01-变压器

1变压器基本结构与理论分析•变压器(6+3学时)：变压器基本结构，额定值;变压器等效电路与运行原理;标么值;三相变压器;三相变压器不对称运行。

主讲：李格教授，Tel: 3420 4527助教：王海田博士.E -mail: whtqx@ftp:// →lige →publicShanghai Jiao Tong UniversitySep. 2007核心链条: 方程式→相量图→等效电路•内容•1变压器常识:铭牌和额定值、用途、基本结构•2变压器空载运行•3变压器负载运行•4 标幺值•5 变压器的运行性能2•1. 变压器的铭牌和额定值•变压器的铭牌/Nameplate•相数，接线图，额定运行效率和温升•特大型变压器还标注变压器的总质量，铁芯的质量及储油量34•电力变压器的额定频率:欧亚为50Hz/北美60Hz •额定容量S N ：额定条件下输出能力, 二次侧视在功率•额定电压U N ：初级额定时，次级空载电压为次级额定电压额定电流I N,•对于单相变压器一次侧二次侧•对于三相变压器一次侧二次侧11/N N N IS U =22/N N N I S U =113N N N S I U =223N N NS I U =OBJECTIVES/基本要求At the conclusion of this chapter, the student should be able to:1. State the users for a transformer, giving examples of each/用途与例子.2. Describe the operation of an ideal transformer/理想变压器运行.3. Develop the relationships between primary and secondary voltage and current in an ideal transformer/推导理想变压器一二次测电压电流关系.4. Solve problems for ideal transformers, involving current, voltage, power and the turns ratio.5. State the differences between an ideal transformer and a practical transformer,with particular reference to the origins of the differences.6. Draw an "exact" equivalent circuit model, a simplified equivalent circuit model or a high frequency circuit model for a transformer.7. Use any required equivalent circuit model to solve for the operating parameters ofa transformer given the load characteristics.8. Given the short circuit and open circuit test results, to determine the parametersfor the simplified equivalent circuit model.5•ELEMENTARY TRANSFORMER: Users/主要用途•1. to increase or decrease the voltage/电压升降,•2. to increase or decrease the current/电流升降,•3. to match the impedance of a load to thatof a source/阻抗匹配, or•4. to electrically isolate one section of anetwork from another/电气隔离.6•Ideal Transformer • A transformer is a devicewhich accepts electrical power at one voltage and current, and "transformers" these quantities through the ratio of turns on the coils to another voltage and current. In the ideal transformer, no power is lost in the transformation.1122 112221121122121122 2112,t o P=P==F=Fd de Nd t d td de N e Nd t d te N id u ee N ie i e iN ig i v i n g N i N i N iψφφφ⎧==⎪⎪⎪⇒==⎪⎪⎪==⎨⎪⇒⎪⎪⎪=⎪⎪⇒⎩78•Impedance Matching•If we wish tomaximize the power toa load given aparticular source, wemay use a transformer.112221212121122121222/,()/(/)e N i For k e N i E E N N N So Z Z Z I I N N N k ===⋅===⋅=⋅9•基本结构• a. the core type design/芯式(绕组和绝缘装配比较容易-电力系统常用),• b. and the shell type design/壳式(机械强度较好-低压大电流或小容量电讯用变压器)•In each case, the core is laminated in order to reduce eddycurrents in the core. The secondary windings are placed over the primary windings tight to the core in order to minimize leakageflux/迭片和漏磁通(漏感与间隙关系?).10•Ideal Transformers vs. Practical Transformers: A SystemsApproach model• 1. Copper Losses: P = I 2R• 2. Core Losses/铁损: mean curve/平均磁化曲线、residual magnetism left in the material (Called B r )/remanence 剩磁、coercive force 矫顽力/coercivity H c 、"soft" materials and "hard" materials with high B r 、hysteresis loss 、Eddy currents, laminated steel and laminations Fe h e P P P =+11•Ideal Transformers vs. Practical Transformers• 3. Magnetizing Inductance • 4. Leakage Inductance • 5. Capacitance between the turns of thetransformer at higher frequencies due to adifference in the charge stored between turns of the conductors.212m m L i 21112L i σ22212L i σ12•Equivalent Circuit Models for Transformers•R 1and R 2are the winding resistances of the primary and secondary coils respectively.•R c is the equivalent resistance associated with the core losses.•X M is the magnetizing reactance, representing the stored energy in the magnetic field.•X L1and X L2are the components of leakage reactance attributable to the primary and secondary coils respectively.13激磁电阻激磁电抗北美(励磁回路:注意箭头方向变化↓→↑) 中文参考书解读(励磁回路)222Fem Fe Rx X R X µµ=+励磁阻抗:mm m jx r Z +=222m FeFeX r R R X µµ=+14•Simplified Model•Placing R c and X M in parallel with the primary source rather than behind the winding resistance of the primary circuit. Our excuse for doing so is that we expect the value of core resistances to be orders of magnitude larger than the value for winding resistance. 移动R c ，原因R c >>R w•NowwenotethatR 2and X L2can be moved to the left of the ideal transformer through the square of the transformation ratio.R w ＝R 1+ k 2R 2 and X L = X L1+ k 2X L215•High Frequency Circuit Models of transformer(不考)•Inter-turn capacitance: capacitance between turns on the primary winding, capacitance between turns on thesecondary winding, and capacitance due to the electric field between the primary and secondary windings.•The effect of the capacitance is to increase the response near the upper cutoff frequency. At higher frequencies, the effect of X M can be ignored, leaving only the tuning effect of X L , togetherwith the equivalent capacitance, C.Figure 01-10Figure 01-11aFigure 01-11b16•Measuring Circuit Parameters•Open circuit thesecondary side of the transformer, thenapply rated voltage to the primary side./空载开路实验1200010%100%N NFe U k U I I I p P ===1002022N m m m mmU z I P r I x z r≈−≈≈中文参考书中文参考书参数：P3417•Measuring Circuit Parameters/短路实验•Short-circuit the secondary winding and pass ratedcurrent through the primary winding/副边短路, 原边加电压222kk k kk k k kkU z I P r I x z r===−中文参考书•问题•１变压器是根据什么原理变压的?它的四个主要用途有哪些？•２铁心的作用是什么？为什么要用厚度为0.35mm且表面涂有绝缘漆的硅钢片迭制成铁心？　•３变压器有哪几个主要部件？各部件的功能是什么？•４一台三相变压器，额定容量S N= 5000 kVA，额定电压U/ U2N= 10 / 6.3kV，Ｙ/Δ联结，试求：1N（1）一次、二次侧的额定电流；（2）一次、二次侧的额定相电压和相电流。