Briggs & Stratton 86262GS, Familiarization & Troubleshooting Manual

Page: 33 / 128

Transformers
A transformer increases (steps up) or decreases (steps
down) an applied voltage.Transformers use the principles of
electromagnetic induction and, more precisely, mutual
induction . An automobile ignition coil (as briefly discussed
on page 7) is just one example of a transformer.
A typical transformer consists of a metal core, which has
two coils of wire wrapped around it.These are called the
primary and secondary windings.To help understand the
operation of a transformer, a discussion of mutual induction
is offered here:
If a changing (collapsing or expanding) magnetic field in one
coil cuts across the windings of a second coil, a voltage is
induced into the second coil.This is the principle of
mutual
induction .
The winding in Figure 2.35 indicated by the letter “S” is
wound over an iron core.This is the secondary winding.
Another winding (called the primary winding) is wound
over
the first winding and is indicated by the letter “P.” When the
switch is closed, current flow
through the primary winding increases, which expands lines
of magnetic force that cut across the secondary winding.This
causes a voltage to be induced into the secondary winding in
one direction.
If the switch is opened, however, the sudden decrease in
current flow through the primary winding (and the resulting
collapse of magnetic lines of flux)
also induces a voltage into
the secondary winding in the other direction.The secondary
winding then becomes a source of voltage and supplies (AC)
current to resistor “R”.The magnitude of the voltage
induced into the secondary winding is primarily determined
by the number of turns in the primary (P) in relation to the
secondary windings (S).
For Example:
(Both windings using the same wire size)
If 12VAC is applied to the primary winding and the
secondary winding has 100 times as many turns of wire as
the primary, the secondary voltage is about
(12 X 100) = 1200VAC.
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Section 2 • Generator Components & Systems
Portable Generator Familiarization & Troubleshooting Guide
Figure 2.35 — The Principle Of Mutual Induction