Fault Analysis And Simulation Of Active Inverter Unit Of Cascade Speed Regulation

Because of its high efficiency and energy-saving,cascade speed control system can not only meet the needs of the production load changes but also improve the operational efficiency of fan and pump load and to reduce the rate of power consumption of motors.For failure of the motor,after decades of research,both at home and abroad have found a mature approach.But for the cascade speed control system with thyristor inverter,the inverter section is the most prone to failure,there is no very effective and economical solution.Thyristor is a semi controlled device,when it is conducting,the gate loses control function.It is easy to cause commutation failure and lead to inverter subversion.The results will lead to rapidly increases of the current which is equivalent to ten times of the rated current and the damage of components in the circuit.Therefore,the inverter failure analysis is particularly important.This article has carried on the analysis and calculation of the equivalent circuit of the commutation failure on the base of the analysis of the basic principle of the cascade speed control system.Analysed the principle and subversion of three-bridge cative inverter,and the cause of subversion.Simulated some inverter subversions caused by insufficient commutation margin angle,thyristor short circuit and open circuit,trigger loss,power failure and network voltage fluction and so on.Put the simulation waveforms of normal operation compared with inverter subversion’s.The characteristics and changing trends of each parameter inversion are obtained after fault.Finally,the fault examples of the field are analyzed.This work has guiding significances for analysis of failure equipment in the field.