Analysis And Design Of Pole-changing Two-speed Three-phase Asynchronous Motors For Cranes

As a mechanical device that completes the vertical lifting and horizontal movement of various materials,the crane is widely used in industrial factories and civil construction projects.The pole-changing multi-speed three-phase asynchronous motor can be used to simplify the speed regulation system and achieve reasonable power matching.It has obvious advantages such as low cost,high reliability and durability.The pole-changing multi-speed three-phase asynchronous motor is the ideal power for mechanical system energy saving.Cranes usually use pole-changing multi-speed three-phase asynchronous motors,and noise has become an important indicator to measure the quality of motor products and has attracted widespread attention.When the pole-changing multi-speed three-phase asynchronous motor runs under a certain number of poles,the problem of high electromagnetic noise often occurs.Therefore,it is very important to analyze the electromagnetic noise of the motor and adopt a reasonable design method to reduce the electromagnetic noise.This article takes a 9.5kW / 1.5kW,2/12 pole variable pole two-speed three-phase asynchronous motor for cranes of Fujian Ningde Anbo Electric Co.,Ltd.as the main research object to optimize the design to achieve noise reduction and improve starting performance.At present,the company’s product motors have difficulties in starting under2 poles and have serious electromagnetic noise problems in 12-pole operation.Afterwards,after modifying the electromagnetic scheme,the use of slot matching 36/42 has reduced the electromagnetic noise under 12 poles,but Under the 2-pole operation,there is a problem that it cannot start normally due to synchronous additional torque,and can only rotate at a certain low speed.Since this motor requires normal starting at both pole numbers,it is necessary to re-analyze and design the motor.By redesigning the rotor slot type,selecting the appropriate slot fit and chute to solve the problems of starting difficulties and appropriate Reduce electromagnetic noise.The main contents are as follows:(1)Analyze the characteristics of crane 2/12 pole-to-pole double-speed three-phase asynchronous motors,and present problems in the motors made according to the originaland improved schemes,and propose new schemes.Then calculate the magnetic circuit method through Rmxprt module in Maxwell,determine the electromagnetic scheme,compare the calculation results of the original prototype scheme and the new scheme,and analyze the parameters such as starting torque.Finally,Maxwell 2D software was used for modeling and simulation to analyze the magnetic field lines and magnetic flux distributions under 2 and 12 poles.(2)Research on the selection of slot coordination for 9.5kW/1.5kW,2/12pole-change pole two-speed three-phase asynchronous motors.First of all,the preliminary analysis and selection of the slot combination are completed by the traditional method of calculating the radial force wave table,in which the starting performance is prioritized and the influence of the synchronous additional torque on the starting performance is avoided.Then,the time-step finite element method is used to simulate the air gap magnetic density and radial electromagnetic force of the motor under different slot coordination,2 pole and 12 pole operation under no load and rated load.The simulation results are summarized and compared with the analysis results of force wave table.Finally,a solution with good starting performance and less influence on electromagnetic noise was selected.(3)Research on the skew slot of 9.5kW /1.5kW,2/12 pole changing pole two-speed three-phase asynchronous motor.A method for selecting the skew angle of the rotor of a pole-changing multi-speed three-phase asynchronous motor.The multi-section method and finite element method were used to simulate the rotor skew slot.The results of air gap magnetic density and radial electromagnetic force under straight groove and different skew degrees were compared to analyze the influence of rotor skew slot.(4)Make and test the motor according to the new electromagnetic scheme,compare the simulation results of Maxwell 2D with the test results of the motor,and compare the noise test results of the original motor with the new motor.This paper designs a 2-pole / 12-pole variable-speed two-speed three-phase three-phase asynchronous motor,and analyzes the effects of slot combination and rotor skew slot on the magnetic field and radial electromagnetic force.The above research results provide theoretical support for the slot combination of the pole-changing motorand the selection of the rotor skew slot,and provide a reference value for the design of the pole-changing two-speed three-phase asynchronous motor.