L2 applications-of-power-electronics-130701122140-phpapp02
-
Upload
neomindx -
Category
Engineering
-
view
9 -
download
0
Transcript of L2 applications-of-power-electronics-130701122140-phpapp02
Some Applications of Power Electronics(Lecture-2)
R S Ananda Murthy
Associate Professor and HeadDept. of Electrical & Electronics Engineering,
Sri Jayachamarajendra College of Engineering,Mysore 570 006
R S Ananda Murthy Some Applications of Power Electronics
Major Areas of Application of Power Electronics
Motor Drives and ActuatorsIllumination EngineeringEnergy Efficient Power SuppliesSustainable Energy SystemsVehicle and Transportation SystemsPower and Control Core Technologies
R S Ananda Murthy Some Applications of Power Electronics
Affinity Laws of Hydraulics
Affinity Laws are applicable to pumps and fans. Accordingto this law, at a given diameter of the impeller,
Q1
Q2=
N1
N2;
H1
H2=
(N1
N2
)2 P1
P2=
(N1
N2
)3
;
where Q is the flow, H is head, P refers to the power and Nis the speed of the pump or fan.Keeping the speed constant, the flow can be controlled byusing a valve or a damper. Then, as per equation givenabove, the power remains constant even at reduced flow.This is not an efficient method of reducing the flow.
R S Ananda Murthy Some Applications of Power Electronics
Variable Speed Drive Saves Power
Suppose, to reduce the flow by 50 %, if we decrease thespeed by 50%, then,
Q1
Q2=
N1
N2=
12
; andP1
P2=
(12
)3
=18
which shows that the power is reduced by a factor of 8 ifthe speed is decreased by a factor of 2.This is more energy efficient than using a valve or adamper.But this requires a variable speed drive.
R S Ananda Murthy Some Applications of Power Electronics
Why A.C. Drive?
Most of the industrial pumps and fans are driven bythree-phase induction motors.The rotor speed of three-phase induction motor is given by
N2 =120f1
P1(1−s)
where f1 is the stator supply frequency, P1 is the number ofpoles in the stator rotating magnetic field, and s is the slip.This shows that the speed can be controlled smoothly bychanging the frequency of the supply given to the stator.
R S Ananda Murthy Some Applications of Power Electronics
Block Diagram of A.C. Drive
Diode BridgeRectifier
3-phSupply
PWMInverter
Control CircuitSpeed
Reference
Output Voltageand FrequencyControl Signals
IM
Variable speed induction motor drives are now used todrive compressors and fans in industries to improve energyefficiency.
R S Ananda Murthy Some Applications of Power Electronics
Other Advantages of A.C. Drive
Limits inrush current at the time of starting preventing utilitysupply voltage dips and thereby prevents maloperation ofother equipment connected to the same power supply.Soft start reduces stress on the insulation of the motorwinding and the power cable and prolong their life.In an induction motor we have Φm ∝ |V1|/f1 where Φm isthe airgap flux, |V1| is the supply voltage per phase, and f1is the supply frequency.Using an A.C. drive we can adjust the motor voltage andfrequency to ensure that iron loss is equal to the copperloss at all loads so that the motor runs at the highestefficiency at any load.
R S Ananda Murthy Some Applications of Power Electronics
Static Kramer Drive for Slip Ring Induction Motor
BridgeRectifier
BridgeInverter
Wound RotorInduction
Motor
Three-phasePower Supply
SlipPower
TransformerStarting
Rheostats
InputPower Feedback
Power
This method of speed control is also known as slip-powerrecovery scheme.
R S Ananda Murthy Some Applications of Power Electronics
D.C. Motor Drive
ControlledRectifier
3-phSupply
ControlCircuit
SpeedReference
Output VoltageControl Signals
MField Coil
DiodeRectifier
+
-
+ -
3-phSupply
D.C. motors are now being replaced by squirrel-cageinduction motors driven by A.C. drives because they aremore rugged and need lesser maintenance.
R S Ananda Murthy Some Applications of Power Electronics
Domestic Fan Speed Regulators
Power electronic fan regulators, shown above right arevery compact and more energy efficient than inefficientresistive old fan speed regulators shown above left.
R S Ananda Murthy Some Applications of Power Electronics
Brushless D.C. Motor Drive
Brushless D.C. motors (BLDC) are special type of D.C.motors which are now being increasingly used inapplications where speed variation is needed as in thecase of electric vehicles.
R S Ananda Murthy Some Applications of Power Electronics
Brushless D.C. Motor Drive
BridgeInverter
Microcontrolleror DSP BasedControl CircuitSpeed
Reference
BLDCMotor
+-
ControlSignals
D.C.Source
Feedbackfrom sensors
A BLDC motor cannot run without power electronic drive circuit.
R S Ananda Murthy Some Applications of Power Electronics
Compact Flourescent Lamp Controllers
EMIFilter
Rectifierwith CFilter
1-Ph Power50 or 60 Hz
HalfBridgeInverter
ControlCircuit
L-C TankCircuit
CFLTube
BrightnessControlSignals
UserBrightnessSet Point
CurrentSensor
BrightnessFeedback
Compared to incandescent lamps, though CFLs arecostlier, they give the same amount of visible light, use 20-30% lesser electric power, and last 8-15 times longer.A CFL can save about five times its purchase price inelectricity costs during the lamp’s lifetime.
R S Ananda Murthy Some Applications of Power Electronics
LED Lamp Driver
EMIFilter
1-Ph Power50 or 60 Hz
BridgeRectifier
CurrentRegulator
Power FactorCorrection
Circuit
The power factor correction circuit – which is a powerelectronic circuit – maintains high power factor on thesupply side.The current regulator – which is another power electroniccircuit – maintains constant current through the seriesconnection of several LEDs.Some of the modern LED driving circuits also providedimming facility.
R S Ananda Murthy Some Applications of Power Electronics
Power Electronics in D.C. Power Supplies
Power electronics helps in realizing switched mode powersupplies (SMPS), shown on the right side above, which arecompact and more energy efficient than conventionalregulated power supplies shown on the left side.
R S Ananda Murthy Some Applications of Power Electronics
Next Lecture...
In the next lecture we will describe some more applications ofpower electronics.
Thank You.
R S Ananda Murthy Some Applications of Power Electronics