Discussion on “application of electric motors to gold dredges” (Rosenblatt), Spokane, Wash., September 11, 1914. (see proceedings for August, 1914)

Ford W. Harris: The problems so clearly defined by Mr. Rosenblatt are, in general, those that confront any engineer proposing to equip rough heavy duty machinery with motors. As electrical engineers we are in duty bound to give electric power the benefit of every doubt when the expediency of a given installation is considered but that the application of motors to dredges, shovels, and the like, is a hard problem must be understood at the outset. It is primarily a problem of applying a constant speed, constant maximum torque motor, to be a variable speed, variable torque load. More particularly it is the application of a constant torque driving means to a variable torque load. We have the problem of a widely variable load that must be economically handled regardless of the speed. The operator wishes to operate the major portion of the time at constant speed with a fairly uniform load. At times this load is enormously increased and at times he desires to greatly reduce the speed for repairs, etc. In general as far as satisfactory operation is concerned the enormous pulls occasionally needed may be and preferably should be exerted at a low speed so that the actual power requirements may be fairly constant.