PREFACE TO THE SECOND EDITION. 



The preparation of this edition for the press has given the 

 author an opportunity to make good certain omissions in the 

 first edition and to include discussions of the induction motor, 

 the induction generator, frequency changers, the synchronous 

 motor, the synchronous converter, wave analysis and a selection 

 of special problems. In a restricted sense the book is now 

 complete. It is not exhaustive and has many short-comings, 

 but it is believed that the reader who has become familiar with 

 the principles of testing herein contained can proceed to conduct 

 such further tests as he desires and to manipulate and use new 

 types of apparatus without special instruction. 



In order to present the discussion of the circle diagram for an 

 induction motor with the utmost conciseness and clearness, the 

 graphical constructions for determining slip, efficiency and power 

 factor which are not essential to the understanding of the circle 

 diagram proper have been omitted from the main discussion 

 and placed in an appendix. For the same purpose, in the dis- 

 cussion of the theory of the synchronous motor (Experiment 

 IO-B), particular emphasis has been laid upon the essential 

 principles which govern the operation of the motor and matters 

 of secondary importance have been sub-ordinated. 



Although much has been written on the subject of wave 

 analysis, common experience has been that it is indeed a laborious 

 task to familiarize one's self with the usual methods and to use 

 them for accurately analyzing a wave. In an endeavor to elimi- 

 nate all unnecessary labor, the author has given explicit instruc- 

 tions for wave analysis that occupy only two pages (pp. 335-6), a 

 numerical example for determining the old harmonics up to the 

 seventeenth occupying two pages more. It is believed that this 



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