Fault diagnosis and numerical simulation of broken rotor bars for small cage induction motors

The failure rate of rotor bars is high, which causes large area of broken conducting bars, shortening the lifetime of motors. Therefore, the diagnosis of broken rotor fault diagnosis is of great importance. First, the mathematical model of induction motors is presented, and the internal and external magnetic field boundary conditions are defined. Second, frequency domain analysis method is combined to establish the open phase model of induction motors. Then, the scheme is designed for fault types of induction motors by considering asymmetry and broken bar number. Simulation results show that the larger the number of broken bars is, the more asymmetric the magnetic field is, except for evenly distributed broken positions; The current fault characteristic component of stators has weak changes; The frequency characteristics of electromagnetic torque increase, and the asymmetric component is larger than the symmetric component; The broken bar number increases under asymmetric distribution conditions of broken bar positions. The content of the 21st and 23rd harmonics is added, providing the idea of predicting broken bar number and the symmetry of magnetic field.