Development of ultra — Low noise transformer technology

Strict limits of the revised Noise Ordinance of NY City require Power Transformers to have ultra — low levels at each of the frequencies of the transformer noise at full load and over-excitation. This paper describes the development of the technology that allowed successful design and production of Ultra — Low noise Power Transformers recently delivered to ConEd (Consolidated Edison) of NY City. The paper presents results achieved by this development effort in the areas of accurate calculation of core resonance frequencies, frequency spectrum of core noise, and load noise. It also presents other aspects of the technology development such as de — coupling of Active Parts vibrations from the tank, proper design of tank plate fields and tank bracing, proper transformer mounting techniques, and accurate measurement of low noise levels in the factory. Finally, the paper presents the difference in design of the generations of these transformers produced at different stages of this development effort.