From my recollection my 4th year power systems engineering course, the reasoning for the choice of 60Hz was to minimize the losses incurred in the transformer cores (ie: magnetic heating of the iron, etc.) Apparently somebody did some math (and a lot of laboratory testing to demonstrate that the losses in transformation are at a minimum at approximately 57 Hz. This odd number got rounded up to 60 Hz by in North America. The Europeans, however, elected to go for the lower number because it reduced the speed of the generators required to produce the desired frequency. Ontario Hydro did remotor everyone's houses in a massive switch from 25Hz to 60 Hz many years ago. However, there is still (at least as of 15 years ago) an industrial 25Hz network in operation in parts of Ontario because the cost to convert for some industries was too great. 400 Hz was chosen as the frequency of choice for computer applications because the higher frequencies are easier to filter to pure DC. Tom -----Original Message----- From: Wayne Foletta To: PICLIST@MITVMA.MIT.EDU Date: Thursday 29 January 1998 20:22 Subject: Re: [OT] off topic AC Power |Ed: | |.... Don't recall the reason for 60Hz choice. |I'll find that history book tonight and let you know. | |- Wayne Foletta |BMI - Saratoga, CA |The Power of Quality |