The universal power system: An evolution [History]

In the third decade of the 21st century, electrical power is taken for granted. We plug a hand drill into an outlet, just as confident that the system will supply power at the correct voltage and frequency as the electrician who hooks up a 500-hp dc motor. We don’t expect to have to hook up to a different system for every class of power that we need. This is a universal system, similar in concept to that of the open architecture computer bus, both of which we now take for granted—but of course, this was not always the case. In North America, the development of the power system can be seen as occurring in four stages.