Per-Unit Quantities

This paper discusses the use of per-unit quantities and their relation to dimensional analysis. It has been written at the request of the committee on education, and designed primarily for those interested in education, to serve as a background for discussion of the need which has arisen in the electrical engineering literature to translate new techniques into language readily understandable by students. The use of per-unit quantities in the current machinery literature, although invaluable to the practicing engineer who wishes to obtain as much similarity as possible in calculations of machines and transformers of various ratings, is confusing to the average student, largely because factors which have physical significance are divided out and dimensions which would aid him in recognizing the origin of the different terms in an equation disappear.