Apparatus for detecting axial displacements in power windings of electric induction machines

摘要

In an induction machine having power windings disposed coaxially about the iron core thereof, means for reducing an axial mechanical force produced in any given winding by the interaction of the radial components of leakage flux produced at a time of short-circuiting and an electric current flowing in the given winding at that time. The reducing means includes a plurality of loops mounted respectively at the ends of the given winding and adapted to link the radial components of leakage flux produced at the ends of the given winding at the short-circuiting to generate induced currents in said loops. These currents produce magnetic flux for cancelling the radial components of leakage flux, respectively. In order to equalize the quantities of the radial flux components having opposite directions at the given winding to each other to reduce the axial force, one or two search coils are mounted at the ends of the given winding so as to link the radial flux components, respectively and then the windings are axially relatively moved till the difference between the elctromotive forces induced in the search coils becomes zero. If the power windings include a winding of a relatively large radial width, or three or more in number, an auxiliary winding arrangement can be used in order to detect the axial displacements between the electromagnetic median planes of the power windings across the length axes thereof, which planes respectively have equal ampere-turns on either side thereof. The auxiliary winding arrangement is adapted to be disposed coaxially around the outermost power winding and which is adapted to be placed in electromagnetically coupled relationship to a given one of the power windings which is being excited, thereby to produce a magnetic flux having opposed radial components linking the search coils.