The Effect Of Long Cable On PWM System And The Suppression Of Overvoltage

In the industrial application of the PWM stystem, due to the limitations ofthe workplace, it is inevitable to connect the motor by the long cable. When thepulse is transmitted to the motor terminals, owing to the impact of cable lengthand cable characteristic parameters, overvoltage and high-frequency dampedoscillation is generated in the motor. Overvoltage of the motor end not onlyexacerbates motor torque ripple, results in local heating problem, but also bringsout the motor or cable insulation breakdown, even burns out the motor and crackscable.Firstly this study describes the reason of the cable causing the over-voltageby the equivalent model of the PWM drive system. And then it studies the impactof cable parameters on line voltage at the motor terminal in details, by analysingthe amplitude, the propagation velocity, the oscillation frequency and theoscillation duration of the line voltage. Secondly depending on the simulation byPSPICE software, we verified the conclusion by building simulation models.Being aim at the phenomenon of over voltage motor terminal, the studyresearches two kinds of filter for suppressing motor terminal overvoltage. Thenbased on PWM long system equivalent model, leading into the transfer function,the study respectively proposes the motor end RC filter and the inverter outputRLC filter parameters design method. Through PSPICE simulation software, thedesigns are feasibility. And the study provides a reference for the parameters ofthe filter in the practical application of the aotimization.At last, this paper deveises a PWM inverter experimental platform, and theanalysis of the PWM long cable drive system is verified by experiment.