Electrical control of a large mine hoist

The most serious problem encountered in the application of electric drive to large mine hoists is that of electrical control. It is necessary, in order to secure continued successful operation of an electric hoist, to furnish a control system which is absolutely reliable at all times. The design must be such that all parts of the apparatus will withstand the most severe, and even unreasonable, conditions of service without giving trouble and without repeated attention and repairs. It should be so designed that it is impossible for the operator to damage the controller or any part of the machinery by a wrong movement of the operating handle or by misjudgment of conditions.