Douwe EgbertsEgberts CAFITESSE 300, Руководство по обслуживанию

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Spark Plugs
Chapter 3 Basics of Ignition
38
2 High Voltage Control
High Voltage Control
Distributor
Rotation angle
Dwell angle Energized duration
Small Short
Large Long
ON
ON
Dwell angle control (1)
The dwell angle expresses the primary
coil energized duration proportion
(magnitude) with the distributor
rotation angle. When the speed is
constant,
Large dwell angle = Long
energized duration
is the relationship.
Dwell angle control is to control the
primary coil energized duration (dwell
angle) according to the speed of the
engine.
Dwell angle control (2)
For example, if the coil resistance is 1
ohm, the primary current is 12 A (for
12 V).
However, until the primary current
reaches 12A, it is obstructed by the
self-induction action, so some time (t)
is required.
Dwell angle control (3)
When the dwell angle is constant, as
the engine speed reaches high speed,
the energized duration becomes
shorter, so the primary current
decreases and the secondary voltage
decreases too.
Therefore, when the engine is rotating
at high speed, if the start of the
energized duration is made earlier to
lengthen the energized duration, the
decrease in the coil primary current
can be prevented.
In this manner, the energized duration
proportion, in other words the dwell
angle, is controlled to be the optimum
value for the engine speed.
I
12A
T
t
Primary current rise characteristic
T: Time I: Primary current
H
I
I
2
I
1
L
T
ON OFF OFF
Primary current and engine speed
T: Time I: Primary current H: For high speed L: For low speed