Research On Off-line Measurement Technology Of Inherent Mechanical Characteristics Of Three-phase Asynchronous Motor

The mechanical characteristics of the motor are the most basic characteristics to ensure the stable and efficient operation of the motor.In order to ensure the normal,stable,reliable and efficient operation of the motor,it is particularly important to accurately test its performance,especially the mechanical characteristic parameters.At present,the steady-state test method and dynamic test method are often used to measure the mechanical characteristics of the motor.Both test methods need to measure and control the electromagnetic torque and speed of the motor by increasing the load,and the implementation process is complicated.The former has high test accuracy,but it has the disadvantages of time-consuming and complex test process.At the same time,when measuring the electromagnetic torque of the motor at low speed,due to the need to test the parameters of the motor under steady-state operation,the motor temperature is high at this time,which has a certain impact on the test accuracy.The latter test process is simple and fast,but there are also defects such as poor test repeatability.Aiming at the defects of the current mechanical characteristic test method,this paper proposes a mechanical characteristic test method based on the off-line parameter identification of the motor from the mechanical parameter expression of the inherent characteristics of the three-phase asynchronous motor.The test method has low power consumption,small impact on the power grid and low manufacturing cost,which can meet the increasing demand of enterprises for the inherent mechanical characteristics test of three-phase asynchronous motors.The main research work of this paper is as follows:(1)On the basis of studying the T-type equivalent circuit of three-phase asynchronous motor and the theory of time-varying characteristics of motor parameters,the mathematical models of three-phase asynchronous motor under no-load and lockedrotor test environments are analyzed.Based on the parameter identification model under no-load test,considering the influence of skin effect on rotor impedance,a variable parameter identification model of three-phase asynchronous motor is established.The parameter extraction problem is transformed into a multi-objective optimization problem,and the optimal solution is searched globally by genetic algorithm.(2)Taking Y160M-4 three-phase asynchronous motor as the research object,the structure,working principle and key parameter calculation method of single-phase square wave inverter power supply for testing starting torque are given.The armature current of motor starting process under different excitation modes required to study starting torque is obtained by using two-dimensional transient electromagnetic field numerical calculation method.Based on the mathematical model of the motor and the coordinate transformation theory,the equivalent circuit model of the motor under single-phase sinusoidal excitation and the theoretical calculation model of the starting torque are studied and given.On this basis,the starting torque data processing method under singlephase square wave excitation is further given.Combined with the two-dimensional transient electromagnetic field numerical simulation,the feasibility and correctness of the calculation model are verified.(3)The inherent mechanical characteristics test system of three-phase asynchronous motor is developed,which includes two subsystems : automatic voltage regulation system and measurement system.Among them,the voltage regulation system consists of a threephase voltage regulator,a stepper motor and a stepper motor driver.The STM32 main controller outputs pulses and directions to control the forward and reverse rotation and speed of the stepper motor,and uses the PID controller to achieve the purpose of automatically adjusting the three-phase voltage regulator.The measurement system is composed of AD7606 acquisition board,three-phase metering module and three-phase asynchronous motor.The STM32 main controller controls the acquisition,storage and transmission of voltage and current of three-phase asynchronous motor.Finally,the upper computer system built by QT Creator is used to control the lower computer system and process the relevant data.The experimental results show that the inherent mechanical properties of the tested motor meet the expected results.