No abstract

The Need for the New Ever since 1935, when their development was announced by Westinghouse, dry-type power transformers have become increasingly important in the distribution of electric power. From the common beginning of ventilated dry-type transformers, there has evolved a wide variety of related !ines of equipment. The best known of these is the open dry-type transformer, which uses class B and C solid insulations along with ambient air as the coolant. Related to these ventilated units are sealed dry-type transformers which use class H insulations and nitrogen as the coolant. Also related are the ventilated class H units which have become more common during the past few years.All these types of equipment have such good customer acceptance that it is quite Jogical to try to extend their voltage and KVA ratings beyoud the limitations imposed by gases and insulations used at present. Therefore, transformer manufacturers are expending a great deal of time and efforts to develop transformers using new gases, new insulations and new methods ( encapsulations, potting, molding) of manufacture, in order to improve the performance and the economics of their designs and to broaden their markets.At the same time, insulation suppliers have developed a staggering array of new matcrials which may be suitable for this very attractive transformer insulation market.Both the suppliers and users of dry-type transformer insulation recognize that until the new matcrials are accepted and properly used by the designer, neither will benefit from their development.Why, then, do the designers of these dry-type and glass-filled transformers appear reluctant to fully accept the new matcrials that they so obviously want?The Designer's DilemmaTo understand this apparent reluctance on the part of the transformer designer, the insulation supplier must recognize the problerns of the designer. First of all, the designer has a conservative customer who expects and plans for about twenty years of service from dry-type transformers. Second, the designer now furnishes equipment that has compiled an enviable service record over the past twenty-five years with relatively few failures, with no explosions, and with no fires. Therefore, he is not prone to change unless he is convineed that he can better his design's performance or economics. In addition, he must be convineed that he can convinee his enstomers of these improvements.The jailure to convince the designer is due entirely to the lack of communication between the insulation supplier and the designer. This is not saying that there is a Jack of articles, advertisements, papers and technica! data; rather there is a super-abundance of them. But most of them have one common fault-a Jack of data technica! papers specific enough to be used by the designer. This Jack of specific information must be recognized by the suppliers who want the business of furnishing insulations to manufacturers of dry-type transformers; these suppliers must find a way past this void of missing information.Consicier the pr...