Induction motors are presently the most widespread kind of electric machinery used in industrial applications. In the engineering practice, it frequently happens that designers or final users have to roughly estimate the size, weight and some basic performance data of an induction motor based on few specification requirements such as its rated speed and power. This paper describes homothety as an effective answer to this problem. The main principles of homothety as an induction motor sizing approach are discussed and quantitative formulas are derived based on theoretical considerations. The homotetic laws are finally assessed considering a set of sample built four-pole machines (whose data are fully available). The assessment confirms homothety as an actually powerful approach for a first-attempt estimation of many motor data including size, weight, utilization factor, current density, electric loading, etc.
