Professor Goldsborough read the following paper:

TRANSFORMER ECONOMY

A great deal has been said and written about the static transformer of alternating currents, and yet we are only just beginning to understand this muchdiscussed piece of apparatus. The manufacturers have made it and experimented with it, the theorists have experimented with it and disputed over it, the underwriters have disputed over it and endured it, and the central-station men have endured it and made use of it to the great good and comfort of the public. No other piece of apparatus in the field of electrical engineering has been lauded higher or been the subject of greater abuse, and to all it has served a purpose. The transformer occupies a higher position to-day than ever before, and it grows in importance. as each new development in the field of applied electricity points out a new department of usefulness for it.

There has, however, been enough agitation lately on the part of manufacturers, in behalf of substituting new types of transformers for the old ones. now in use, and of relegating the small transformer to the scrap heap, to cause some unrest to the central-station men that are responsible for the successful operation of alternating-current generating plants. The foundations of many of these plants were laid before the time of skilled designers of electrical machinery, and at a period when the factory motto

was "cut and try." As the public demands increased, the plants developed and expanded before the practical men were amenable to "theories," and before the exact methods of the laboratory had become the daily practice of the constructing engineer. Managers see that engineers are still making mistakes, and that faulty design is still a factor in electrical development; and when they call to mind the enormous sums of money that have been spent in this country on illadvised improvements, it is not to be wondered at that they hesitate.

There is, however, a gradual change for the better in the number of the yearly contributions to the records of our electrical societies, and as these records are the expression of the best thoughts of the men. that have made America famous as the land of electricity, they may be taken as signs of the times in our department of engineering activity.

We are constantly impressed with the fact that the refinements of exact scientific methods are being made the subject of everyday discussion, and that the more difficult problems of the technical side of the profession are being so well elucidated by our "practical theorists" that it is possible for all of us to enjoy a concrete appreciation of electrical science without an excessive expenditure of mental energy on the theoretical. We are coming to a time when exact methods will be the universal rule and when the reputation of having a high "guessing factor" will no longer be a sufficient recommendation. These influences are noticeable in the improved electrical intelligence of our workmen, as well as of our station. engineers, and I find that it extends even to the general public. Indeed, a careful record of the number of times that I am asked, "How does the little

trolley wheel push the car along?" shows a yearly decrease of nearly fifty per cent. So we see that matters adjudged to be of slight importance a few years ago are being allotted their normal position. A fault is a fault at the present day, and is not often disregarded as "too small to be appreciable.” The old saying that "if you take care of the pennies, the dollars will take care of themselves" applies just as well to electrical engineering as it does to other professions, and it is the pennies that I am about to deal with.

Our principal manufacturing companies freely advertise and guarantee the specific economic performance of which each and every one of the transformers that they place upon the market is capable. They severally advertise to supply us with transformers equaling in efficiency, regulation (and what not), any other transformer that can be found upon the market. The manufacturing companies are unanimous in their guarantee of high efficiency, low core losses, negligible aging and close regulation. If we can purchase transformers freely on these representations, with sufficient guarantee that the specifications advertised are strictly conformed to or improved upon, there is little to be desired on the part of the purchaser over and above what is offered. Any slight improvement that it shall be possible to make upon the best of the performances advertised by the competing factories will be forthcoming in consequence of the rivalries of trade, and the purchaser need only seek now for means of protecting himself against occasional faulty manufacture.

When, therefore, we consider the perfection to which this type of apparatus has been brought, in its every detail, and in sizes varying in capacity from a

fraction of one to over eight hundred kilowatts, we have cause for congratulation. If you have followed the design and manufacture of the commercial transformer, I think you will admit that at the present time the best of them are figured just about as close as is possible; and, in fact, we have almost reached the point beyond which any further advance in the direction of improved efficiency must be made by getting better insulating materials, requiring less space and giving this space to the iron and copper.

With a view to investigating the present status of the transformer and the ability of transformer manufacturers to meet in all cases the exacting specifications which they have laid down for themselves, I have had a number of transformers of recent design tested in the Purdue laboratories within the last year. The results of these tests are especially gratifying when gauged from the standpoint of our present commercial requirements, and to the specialist a detailed statement of the results would be interesting. In view of the fact, however, that the electrical literature of the day contains numerous matter of this kind, I will not bore you with many figures, but will rather discuss the results in a general way.

With but one exception the transformers tested have surpassed the requirements of the specifications laid down by Professor Jackson in his excellent article on transformer testing, with which we are all familiar, and, generally speaking, they have conformed fairly closely to the published guarantees of the companies submitting the transformers for test. To what extent this is true may be better appreciated if I cite one or two examples.

A 2.5-kilowatt transformer was submitted for test, which was guaranteed to conform or improve

upon the following specifications: Core loss, fortyeight watts; regulation, 2.1 per cent, and full load efficiency, 96.1 per cent. The test of this transformer gave, core loss, 42.19 watts; regulation, 1.9 per cent; full load efficiency. 96 2 per cent. The showing made by this transformer is good. The core loss is 5.81 watts less than the stipulated value, and the efficiencies are in excess of the stipulated values. In this case the manufacturers more than substantiated their guarantee, and supplied a transformer that is a greater revenue producer than the specifications call for. If the core iron of this transformer can be relied upon as not materially increasing in its hysteretic loss with age, it is an easy matter to figure the money value of the excess economy that the transformer develops.

Suppose, for instance, a contract should be made for forty of these transformers at $30 each, to meet an increase in a station load of 100 kilowatts. On an all-day schedule these transformers would probably carry a commercial load equivalent to full load working for five hours. This assumption may seem to represent a better condition of service than is usually met with in practice, but it is an assumption that is fair to the manufacturer in considering the all-day efficiency. The transformers would therefore be working under no load for 6,935 hours and under full load for 1,825 hours per year, and under the conditions of the test would save 1,794 kilowatthours to the station. If we figure the cost of producing this power at two cents per kilowatt-hour, the saving per year would be $35.88 for the forty transformers, or practically three per per cent on the amount invested in the transformers. If this power were sold for six cents per kilowatt-hour, it would represent a net gain to the purchaser of $107.64 per