Fluid circulating pump

Electrical apparatus comprising:

• a tank;
• a liquid dielectric disposed in said tank;
• a motor-pump unit for circulating said liquid dielectric within said tank, said motor-pump unit including a housing having a motor portion and a pump portion, said motor portion of the housing being in fluid communication with the liquid dielectric being circulated by the pump portion, to thereby cool and lubricate said motor portion;
• a rotatable metallic shaft extending between said motor portion and said pump portion;
• first and second sleeve bearings mounting said shaft for rotation in said housing;
• said first and second bearings being constructed of non-electrically conductive material;
• said first and second bearings each having a sleeve surface disposed radially adjacent to and in contact with the periphery of said shaft, and a thrust surface disposed at an angle relative to said sleeve surface which will accept thrust loads,
• first and second metallic thrust collars disposed on said shaft axially adjacent to said thrust surfaces of the first and second bearings, respectively;
• said first and second bearings including at least two recesses disposed in each of their sleeve and thrust surfaces;
• and detecting means for detecting bearing wear in both the radial and axial direction, including electrically conductive contact rings disposed in said recesses to effect an electrical connection between said contact rings through said shaft and said thrust collars upon a predetermined radial or axial displacement of the shaft in any direction due to wear of the first and second bearing's sleeve and thrust surfaces;
• said detecting means additionally including means electrically connecting said contact rings which is adapted for connection to protective apparatus.

A protected motor-pump unit for circulating liquid in a liquid-cooled electrical apparatus, including means for minimizing undesirable dislodging of contaminant particles into the circulating liquid by the motor-pump unit, comprising:

• a pump and an electrical motor having a common shaft and disposed in a common housing, the housing including liquid passages for allowing a portion of the liquid passing through the pump to cool the electrical motor, said shaft comprising electrically conductive material;
• bearing means comprising electrically non-conductive material and having at least first and second journal bearing surfaces providing support for the shaft in radial and axial directions, respectively;
• at least first, second, and third conductive annular members stationarily disposed respectively in said bearing surfaces, said annular members being recessed below the bearing surfaces by a predetermined wear-dimension;
• and
• electrical circuit means for detecting when the wear of the bearing means in either of the first and second journal bearing surfaces just exceeds said predetermined wear dimension, enabling the conductive shaft to selectively contact the first and second conductive annular members, said electrical circuit means comprising connections to said first and second annular members, said electrical circuit means being adapted for warning or tripping purposes.