Motor driving force of bridge-type crane lifting mechanism under real operating use

Abstract

Introduction. The requirement for modelling the dynamic processes of a hoisting mechanism in real operating situations has been revealed. The necessity of increasing the accuracy of moving effort description for the most common types of crane hoist drive control has been determined.Materials and Methods. The operation of a single-speed electric motor with squirrel-cage rotor without speed control, with a phase rotor and additional resistors in the rotor winding and with a squirrel-cage rotor and control by a frequency converter has been considered. The static characteristic of the electric motor is taken as the initial function. The Clauss formula with the corresponding values of the parameters synchronous speed, critical force and critical slip was used to take into account the driving force of the motor for frequency control and for relay-contactor control and a motor with a phase-rotor and additional resistances in the rotor circuit.Results. The dependences for the motor driving force with the most common methods of speed control of the crane hoisting mechanism drive are presented. In the case of the frequency control system, the form of the motor driving force is given in the case of steady-state motion and in the case of transient starting/braking processes when the corresponding algorithms are implemented by a frequency converter. Experimental and theoretical graphs of the load lifting processes for the cases of lifting with pickup in the relay-contactor control system and with elastic pickup in the frequency control system are given.Conclusion. The conclusion about applicability of static mechanical characteristic for description of electric motor operation in crane drives is given. The presented dependences provide an opportunity to model the full working cycle of the hoisting mechanism. The dependences are valid both during steady motion of the mechanism and during transients. It is concluded about the use of the dynamic model taking into account the presented form of the motor driving force for practical purposes for the analysis of the crane operation with regard to the effect of the lifting capacity limiter.