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
Woman in Blue Reading a Letter day. Although the woman's loose clothing may be suggestive, pregnancy was very rarely depicted in art during this period. While the contents of the letter are not depicted, the composition of the painting is revealing. The map of the Netherlands on the wall behind the woman has been interpreted as suggesting that the letter she reads was written by a traveling husband. Alternatively, the box of pearls barely visible on the table before the woman might suggest a lover as pearls are sometimes a symbol of vanity. The very action of letter-reading reflects a thematic pattern throughout Vermeer's works, as