Upload
werewaro
View
222
Download
0
Embed Size (px)
Citation preview
8/10/2019 Lecture 11 (DC Converters) - Overhead
1/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 1 of 15
Power Electronics
Types
DC ConverterTo raise ( ) or Lower ( ) voltage
AC to DC Rectifier
To converter AC voltage/current to DC voltage/currentMay control voltage level as well
DC to AC Inverters
To convert DC voltage/current to AC voltage/current
Basic Components
Power DiodeSimplest switch
Passive
Controlled by the voltage/current that is imposed on it
Conducts current in the forward directionBlocks current in the reverse direction
Like an electrical valve
8/10/2019 Lecture 11 (DC Converters) - Overhead
2/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 2 of 15
Thyristor
aka. Silicon Controlled Rectifier (SCR)Similar to a diode
Has some control
The can only turn ON the thyristorCannot turn it off
8/10/2019 Lecture 11 (DC Converters) - Overhead
3/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 3 of 15
Transistors
Active switchesCan be turned on and off via their base or gate
BJT MOSFET IGBT
Ideal Operation
BJT: Bipolar Junction TransistorSimplest transistor
Moderately robustModerately fastRequires base current
MOSFET: Metal Oxide Field Effect TransistorNot very robust cannot block large voltages or conduct large
currentsExtremely fast
No gate current required
Fragile
IGBT: Insulated Gate Bipolar TransistorRobust
Slow
No gate current requiredConstructed from a MOSFET and BJT
SCR: Silicon Controlled RectifierExtremely RobustVery Slowbase current required to turn on only
Constructed from two BJTs
8/10/2019 Lecture 11 (DC Converters) - Overhead
4/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 4 of 15
Pulse Width Modulated (PWM) DC to DC ConverterBasic Idea: turn on and off a DC voltage source
We control the voltage
Switching Quadrants
We describe converters by the number of Quadrants they operate in
=aV
8/10/2019 Lecture 11 (DC Converters) - Overhead
5/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 5 of 15
One Quadrant Converter
Positive .Forward .
Forward only
Allows us to only be able to control DC machineas a Motorin 1 direction
8/10/2019 Lecture 11 (DC Converters) - Overhead
6/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 6 of 15
One Quadrant Converter
8/10/2019 Lecture 11 (DC Converters) - Overhead
7/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 7 of 15
Two Quadrant Converter
Positive onlyForward or Reverse .
Allows us to only be able to control DC machineas a or .in 1 direction
8/10/2019 Lecture 11 (DC Converters) - Overhead
8/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 8 of 15
Two Quadrant Converter
Motor Mode
8/10/2019 Lecture 11 (DC Converters) - Overhead
9/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 9 of 15
Two Quadrant Converter
Generator Mode
8/10/2019 Lecture 11 (DC Converters) - Overhead
10/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 10 of 15
Four Quadrant Converter
Positive or negative .Forward or Reverse .
Forward and Reverse .
Allows us to only be able to control DC machineas a or .
in directions
21 ssa iii ==
43 dda iii ==43 ssa iii ==
21 dda iii ==
8/10/2019 Lecture 11 (DC Converters) - Overhead
11/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 11 of 15
Four Quadrant Converter
Motor Mode
8/10/2019 Lecture 11 (DC Converters) - Overhead
12/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 12 of 15
Four Quadrant Converter
Generator Mode
8/10/2019 Lecture 11 (DC Converters) - Overhead
13/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 13 of 15
( )tVVrmss sin2=
Active (Thyristor Controlled) Rectifiers
Converters AC to DCCan control output with of thyristor
Single Phase-Half Wave RectifierThyristor begins conducting when turned on at angle .Thyristor stops conducting when .
Output voltage is:
Where
rmst VV
20
0
( ) ( ))cos(12
1
0
+== rmsT
tt
VdttV
TV
8/10/2019 Lecture 11 (DC Converters) - Overhead
14/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 14 of 15
( )tVVrmss sin2=
Single Phase-Full Wave Rectifier
Thyristors and begin conducting when turned on at angle
Thyristor stops conducting when 0s
V
Thyristors and begin conducting at angle .
Thyristor stops conducting when 0sV
Output voltage is:
Where
rmst VV
220
0
( ) ( ))cos(121
0
+== rmsT
tt
VdttV
TV
8/10/2019 Lecture 11 (DC Converters) - Overhead
15/15
University of British Columbia Elec Machines & Electronics
EECE 365 Winter 2012 Lecture 11: Power Electronics
Nathan Ozog 2013 Page 15 of 15
( )tVVrmsa sin2=
( )o= tVV rmsb sin2
( )o+= tVVrmsc sin2
Three Phase-Full Wave Rectifier
Output voltage is:
rmst VV
630 ( )dttV
TV
T
tt = 01