Identifier: cyclopediaofappl04amer (find matches)
Title: Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc.
Year: 1916 (1910s)
Authors: American Technical Society
Subjects: Electric engineering
Publisher: Chicago : American Technical Society
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
CON/V£CT CAL/BffAT/NGV-OL TMfTEff B£TW££Ny^AfyDB. Li AfrAffATUS U/VDZ/f T£3T L^ WA Tf/f /?/-/£€3 TA T Fig. 187. Diagram of Connertions for Dielectric Strength Test with HighPotential Transformer The use of a water rheostat in series with the primary (lowvoltage) coil of the testing transformer, as shown in Fig. 187, forvarying the impressed voltage, is open to some objection. Such aresistance is liable to seriously affect the wave form of the electro-motive force, thereby causing its maximum value to bear a differentand unknown ratio to its effective value. The most approved wayof securing voltage control is by adjusting the field excitation of thealternator supplying the testing transformer with current. Anothermethod, though not as satisfactory, is by using a transformer witha variable ratio of primary to secondary turns. 202
Text Appearing After Image:
ALTERNATING-CURRENT MACHINERY 191 Tests of dielectric strength are made with voltages rangingfrom 11 to 10 times the rated terminal voltage of a piece of apparatus,according to the rated voltage and output of the apparatus. Forexample, a transformer of any output whose rated terminal vol-tage is 20,000 would, according to the recommendations of theAmerican Institute of Electrical Engineers, be tested with 40,000volts, whereas a 1,000-volt transformer would be tested wdth 3,500volts. An induction motor under 10 h. p. rated at 110 volts wouldbe tested with 1,000 volts. Break-Down. The break-down test is freouently applied in the

Note About Images