I think you're referring to Nikola Tesla, who did a lot of development work on AC machines. He often seems to be the "forgotten pioneer" in some electrical histories.
No, it was not Nikola Tesla i was thinking of, it was Karl Steinmetz.
See:
http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=Steinmetz&as_q=%22Alternating+Current%22
http://inventors.about.com/library/inventors/blsteinmetz.htm
