Portable Generator Familiarization & Troubleshooting Guide
The alternating current flowing through the primary
windings creates a magnetic field which cuts through the
secondary coil thereby inducing a current flow into the
secondary windings.
The amount of induced EMF (voltage or current flow)
depends on:
• The current flow through the primary winding.
• The number of wire turns in the secondary coil.
• The greater the current flow through the primary
coil, the greater the current flow induced in the
secondary coil.
• The larger the number of wire turns in the
secondary coil (proportional to the wire turns in
the primary coil), the greater the induced current
flow in the secondary windings.
The reactor method of excitation uses a current
transformer (also known as a reactor).This type of
transformer changes current from one level to a higher or
lower level. In a
Generac®
circuit, it serves as a voltage
regulator (Figure 2.66).
This type of alternator differs from the direct excited type in
two basic ways.
• Reactor Excitation requires a reactor (current
transformer) as an additional component in the circuit.
• The (AC) output to the load (using reactor excitation)
is taken from the same stator winding that the
excitation current is taken from (instead of having an
“A” and “B” winding).
Compare Figure 2.64 with 2.66.
The operation of a “Reactor-Excited” alternator may be
described as follows;
• The Rotor turns at a pre-determined speed.
• Residual or ”stored” magnetism in the rotor creates
magnetic lines of flux which cut through the stator
windings.
• The reactor is an additional component connected in
series with the (AC) output to the load.The greater the
flow of current to the load, the greater the current flow
through the reactor’s primary winding.The greater the
current flow through the reactor’s primary winding, the
greater the current induced into the reactor’s
secondary winding.Thus, the greater the current
demand of the connected load, the greater the current
flow through the plug-in bridge rectifier.
• The bridge rectifier then converts the alternating
current (AC) output of the reactor to direct current
(DC).This direct current (DC) is then applied to the
rotor via the slip ring and brush assembly.
• The current flow through the rotor creates a stronger
magnetic field which, in turn, induces more current flow
(EMF) in the stator.
• The greater the current flow demanded by the
load, the greater the current flow through the
rotor and the stronger the magnetic field that
induces current flow in the stator.
Thus, the more current required by the load, the higher the
current flow delivered by the stator.
Figure 2.66 — Operation Of Reactor-Excited Alternator