電工學(xué)原理及應(yīng)用(Electrical-Engineering)經(jīng)典雙語詳解講義-(1)課件

1、電工學(xué)原理及應(yīng)用(Electrical_Engineering)經(jīng)典雙語詳解講義_(1)電工學(xué)原理及應(yīng)用(Electrical_EngineerinElectrical Engineering and Electronics II He is currently a lecturer with the College of Information Engineering, Zhejiang University of Technology. His research interests include support vector machine, neural network control

2、, adaptive control with applications to motion control systems, etc.Qiang Chen was born in Shandong province, in 1984. He received the B.S. degree in measurement and control technology and instrument from Hebei Agricultural University in 2002 and the Ph.D degree in control science and engineering fr

3、om Beijing Institute of Technology in 2012.Final Score = 20% experiment performance + 30% exercise performance + 50% exam scoreElectrical Engineering and EleElectrical Engineering and Electronics II Electrical Engineering and EleChapter 1 IntroductionElectrical Engineering and Electronics II 4 Cours

4、e HoursChapter 1 Electrical Engineeri1. Introduction 1.1 Overview of Electrical Engineering 1.2 Circuits, Currents, and Voltages 1.3 Power and Energy 1.4 Kirchhoffs Current Law 1.5 Kirchhoffs Voltage Law 1.6 Introduction to Circuit Elements 1.7 Introduction to Circuits 1. Introduction 1.1 Overview o

5、f Electrical EngineeringElectrical systems have two main objectives:To gather(采集), store(存儲), process (處理) , transport(轉(zhuǎn)換), and present(顯示）informationTo distribute and convert energy between various forms1.1 Overview of Electrical EngCommunication systems radio, satellite TV, cellphone.Computer syst

6、ems process and store information in digital form.Control systems gather information with sensors and use electrical energy to control a physical process.Electromagnetics is the study and application of electric and magnetic fields.Electronics is the study and application of materials, devices and c

7、ircuits used in amplifying and switching electrical signals.Photonics is an exciting new field of science and engineering that promises to replace conventional computing.Power systems convert energy to and from electrical form.Signal processing is concerned with information-bearing electrical signal

8、s.Electrical Engineering SubdivisionsCommunication systems radio, Reasons:To pass the Fundamentals of Engineering (FE) ExaminationTo have a broad knowledge and you can lead design projects in your own fieldTo be able to operate and maintain electrical systemsTo communicate with electrical engineerin

9、g consultantsWhy Study Electrical Engineering?Reasons:Why Study Electrical E1.2 Circuits, Currents and VoltagesSimple example: the headlight circuit of an automobile1.2 Circuits, Currents and VolElectrical CircuitAn electrical circuit consists of various types of circuit elements connected in closed

10、 paths by conductors.Electrical CircuitAn electricaiuuLLuRuCRCR0EURabcd+-IVCCRBRCIC+_UCE+_VCC+_UBEIB國標(biāo)符號iuuLLuRuCRCR0EURabcd+-IVCCRBElectrical current is the time rate of flow of electrical charge through a conductor or circuit element. The units are amperes (A), which are equivalent to coulombs per

11、 second (C/s).Electrical CurrentThe charge on an electron is -1.602E-19 CElectrical CurrentThe charge oElectrical CurrentActual direction： Moving direction of positive chargeFig.1.4 Current is the time rate of charge flow through a cross section of conductor or circuit elementThe electrical current

12、flowing through the element in the reference direction is given byElectrical CurrentActual direc2Example 1.1 Determining Current Given ChargeSuppose that charge versus time is given by2Example 1.1 Determining CurrDirect Current When a currents direction is constant with time, we say that we have dir

13、ect current, abbreviated as DC. Alternating CurrentOn the other hand, a current that varies with time, reversing direction periodically, is called alternating current, abbreviated as AC.Direct Current .Sinusoidal current.Sinusoidal current三角波方波三角波方波Reference Directionsi1=-2AActual Directioni2=2Ai3=-

14、1AReference Directionsi1=-2AActuDouble-Subscript Notation for CurrentsExample: if , then Double-Subscript Notation for Voltages The voltage associated with a circuit element is the energy transferred per unit of charge that flows through the element. The units of voltage are volts (V), which are equ

15、ivalent to joules per coulomb (J/C). For example, consider the storage battery in an automobile. The voltage across its terminals is 12V. This means that 12J are transferred to or from the battery for each coulomb that flows through it.Voltages The voltage associVoltages Voltages are assigned polari

16、ties that indicate the direction of energy flow. If positive charge moves from the positive polarity through the element toward the negative polarity, the element absorbs energy that appears as heat, mechanical energy, stored chemical energy, or as some other form. On the other hand, if positive cha

17、rge moves from the negative polarity toward the positive polarity, the element supplies energy.Voltages Voltages are assigVoltagespositive chargepositive chargepositive polaritynegative polarityVoltagespositive chargepositivVoltages reference polarityVba=-VabVab=-5VAnother two ways to indicate the r

18、eference polarity of a voltage: double subscripts on the voltage variable and an arrow+-Voltages reference polarityVb1.3 Power And EnergyConsider the circuit element shown in Figure 1.14. Because the current i is the rate of flow of charge and the voltage v is a measure of the energy transferred per

19、 unit of charge, the product of the current and the voltage is the rate of energy transfer. In other words, the product of current and voltage is power.1.3 Power And EnergyConsider tUnit: WattUnit: JoulePower And EnergyUnit: WattUnit: JoulePower AndReviewDefinitions:Current i the rate of charge flow

20、;Voltage v a measure of the energy transferred per unit of charge;Power the rate of energy transfer (the product of the current and the voltage).Reference direction and Actual directionWhen i or v has a positive value, the two directions are same;When i or v has a negative value, the two directions

21、are opposite.ReviewDefinitions: IUabAs shown in the figure above, the current reference enters the positive polarity of the voltage, we call this arrangement the Passive Reference Configuration.If the reference directions of the current and voltage are same, it is the passive reference configuration

22、.If the reference directions of the current and voltage are opposite, it is the non-passive reference configuration.Passive Reference Configuration IUabAs shown in the figure Passive reference configuration:Non passive reference configuration:Function of Elementi+-ubpai+-ubpaPassive reference config

23、uratioCalculate the power for each element. If it is a battery, is it being charged or discharged?Absorbing energy, being chargedSupplying energy, being dischargedSupplying energy, being dischargedCalculate the power for each e12U5345U1U2U3U4ExampleSolution：box 1Load: Absorb Box 2Load: AbsorbIn the

24、figure below, the reference directions of voltages and currents are given. Please calculate the power of each element and point out which are sources (supply energy) and which are loads (absorb energy).-+-+-+-12U5345U1U2U3U4ExampleSolutionBox3Source: SupplyBox4Box5Notice：Power balance！The sum of the

25、 power of all circuit elements is equal to 0 ！The criterion of the calculation result inspection.12U5345U1U2U3U4-+-+-+-Load: Absorb Load: Absorb Box3Source: SupplyBox4Box5NotiHomework 1 (page 46 in textbook)P1.1P1.3 In electrical textbook (fifth edition), p1.10 and p1.20Hand in the homework next Wed

26、nesday!Homework 1 P1.1In electrical tAbout Kirchhoff/wiki/Gustav_Kirchhoff古斯塔夫羅伯特基爾霍夫(Gustav Robert Kirchhoff )About Kirchhoffhttp:/en.wik+-E1E2R2R1R3I1I2I3cabdn=2l=3b=3branch(支路): the subcircuit with the same current flowing through it.node(節(jié)點(diǎn)): a point at which three or more branches are joined to

27、gether.loop(回路)：a closed path composed of branches.Concepts+-E1E2R2R1R3I1I2I3cabdn=2l=3n=3,b=5,l=6b=6,n=4,l=726a4I 3bcdef10V26a 4 310VbdefHow many branches, nodes and loops in the following circuits?(a)(b)Examplen=3,b=5,l=6b=6,n=4,l=726abcd1.4Kirchhoffs current LAW (KCL)The net(總的) current entering

28、a node is zero.Alternatively, the sum of the currentsentering a node equals the sum of the currents leaving a node. = 0 in= out1.4Kirchhoffs current LAW (KC I1+ I2-I3=0Or -I1- I2+I3=0Rewritten as： I1+ I2 = I3 （in） （out）+-U1U2R2R1R3I1I2I3cabd I1+ I2-I3=0Rewritten as：Expend to a supernode (a closed su

29、rface)IAIBICIABIBCICAABCIC= ICA- IBCAdd all three equations：IA= IAB- ICAIB= IBC- IABIA+IB+IC=0【Prove】 IA+IB+IC=0or I=0Expend to a supernode (a closeI6V12V51152+-baN=2,B=3,L=2I=0,Uab=0Example N、B、L=？ I、Uab=？I6V12V51152+-baN=2,B=3,In the following circuit，I1=11mA，I4=12mA，I5=6mA. Solve I2，I3 and I6. (U

30、sing KCL)I1R1R2R3I2I3I4I5I6Examplesolution：I3=I1I5=116=5（mA)I2=I3I4=512=7（mA)I6=I1I2=11(7)=18（mA)I6=I4+I5=12+6=18（mA)In the following circuit，I1=11Series Circuitsia=ib=icThe current is identical.Series: Elements are connected end to end, no other element can be connected to their common node.No othe

31、r path for current can be connected to the node joining A,B,C. Thus, all elements in a series circuit have identical currents.Series Circuitsia=ib=icSeries:Ex.1 Use KCL to determine the values of the unknown currents shown in Fig. 1.21Answer:ia=4A ib=-2A ic=-8AEx.1 Use KCL to determine theIdentify t

32、he groups of the circuit elements that are connected in series shown in Fig. 1.22Answer:A、B ； E、F、GIdentify the groups of the cirHomework 1 (page 46 in textbook)P1.1P1.3P1.7 In electrical textbook (fifth edition), p1.10, p1.20 and p.1.37Hand in the homework next Wednesday!Homework 1 P1.1In electrica

33、l t1.5 kirchhoffs voltage law(KVL)The algebraic sum of the voltages equals zero for any closed path (loop) in an electrical circuit. U = 01.5 kirchhoffs voltage law(KVThe voltage is positive when reference direction is the same as travel direction, or the voltage is negative 。The voltage is positive

34、 when r As shown in the figure，UAB=5V，UBC=4V，UDA=3V. Solve：（1）UCD；（2）UCAUBCSolution：（2）ABCA is not a closed loop（1）KVLUAB+UBC+UCD+UDA=05+（4）+UCD+（3）=0UCD=2VUAB+UBC+UCA=0UCA=（UAB+UBC）1VExample+-UABUDAUCDUBCABCD+-UCAextended kirchhoffs voltage law As shown in the figure，UAB=5VParallel CircuitsTwo comp

35、onents are in parallel if both ends of one element are directly connected to the corresponding ends of the other element.Parallel CircuitsTwo componentva=vb=-vcThe voltage is identical.Parallel Circuitsva=vb=-vcParallel CircuitsUse repeated application of KVL to find the values of vC、ve for the circ

36、uit of Fig. 1.29.Answer: vC=8V; ve=-2VUse repeated application of KVHomework 1 (page 46 in textbook)P1.1P1.3P1.7P1.8 In electrical textbook (fifth edition), p1.10, p1.20, p.1.37 and p.1.41Hand in the homework next Wednesday!Homework 1 P1.1In electrical t1.6 Introduction to Circuit ElementsConductors

37、 導(dǎo)線Voltage source 電壓源Current source 電流源Resistors 電阻器1.6 Introduction to Circuit ElAn unbroken lineOpen circuitIab=0Uab=?Short circuitUab=0Iab=? ConductorsThe resistance of an ideal conductors is zero.abAn unbroken lineOpen circuitShIndependent Voltage SourceMaintains a specified voltage across its t

38、erminal, regardless of other currents or voltages of any other elements.Circle enclosing reference polarityIndependent Voltage SourceMain+-US1US2US+-US+-+-US1US2US+-US+-Named as equivalent conversionVoltage Sources in SeriesSubstitute several series voltage sources for one equivalent voltage source.

39、與等效電壓參考極性相同取正，相反者取負(fù)。+-US1US2US+-US+-+-US1US2USIdeal Circuit Elements versus RealityIdeal Circuit Elements versus Dependent/Controlled Voltage Source2, unitless3, unit of ohmDependent/Controlled Voltage SIndependent Current SourceMaintains a specified current flowing through itself, regardless of oth

40、er currents or voltages of any other elements.Circle enclosing an arrowIndependent Current SourceMainIS1IS2USISUSIS1IS2USISUSCurrent Sources in ParallelSubstitute several parallel current sources for a equivalent current source.與等效電流參考方向相同取正，相反者取負(fù)。IS1IS2USISUSIS1IS2USISUSCurrenDependent/Controlled C

41、urrent Source2, unitless3, unit of SiemensDependent/Controlled Current SVoltage-controlled voltage sourcesVCVSCurrent-controlled voltage sourcesCCVS Voltage-controlled current sourcesVCCSCurrent-controlled current sourcesCCCSTheSummaryofDependentSourcesVoltage-controlled voltage souRresistance value

42、resistivityLlength of conductorAcross sectional areaResistorsThe voltage v across an ideal/linear resistor is proportional to the current i through the resistor.The constant of proportionality is the resistance R.Rresistance valueResistorsTAbout Ohm/wiki/Georg_Ohm格奧爾格西蒙歐姆(Georg Simon Ohm )About Ohmhttp:/en.wikipedia0 viPassive reference configurationOhmsLawIt shows the proportional relationship between current and voltage.0 viPassive reference configConductance電導(dǎo)單位：SiemensNonPassive referen