ELECTRICAL INDUSTRY — SMITH 205 



field where political threats and limitations have seriously curtailed 

 expansion and thus retarded the use of scientific developments di- 

 rectly in the generation and distribution of electricity. 



ELECTRICAL INDUSTRY DRAWS FROM ALL BASIC SCIENCES 



Contributions to the development and progress of the electrical 

 industry have come from practically every branch of the basic 

 sciences. This is not surprising when we consider the large variety 

 of materials used in the manufacture of electrical equipment. 



Metallurgy. — Improvement in electrical apparatus is largely de- 

 pendent on the improvement made in the properties of the materials 

 used. This applies to both physical and chemical properties of vari- 

 ous kinds. The limitations in physical properties of materials are 

 most likely to be encountered in high-speed rotating machinery such 

 as steam turbines, where centrifugal and steam forces are likely to be 

 large under conditions of high temperature, which in turn tends to 

 lower permissible stress limits. 



Research work done in recent years by both electrical and steel 

 manufacturers to determine and improve the fatigue, creep,^ cor- 

 rosion, and other physical properties of various alloy steels used 

 in highly stressed machines has resulted in such marked advances 

 in design that output ratings have been more than doubled at the 

 highest operating speed in less than 5 years. 



The electrical industry has also called on the metallurgist for new 

 and improved magnetic steels and alloys. Magnetic steel, particularly 

 electrical sheet steel, has been a subject of continued research by both 

 electrical and steel manufacturers. This has involved studies of 

 molecular and grain structures as well as of chemical compositions 

 and purity. This work has resulted in a steady decrease in iron 

 losses ® in the cores of transformers and machines of such magnitude 

 that they have been reduced by more than half in the last 20 years, 

 with a saving to the industry of millions of dollars annually. 



Until recently, the improvement in electrical sheet steel was con- 

 fined largely to iron losses. Practically no improvement in perme- 



' When a load or strain is applied to a structural member such a? a steel bar, the bar 

 elongates or stretches proportional to the load applied up to the elastic limit of the material. 

 For most practical applications, this elongation for a given stress is presumed to remain 

 fixed or constant. Actually, most materials will continue to elongate at a very slow rate 

 (in some cases over a period of years), even though the stress remains constant at a value 

 below its elastic limit. This property or characteristic of materials to slowly elongate 

 on a constant stress with time is commonly referred to as "creep." 



* In the iron cores of electrical devices, such as generators, motors, and transformers, 

 which either generate or receive alternating current, the magnetic flux is subject to 

 reversal at the same frequency as the generated or applied alternating current. This 

 reversal of magnetism produces a molecular friction loss inside the iron core which results 

 in an energy loss that appears in the form of heat. This energy loss is commonly referred 

 to as "iron loss." 



