Similitude in Design

Charts such as Fig. 63 show that ratings are related to size in an orderly sequence, provided that certain proportions between core dimensions are maintained. Figure 63 is for 60 cycles. If a transformer is desired for another frequency, its size may be estimated from Table VIII, provided that the same core proportions apply, and similar values of induction and temperature rise are used. If the new conditions are widely different, due allowance must be made for them or the estimate will not be accurate.

Table VIII and Figs. 63 and 71 are examples of similitude. If all variations between ratings are taken into account, similitude provides a very accurate basis for estimating new sizes; for the transformer designer there is no better basis for starting a new design.