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Early Western Electric Bell Laboratories

Transformer Coil & Core Papers

     Many early Western Electric & Bell Laboratory technical papers have been placed in the public domain. The papers that are posted on this page are available in public domain at various web archives (Google etc.). Unfortunately these papers are usually buried inside old technical journals or symposium books and are very hard to find, especially when you're not sure what to look for. The scans at those sites also tend to leave much to be desired. Presented here are good scans of original early Bell Labs papers on coil winding and transformer engineering. This collection will be added to as time permits. These papers will also include Bell magnetic metal papers as those are very revealing regarding the metal composition of mythical Western transformer iron. Downloading and linking is welcomed but please don't post these scans on another site.

Western Electric transformers from the early to mid 1900's are the stuff of legends. Some WE tube amplifier input and output transformers sell today on the used markets for prices that are more fitting for an entire automobile. The prices seem to reflect the notion that these early transformers could never be duplicated. While it certainly could be argued that WE wrote the book on coil & core design during that period, it's not as if the book has been lost. Western Electric was very meticulous about documenting their processes and thanks to their technical journals and other publications, many of these processes can be uncovered. Such is the case with WE transformer core metal. In a number of papers appearing in the Bell Technical Journals during the early and mid 1900's, Bell Labs authors reveal exact core metal alloy formulations, how small quantities are prepared in the laboratory, and, most importantly, heat treatment for various applications. According to WE engineers annealing is the single most important factor for determining the final magnetic characteristics of the transformer core material. These papers not only contain the alloy formulations, they also explain in detail how the engineers perfected the protocols they finally arrived at. In other words one of the most important lessons in these papers is the methodology. The original Western Electric core formulations can be reproduced today and all of the info needed is sitting in those journals. Enjoy!

Permalloy, A New Magnetic Material of Very High Permeability
by H. D. Arnold and G. W. Elmen
This paper is one of the most important papers in the audio transformer world. Today FeNi alloys are common in the audio industry and this paper is the reason. Exact alloy formulations are discussed as are the annealing procedures and how those procedures were arrived at. Many Western Electric transformers from the golden era of the 30's & 40's used these alloys.

Magnetic Alloys of Iron, Nickel, and Cobalt by G. W. Elmen
Another very important paper discussing communication alloys and procedures for preparing small quantities. Today transformer manufacturers speak of these alloys as being state of the art. They were, in the 1930's!! Heat treatment variations are described in detail.

Factors Affecting Magnetic Quality by R. M. Bozorth
Bozorth actually did write the book on electromagnetic theory. "Ferromagnetism" is part of the Western Electric, Bell Laboratories engineering series. This paper has excerpts from that book. The paper discusses how to produce small quantities of magnetic core material in the lab and the processes Bell used to develop application specific heat treatments. The annealing information in this short paper is an absolute must read for anyone interested in the fine points of audio transformer engineering.

Note: I highly recommend "Ferromagnetism" to anyone seriously interested
in audio transformer engineering.

The Ajax Northrup Induction Furnace
used for small samples.

Heat Treatment of Magnetic Materials in a Magnetic Field
by Joy F. Dillinger and Richard M. Bozorth
This is very deep two part paper and is worth reading several times.

Compressed Powdered Molybdenum Permalloy for High Quality Induction Coils
by V. E. Legg and F. J. Given
VintageWindings Pultec style inductors use MPM cores. This paper explains why.

The Moly-Permalloy Core by J. P. McKune
Another paper describing the incredibly important MPM core.

Study of Magnetic Losses at Low Flux Densities in Permalloy Sheet
by W. B. Ellwood and V. E. Legg
The study of Permalloy sheets, the type used for lamination stamping. This is a very informative paper.

Manufacture of Tape Toroidal Cores by A. C. Cowen
This paper was given at a Western Electric Coil Conference (more papers from that conference below). This paper describes the process that WE used to make the cores from their loading and line coils (111C).

These Western Electric audio transformer papers came from the late 1920's to the 40's. Many audio enthusiasts consider the transformers that were produced by WE during this era to be gifts from the gods. Most of the audio transformer engineering that has occurred since that time is based on these works.

Improvements in Communication Transformers by A. G. Ganz and A. G. Laird 1936
More Western Electric audio transformer engineering practices from 1936. This is right around the time of the 618's etc.

Telephone Transformers by W. L. Casper
This is an excellent paper describing WE design practices for designing audio transformers in varying applications. This is an excellent treatise on the compromises that must be made in the design process in order to bring a design to manufacture.

Permalloy in Audio Transformers by E. L. Schwartz
This paper appeared in the April 1928 issue of the Bell Laboratories Record. The title says it all and the era is just right. The articles in the Record were not as detailed as the ones appearing in the Journal but the info is excellent just the same. This paper is very hard to find.

The Evolution of the Input Transformer by F. E. Field
Covering audio transformers from the very beginning, this great paper details the who's and how's of early audio transformer evolution. The names of early WE transformer pioneers are revealed here. This is another very hard to find paper.

Magnetic Shielding of Transformers at Audio Frequencies by W. G. Gustafson
Western Electric transformer shielding practices from about the same time of the 618a. This was a landmark paper on the subject.
This group of papers is from a Western Electric Interworks Coil Conference conducted at the Merrimack Valley Works June 2, 3, 1964. The conference took place just as the control of winding machines was being automated and WE was at the forefront of those efforts. These papers are very interesting because they are a snapshot of the coil winding processes WE had perfected up to that time.

Coil Studies at Princeton by J. S. Cartwright
This paper covers a joint project between Western Electric and Princeton University where a Meteor 301 was modified to full automation. We're talking taping and everything. Many drawings and photos are included.

Manufacture of Fine Gage Enameled Wire at Buffalo by C. L. Erickson
This paper has everything you wanted to know about how the magnet wire that WE used in their audio components was manufactured. The type of coatings and how they were applied are fully discussed. There are fantastic photos in this paper!

Western Electric Wire Plant Buffalo, NY 1950's
Western Electric Wire Plant Buffalo, NY 1950's

The Classification of Film Coated Magnet Wire
by E. H. Brink
Discusses enamel and other coatings for magnet wire.

Improvements in Inductor Q Through the Use of Sectionalized Spool Windings
by W. L. McIsaac
A very informative paper detailing the technical side of inductor Q.

Coil Winding Tension as it Applies to Wire Spring Relay and Other Filled Type Coils
by Clair C. Poulson
This paper has excellent empirical data regarding wire tension and it's effect on a coil. This is a must read for any transformer winding personnel.



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