Prob.7. A 3-phase, star-connected, 11 kV, 12-pole, 50 Hz salient-polesynchronous machine has reactance of X, = 5 2 and X, = 3 Q at certainload, the motor draws 20 MW at unity p.f. Compute synchronising powerper electric degree and corresponding torque.%3D

Prob.7. A 3-phase, star-connected, 11 kV, 12-pole, 50 Hz salient-pole synchronous machine has reactance of X, = 5 Q and X, = 3 Q at certain load, the motor draws 20 MW at unity p.f. Compute synchronising power electric degree and corresponding torque. per

Prob.7. A 3-phase, star-connected, 11 kV, 12-pole, 50 Hz salient-pole synchronous machine has reactance of X, = 5 Q and X, = 3 Q at certain load, the motor draws 20 MW at unity p.f. Compute synchronising power electric degree and corresponding torque. per

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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A 6.6 kV, star-connected,3-phase, synchronous motor works at constant voltage and constant excitation. Its synchronous impedance is (2.0 + j 20) per phase. When the input is 1100 kW, its power factor is 0.8 leading. Find the power factor when the input is increased to 1800 kW. (ILLUSTRATIONS such as diagrams and graphs are Required).
A 420 Vdc, 8 pole Compound DC motor runs at 729 rev/min when drawing a load of 60 A from the supply when meeting a load demand of 28 kW. The compound motor has a Lap connected armature with 816 conductors. The Armature, Interpole, Series, and Shunt resistances are 0.295 Q, 0.0155 Q, 0.00118 Q, and 147 Q respectively. The series field has 6 turns per pole while the shunt field has 2800 turns per pole. Under full load conditions, the shunt current is 3.75 A, and the Friction and windage loss is Pf/w = 0.782 kW. Consider c =6 for lap winding. Assume constant shunt current and friction and windage loss, determine for a reduced output load of 14.5 kW; (a) The new armature current; (b) The new speed of the motor
A 3-phase 50 Hz I.M. has a rated torque = 16.7 N.M and maximum torque = 40.5 N.M. If its rated speed = 910 R.P.M, the speed at :maximum torque will be R.P.M 578.280 R.P.M 421.640 R.P.M 590.160 None O
If the average pole flux of a dc machine with 24 coils, each of which contains 16 windings, 4 poles, double layered parallel winding (duplex lap winding), with a speed of 1000 rpm, is 15mWb, what is the idle winding voltage and (Note: In your operations, two digits after the comma) take it)
A 220-V Y-connected synchronous motor is drawing 50 A at unity power factor from a 220-V power system. The field current flowing under these conditions is 2.7 A. Its synchronous reactance is 1.4 ohms. Assume a linear open-circuit characteristic. (a) Find phase voltage and induced emf for these conditions. (b) Find the torque angle. (c) What is the maximum power that the machine can handle under these conditions? (d) How much armature current would be required to make the motor operate at 0.80 PF leading?
With the aid of diagrams describe the basic topology of a wound field 3 phase synchronous generator and outline the relationship between the excitation voltage and rotor current. Q2 (a) (b) Outline with the aid of a suitable diagram the necessary power conversion stages required to interface a small permanent magnet (PM) generator to a stand alone DC system. A star connected 3 phase wound field synchronous generator with a synchronous reactance of 20 N is connected to a 6.6 kV (phase voltage) grid and supplies 1.5 MW at 0.95 lagging power factor at its terminals. Calculate the phase current and resultant voltage across the synchronous reactance (Vxs), and from a scaled phasor diagram graphically determine the required excitation voltage (Eph) and load angle (8). (c) The load is now increased to 3 MW with the Excitation Voltage kept constant. Using the phasor diagram drawn in part (c) graphically determine the resultant phase current, power factor and load angle. (d)
2) A large 3-phase, 4000 Va (phase to phase), 60 Hz squirrel-cage induction motor draws a current of 385 A/phase. The total active power at the stator input terminals is 2344 kW, when operating at full load. The corresponding speed is accurately measured and found to be 709.2 r/min. The stator is connected in wye and the resistance between two stator terminals is 0.10 Q. The total iron losses are 23.4 kW and the windage and friction losses are 12 kW. Calculate the following: c) The total 1²-R losses in the rotor d) The load mechanical power (kW), torque (kN•m), and efficiency. S = Va · V3 - I S= Vy•3·I %3D
h has rotor e.m.f. Speed of the induction motor and the frequency of its [970 r.p.m.; 1.5 Hz] 4. A 3-phase, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between the slip-rings on open-circuit. Calculate the current and power factor at standstill when the rotor winding is joined to a star-connected external circuit, each phase of which has a resistance of 10 2 and an inductance of 0.04 H. The resistance per phase of the rotor winding is 0.2 2 and its inductance is 0.04 H. Also, calculate the current and power factor when the slip-rings are short-circuited and the motor is running with a slip of 5 per cent. Assume the flux to remain constant. [10.67 A; 0.376; 21.95 A; 0.303] 5. Obtain an expression for the condition of maximum torque of an induction motor. Sketch the torque- slip curves for several values of rotor circuit resistance and indicate the condition for maximum torque to be obtained at starting. If the motor has a rotor resistance of…
A 15-kV 35-KVA 0.76-PF-lagging 50-Hz four-pole Y-connected steam-turbine generator has a synchronous reactance of 3.50 0 per phase and an armature resistance of 0.75 0 per phase. This generator is operating in parallel with a large power system (infinite bus). a) What is the magnitude of E, at rated conditions? b) What is the generator's torque angle at rated conditions? c) If the field current is constant, what is the maximum power possible out of this generator? How much reserve power or torque does this generator have at full load? d) Sketch the corresponding phasor diagram and calculate for the armature current (assume the field current is still unchanged) e) At the absolute power possible, how much reactive power will this generator be supplying or consuming?
A synchronous machine is a three-phase, two-pole machine with 36 stator slots and 5/6 full-pitched balanced armature windings. Each phase winding is made up of eight identical coils connected in sequence. Balanced three-phase 66 Hz currents with a peak amplitude of 16 A are used to drive the stator phases. a) What is the basic stator space mmf's maximum amplitude? (A.turns) b) How fast does the fundamental stator space mmf rotate mechanically? (rpm) c) What is the third-harmonic stator space mmf's maximum amplitude? (A.turns) d) What is the fifth-harmonic stator space mmf's maximum amplitude? (A.turns) e) How fast does the fifth-harmonic stator space mmf rotate mechanically? (rpm)
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