MTD 700 Series Professional Shop Manual page 119

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Regulators
Charging system drawings
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zener
diode
Figure 7.31
A voltage regulator is a devise that voltage output to a
specified value or range of values. Voltage regulators are
commonly built into the rectifiers.
A rectifier uses a special kind of diode, called a zener
diode. Zener diodes are made to be installed in a circuit
reverse biased. That means that it is installed backward to
prevent current flow. When the voltage applied to the
zener is within a specific range (determined by the con-
struction of the diode), The diode will break down and
allow current to flow through it in the reverse direction.
See Figure 7.31.
The amount of current the charging circuit pulls
depends on the loads applied to it. A dead battery will
draw a lot of current, but as the battery charges, the cur-
rent draw lowers.
When current draw increases, the system voltage low-
ers. As the voltage drops, the zener allows more current to
pass through it to bring the voltage back up to the regu-
lated voltage.
Figure 7.32
Electrical
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