Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and...
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Transcript of Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and...
![Page 1: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/1.jpg)
ElectronicsElectronics
Principles & ApplicationsPrinciples & ApplicationsFifth EditionFifth Edition
Chapter 14Electronic Control
Devices and Circuits
©1999 Glencoe/McGraw-Hill
Charles A. Schuler
![Page 2: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/2.jpg)
• The Silicon-Controlled Rectifier• Full-Wave Devices• Feedback in Control Circuitry• Troubleshooting
INTRODUCTION
![Page 3: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/3.jpg)
This two-transistor circuit isstable in either of two states.
On state Off state
Q1
Q2
![Page 4: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/4.jpg)
Q1
Q2
p
p
n
n
A four-layer structure replacesthe two-transistor circuit.
Q1}{Q2
![Page 5: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/5.jpg)
The silicon controlled rectifier (SCR)
Q1
Q2
Anode
Gate
Cathode
p
p
n
n
Anode
Gate
Cathode
Anode
Gate
Cathode
![Page 6: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/6.jpg)
Gate
Anode
CathodeL
oad
curr
ent
TimeGate pulseoccurs here
LoadWith a dc source, the SCR stays
on after it is gated.
The SCR can be turned on at its gate terminal.
![Page 7: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/7.jpg)
Gate
Anode
Cathode
Loa
dcu
rren
t
TimeGate pulseoccurs here
LoadWith an ac source, the SCR turnsoff at the
zero-crossing.
Turns off here
on
off
![Page 8: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/8.jpg)
Gate
Anode
Cathode
Loa
dcu
rren
t
Time
LoadThe gate canbe pulsed foreach positivealternation.
![Page 9: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/9.jpg)
Gate
Anode
Cathode
Loa
dcu
rren
t
Time
LoadThe averageload current
can bedecreasedby gating
the SCR later.
![Page 10: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/10.jpg)
Gate
Anode
Cathode
Loa
dcu
rren
t
Time
Load…. and later.
![Page 11: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/11.jpg)
Load
A full-wave rectifier allows use of both alternations.
Bridge rectifier
Load current
Gate
![Page 12: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/12.jpg)
Load
Two SCRs can providefull-wave control.
Gated early for full power
Gated later for low power
![Page 13: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/13.jpg)
Load
Main terminal 1
Main terminal 2
Gate
The TRIAC provides control of both ac alternations.
Gated early
Gated late
![Page 14: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/14.jpg)
DIAC volt-ampere characteristic curves
+I
-I
+V-V
VP+
VP-
![Page 15: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/15.jpg)
Load
A popular diac-triac control circuit
Decreasing R will gate the TRIAC
earlier.
![Page 16: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/16.jpg)
Thyristor quiz
The three terminals of an SCR are anode,cathode and _________. gate
SCR turnoff in ac circuits occurs at the__________ crossing. zero
In ac control, load power is increased by gatingthe SCR ______ in the cycle. earlier
The device equivalent to two SCRs for full-wave control is the __________. triac
The diode often used to trigger triacs is the_________. diac
![Page 17: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/17.jpg)
Servomechanisms use negative feedback to control velocity and/or position.
Motor
Tachometer
ErrorAmplifier
Negative feedback
Velocityset
VREF
If the mechanical load changes, causing the velocityto change, the error amplifier will respond by
adjusting the motor drive to reduce the change.
![Page 18: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/18.jpg)
Motor
ErrorAmplifier
Positionset
VREF
VREFGearbox
In this servo,gears drive a
variable resistor to provide
position feedback.
Feedback
![Page 19: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/19.jpg)
Pos
itio
n
Time
t1
Suppose, at time t1, a servo is commanded to a new position.
This is the ideal response
![Page 20: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/20.jpg)
Pos
itio
n
Time
t1
This is the critically damped response
![Page 21: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/21.jpg)
Pos
itio
n
Time
t1
This is the overdamped response
![Page 22: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/22.jpg)
Pos
itio
n
Time
t1
This is the underdamped response
![Page 23: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/23.jpg)
Pos
itio
n
Time
Tuning a servomechanism involves adjusting the loop gain and the phase
to achieve the best response.
Which response is the best?
![Page 24: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/24.jpg)
Troubleshooting
• SCRs can fail by opening or shorting
• A shorted SCR means full load power
• An open SCR means no load power
• A defective gate circuit can produce either full power or no power
• TRIAC troubleshooting is much the same
![Page 25: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/25.jpg)
Servo Troubleshooting• Mechanical problems can be confused with
electrical faults
• Slippage and excessive mechanical play can cause various symptoms and should be eliminated before tuning or troubleshooting
• The underdamped response is often caused by excessive gain
• The overdamped response is often caused by insufficient gain.
![Page 26: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/26.jpg)
Servo quiz
Servos use negative _________ to controlposition or speed. feedback
When servo response is sluggish, theresponse is ___________. overdamped
When servo response is oscillatory, theresponse is ___________. underdamped
The overdamped response can be causedby _________ gain. insufficient
The underdamped response can be causedby _________ gain. excessive
![Page 27: Electronics Principles & Applications Fifth Edition Chapter 14 Electronic Control Devices and Circuits ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader030.fdocuments.in/reader030/viewer/2022012910/56649f2a5503460f94c44c0b/html5/thumbnails/27.jpg)
REVIEW
• The Silicon-Controlled Rectifier• Full-Wave Devices• Feedback in Control Circuitry• Troubleshooting