Abstract: There is disclosed a direct current motor drive system comprising a direct current motor operable in a forward motoring mode receiving current from a power source and in a reverse inversion mode providing inversion current to the power source. The drive system includes a converter for controlling motor operation. The converter converts alternating current, received from the power source, to direct current. The converter supplies direct current across terminals of the motor when operating in the forward motoring mode. The system includes an inversion fault current limiter for limiting inversion fault currents associated with motor operation in the reverse inversion mode without effecting the supply of current to the motor in the forward motoring mode. The inversion fault current limiter is electrically connected in series between the converter and one armature terminal of the motor. The inversion fault limiter includes a diode switch connected in parallel with a resistor.

Abstract: A grinding mill such as an autogenous mill or ball mill, having a large driving gear driven by two motors, wherein a soft start capability is provided by a clutch or clutches, is "finger-printed" in relation to the reduction gear system in order to identify optimum conditions for locking up the drive to achieve substantially equal loading between the drive motors, and to diminish cyclic variations in loading between the motors.

Abstract: The self-adjusting limit switch assembly of this invention has two switches mounted on a slide for sliding movement on a bracket. A transverse slot in the slide has two facing surfaces. The switches are mounted on each side of the slot with their operating members extending slightly past the slot. The actuator is positioned to extend into the slot. When the brakes are first moved to the brake released position the actuator engages not only the operating member of the switch on that side, but also a wall of the slot and moves the slide to a brake released position thereby correctly adjusting the position of the switches. When the brakes require adjustment due to wear, the actuator engages the operating member of the second switch, as before, causing an indicator to function.