General Electric Co. v. Wagner Electric Mfg. Co.

• Decision Date: 05 May 1904
• Docket Number: 105.
• Citation: 130 F. 772
• Parties: GENERAL ELECTRIC CO. v. WAGNER ELECTRIC MFG. CO. et al.
• Court: U.S. Court of Appeals — Second Circuit

130 F. 772

GENERAL ELECTRIC CO. v. WAGNER ELECTRIC MFG. CO. et al.

No. 105.

United States Court of Appeals, Second Circuit.

May 5, 1904

Appeal from the Circuit Court of the United States for the Southern District of New York.

James H. Bryson, for appellants.

Thomas B. Kerr, for appellee.

Before LACOMBE, TOWNSEND, and COXE, Circuit Judges.

TOWNSEND Circuit Judge.

The patent in suit relates to transformers with a voltage of twenty to thirty thousand volts. Its objects, as stated by the patentee, are 'to so arrange the energizing coils that they are well insulated from the surrounding core and from each other, at the same time providing suitable means for ventilation,' and 'to provide a transformer having two complete and separately controlled systems of cooling, one being for the coils and the other for the laminated core. ' The only issue herein is anticipation.

The patented transformer comprises an outer inclosing case mounted on a base provided with a chamber open at the bottom for the admission of air or other insulating medium. Within the said case, are primary and secondary coils, vertically placed, and the laminated core, horizontally placed, and divided into sections separated by passages through which the insulated and cooling medium can flow. The fundamental principle of construction consists in so inclosing the coils and their ventilating passages in an inner inclosing case, extending from a point at a considerable distance above the coils to a point equally below the coils, as to insure complete electrical and mechanical insulation of the core, and its ventilating system from the coils, and adapt it to independent regulation. It further consists in insulating the primary coils from the secondary coils and providing ventilating spaces between and around the coils in such a way as to materially reduce the quantity of heat inclosing wrappings and still preserve sufficient electrical insulation. It is sufficient for the purpose of this inquiry to say that the patentee substituted for the large quantity of insulating covering required by the prior art a small amount of such mechanical insulation, and also ventilating air spaces, and thereby overcame the objections of overheating attendant upon the use of insulating material alone. One current of air enters at the base, passes up through the vertical passages between the coils; another current passes up at the side, and through the horizontal passages between the laminations of the core, and to the outside of the case. 'It will be seen that there are two separate ventilating systems for cooling the transformer, one for the coils, the other for the iron, and that each of them is controlled independently of the other.'

The claim of complainant as to the prior art, and the nature of the patented improvement thereon, is shown by the following extract from the deposition of the patentee, Moody:

'The arrangement differs from the earlier forms on which our experiments above mentioned were made, and in accordance with which our first two or three years' commercial production was carried out, in that there is no connection between the spaces between the coils and the spaces between the sections of the iron. We found it necessary to adopt this arrangement for the following reasons: I am referring to transformers would for quite high potentials, say from 10,000 to 40,000 volts. To insulate such potentials with the best-known insulating materials, one must have a considerable thickness of insulation-- so great a thickness as to greatly retard the dissipation of the heat from the windings if the insulation is wrapped upon the coil itself. Having found this to be so, we attempted to arrange a considerable portion of the insulation exterior to the coils. This was at first accomplished by the use of various forms of spacing strips, which held the coils some distance from each other and from the iron; also by the use of sheets of solid insulation placed between the coils.

'As we attempted to design for higher and higher potentials however, we soon found that, in an air-cooled transformer at least, this construction soon reached its limit, due to the fact that the surfaces on which is dusty and dirty is a very poor insulator. For instance, such a surface under a strain of 20,000 volts might break down when the distance between the parts between which such difference of potential existed was 8 or 10 inches.

'In the form in which we originally arranged our cooling ducts, the air first passed through a section of the iron core, then through one side of the coils, then to the center of the core, next through the other side of the coils, and finally escaped through the outer section of the core on the opposite side from where it entered. We had therefore four places between the coils and the iron in which it was necessary to have insulating spacing strips, and the width of these strips had to be sufficient to stand the pressure against which they were supposed to insulate, and then the spacing strips were dirty. In other words, if we were building a 20,000 volt transformer, and expected the insulation on the coils to take one-half of the total strain, the dirty spacing strips must take the remaining 10,000 volt strain. For this a distance of three inches might, perhaps, be necessary; consequently six inches of the space available for winding within the transformer's iron core was sacrificed for insulation.

'Due to these facts, we found it commercially impossible to design transformers along such lines, and intended for air cooling, for potentials much above 10,000 volts. I began to see that it was necessary that we should have nothing but solid and continuous insulation between the winding and the iron core and between the high-pressure winding and the low-pressure winding, and consequently that all openings for the entrance and exit of the air must be outside of the transformer's core, where the necessary projections could be made of the solid insulation to obtain safe distances against the leakage of the current, without increasing in any way the dimensions of the coils or core in order to give space for such insulation.

'The arrangement as shown in the patent is the outcome of this thought. In it we have a construction where high potential coils are completely incased in a solid insulating box, separated from the coils by the necessary air passages, and projecting beyond the core at either end a sufficient distance to safely allow of the opening of the box for the entrance and egress of the air. The cooling of the iron is taken care of separately, and solid insulations completely separate the windings as a whole from the iron core.'

The claims in suit are as follows:

'(4) In a transformer, the combination of primary and secondary windings with passages extending between the windings for the circulation of a cooling medium, and a laminated iron core with a second set of passages, through which circulates an insulating cooling medium, said sets of passages forming independent cooling and ventilating systems, one for the coils and one for the core.

'(5) In a transformer, the combination of primary and secondary windings, a laminated iron core, passages extending between the windings through which an insulating medium circulates to cool the windings, a second set of passages extending through the iron core, independent of the first, in which an insulating medium circulates to cool the iron,...