When were power transformers made with less materials, thus decreasing their performance, to save money?

I was told that there was a period of time when power transformers were made with less copper to cut back on manufacturing costs but in doing so the transformers were made less efficient. There was also a time when transformers were made with an excess of copper making them very efficient. Does anyone know where I can find information on this timeline or at least tell me when transformers were made best and worst, excluding the most up-to-date transformers.



ThanksWhen were power transformers made with less materials, thus decreasing their performance, to save money?Sorry I can't really help you with anything authoritative but then neither, it would appear, can anyone else.



A general cutting down on material use at the expense of performance sounds like a wartime measure due to acute material shortages and transport difficulty. So I'd estimate the "less copper" phase was from 1939 to 1945 with gradually thereafter a return to normal. I doubt if there was ever a time of intentional excess material use although in the early days of engineering things were certainly "built to last", probably because design knowledge and calculation accuracy were not there and generous factors of safety were used. For example it was only in the 1930s that creep was fully investigated.