Analysis of Abnormal Modes of Hoisting DC Electric Drive System

Abstract

Problem statement: Host number of publications in which special attention was given to the behavior of the hoisting drives in abnormal modes was found. The effect of the failure of the main power supply on the electrical and mechanical parts of the hoisting drive when the motor is operating in the regenerative braking mode was not enough studied. Approach: In this study, the effect of the failure of the main power supply on the electrical and mechanical parts of the hoisting drive when the motor was operating in the regenerative braking mode and give recommendations and solutions to minimize the negative consequences of that abnormal mode. A special comprehensive mathematical mode was developed. The model comprised different submodels that describe the real operation of the power supply, four-quadrant thyristor AC/DC dual converter, firing system, protective devices and mechanism including the elastic elements like ropes and long shafts. This comprehensive model was used to study the behavior of the drive and choose the optimum protective device against the corresponding abnormal mode. Results: The failure of the supplying voltage of the dc hoisting drive at power regeneration leads to a significant increase in the motor armature current due to the formed closed loop comprising the armature winding, pair of thyristors and the secondary coil of the supplying transformer, in this mode the converter counter EMF will disappear. The protective device should protect the converter and the motor against such abnormal mode. The produced inrush current in role generates a huge motor torque that result in possible ropes and crane boom deformation, thus the mechanism design should include such possible abnormal mode. Conclusion: These results were implemented in the design of a special fast-responding circuit breaker which guarantees the exclusion of the armature current increase in the mentioned mode.