A 690 KVA, 4200-V, 60 Hz, 0.9 PF lagging, Delta-connected, 8- pole synchronous generator has an armature resistance of 0 Q. The OC and SCC characteristics are given below in a tabular form. Find the generator's synchronous reactance at rated armature current. IF (A) 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 VT (V) 400 1200 1850 2450 2950 3500 3800 4200 4400 4550 4650 4750 4820 lA (A) 20 45 70 95 125 150 175 200 230 255 280 310 340 Select one: O a. Xs = j25.8 Ohms O b. X = 8.6 Ohms O c. X, = 14.9 Ohms O d. None e. Xg = 25.8 Ohms Clear my choice

A 690 KVA, 4200-V, 60 Hz, 0.9 PF lagging, Delta-connected, 8- pole synchronous generator has an armature resistance of 0 Q. The OC and SCC characteristics are given below in a tabular form. Find the generator's synchronous reactance at rated armature current. IF (A) 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 VT (V) 400 1200 1850 2450 2950 3500 3800 4200 4400 4550 4650 4750 4820 lA (A) 20 45 70 95 125 150 175 200 230 255 280 310 340 Select one: O a. Xs = j25.8 Ohms O b. X = 8.6 Ohms O c. X, = 14.9 Ohms O d. None e. Xg = 25.8 Ohms Clear my choice

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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Explain the conditions for parallel operation of synchronous generators. A three phase, wye connected, synchronous generator is rated 150 MW, 0.85 lagging power factor, 12.6 kV, 60 Hz, and 1800 rpm. Each winding has an armature resistance of 0.05Q and a synchronous reactance of 0.6Q. Draw the phasor diagram with values, show torque angle and determine the induced voltage for the condition of rated load.
The terminal voltage of a 150 kW series generator is 600 V at rated load. The armature resistance is 0.06 ohms and the series field resistance is 0.04 ohms. Find generated emf.
A 250-MW, 60-Hz turbine generator set has a speed regulation of 5 percent based on its own rating. The generator frequency decreases from 60 Hz to a steady state value of 59.7Hz. Determine the increase in the turbine power output.
7 A three-phase, 60-cycle, 32-pole synchronous generator has a sinusoidally distributed air-gap flux of 0.025 weber/pole. The armature core has 324 slots. The armature winding is Y-connected. There are two coil sides per slot and two turns per coil. The coil pitch is 9 slots. Find the generated voltage between the line terminals. Ans. 2,445 V
A separately-excited generator develops a no-load e.m.f. of 150V at an armature speed of 20 rev/s and a flux per pole of 0.10Wb. Determine the generated e.m.f. when (a) the speed increases to 25 rev/s and the pole flux remains unchanged, (b) the speed remains at 20 rev/s and the pole flux is decreased to 0.08Wb, and (c) the speed increases to 24 rev/s and the pole flux is decreased to 0.07Wb.
2.2 A three-phase synchronous generator has a reactance of 1.5 p.. and negligible resistance. It supplies a rated current of 1.0 p.. at 1.0 p.u. terminal voltage to a lagging load of 0.9 power factor. Determine the rated excitation voltage in p.u. and the internal load angle. Construct the performance chart of the generator in 2.1 (above) assuming its rating is 450 MVA.
A seperately excited DC generator has a no load voltage of 127 V, Ra= 0.02 ohm and Rsh=15 ohm. Find the armature current when the generator terminal voltage is 120 V on load.
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)
4 The field current of a synchronous generator is adjusted to give an air-gap flux of 0.01 weber per pole. The flux is sinusoidally distributed along the air gap. The armature winding is Y-connected. There are 5 slots/phase/pole and the coil pitch is 12/15. The frequency is 60 hertz at 1,200 RPM. (a) Calculate the emf/turn. (b) If there are 10 turns/ coil and two coil sides per slot, calculate the emf per phase. (c) Calculate the emfbetween terminals. Ans. 2.53V; 728V; 1,260V.
A three-phase Y-connected synchronous generator is rated 120 MVA, 13.2 kV, 0.8 PF lagging, and 60 Hz. Its synchronous reactance is 0.9 Q, and its resistance may be ignored. (a) What is its voltage regulation? (b) What would the voltage and apparent power rating of this generator be if it were operated at 50 Hz with the same armature and field losses as it had at 60 Hz? (c) What would the voltage regulation of the generator be at 50 Hz?
A 6 pole wave wound d.c. shunt generator has 500 conductors. A generator delivers 50 kW of power at 250 voltage at full load. The resistance of the field circuit is 125 2. Actual brush shift is 10°. Then find the demagnetizing and cross magnetizing ampere turns per pole and how many additional turns must be wound on each pole to eliminate the demagnetizing effect.
A three-phase induction motor operates at a slip of 3% and has a rotor copper loss of 300W. The rotational loss is 1500W. Determine (a) the airgap power and (b) the power output.