Miksa Déri (27 October 1854 November, Bács, Kingdom of Hungary, (now: Bač, Serbia) – 3 March 1938) was a Hungarian electrical engineer, inventor, power plant builder. He contributed with his partners Károly Zipernowsky and Ottó Bláthy, in the development of the closed iron core transformer and the ZBD model. His other important invention was the constant voltage AC electrical generator in the Ganz Works in 1883. The missing link of a full Voltage sensitive - voltage intensive (VSVI) system was the reliable AC Constant Voltage generator. Therefore, the invention of the constant voltage generator at the Ganz Works had crucial role in the beginnings of the industrial scale AC power generating, because only these type of generators can produce a stated output voltage, regardless of the value o