Circle diagram Circle diagram First conceived by A. Heyland in 1894 and B.A. Behrend in 1895, the circle diagram is the graphical representation of the performance of the electrical machine drawn in terms of the locus of the machine's input voltage and current. The circle diagram can be drawn for alternators, synchronous motors, transformers, induction motors. The Heyland diagram is an approximate representation of circle diagram applied to induction motors, which assumes that stator input voltage, rotor resistance and rotor reactance are constant and stator resistance and core loss are zero. Another common circle diagram form is as described in the two
Dividing a circle into areas of regions can also be determined in a non-inductive way, using the formula for the Euler characteristic of a connected planar graph (viewed here as a graph embedded in the 2-sphere S). A planar graph determines a cell decomposition of the plane with "F" faces (2-dimensional cells), "E" edges (1-dimensional cells) and "V" vertices (0-dimensional cells). As the graph is connected, the Euler relation for the 2-dimensional sphere S holds. View the diagram (the circle together with all the chords) above as a planar graph. If the general formulas for "V" and "E" can both be found, the formula for