Non-contaminating transformer oil pump, static arrester, and control circuit

Claim 1

A motor-pump unit for circulating a fluid, comprising: (a) a housing having a motor portion and a pump portion including a motor and a pump respectively; (b) a rotatable, electrically conductive shaft extending between the motor and the pump; (c) first and second sleeve bearings mounted on the shaft for rotation in the housing; (d) each bearing having a sleeve surface disposed radially adjacent to and in contact with the periphery of the shaft; (e) at least one of the bearings including the bearing constructed of non-electrically conductive material including a recess in the surface thereof; (f) detecting means for detecting bearing wear including an electrically conductive contact ring in the recess to effect an electrical connection between the contact ring through the shaft upon a predetermined displacement of the shaft due to wear of the bearing sleeve; (g) means electrically connecting the shaft to ground; (h) a ground source of electrical energy at a predetermined voltage and including electrical conductor means leading to the motor; (i) a circuit breaker in the electrical conductor means and comprising an actuating coil having a first end connected to ground and having another end; (j) a circuit leading from the grounded source of electrical energy to the electrically conductive contact ring; (k) the circuit including a circuit interrupter having a predetermined breakdown rating and including a branch conductor connected between the other end of the actuating coil and the downstream end of the circuit interrupter; whereby static electricity buildup is prevented on the moving parts of the motor portions and pump portions and a trip circuit is provided for the motor portions.