Lec11 - 341 Energy Conversion

# Lec11 - 341 Energy Conversion - 341 Electric Machinery...

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Unformatted text preview: 341 - Electric Machinery Fundamentals MI - 1 Lec 11 Synchronous Generators Mahesh S. Illindala 341 - Electric Machinery Fundamentals MI - 2 Objectives • Comprehension: – Discuss the concept of armature reaction – Estimate the equivalent circuit parameters from the open-circuit and short-circuit tests • Analysis: – Analyze the voltage and induced in the synchronous generator – Connect the phasor diagram with the equivalent circuit – Derive the expressions for power and torque from the phasor diagram • Synthesis: – Integrate the excitation systems for a large synchronous generator to obtain an internal voltage – Create an equivalent circuit using the concept of armature reaction 341 - Electric Machinery Fundamentals MI - 3 AC Synchronous Machine Large- scale generation Salient-pole type 341 - Electric Machinery Fundamentals MI - 4 Recall Voltage Induced in a 2-Pole Stator Coil by a Sinusoidal Rotating Magnetic Field e ind = ( v X B ) l The voltage induced on each wire segment moving in the magnetic field e ba = - vBl = - vB M l cos ( w m t – 180 o ) into the page Segment ab: e cb = Segment bc: e dc = vBl = vB M l cos w m t out of the page Segment cd: e ad = Segment da: e ind = e ba + e cb + e dc + e ad The total voltage induced on the stator coil e ind = 2 vB M l cos w m t e ind = N C f w m cos w m t or i.e. where f is the airgap flux and N C is the no. of turns of wire Voltage induced depends on flux linkage and speed of rotation Magnitude of flux density in the air-gap 2-Pole Stator Coil Stator coil is perpendicular to the plane Rotating rotor magnetic field 341 - Electric Machinery Fundamentals MI - 5 AC Synchronous Machine – Internal Generated Voltage e ind = e A = N C f w cos w t Field windings in a non-salient 2-pole synchronous machine rotor E A = ( N C f w ) / 2 Magnetization curve of a synchronous generator 341 - Electric Machinery Fundamentals MI - 6 AC Synchronous Machine Rotor with a Brushless Exciter Courtesy of Teco Westinghouse Exciter Rotor 341 - Electric Machinery Fundamentals MI - 7 Brushless Exciters for Larger Synchronous Generators The permanent magnets of the pilot exciter produce the field current of the exciter, which in turn produces the field current of the main machine 341 - Electric Machinery Fundamentals MI - 8 Exciter Operating Characteristics The commutator and brush arrangement (of a dc machine) is not employed. Instead a rectifier circuit is used to obtain a dc voltage similar to that in a brushless dc...
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Lec11 - 341 Energy Conversion - 341 Electric Machinery...

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