Automation of mine hoisting with asynchronous drive at skips with bottom unloading

Abstract

Lift automation at skips with bottom unloading in the period of deceleration can be realized by application of dynamic braking mode of asynchronous lifting motor. In Fig. 1 the calculated diagram of velocity during the deceleration period t₃ is shown by the dotted line λr. During the unloading period t4', a constant velocity v3 (line ρϕ) is assumed, which drops to zero during the period t₄' along the line ϕѱ. According to the force diagram of the induction machine shown in Fig. 2, the acceleration of the hoisting motor during the start-up period occurs along the broken line BCDEFGHIKLT, varying about the given (design) force value F₁ as about the average value between the extreme limits F₁' and F₁“. At the end of the start-up period, there is a full stroke period during which the driving force follows all changes in the static force. Assuming a statically unbalanced lifting system, let the static force, and hence the driving force developed by a motor operating on the natural characteristic R2, vary from the value of F'_s2 at the beginning of the full stroke period (point N') to the value of F“_s2 at the end of this period (point N). At the end of the full stroke period, there comes a deceleration period t3, during which a braking mode is assumed, which is realized in the form of dynamic braking.