Abstract: A process and apparatus for preventing film stripping and grooving of a dynamoelectric machine commutator. The process is usable in either repairing or initially manufacturing a high-powered, high-speed dynamoelectric machine. In the process, extra-wide brushes and associated brush holders are mounted in place of conventional standard size brushes and brush holders in order to restrict variations in current unbalance between a plurality of electrically paralleled brushes to a range of 10 to 15% of rated full load brush current density in the brushes at rated load. A machine constructed according to the invention is made with a plurality of extra-wide brushes and brush holders, with no more than four brushes electrically connected in parallel on respective brush holder studs positioned in operating relationship around the commutator thereby to so restrict the permitted range of current density unbalance between brushes.

Abstract: An earth excavator including apparatus for stabilizing performance by compensating for changes in temperature. The apparatus includes a temperature compensating voltage regulator for regulating and controlling the output voltage of an exciting generator as a function of sensed temperature. The exciting generator supplies field excitation voltage and current to electric motors in the earth excavator. In order to maintain substantially constant current through the motor field windings with variations in temperature of the windings, and therefore to maintain the performance of the motors and thus of the excavator substantially constant with variations in temperature, the exciting generator output voltage is regulated in a manner such that the regulated voltage supplied by the exciting generator is a direct function of the temperature of the motor field windings. The output voltage of the exciting generator is controlled by controlling the average current through the exciting generator field winding.