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FOWLER CHAPTER 11 LECTURE 11 INDUCTANCE

FOWLER CHAPTER 11 LECTURE 11 INDUCTANCE. INDUCTANCE, CHAPTER 11 OPPOSES CHANGE OF CURRENT IN A CIRCUIT. DEVICES THAT USE INDUCTANCE (L) ARE CALLED INDUCTORS. A.K.A. AS CHOKES, REACTORS, COILS. INDUCTANCE IS THE RESULT OF A VOLTAGE INDUCTED IN A CONDUCTOR FROM A MAGNETIC FIELD.

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FOWLER CHAPTER 11 LECTURE 11 INDUCTANCE

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  1. FOWLER CHAPTER 11LECTURE 11 INDUCTANCE

  2. INDUCTANCE, CHAPTER 11 OPPOSES CHANGE OF CURRENT IN A CIRCUIT. DEVICES THAT USE INDUCTANCE (L) ARE CALLED INDUCTORS. A.K.A. AS CHOKES, REACTORS, COILS. INDUCTANCE IS THE RESULT OF A VOLTAGE INDUCTED IN A CONDUCTOR FROM A MAGNETIC FIELD.

  3. CES 2009 - Kitchen of the Future From Powermat http://www.youtube.com/watch?v=Z9a_Ihhtnx4

  4. WHEN CURRENT FLOWS A MAGNETIC FIELD IS CREATED AROUND THIS WIRE. THIS EXPANDING FIELD INDUCES ITS OWN SMALL VOTAGE IN THE WIRE. IF THE FLUX IS EXPANDING, POLARITY IS IN THE SAME DIRECTION AS THE CURRENT FLOW IN THE WIRE. IF THE FLUX IS COLLASPING, THE FLUX INDUCED IN THE WIRE IS OF THE OPPOSITE POLARITY.

  5. IFTHE FLUX IS COLASPING, THE FLUX INDUCES A CURRENT IN THE WIRE OF THE OPPOSITE POLARITY.THIS IS CALLED SELF INDUCTANCE.

  6. INDUCTANCE OF A WIRE CAN BE INCREASED BY FORMING THE WIRE IN A COIL. Inductor basics http://www.youtube.com/watch?v=NgwXkUt3XxQ

  7. DC Theory 13 Segment 3A - Inductance & the Inductor http://www.youtube.com/watch?v=X2e9x104AnE

  8. MUTUAL INDUCTANCE P278 OCCURS WHEN THE MAGNETIC FIELD FROM ONE WIRE INDUCTS A CURRENT IN A SEPARATE WIRE. TRANSFORMERS WORK USING MUTUAL INDUCTANCE. http://www.youtube.com/watch?v=aphgli-RHm0 YOU TUBE:DC THEORY 13 SEGMENT 3B

  9. CONTERELECTROMOTIVE FORCE (CEMF) P.278 IS THE VOLTAGE INDUCED IN A CONDUCTOR BY ITS OWN MAGNETIC FIELD IS CALLED COUNTER EMF OF BACK EMF. LENZ’S LAW A CEMF POLARITY ALWAYS OPPOSES THE CURRENT THAT CREATED IT.

  10. Eddy Currents and Lenz's Law http://www.youtube.com/watch?v=kU6NSh7hr7Q

  11. ENERGY STORAGE AND CONVERSION. P.279 CURRENT FLOW THRU A CONDUCTOR CREATES A MAGNETIC FIELD. INDUCTORS CONVERT ELECTRICAL ENERGY INTO MAGNETIC ENERGY. AS CURRENT DECREASES MAGNETIC ENERGY IS CONVERTED BACK TO ELECTRICAL ENERGY. INDUCTANCE DOES NOT CONVERT ELECTRCIAL ENERGY INTO HEAT, ONLY RESISTANCE CAN. MAKE presents: The Inductor http://www.youtube.com/watch?v=STDlCdZnIsw

  12. FOR THESE 2 QUARTER CYCLES,ENERGY IS TAKEN FROM THE CURRENT. (ELECTRICAL TO MAGNETIC) I FOR THESE 2 QUARTER CYCLES, ENERGY IS RETURNED TO THE CURRENT. (MAGNETIC TO ELECTRICAL) INDUCTORS CAUSE NO NET ENERGY LOSS.

  13. HENRY P. 280 1 HENRY (H) PRODUCES 1 V OF CEMF THE WHEN CURRENT CHANGES AT A RATE OF 1A/S. INDUCTANCE OF A INDUCTOR DEPENDS ON 4 FACTORS. 1. TYPE OF CORE MATERIAL; AIR OR IRON CORE. Fe IS BETTER THEN AIR, SINCE ITS PERMEABILITY IS HIGHER ( ABILITY TO CONDUCT FLUX). CARRIES MORE FLUX. MORE FLUX CHANGE, MORE CEMF.

  14. 2.THE # OF TURNS OF WIRE; MORE TURNS, GREATER THE MAGNETIC FIELD. 3.THE DIAMETER OF THE COIL (CORE): WITH LARGER COIL DIAMETERS ALL THE FLUX LINES GO THRU THE COIL, WHICH INCREASES THE FLUX DENSITY.

  15. 4.SPACING BETWEEN TURNS OF WIRE: WHEN DISTANCE DECREASES, FIELD STRENGTH INCREASES,SINCE FLUX LINES LINK TOGETHER.

  16. TYPES OF INDUCTORS P.282 CLASSIFIED BY THE TYPE OF MATERIAL USED FOR THE CORE. CAN BE FIXED OR VARIABLE. CORES CAN MAGNETIC OR NONMAGNETIC.

  17. INDUCTOR SYMBOLS

  18. IN VARIABLE INDUCTORS, INDUCTION IS CHANGED BY MOVING THE POSITION OF THE CORE.

  19. AIR CORE OFTEN WAPPED AROUND NONMAGENTIC FORM WITH HIGH RELUCTANCE (ABOUT THE SAME AS AIR.) OTHER AIR CORE MATERIALS USED:CERAMIC, PHENOLIC (HARD RESIN, MADE OF PHENOL) , USUALLY LESS THAN 5mH.

  20. FERRITE (Fe ALLOY ), POWERED CORE, L LESS THAN 200mH

  21. FERRITE CORE IN AM RADIO ANTENNAS

  22. TOROID CORE: FLUX LOOPS ALL EXIST INSIDE THE CORE.

  23. SMD INDUCTORS: L RANGES FROM nH TO mH

  24. Fig. 11-11 Surface mount inductor positioned in the end of a small paper clip.

  25. MOLDED INDUCTORS ARE INCASED IN INSULATION MATERIAL TO PROTECT WINDINGS, CORES CAN BE AIR, FERRITE, POWERED Fe.

  26. SHIELDED INDUCTORS SHIELDED FROM EXTERNAL MAGNETIC FILEDS TO PREVENT INTERFERENCE. SHEILD ITSELF IS MADE FROM MAGNETIC MATERIAL.

  27. LAMINATED Fe CORE. L RANGES FROM 0.1 H TO 100H. MADE FROM E AND I LAMINATIONS, STACKED TOGETHER FOR DESIRED THICKNESS.

  28. WINDINGS ARE PLACED ON THE CENTER OF THE “E”. THIS SECTION IS TWICE AS THICK,SINCE IT CARRIES TWICE AS MUCH FLUX. INDUCTION DEPENDS ON THE AMOUNT OF CURRENT FLOWING THRU IT. PERMABILITY DECREASES AS FLUX INCREASES. WHEN SATURATED ALMOST NO CHANGE IN FLUX OCCURS.

  29. l

  30. 3 PHASE TRANSFORMER CORES. 3 PHASE TRANSFORMER

  31. FILTER CHOKES P. 285 AKA LAMINATED Fe CORE INDUCTORS USED IN POWER SUPPLIES TO SMOOTH OUT PULSATING D.C.

  32. RF CHOKES USED IN HIGH FREQUENCY RADIO’S ETC.

  33. RATING OF INDUCTORS. RATED BY: 1. DC RESISTANCE: THE RESISTANCEOF WIRE IN THE COIL, CALLED OHMIC RESISTANCE. 2. CURRENT: AMOUNT OF CURRENT INDUCTOR CAN CARRY WITHOUT HEATING. 3. VOLTAGE: HOW MUCH VOLTAGE THE WINDING INSULATION CAN HANDLE BEFORE BREAKING DOWN. 4. QUALITY: RATIO OF REACTANCE TO RESISTANCE. HIGHER THE QUALITY THE BETTER. 5.TOLERANCE: +/- 1% COSTLY +/- 10% TYPICAL

  34. INDUCTORS IN DC CIRCUITS. INDUCTORS IN DC CIRCUITS FORCE CURRENT TO RISE SLOWLY. THIS IS DUE TO THE INDUCTORS CEMF. THE TIME FOR THIS TO OCCUR DEPENDS ON THE AMOUNT OF INDUCTANCE AND RESISTANCE.

  35. IDEAL INDUCTORS IN AC CIRCUITS IDEAL INDUCTORS HAVE NO RESISTANCE. NO ENERGY CONVERSION TAKES PLACE. NO ELCTRICAL ENERGY IS CONVERTED TO HEAT. INDUCTORS CONTROL CIRCUIT CURRENT WITHOUT POWER LOSS.

  36. INDUCTIVE REACTANCE ( XL) OPPOSITION OF AN INDUCTOR TO AC. XL COMES FROM THE CEMF OF THE INDUCTOR. VOLTAGE LEADS CURRENT BY 90° IN A IDEAL INDUCTOR. XL

  37. INDUCTIVE REACTANCE EQUATION

  38. XL =2πfL = 6.28fL XL IS DIRECTLY PROPORINAL TO FREQUENCY f AND INDUCTANCE L WHY? 1. AS f INCREASES I CHANGES MORE RAPIDLY, MORE CEMF AND REACTANCE ARE PRODUCED. 2. AS L INCREASES THE MORE FLUX CHANGES AS THE CURRENT CHANGES. DO E. 11-1 P.289 OHM’S LAW FOR XL VL = ILXL DO E.11-3 P.290

  39. POWER IN INDUCTORS IDEAL INDUCTOR USES NO POWER SINCE I AND V ARE 90° OUT OF PHASE. P = IVcosØ , SINCE I AND V ARE 90° OUT OF PHASE COS90° = 0 THEREFORE P = IV(0) = 0W NO NET CONVERSION OF ENERGY TAKES PLACE. ENERGY IS TRANSFERED BACK AND FORTH BETWEEN THE SOURCE AND THE INDUCTOR.F.11-23 P.291 REAL INDUCTORS IN AC CIRCUITS. REAL INDUCTORS USE POWER, SINCE THEY HAVE RESISTANCE AS WELL AS REACTANCE. QUALITY: Q = XL/R THE HIGHER THE Q OF A COIL ,THE LESS POWER IT USES.

  40. IMPEDANCE (Z) COMBINATION OF RESISTANCE AND REACTANCE. SINCE INDUCTORS HAVE BOTH RESISTANCE AND REACTANCE, THERE IS IMPEDANCE IN AC CIRCUITS. SINCE REACTANCE IS HIGH AND RESISTANCE IS LOW. WE CAN SPECIFIC ANY INDUCTOR INTERMS OF ITS REACTANCE ONLY.

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