All General Electric transformers of over 50 Kw. capacity are built at Schenectady in Building No. 84, one of the newest and largest shops (160 feet x 855 feet), devoted to transformer manufacture.
[Photo: Main Floor of Transformer Building: original size (34K) | 4x enlarged (110K)]
In this department, the de-centralization plan is adopted; that is, instead of depending on the central engineering, drafting and production offices and on the other factories for manufacturing and shipping, the whole organization is contained within the one building. Moreover, all transformer parts, except the castings and punchings, are made in the building.
A spacious storage yard for castings, covered by a 20-ton gantry crane, adjoins the building. The engineering office, in the front end of the second story, receives an order from the general office and then proceeds with the work independently, except for necessary conferences with other departments. Adjoining are the drafting room, the offices of the shop foremen, the production clerks and cost clerks, and a stock room for insulations and copper.
Every department of the building is equipped to co-operate in turning out the immense output of 70,000 to 80,000 Kw. per month in units ranging from 50 to 3000 Kw. The great aim of the organization is to simplify the work from engineering to shipment, dividing responsibility as little as possible and preserving the closest relations throughout. A 4" pneumatic tube will shortly be installed to the central office building.
The factory portion of the second floor is devoted to the winding of coils, which is done exclusively by machines with individual motor drive. The abundant light and the absence of any belting or shafting are noteworthy. Nearly all winding is done on forms rather than directly on the transformer cores. The application of varnished wrappings to high potential portions is done by hand in a small building adjacent, to avoid fire risk.
Beyond the winding machines are appliances for clamping the finished coils into compact form for treatment with insulating compound by the interesting "Vacuum Drying and Compound Filling Process." This is done in a fireproof annex building. All ovens are heated by steam, ventilated by electric blowers, and equipped with recording thermometers, and special doors for saving time and heat. Many coils are subjected to over 30 successive coats of varnish, and it is therefore important to provide facilities for hastening the process of drying. The insulated coils are held ready for assembly in a large storeroom with racks.
For shell type transformers the coils are stacked up with special insulating diaphragms between the high and low potential sections and built into a finished structure ready to be assembled within the iron core, which is finally mounted in the lower casting that is to support the transformer. The sheet iron that forms the core is then assembled and pressed together by the aid of two large hydraulic presses and the cap bolted in place.
Self-cooling transformers are enclosed in oil-filled cast-iron cases having corrugated surfaces of very large area for their size. These are difficult castings to make, especially in the larger sizes, some of which weigh over 12,000 pounds; but they are much superior to the customary thin sheet iron tanks with soldered seams, which are liable to leak. Oil-immersed transformers designed for cooling by water circulation are enclosed in heavy boiler plate tanks with cast iron bases. In high voltage transformers, this tank and cover make an air-tight joint which permits the air to be exhausted as an aid in thoroughly removing moisture without having to unduly heat the windings. Transformers cooled by "air blast" are enclosed in open top and bottom frames connected by sheet iron casing, the transformers being designed to be placed over a duct or chamber furnishing fresh air. The top of the case contains a sliding damper.
[Engraving: 50 Kw., 100,000 Volt, Type H Transformer: original size (8K) | 4x enlarged (25K)]
Under the gallery at the front end of the building is a space devoted to the assembly of starting compensators used with nearly all General Electric Form K induction motors, and having a function analogous to that of the starting resistance of a direct current motor. In addition to transformers and compensators, several forms of feeder regulators are built in this department and may be seen in various stages of completion.
[Engraving: "X-Ray" View of 2000 Kw. Water Cooled Oil Transformer; 60,000, 50,000 or 40,000 Volts Primary, 3800, 4000, or 4200 Volts Secondary: original size (10K) | 4x enlarged (32K)]
The entire product of the Transformer Department is tested in the same building and a large amount of floor space is set aside for this purpose. The cement floor for oil transformer tests is sunk slightly below the main floor, and that for air blast transformers contains large chambers with blowers for supplying air at varying pressures. All tests under load are made by the "motor-generator method," the power furnished being only sufficient to supply the losses of the apparatus under test. High voltage transformers for testing insulation are provided, including one large transformer capable of producing 500,000 volts.
After the transformers have been tested and the results approved by the Engineering Department, they are packed for shipment in the large Shipping Department on the main floor. Standard gauge tracks and three large traveling cranes, including one of 50-ton capacity, facilitate handling in manufacture and shipment.
Maintaining the proper standard of excellence in an insulating oil is very important in building large high voltage transformers. Traces of moisture, hard to keep out, will reduce its insulating qualities fifty or even ninety per cent. At the Transformer Department, oil that passes the tests is stored in steel tanks in the adjacent oil house, whence it is piped direct to the Testing Department as needed, to be returned when tests are complete. Oil for extra high voltage insulation is specially treated by a patented drying process.
Among the largest sizes of transformers we may mention those supplied to the power transmission plant "Puyallup River in Pierce County to Tacoma, Seattle, Wash." The insulation includes eighteen transformers rated at 2333 Kw. but standing without excessive temperature rise 25% overload, or 2916 Kw. They are used with a primary voltage of 2300 volts and supply high tension of 22,500 to 55,000 volts. The height is 12 feet 3 inches, and the weight of each transformer is 37,650 pounds without oil. In this transformer the oil transfers the heat developed to a water cooling coil placed in the top of the case.
[Engraving: Nine different sizes of transformers: original size (7K) | 9x enlarged (48K)]
