| The traditional crane hoisting mechanism is usually driven by an asynchronous motor acceleration and decelerator.This structure has many problems,such as long transmission chain,high failure rate,poor load-carrying performance of asynchronous motor,low transmission efficiency of gearbox,and oil leakage polluting the environment.It is no longer suitable for the view of energy saving and carbon reduction in contemporary society.The use of high-efficiency and energy-saving permanent magnet motor-driven hoisting mechanism systems is the new trend of crane development.In view of the characteristics of frequent starting and stopping,periodic circulation and short-time working system of the driving system of the crane hoisting mechanism.When the permanent magnet motor is applied to the crane,the three key technical issues of the selection of the driving form of the hoisting mechanism,the cooling of the permanent magnet motor and the speed regulation are studied in this paper as follows:Firstly,study the drive forms of the asynchronous motor acceleration and decelerator drive of the crane hoisting mechanism,the permanent magnet external drum drive,the permanent magnet built-in drum drive and other drive forms,compare their advantages and disadvantages,and determine the use of the external rotor permanent magnet motor built-in drum drive form;Calculate the permanent magnet motor schemes with different reel sizes and different pole-slot ratios,compare the cogging torque,efficiency and overall cost of the permanent-magnet motor under different schemes,and select the appropriate reel size and pole-slot ratio;The stress field simulation is carried out on the outer rotor of the permanent magnet motor of the direct drive hoisting mechanism of the crane,that is,the drum.According to the obtained maximum deformation and maximum stress of the drum,it provides information for the selection of the drum wall thickness and the selection of the air gap length of the permanent magnet motor;Comparing the direct drive and semi-direct drive systems of the hoisting mechanism with the performance parameters such as the no-load back EMF waveform,cogging torque,and air gap harmonic content of the permanent magnet motor,the overall hoisting semi-direct drive system is obtained.The overall price of the hoisting semidirect drive system is lower and more competitive in the market,which provides a clearer direction for the application of permanent magnet motors in the field of cranes.Secondly,the drive system of the crane hoisting mechanism requires the drive motor to provide a large torque.After removing the various problems caused by the reducer and the asynchronous motor,the temperature rise of the permanent magnet motor is the key to the safe operation of the drive system.In this paper,forced air cooling is adopted for heat dissipation.Through the design of the heat dissipation structure of the reel,the simulation of the temperature field,and the verification of the experiment,the temperature rise of the motor is guaranteed to be within a reasonable range,and the influence of the temperature rise of the motor on the safe operation of the drive system is solved.Finally,the speed regulation method of permanent magnet electric drum motor is researched.Cranes require not only the drive motor to provide explosive force when lifting heavy objects,but also stable and fast performance under no-load or light load.The traditional weak field speed expansion has a limited range and is not suitable for the operating conditions of the crane.Using the stator winding series-parallel switching speed regulation technology,the motor winding wiring method is given,and the control process of the winding seriesparallel switching is formulated to realize the adjustment of the electric drum speed;The simulation analysis of the efficiency MAP diagram of the permanent magnet motor with winding series-parallel switching speed regulation is carried out.At the same time,the speed expansion performance of traditional field weakening speed regulation and winding seriesparallel switching speed regulation is compared and analyzed,and the speed expansion of winding series-parallel switching speed regulation is obtained.The range is more than twice that of the weak magnetic expansion speed,and this method is more in line with the speed regulation requirements of the permanent magnet electric drum motor of the crane. |
