Power Electronics Introduction What is Power Electronics Power

Power Electronics Introduction

What is Power Electronics? • Power Electronics is to process and control the flow of electric energy that is optimally suited for load requirements.

Difference between General Electronics and Power Electronics General Electronics 6 Volts / 100 m. A GSM charger 30 Volts 2 Amperes Regulated Power Supply Small Emergency Light of Inverter 100 watts. (60 min back up) Telecommunication data transferred 5 V In general : 12 -15 V/5 -10 A Power Electronics 10 KW AC/DC drive 250 Watts Computer Power Supply (SMPS) 100 KW Power (more than 24 hours back ups) 11 KV/66 KV/132 KV AC & 100 k. V/100 k. W DC link 6000 V/500 A or more

Applications……Induction Motors Ø Rugged, Cheap and less maintenance Ø In a DC Motor, Ia and If are always at 90. So they can be independently used for controlling the speed of a DC motor. In an Induction motor, The rotor current, Ir, and the Magnetizing current, Im, are both functions of stator current , Is. Less flexibility. Ø Is it possible to get the characteristics of a separately excited dc motor in an IM?

Applications Cont…Synchronous Motors Ø High Power Motor Ø Not Self Starting, Speed depends on Stator supply Frequency. Ns depends on f. Ø Stability Problems: A transient loading can bring the motor out of step. How to address this? Ø Can I generate Stator frequency from the rotor Speed? Ø When there is a transient loading, rotor speed reduces, if we can reduce the stator frequency correspondingly, the machine will keep running at a new synchronous speed and it will not come out of step. Can we implement this?

Applications Cont… Regenerative Braking Ø All industrial motors are connected to a high inertia load. High J. Ø Is it possible to capture this energy and decelerate faster?

Applications Cont… Power Supplies Ø Old Power supplies are Big and Heavy due to the 50 Hz transformer. Can we eliminate this?

Applications Cont… Processors. . A History Current CPU Speed is 4. 2 GHz

Applications Cont… Personal Computers Ø As clock frequencies increases, Most ICs also should work at that speed. Ø With increased frequency, increased switching speed also Ø With increased switching speed, increased switching losses. Ø Can we reduce switching frequency? No. Ø An alternate is to reduce bias voltage. Bias voltages can be brought down to 0. 9 V. So we need DC power supplies of the range of 0. 9 V, 100 A. Ø Can traditional transformer technology design it? Or shall we look into a different technology?

Applications Cont… Power Systems Ø In a long transmission line we desire the sending end voltage, Vs, should be equal to receiving end voltage, Vr. Possible? Ø We also desire Vr remains constant with load. Ø But Vr<<Vs for lagging p. f. due to reactive power increase. Ø How to keep Vr constant? Provide reactive power (Q) support by connecting capacitor banks near load. Ø As Vr falls Q should increase but unfortunately Q decreases. Ø Can we design a circuit which can supply + ve or –ve VARs independent of Vr? ?

Applications Cont… Transmission Ø We need only two wires for transmission. Lot of savings and reduce transmission losses. Ø Can the bulk power be transmitted by converting to DC?

Applications Cont… Fluorascent Tubes Ø Ballast: Lossy, Noisy (Audio Range), stroboscopic effect and poor p. f. Ø Output luminance increases and ballast size reduces with increase in frequency. If frequency above 20 KHz (Above audio range), noise effects can be get rid off. Ø Can we increase the frequency?

Applications Cont… Distributed Power Generation Ø Set up small power plants at load centers using renewables Ø Micro grids Ø Solar- Output is DC but loads are AC, not reliable. Need AC-DC and DC-AC power converters. Ø Wind- Seasonal, unreliable Ø How to tap energy optimally? Need frequency Converters

Applications Cont… Wind Power Generation

Applications Cont… Electrical Vehicles

Power Electronic Device Requirements • Cost, size and weight should be as small as possible • Initial Cost might be high but the pay back period should be reasonable • Passive Elements: R, L and C • R-Consume Power • L & C – Does not consume power • Should use only L & C as far as possible • Active Elements: BJT, Mosfet etc • What is the power loss in this transistor when it is “ON” ? • VCE x Ic

Power Electronic Device Requirements…. . • VCE is high when the transistor is in active region, hence high power loss. • At saturation, VCE = 0. 2. • So active devices should be operated either in saturation or Cut-Off.

Eg: -Power Supply Circuit 1 • A Potential Divider Circuit • High copper losses Circuit 2 • Use an active device which can be turned On and OFF • High VCE and hence high power loss

Eg: -Power Supply Circuit 3 • Switch operated in saturation or Cut-Off • What is the Output Voltage?

Power Diodes

Power Transistors

Thyristors

Power Ranges

Rectifiers: AC - DC : Power Diodes - Uncontrolled

Rectifiers: AC – DC- Controlled

Single-Phase ac-ac Converter

DC-DC Converter

DC-AC Converter

Power Conversion Cycle

Types of Power Converters ☼ Rectifiers: AC - DC : Power Diodes - Uncontrolled : SCR/IGBT- Controlled ☼ Chopper: DC - DC : IGBT/SCR/MOSFET ☼ Inverter: DC - AC : IGBT/SCR/MOSFET ☼ AC Voltage Reg: AC - AC: TRIAC/SCR/IGBT ☼ Cycloconverter: AC - AC : TRIAC/SCR/IGBT

Two Content Layout with Table • First bullet point here Class • Second bullet point here • Third bullet point here Group 1 Group 2 Class 1 82 95 Class 2 76 88 Class 3 84 90

Two Content Layout with Smart. Art • Add your first bullet point here • Add your second bullet point here • Add your third bullet point here Group 1 Group 2 Group 3 Group 4 Group 5 Group 6

Picture with Caption Layout Caption

Add a Slide Title - 1

Add a Slide Title - 2

Add a Slide Title - 3

Add a Slide Title - 4

Add a Slide Title - 5

Add a Slide Title - 6

Add a Slide Title - 7