Linear synchronous motor propelled hoists for mining applications

The idea of using linear synchronous motors (LSMs) to propel ropeless elevators is extended to the South African mining industry, where ultra-deep shafts are to be sunk to mine at depth of 4000 m and greater. A small prototype is designed and constructed to test the feasibility of the proposed hoisting system, and a position and speed control algorithm is implemented to show that accurate control of the lift cage (or mover) can be achieved. Stringent safety requirements have to be met, particularly in the event of a power failure. Thus, the model is used to demonstrate the fact that if an interruption occurs in the electrical supply, the dynamic braking characteristics of the system can control the falling mover. The vertical thrust force is calculated using the finite element method (FEM) and compared to measured values. The results of this study show that a linear synchronous motor propelled hoist is both a feasible and safe option for ultra-deep level mining applications.