Notes from Research Division, Electrical Engineering Department, Massachusetts Institute of Technology

• Publisher: Elsevier Science
• Year: 1917
• Tongue: English
• Weight: 172 KB
• Volume: 183
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/s0016-0032(17)91052-x

✦ Synopsis

This research is a continuation and extension of preceding M. I. T. researches on skin effect already published.

The research deals with straight loops of copper conductor, the two sides of the loop being parallel, one being the outgoing and the other the return conductor. The source of alternating currents was an Alexanderson high-frequency alternator. The testing current in the loops of conductor was ordinarily 2 or 3 amperes. The testing frequencies ranged from 5000 to roo,ooo cycles per second. The conductors included simple round copper wires, copper stranded cords, and copper strips. Two concordant methods of testing were employe~. The preferred method involved a particular type of inductive bridge, with the parts fastened on the testing table. The observer had to maintain a constant position at this table during the tests; but, with this precaution taken, metallic shields or enclosures for the testing apparatus were not found requisite. The details of the apparatus are recorded in the paper.

It was found that the skin-effect resistance ratio--i.e., the ratio of a.-c. to d.-c. effective resistance of round copper wires-conformed to the standard Heaxiside-Kelvin Bessel-function formulas within the limits of experimental error. There seems to be 11o reason why this conformity should not exist up to Ioo,ooo cycles per second; but .at least there is satisfaction in arriving at the experimental check.

The resistance ratio of a strand of seven bare copper wires,