Variable-voltage equipment for electric power shovels

ALTHOUGH the power shovel was developed and brought to a high state of perfection by using steam as a motive power, a constantly increasing number of power shovels is being supplied for electrical operation. These electric power shovels are being used for all sorts of work although they are in particular favor for projects of a permanent nature or for those requiring a considerable period for completion. In some cases the electric power shovel has been adopted when starting these projects, or in other cases it has replaced the steam power shovel because of its superior operating economies. This process of replacement is very active at the present time in connection with open-pit copper and open-pit iron mines. Other extensive uses for electric power shovels are found in “strip” coal mines, quarries with output used in crushed form (such as for blast-furnace purposes), road materials, cement manufacturing steel plants for rehandling ore and slag, and contract work on dams, canals, tunnels, etc.