Circle diagram constant air-gap induction motor images shown here, where, The circle diagram is drawn using the data obtained from no load and either short circuit or, in case of machines, blocked rotor tests by fitting a half-circle in points O and A. Beyond the error inherent in the constant air-gap assumption, the circle diagram introduces errors due to rotor reactance and rotor resistance variations caused by magnetic saturation and rotor frequency over the range from no-load to operating speed. Steinmetz equivalent circuit Circle diagram First conceived by A. Heyland in 1894 and B.A. Behrend in 1895, the circle diagram is the
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