CHAPTER X 



PROCEDURE IN DESIGN OF D.C. GENERATOR- 

 NUMERICAL EXAMPLE 



61. Introductory. Since the procedure about to be followed 

 in working out a numerical example in dynamo design is not 

 likely to meet with the approval of every practical designer, it 

 is well to remember that an attempt is here made to base the 

 work on fundamental principles and show how these principles 

 may be applied in the detailed design of dynamo-electric 

 machinery. The method here presented is one that will yield 

 very satisfactory results when developing new types of machines, 

 or when no account need be taken of existing patterns or tools. 

 The practical designer is usually compelled to use stock frames 

 and armature punchings, and adapt these to the requirements 

 of the specification. He must effect some sort of compromise 

 between the ideal design and a design that will comply with 

 manufacturing conditions. In the method here followed, the 

 assumption is made that the designer is given a free hand to 

 produce a machine that shall, in all respects, be suitable for 

 the work it has to perform, and of which the cost and efficiency 

 shall be generally in accordance with present-day requirements. 

 The various steps in the electrical design of a D.C. generator will 

 be followed in logical sequence, and if the work appears unneces- 

 sarily detailed and drawn out, it must be remembered that 

 the method has an educational, apart from a practical, value; 

 it illustrates the application of theoretical principles to a con- 

 crete case, and shows how the practice of engineering is largely 

 a matter of scientific guesswork. The experienced designer will 

 be able to skip many of the intermediate steps here purposely 

 included; because he will be able to rely on the engineering judg- 

 ment he has acquired during years of practice in similar work. 

 The point that must never be lost sight of is that, when an engi- 

 neer makes a guess in respect to a dimension or any quantity 

 of doubtful or indeterminate value, he is always able to check 



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