Abstract :
There are many engineering problems which can be solved step by step, and there are others which contain two or more inter-dependent unknown quantities and therefore cannot be solved step by step. For example, the diameter of a short transmission shaft, mainly subjected to torsion, can be computed directly for a desired shearing stress; then the pulley can be designed, the belt for the pulley, etc. This is a step-by-step solution. On the other hand, let it be required to determine the diameter D and the length L of a cylindrical tank, to hold a given quantity of liquid and to possess a given cooling surface. This problem either requires two simultaneous equations for D and L, or else has to be solved by trials. The problem of determining theoretically the internal voltage drop and voltage regulation of a given synchronous generator at a given load is one of the second kind, that is, several conditions must be satisfied simultaneously. The problem of predetermining the armature current and the power factor of a given synchronous motor at a given excitation and load is of a similar nature. The purpose of the kinematic device described in the paper is to enable one to solve these two problems on synchronous machines mechanically, almost without any mathematics and without constructing vector diagrams.
