A three-phase star-connected alternator delivers at rated load a current 1= 200 A under a voltage of 5 kV-50 Hz (between phases). The load is inductive of power factor equal to 0.87, the resistance of each stator winding is 0.252 and the speed of the Cotor is n = 750 r.p.m. The sum of the constants losses and the stator Joule's losses and the rotor Joule's losses is 55 kW. The no load test, at rated frequency, gave: E-4200 V (between phases) for an excitation current lexc = 40 A. The short-circuit test, for an excitation current lexe = 40 A, gave a short-circuit current in the stator windings Isc =2.5 kA. 1- Calculate the numbers of poles of the alternator. 2- Calculate the synchronous reactance (X₁). 3- Calculate the electromotive force of the alternator (E) between phases for the same excitation current. 4- Calculate the power absorbed by the alternator (P₂).

A three-phase star-connected alternator delivers at rated load a current 1= 200 A under a voltage of 5 kV-50 Hz (between phases). The load is inductive of power factor equal to 0.87, the resistance of each stator winding is 0.252 and the speed of the Cotor is n = 750 r.p.m. The sum of the constants losses and the stator Joule's losses and the rotor Joule's losses is 55 kW. The no load test, at rated frequency, gave: E-4200 V (between phases) for an excitation current lexc = 40 A. The short-circuit test, for an excitation current lexe = 40 A, gave a short-circuit current in the stator windings Isc =2.5 kA. 1- Calculate the numbers of poles of the alternator. 2- Calculate the synchronous reactance (X₁). 3- Calculate the electromotive force of the alternator (E) between phases for the same excitation current. 4- Calculate the power absorbed by the alternator (P₂).

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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Question

A three-phase star-connected alternator delivers at rated load a current I = 200 A under a voltage of 5 kV-50 Hz (between
phases). The load is inductive of power factor equal to 0.87, the resistance of each stator winding is 0.292 and the speed of the
rotor is n = 750 r.p.m.
The sum of the constants losses and the stator Joule's losses and the rotor Joule's losses is 55 kW.
The no load test, at rated frequency, gave: E-4200 V (between phases) for an excitation current lexc = 40 A.
The short-circuit test, for an excitation current lexc = 40 A, gave a short-circuit current in the stator windings Ise =2.5 kA.
1- Calculate the numbers of poles of the alternator.
2- Calculate the synchronous reactance (X).
3- Calculate the electromotive force of the alternator (E) between phases for the same excitation current.
4- Calculate the power absorbed by the alternator (Pa).

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