PREFACE TO SECOND EDITION 



After using this book for four years as a text in teaching Elec- 

 trical Design at Purdue University, the writer believes that, 

 although few types of machines have been dealt with, no advan- 

 tage would be gained by introducing designs of other dynamo- 

 electric machines such as induction motors or rotary converters. 



The book is intended mainly for the use of students following 

 courses in Electrical Engineering, and since the application of 

 fundamental laws to the practical problems of the engineer can 

 be adequately illustrated by the few examples which have been 

 selected, there would appear to be no reason for adding new 

 material in the form of additional design problems. 



The revision covers many minor alterations which are mainly 

 corrections of errors which have crept into the first edition; but 

 the method of deriving the formula for the flux cat by the short- 

 circuited coil during commutation has been modified, and a new 

 treatment has also been introduced in connection with the arma- 

 ture m.m.f. in alternating current generators. Two or three new 

 cuts have been made to replace those in the first edition which 

 it was thought might be modified with advantage. 



PURDUE UNIVERSITY, IND., 

 January, 1921. 



