INDUSTRIAL
ELECTRONICS
“Your attitude determines your attitude.”
II.
INDUSTRIAL ELECTRONIC DEVICES
1.
ELECTRON TUBES
a.
Thyratron
b.
Ignitron
2.
THYRISTOR
a.
Silicon Controlled Rectifier (SCR)
b.
Triac
3.
BREAK-OVER DEVICES
a.
Shockley Diode
b.
Silicon Unilateral Switch
c.
DIAC
d.
Silicon Bilateral Switch (SBS)
e.
Silicon Controlled Switch (SCS)
f.
Gate Turn Off Switch
g.
Unijunction Transistor (UJT)
h.
Programmable Unijunction Transistor (PUT)
ELECTRON TUBES
a.
THYRATRON
A
gas
filled
triode
used as an electrode
switch.
Giant GE Hydrogen Thyratron,
used in pulse radars
ELECTRON TUBES
b.
IGNITRON
Electron tube containing
mercury and function as a
rectifier.
IGNITRON
1. Anode
2. Cathode
3. Ignitor
4. Mercury
5. Ceramic Insulators
6. Cooling Fluid
THYRISTOR
Solid state devices used as a switch
in applications that handles larger
voltage and currents.
Have at least four semiconductor
layers.
Regenerative switching devices and
cannot operate in linear manner.
SCR Basic Construction and
Equivalent Circuit
SCHEMATIC
SYMBOL
SCR CHARACTERISTIC CURVE
THYRISTOR
V
BR
- BREAK-OVER VOLTAGE
Voltage through which SCR starts
to conduct when gate current is
zero.
I
H
- HOLDING CURRENT
Anode
current
between
the
conducting
state
and
non-
conducting state.
Turning ON an SCR
Apply enough gate triggering
current.
Apply anode voltage equal to
break-over voltage.
Turning OFF an SCR
Anode current interruption
Forced commutation
THYRISTOR
b.
TRIAC
Triode AC
A
three-terminal
device
used
to
control the average current flow to a
load.
Can
conduct
current
in
either
direction when it is turned on so it is
called
a
bidirectional
triode
thyristor.
Acts like two SCR’s connected in
inverse parallel so that each SCR
conducts alternately for every half
cycle of an AC signal.
Gated DIAC
TRIAC Schematic and Construction Diagram
ELECTRICAL CHARACTERISTICS
OF TRIAC
1
.
Maximum Allowable Main
Terminal RMS Current
1 A, 3 A, 6 A, 10 A, 15 A and 25 A
2.
Breakdown Voltage
Highest main terminal peak voltage the
triac
can
block
in
either
direction
typically 100 V, 200 V, 400 V and 600 V
3.
On Stage Voltage Across the
Terminals
Ideal value is 0 V
Typical value is 1-2 V
No contact bounce
No arcing across partially opened
contacts
Operates much faster
More precise control element
ADVANTAGES OF TRIAC OVER
MECHANICAL SWITCHES
BREAK-OVER DEVICES
Small thyristors which do not
switch the main load current.
Useful as triggering devices.
BREAK-OVER DEVICES
gate
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- Fall '16
