Abstract : This paper introduces the transformation of a bridge crane using a variable frequency speed control system, which achieves stable operation of the crane, energy saving, consumption reduction, and fewer malfunctions.
Keywords : Bridge crane frequency converter
1 Introduction
Bridge cranes are a widely used type of lifting machinery in industrial and mining enterprises. The Handan Locomotive Depot currently has several heavy-duty bridge cranes, which are used frequently every day with large workloads. The proper functioning of these bridge cranes directly affects the completion of locomotive maintenance tasks and the safety of personnel and equipment. The original bridge crane drive system used a wound-rotor AC asynchronous motor with multiple external resistors connected in series in the rotor circuit for speed control, employing a cam controller and relay contactor. The main disadvantage of this control system is:
(1) Motor rotor series resistance speed regulation is an energy-consuming slip speed regulation, which has high energy consumption, soft mechanical characteristics, small speed regulation range and poor smoothness;
(2) When the relay-contactor control system is frequently switched, the inrush current is large, and the contact burnout, brush sparking, motor and rotor series resistor burnout and breakage occur frequently, with a failure rate of 2.5 cases per month.
(3) Poor speed regulation smoothness, resulting in significant mechanical impact on the reducer, coupling, and wire rope, which affects service life;
(4) The system brake is operated while in motion, which causes great damage to the brake and severe wear of the brake pads.
Therefore, only by completely changing the original speed control method can the problem of high failure rate of bridge cranes be fundamentally solved with the rapid development of electronic technology.
For details, please click: Variable Frequency Speed Control Retrofit of Bridge Cranes
