Download ME 8843 Advanced Mechatronics

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Current source wikipedia, lookup

Islanding wikipedia, lookup

Stray voltage wikipedia, lookup

Pulse-width modulation wikipedia, lookup

Three-phase electric power wikipedia, lookup

Power engineering wikipedia, lookup

Variable-frequency drive wikipedia, lookup

History of electric power transmission wikipedia, lookup

Distribution management system wikipedia, lookup

Surge protector wikipedia, lookup

Voltage optimisation wikipedia, lookup

Power inverter wikipedia, lookup

Metadyne wikipedia, lookup

Mains electricity wikipedia, lookup

Alternating current wikipedia, lookup

Buck converter wikipedia, lookup

Diode wikipedia, lookup

Switched-mode power supply wikipedia, lookup

Mercury-arc valve wikipedia, lookup

Opto-isolator wikipedia, lookup

Rectifier wikipedia, lookup

Transcript
ME 8843
Advanced Mechatronics
Instructor: Professor I. Charles Ume
Power Rectifiers
Advanced Mechatronics, Georgia Tech
Outline
• 
• 
• 
• 
• 
Motivation
Rectification Technologies
Diode Rectification
Implementation
Applications
Advanced Mechatronics, Georgia Tech
Motivation
•  Early experiments with Direct
Current (DC) power relied on
Leyden jars (rudimentary
batteries) which had to be
recharged via manual labor
Leyden Jar
(e.g. grad students)
•  Due to efficiency and safety
reasons, Alternating Current
(AC) is used for providing
electrical power
•  A means to convert AC to DC is
required - called Rectification
Advanced Mechatronics, Georgia Tech
AC Power
Transmission
Lines
Rectification Technologies
•  Electromechanical
•  Synchronous rectifier
–  Used a motor attached to metal contacts that switched direction
of current flow in time with AC input voltage
•  Motor-generator set
–  An AC motor coupled to a DC generator
•  Electrolytic
–  Two different material electrodes suspended in an electrolyte
provide a different resistance depending on current flow
•  Mercury arc rectifier
–  A sealed vessel with mercury in it provides a DC power by
transmitting electricity through ionized mercury vapor
–  Capable of power on the order of hundreds of kilowatts
•  Vacuum Tube
Advanced Mechatronics, Georgia Tech
–  Capable of high voltages, but relatively low current
Mercury Vapor Rectifiers
From steel manufacturing plant in Germany
Advanced Mechatronics, Georgia Tech
Types of Rectification
•  Half Wave:
–  Negative components
of sine wave are
discarded
•  Full Wave:
–  Negative components
are inverted
Advanced Mechatronics, Georgia Tech
Diode based Rectification
•  Diodes provide a compact, inexpensive
means of rectification
•  Can create rectifiers from multiple diodes
or purchase integrated module
Diodes
Diode Rectifier Modules
Advanced Mechatronics, Georgia Tech
Half and Full Wave Diode
Rectification
Half Wave Rectifier
Full Wave Rectifier
•  While the output of the rectifiers is now DC (current
only flows in one direction), the output oscillates
Advanced Mechatronics, Georgia Tech
Poly-phase rectification
•  Industrial settings usually have 3-phase
power available for machines
•  Rectifying 3-phase power results in a DC
voltage with less ripple
Three-phase full-wave bridge rectifier circuit
Input and output voltages for three-phase rectifier
Advanced Mechatronics, Georgia Tech
Output Voltage
•  Full wave rectification will produce a
voltage roughly equal to
Vo ≈ 2Vi,RMS
•  In practice, there will be a small voltage
drop across the diodes that will reduce
this voltage
€ accurate supplies, regulation is
•  For
necessary
Advanced Mechatronics, Georgia Tech
Output Ripple
•  Output ripple will always be present in the circuits shown above
•  Amplitude of ripple can be reduced by adding a smoothing capacitor
•  Capacitor and load (shown here as a resistor) form low pass filter
with time constant τ=RC
•  Time constant should be much longer than one ripple
•  For a given ripple amplitude capacitor size (in microfarads) given by
Iload
C=
×10 6 (Half wave)
fVrip
or
Iload
C=
×10 6 (Full wave)
2 fVrip
f: line frequency
Iload: Load Current
Vrip: Amplitude of ripple voltage
NOTE: Voltage rating of the capacitor must be > 1.4*Vout and large
Advanced
Mechatronics,
Georgia
capacitors should
have bleeder
resistors
for Tech
safety!
Applications
•  DC Power supplies
–  Used to provide DC power to drive loads
•  Radios
–  Used to rectify received radio signals as part of AM
demodulation
–  Signal to be transmitted is multiplied by a carrier wave
–  Diode in receiver rectifies signal
Audio Signal
Carrier Wave
Modulated
Signal
Radio Transmission
Advanced Mechatronics, Georgia Tech
Rectified Radio
Wave
Diode
Applications
•  Light Dimmer
–  Sends unrectified or half
wave AC power through
light bulb
•  Automobile Alternators
–  The output of the 3-phase
AC generator is rectified
by a diode bridge
–  More reliable than DC
generator
6 Rectifier Diodes
Advanced Mechatronics, Georgia Tech
References
• 
• 
• 
• 
• 
http://en.wikipedia.org/wiki/Rectifier
http://en.wikipedia.org/wiki/Diode_bridge
http://www.allaboutcircuits.com/vol_3/chpt_3/4.html
http://my.integritynet.com.au/purdic/power1.html
http://electronics.howstuffworks.com/radio.htm
Advanced Mechatronics, Georgia Tech