THE PRESIDENT:-Gentlemen, I would like to say a few words. I trust the INSTITUTE will do all that it can to further work of this character. I feel that in undertaking it the INSTITUTE is entering upon an era of usefulness greater even than the marked usefulness it has shown in the past. We certainly have in the AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS an exceedingly able body of men. We are competent to take up questions of this character and thoroughly deal with them. The Council urges on each and all of you the importance of this work. As to whether or not it will be successful depends of course entirely on the amount of intelligent effort which is put into it. If we all pull together and work in this matter we can do a great deal of good to that science of which we are so fond. It has been determined to make this distinctively INSTITUTE work, so that nobody will be asked to take part in the work who is not a member of the INSTITUTE.

I would like to say on behalf of the committee that I represent, that it will be pleased to receive suggestions from any members of the INSTITUTE, either as regards the method of carrying on this work, or the names of the parties to whom it would be proper to relegate it. The work will be apportioned somewhat in this way it is our idea to invite co-operation of every institute of learning, such as a college or university, or any institution that has a good working physical laboratory. Local sub-committees will be appointed to undertake experimental work to deter mine these quantities.

I take great pleasure in introducing to you Dr. Frederick Bedell, who will read a paper on "Hedgehog Transformer and Condensers."

American Institute of Electrical Engineers,
New York, October 18th, 1893. President
Houston in the chair.

HEDGEHOG TRANSFORMER AND CONDENSERS.

BY FREDERICK BEDELL, K. B. MILLER and G. f. wagner.

The transformer is an instrument which still continues to attract the attention of the scientist and of the engineer, and no method for its investigation and study is more interesting than the experimental method whereby the instantaneous changes in the periodically varying quantities are made known. We refer to the method of instantaneous contact. The transformer with an open magnetic circuit has been the subject of much controversy, and it is upon such a transformer that the following experiments were made. We have no intention, however, of reviving the question of "open versus closed magnetic circuit transformers," which received so much attention a few years ago.

In this investigation a modification of the method of instantaneous contact was applied to the study of an open-magneticcircuit transformer known as the "Hedgehog," experiments being made, first with the transformer under usual conditions, and then with condensers connected in parallel with the primary.

A large part of the credit for this work should be given to Prof. Ryan, who was interested in it from the start, and to whom we are indebted for valuable assistance throughout the investigation.

For convenience, we will divide the paper into three parts, describing: first, the apparatus and methods of measurement; second, the experiments with the transformer alone under the ordinary conditions of working on a 1,000-volt circuit; and third, the experiment in which condensers were shunted around the primary of the transformer.

PART I.

APPARATUS AND METHOD EMPLOYED.

For the complete analysis of alternating current phenomena, we should know not only the value of each changing quantity at every part of its period, but we should know the phase relations between the several varying quantities; that is, the relations between their respective zero and maximum values. To enable us to do this, the method of instantaneous contact has come into use, in which a revolving contact is made at a particular part of the period in such a way that we may ascertain the value at that particular instant of any of the varying quantities measured. This method is of historical as well as scientific interest, inasmuch as it was, originally devised simultaneously on each side of the Atlantic, and has since been modified and developed by many investigators.

An interesting account of the development of the method of instantaneous contact is given by Dr. Nichols in his address, as Vice-President, before the physical section of the American Association for the Adancement of Science, upon "The Phenomena of the Time-infinitesimal,"1 and a brief review may now be in place, previous to the description of the present modifica

tion.

2

In the year 1880, Joubert made use of the device in his study of the changes in potential of an alternating current dynamo and between the terminals of the Jablochkoff candle, and pointed out the use of the quadrant electrometer in alternating current measurement. In the same year B. F. Thomas, in this country, devised the method independently, and made use of a condenser and ballistic galvanometer. His paper before the American Association for the Advancement of Science that year was published by title only, and his experiments were unpublished until presented, by request, at a meeting of this INSTITUTE last year.

1. E. L. Nichols: Proceedings Am. Assoc. for the Adv. of Sc., Madison Meeting, vol. xlii., 1893.

2 Joubert: "Sur les Courants alternatifs et la force electromotive de l'arc electrique." Comptes Rendus, 91, p. 161, July 19, 1880.

3. Henry Morton and B. F. Thomas: "Observations on the Electromotive Forces of the Brush Dynamo-electric Machine." Proceedings A. A. A. S., vol. xxix., p. 277, 1880.

4. B. F. Thomas: "Notes on Wiping Contact Methods for Current and Poential Measurement." TRANSACTIONS, A. I. E. E., vol. ix., p. 263, 1892.

In 1888, the method was used by Duncan, Hutchinson and Wilkes,' who applied it to the study of induction coils and transformers, and obtained the first complete set of curves for this class of alternating current apparatus. In the same year it was used in France by Meylan, in a study of the vibratory call-bell of Abdank, and at Stevens Institute, in an investigation of the Westinghouse Alternator by Searing and Hoffman.3

Then followed its use by various investigators, Ryan and Merritt, Humphrey and Powell, Tobey and Walbridge, Marks, Herschel, Fortenbaugh and Sawyer, all of whom used it in the study of alternating current phenomena and have communicated their results before this INSTITUTE. Subsequently the method has been employed for different lines of investigation by Archibald and Teeple,10 Thompson," Ryan,"2 Hopkinson,18 and a modification has been used by Duncan1 in which simultaneous curves are rapidly obtained by the use of several dynamometers. This is the history of the method from its first use to the writing of this paper.

The features introduced in the method as employed in the present investigation are two; first, the use of a revolving contact-maker, in which the contact is made by a needle passing

1. Duncan, Hutchinson and Wilkes: "Experiments on Induction Coils." Electrical World, vol. xi., p. 160, 1888.

2. Meylan "Sur les Apples Magnetiques." La Lumière Électrique, vol. xxvii, p. 220, 1888.

3. Searing and Hoffman: "Variation of the Electromotive Force in the Armature of a Westinghouse Dynamo." Journal of the Franklin Institute, vol. 123, p. 93.

4. Ryan; "Transformers." TRANSACTIONS, vol. vii, p. 1. 1889.

44

5. Humphrey and Powell; Efficiency of Transformers." TRANSACTIONS, vol. vii, p. 311.

6. Tobey and Walbridge; "Investigation of the Stanley Alternate-current Arc Dynamo." TRANSACTIONS, vol. vii, p. 367.

7. Marks; TRANSACTIONS, Vol. vii, p. 324.

8. Herschel; TRANSACTIONS, vol. vii, p. 328.

9. Fortenbaugh and Sawyer; TRANSACTIONS, vol. vii, p. 334.

10. Nichols; On Alternating Electric Arc between a Ball and a Point." American Journal of Science, vol. xli, p. 1.

11. M. E. Thompson; "Study of an Open-coil Arc Dynamo." TRANSACTIONS, vol. viii, p. 375.

12. Ryan; "Relation of the Air Gap and the Shape of the Poles to the Performance of Dynamo-electric Machines." TRANSACTIONS, vol. viii, p. 451. 13. Hopkinson; "Dynamo Machinery and Allied Subjects," p. 187.

་་

14. Duncan; Note of some Experiments with Alternating Currents." TRANSACTIONS, vol. ix, p. 179.

through a water-jet; and, second, the use of a condenser to displace the zero of an electrostatic potential instrument, so that readings are taken at the best portion of the scale.

A general view of the revolving contact-maker is given in Fig. 1, and a detailed view in Fig. 2. The whole instrument is supported by a stationary frame F. The shaft s is connected to the

armature shaft of the dynamo by a coupling (not shown) on the end of the rod R, and carries the disk D, which revolves with it. The needle N projects from this disk and forms one of the elec trodes of the contact. The other electrode is a fine water-jet (not shown) issuing from the nozzle J, well insulated by hard rubber