Research On The Filter Of Long Cable Transmission At The Output End Of Inverter

PWM drive motor system become one of the important ways of industrial production, with significant energy saving effect and economic benefits. However, It also bring some notable adverse effects in the wide industrial applications. For example, in PWM drive system, the high dv/dt is produced when the inverter switching devices in a fast turn-on and off at the moment, due to high dv/dt, it will be big impact to the PWM inverter driving motor; if the distance between the inverter and the motor is long, it need long cable to transmit PWM voltage pulse to the motor terminal, causing the phenomenon of the motor terminals over-voltage and high frequency damped oscillation more obvious, in the severe situation, will cause motor or cable insulation breakdown, and even burn out the motor, burst cable. So, studying the generation of the motor terminals over-voltage phenomenon and suppressing its negative effect have important theoretical and practical significance.This topic first using transmission line theory, analyze the voltage of the motor terminal vary with voltage pulse rise time (the rise time tr and cable length, cable distribution inductance, cable capacitance has a close relationship), resulting in the ideal quantitative relationship between the motor terminal overvoltage and the rise time, on the basis of the quantitative relationship, reasonable rise time is deduced. Based on PWM inverter switch model, deduce the quantitative relationship among the minimum value of RLC filter’s inductance and capacitance and the rise time and the resister, on the basis of this relationship, put forward the optimization of rise time, filter resistance, so as to achieve the purpose of optimizing the filter inductance and capacitance.Studies two kinds of motor terminal over-voltage RLC filter scheme, and the simulation effect is compared before and after the suppression measures, but as a result of the two methods of inhibiting on the filter loss bigger difference and the common mode of dv/dt inhibition effect on the difference, we need to consider using what kind of RLC filter can achieve the best effect. So this topic is based on the mathematical model of PWM drive system, in view of the filter to achieve the design of the index, the integrated PWM pulse rise time and the motor end filter loss of second-order RLC parameter design method of inverter output filter, and through the simulation verify its feasibility and effectiveness.Finally, Design with the DSP28335 high performance microprocessor as the core, combined with CPLD as the auxiliary control experiment platform. Experimental platform for the corresponding software process and the corresponding hardware module, establish with RS232 serial communication port, VB programming based human-machine interface, and on the experiment platform for long-term RLC filter research experiment.