Thyristor (Scr); Transistor - Honda Motorcycle Service Manual

ELECTRICAL FUNDAMENTALS
Thyristor
(SCR)
Thyristors have three terminais: anode, cathode, and gate.
The current flowinq from the anode t o cathode is said t o be in
"
to flow from anode t o cathode only.
I I
G GATE
THYRISTOR
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the positive direction.
Like diodes, thyristors do not allow current to flow i n the
neaative direction. When turned on. thvristors allow current
I
- S
----
NO CURRENT FLOWS
0
0
ANODE A K CATHODE
1
----
a
NO CURRENT FLOWS
The thyristor is turned on when a certain amount of voitage is
applied to the gate. This input t o the gate is called gate voltage
or trigger voltage.
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I
Once the thyristor is turned on, there is no need t o continuous-
ly apply voltage t o the gate, and its characteristics become
identical t o a regular diode.
-
CURRENT FLOWS WHEN
SCR IS ON
*-----
NO CURRENT FLOWS
Transistor
A transistor has three terminais; emitter (El, collector IC), and
base (BI.
There are t w o types of transistors: PNP and NPN type.
TRANSISTOR SYMBOLS
I
PNP TYPE NPN TYPE
E: EMITTER
C: COLLECTOR
B: BASE
In PNP type transistors, when a positive voitage is applied t o
the emitter and negative voltage t o the collector, almost no
current flows from the collector t o the emitter. If the emitter
voltage is raised slightly higher than the base voltage and a
small amount of current flows from the emitter t o the base, a
large amount of current flows from the emitter t o the collector.
Date of issue: March.1995
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HONDA MOTOR CO.,LTD.
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