Synchronous Machine.rar

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  • 2019-07-10 02:48
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Synchronous Machine.rar
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<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/625184c074bc5c01059ce537/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/625184c074bc5c01059ce537/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">48550 Electrical Energy Technology</div><div class="t m0 x2 h3 y2 ff1 fs1 fc0 sc0 ls1 ws1">Chapter 6.</div><div class="t m0 x3 h3 y3 ff1 fs1 fc0 sc0 ls2 ws2">Synchronous Machines</div><div class="t m0 x2 h4 y4 ff1 fs2 fc0 sc0 ls3 ws3">Topics to cover:</div><div class="t m0 x2 h5 y5 ff2 fs2 fc0 sc0 ls4 ws4">1) <span class="ls5 ws5">Introduction</span></div><div class="t m0 x2 h5 y6 ff2 fs2 fc0 sc0 ls4 ws4">2) <span class="ls6 ws6">Synchronous machine structures</span></div><div class="t m0 x2 h5 y7 ff2 fs2 fc0 sc0 ls4 ws4">3) <span class="ls7 ws7">Rotating magnetic field</span></div><div class="t m0 x4 h5 y5 ff2 fs2 fc0 sc0 ls4 ws4">4) <span class="ls8 ws8">Equivalent circuit model</span></div><div class="t m0 x4 h5 y6 ff2 fs2 fc0 sc0 ls4 ws4">5) <span class="ls9 ws9">Performance as a generator</span></div><div class="t m0 x4 h5 y7 ff2 fs2 fc0 sc0 ls4 ws4">6) <span class="lsa wsa">Performance as a motor</span></div><div class="t m0 x2 h6 y8 ff1 fs3 fc0 sc0 lsb ws5">Introduction</div><div class="t m0 x5 h7 y9 ff3 fs2 fc0 sc0 lsc wsb">A synchronous machine is an ac rotating machine whose speed under steady state</div><div class="t m0 x2 h7 ya ff3 fs2 fc0 sc0 lsd wsc">condition is proportional to the frequency of the current in its armature. The magnetic field</div><div class="t m0 x2 h7 yb ff3 fs2 fc0 sc0 lse wsd">created by the armature currents rotates at the same speed as that created by the field current</div><div class="t m0 x2 h7 yc ff3 fs2 fc0 sc0 lsf wse">on the rotor, which is rotating at the synchronous speed, and a steady torque results.</div><div class="t m0 x5 h7 yd ff3 fs2 fc0 sc0 ls10 wsf">Synchronous machines are commonly used as generators especially for large power</div><div class="t m0 x2 h7 ye ff3 fs2 fc0 sc0 ls11 ws10">systems, such as turbine generators and hydroelectric generators in the grid power supply.</div><div class="t m0 x2 h7 yf ff3 fs2 fc0 sc0 ls12 ws11">Because the rotor speed is proportional to the frequency of excitation, synchronous motors</div><div class="t m0 x2 h7 y10 ff3 fs2 fc0 sc0 ls13 ws12">can be used in situations where constant speed drive is required. Since the reactive power</div><div class="t m0 x2 h7 y11 ff3 fs2 fc0 sc0 ls14 ws13">generated by a synchronous machine can be adjusted by controlling the magnitude of the</div><div class="t m0 x2 h7 y12 ff3 fs2 fc0 sc0 ls15 ws14">rotor field current, unloaded synchronous machines are also often installed in power systems</div><div class="t m0 x2 h7 y13 ff3 fs2 fc0 sc0 ls16 ws15">solely for power factor correction or for control of reactive <span class="ls17 ws16">kVA flow. Such machines,</span></div><div class="t m0 x2 h7 y14 ff3 fs2 fc0 sc0 ls18 ws17">known as <span class="ff4 ls19 ws18">synchronous condensers</span><span class="ls1a ws19">, may be more economical in the large sizes than static</span></div><div class="t m0 x2 h7 y15 ff3 fs2 fc0 sc0 ls1b ws5">capacitors.</div><div class="t m0 x5 h7 y16 ff3 fs2 fc0 sc0 ls1c ws1a">With power electronic variable voltage variable frequency (VVVF) power supplies,</div><div class="t m0 x2 h7 y17 ff3 fs2 fc0 sc0 ls1d ws1b">synchronous motors, especially those with permanent magnet rotors, are widely used for</div><div class="t m0 x2 h7 y18 ff3 fs2 fc0 sc0 ls1e ws1c">variable speed drives. If the stator excitation of a permanent magnet motor is controlled by</div><div class="t m0 x2 h7 y19 ff3 fs2 fc0 sc0 ls1f ws1d">its rotor position such that the stator field is always 90</div><div class="t m0 x6 h8 y1a ff3 fs4 fc0 sc0 ls20 ws5">o</div><div class="t m0 x7 h7 y19 ff3 fs2 fc0 sc0 ls21 ws1e"> (<span class="ff4 ls22 ws5">electrical</span><span class="lsd ws1f">) ahead of the rotor, the</span></div><div class="t m0 x2 h7 y1b ff3 fs2 fc0 sc0 ls23 ws20">motor performance can be very close to the conventional brushed dc motors, which is very</div><div class="t m0 x2 h7 y1c ff3 fs2 fc0 sc0 ls24 ws21">much favored for variable speed drives. The rotor position can be either detected by using</div><div class="t m0 x2 h7 y1d ff3 fs2 fc0 sc0 ls25 ws22">rotor position sensors or deduced from the induced <span class="ff2 ls26 ws5">emf</span><span class="ls27 ws23"> in the stator windings. Since this</span></div><div class="t m0 x2 h7 y1e ff3 fs2 fc0 sc0 ls28 ws24">type of motors do not need brushes, they are known as <span class="ls29 ws25">brushless dc motors.</span></div></div><div class="pi" data-data='{"ctm":[1.611639,0.000000,0.000000,1.611639,0.000000,0.000000]}'></div></div> </body> </html>
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