Techniques For Rotor Broken Bar Detection Of Three Phase Squirrel Cage Asynchronous Motor

Three-phase asynchronous motor is an indispensable equipment in the transmission system.When it fails,it will reduce production efficiency and even cause safety accidents.Among the many faults of the motor,the rotor broken bar fault accounts for about 10%of the total failure rate of the motor,and it is difficult to find.Therefore,the research on rotor broken bar fault detection technology has received more attention.However,for the traditional non-invasive motor current signal analysis（MCSA）,the slip rate s is very small in the no-load operation state,and the form of expression in the spectrum is that the rotor broken bar fault component is very close to the fundamental wave,which makes the rotor broken bar fault component easy to be submerged by the fundamental wave.It is difficult to accurately extract,which makes the MCSA method have great limitations in practical application.In this regard,this paper takes the stator current and zero-sequence component of asynchronous motor as the research object,and extracts the rotor broken bar fault component and rotor slot harmonic component by SVD-Prony algorithm based on singular value growth rate,so as to realize the rotor broken bar fault extraction and verification of asynchronous motor.The specific research contents are as follows:Firstly,this paper studies the mechanism of rotor broken bar fault and the mechanism of rotor slot harmonic velocity measurement,and puts forward the theoretical calculation formula of integer multiple rotor slot number.According to the relationship between the rotor broken bar fault component frequency and the slip rate,the rotor slot harmonic frequency is used as the reference value to extract the rotor broken bar fault component from the stator current and verify its correctness.The SVD filtering method based on singular value growth rate,which needs to set the initial effective order,and the Prony algorithm for identifying rotor slot harmonics and rotor broken bar fault components are studied.The correctness and reliability of the algorithm for detecting rotor slot harmonics and rotor broken bar fault components are verified by MATLAB simulation.Taking Y160 M-4 motor as the research object,the simulation is carried out under the condition of no-load and low-voltage operation.The results show that the proposed method can effectively extract the rotor slot harmonic component and the rotor broken bar fault component.Secondly,the influence of the number of broken rotor bars,the position of broken rotor bars and the degree of broken rotor bars on the rated performance of the motor is analyzed and studied,and whether the rated performance parameters of the motor meet the national standards is judged.When multiple broken bars occur in the motor,the mutual position of the broken bars has a great influence on the motor.Therefore,the influence of the mutual position of the broken bars and the fracture degree of the rotor guide bar on the fault component of the rotor broken bar is discussed.The simulation results show that the more the number of broken rotor bars or the heavier the degree of broken rotor bar,the more the frequency of the broken rotor bar fault component deviates from the fundamental component,the larger the amplitude,and the more the rated performance of the motor does not meet the national standard.When two broken bars are broken,the amplitude of the broken bar fault component and the rated performance of the motor change periodically with the mutual position of the broken bars,and the period is approximately the number of rotor bars per pole.Then,the feasibility of zero-sequence component detection for rotor broken bar fault is studied theoretically,and the proposed algorithm is used to analyze the harmonic region of stator zero-sequence component frequency band close to 3f₁ related to fault to detect rotor broken bar fault.Finally,the off-line diagnosis system of squirrel cage rotor broken bar of asynchronous motor is designed.The overall architecture of hardware and software mainly includes automatic voltage regulation system and rotor broken bar fault test system.The experimental test platform is built to measure the YE3-90S-2 motor.The experimental results show that it is feasible to apply the proposed algorithm to the rotor broken bar fault detection of three-phase asynchronous motor under no-load and low-voltage operation,and solve the problem that the rotor broken bar fault is difficult to detect under no-load operation.