Influence Of Load Side Cable On Medium Voltage Frequency Conversion System Performance

In applications,frequency converters and motors are often installed far apart.This requires the load cable to transmit the inverter output capacity to the motor end.Long cable will lead the drive to trip by over-current,increase the motor’s temperature and damage the insulation of motor.These issues will make the inverter system unable to work.So,it is great significance and practical value to analyze the influences of long cable on the performance of medium voltage conversion system.First,the composition of medium voltage frequency conversion system of long cable is briefly introduced in this page.The inherent characteristics of medium voltage frequency conversion system and the formation process of reflected wave in medium voltage frequency conversion system of long cable are analyzed.The phenomenon of over voltage at the motor end,high dv/dt and inverter over current due to reflected wave and cable distributed capacitance is studied.Secondly,the distribution parameters of the cable are tested.By modeling the power unit and the whole medium voltage frequency conversion system of the long cable,the influence of the long cable is further analyzed.Thirdly,by building an experimental platform to test the over-voltage and high dv/dt at the motor end and the leakage current of the system,it is verified that the serial-superposition inverter does not exist in the common mode current in the previous three-level inverter circuit.This proves the results of previous theoretical analysis.Fourthly,through the comparison and analysis of several solutions,after observing the simulation results,it is concluded that installing reactor is the preferred solution in practical application.Put the reactor into the long cable frequency conversion system test platform built before,and verify that the reactor can effectively solve the problems of over-voltage,high dv/dt and leakage current at the motor end.Finally,get the conclusion is that: the reactor can effectively solve the influence of long load cable on medium voltage frequency conversion system performance.Combined with the results of simulation and test,the longest transmission distance of products series are obtained and provided effective preventive measures for customer and other inverter manufactures.