3-B] PREDETERMINATION. 97 



APPENDIX II. 

 OTHER METHODS. 



50. There are a number of methods for determining the regula- 

 tion and characteristics of alternators which are essentially modifi- 

 cations of the electromotive force and magnetomotive force methods, 

 or a combination of the two; these methods are based on test data 

 alone (obtained from open-circuit and short-circuit tests, 9), on 

 design data alone, or partly on design and partly on test data. 

 Methods based on design data are of particular interest to the design- 

 ing engineer but cannot be taken up here; they include methods for 

 calculating armature reaction and reactance and for predetermining 

 the behavior of a machine before its construction. (For further dis- 

 cussion, see references, 55.) 



In all methods use is made of the fundamental principles brought 

 out in the electromotive force and magnetomotive force methods, 

 which should therefore be carefully studied before other methods are 

 undertaken. For those whose object is a general understanding of 

 the behavior of alternators, a study of these two methods is sufficient ; 

 but those who desire to pursue the subject further should consult 

 the references in 55. It has been pointed out that, so far as results 

 are concerned, these two methods give the pessimistic and optimistic 

 limits. Other methods give intermediate, and in some cases more 

 correct results; there is, however, no one absolutely correct method. 

 In reference to this, Mr. Behrend says : 



" It appears wise to admit the existing dilemma. The question of accu- 

 rately determining the regulation of alternators can not be solved. . . . 

 It seems to the speaker far more dignified and more in accordance with 

 the science that we are working in, to say that this case is so complex, so 

 intricate, there are so many factors to be taken into account, that it can no 

 more be solved than you can sfate to one thousandth of an inch the dis- 

 tance between two chalk marks drawn on the floor." (A. I. E. E., Vol. 

 XXIII., p. 326.) 



51. Test Methods. The aim in various methods is to test the 

 alternator under real or equivalent load conditions with only a small 

 expenditure of power. The machine may be actually loaded and the 

 power returned by some opposition method (27, 27a, Exp. 2-B), 

 or it may be tested without any load by simulating working load 

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