Dynamic characteristics of starting the crane rotation mechanism with a frequency-controlled drive

Abstract

The use of a variable frequency drive is widely used in the mechanisms of hoisting-and-transport machines. Electric drives based on wound rotor motors are also increasingly being transferred to frequency control. The lack of research on the crane variable frequency drive leads to the fact that its advantages and capabilities are not fully utilized. The article is aimed at studying the change in the dynamic characteristics of the drive under various operating modes in the transient stages of the operating cycle, since these characteristics significantly affect the value of maximum stresses and, accordingly, the durability of elements of lifting machines.

In the field of hoisting-and-transport machines, the use of a frequency-controlled electric drive has been studied mainly for elevators; the operation of a crane electric drive is traditionally considered based on the assumption of a linear law of change in the supply frequency. The characteristics of the operation of a frequency-controlled drive of crane mechanisms with other laws of change in the supply frequency remains insufficiently studied.

The study of starting and braking processes was carried out on the example of a crane swing mechanism on a column with a lifting capacity of 5 tons, equipped with a frequency-controlled drive with appropriate settings. The main characteristics of the crane and swing mechanism are given. The crane slewing mechanism is presented in the form of a single-mass dynamic model with an absolutely rigid connection.

The regularities of changes in the dynamic characteristics of the drive operation at various acceleration modes and frequency regulation of the engine speed are investigated. The type of frequency change from zero to the nominal value according to the linear law, parabolic and two types of S-shaped law is considered. A mathematical model of the crane mechanism was compiled, the regularities of changing the control parameter - the frequency of the drive motor power supply - were established. Regularities of changes in angular speed and torque during acceleration are determined. It has been established that for all types of acceleration, shockless load application is provided, which has a positive effect on the service life of crane mechanisms and metal structures.