Transcript Slide 1
RE1345 KONVERSI TENAGA LISTRIK II Vita Lystianingrum 1 References 1. Theraja, B. L., ‘Electrical Technology’, S. Chand & Company Ltd., 1978. 2. Karady, G., ‘Lecture Notes on Synchronous Generator’, www.eas.asu.edu/~karady/360_pp.html. 3. Zuhal, ‘Dasar Tenaga Listrik’, ITB Bandung. 2 RE1345 KONVERSI TENAGA LISTRIK II 1: Klasifikasi mesin-mesin listrik dan konstruksi 2: Generator sinkron: proses terbangkitnya EMF dan macam-macam generator sinkron 3: Generator sinkron: berbeban, kerugian tegangan, diagram vektor untuk pf. lagging, pf. leading 4: Generator sinkron: menentukan voltage regulator dengan metode EMF dan karakteristik 5: Generator sinkron: kerja paralel 6: 7: Motor sinkron: metode start dan pengaruh perubahan arus eksitasi 8: Motor sinkron: torque dan contoh soal 9 & 10: UTS 3 Review KTL 1: DC Machines • Faraday’s Law -> Dynamically & statically induced. 4 Review: Fleming’s Right-hand Rule Fleming's right hand rule (for generators) shows the direction of induced current flow when a conductor moves in a magnetic field. The Thumb represents the direction of Motion of the conductor. The First finger represents the direction of the Field. The Second finger represents the direction of the induced or generated Current 5 http://www.walter-fendt.de/ph11e/generator_e.htm 6 • Emf generation 7 Energy Conversion B L D B 8 Energy Conversion B 9 • Synchronous Generator • Assumption: rotors are round rotor -> related to flux distribution 10 Voltage generation (Generator) • A wire loop is rotated in a magnetic field. • The magnetic flux through the loop changes by the position B D L B 1 cos wt 2 11 Voltage generation (Generator) • Position 1 all flux links with the loop • Position 2 the flux linkage reduced 1 cos wt B 2 t B D L cos w t w 2 n 12 Voltage generation (Generator) • The induced voltage is an ac voltage 1 B • The voltage is sinusoidal Vt N 2 cos wt d t d cos w t N B DL N B D L w sin w t dt dt 13 • Stator winding 14 1 Winding beginning, 2 Winding end, 3 Voltage, 6 A rotation = one cycle, 7 Coil 15 Figure 33 Principle of the two-phase alternating voltage generator 1 Casing, 2 Stator, 3 Field spider 4 Beginning winding one, 5 End winding one 6 Beginning winding two, 7 End winding two **Figure 35 Principle of the three-phase alternating generator 1 1. Winding one beginning 1.2. Winding one end 2.1. Winding two beginning 2.2. Winding two end 3.1. Winding three beginning 3.2. Winding three end 16 www.crystal-netbook.info/e148915/e149917/e150166 SYNCHRONOUS MACHINES • • The rotor is supplied by DC current If that generates a DC flux f. Operation (two poles) Flux f ns The rotor is driven by a turbine with a constant speed of ns. B- C+ N • The rotating field flux induces a voltage in the stator winding. • The frequency of the induced voltage depends upon the speed. A- A+ S C- B+ 17 • 17 **frequency, speed, and poles • Synchronous generator -> means that electrical frequency produced is synchronized with the mechanical rate of rotation of the generator. • A synchronous generator’s rotor consists of an electromagnet (DC supplied). • Rotor’s magnetic field points in whatever direction the rotor is turned. • Now, the rate of rotation of the magnetic fields in the machine is related to the stator electrical frequency by: nm P fe 120 18 • 18 ** The frequency - speed relation nm P fe 120 f = electrical frequency, Hz nm= mechanical speed of magnetic field, rpm P = number of poles • Typical rotor speeds are (for 60 Hz) • 3600 rpm for 2-pole, • 1800 rpm for 4 pole and • 450 rpm for 16 poles. 19 • 19 • Rotor generated Flux and Induced Voltage, Round rotor machine 20 • 20 SYNCHRONOUS MACHINES Rotor generated Flux and Induced Voltage, Round rotor machine • For the calculation of the induced voltage, the machine is simplified. • On the stator windings of each phase is represented by one equivalent coil. • • Similarly on the rotor’s dc winding is represented by an equivalent coil. The rotor coil is supplied by a dc current I f and has N f turns. This generates a flux Magnetic axis of phase A Qm= 00 C+ BN A+ AS C- B+ 21 • 21 SYNCHRONOUS MACHINES Round Rotor generated flux Magnetic axis of the rotor • Q m= 0o The rotor generated field is constant along the gap. The field is calculated by the Ampere law. C+ BN A+ AS • The upper part of the rotor the B lines going out, the lower part entering into the rotor. C- B+ 22 • 22 SYNCHRONOUS MACHINES Q • The rotor and with the rotor the flux rotates with an angular speed of w Qm C+ BN A+ A- S C- B+ • The flux linkage depend on the rotor position. 23 • 23 SYNCHRONOUS MACHINES All flux links with phase A, when Q is 00 deg. Magnetic axis of phase A The flux linkage is zero, when Q is +/-900. Magnetic axis of phase A Qm= 00 C+ B- Qm= 900 C+ B- N N A+ A- A+ A- S S C- B+ C- B+ 24 • 24 • Ende.. 25 • 25 26 • 26 27 • 27 1 Winding beginning, 2 Winding end, 3 Voltage, 4 A cycle 5 A rotation = two cycles, 6 A rotation = one cycle, 7 Coil 8 Coil connection 28 • 28 • Breadth factor, distribution, etc… • Exciter -> w/ brush; brushless; etc -> chapman • Open-circuit characteristic / magnetization curve of the machine 29 • 29