A new design tool to protect industrial long-cable PWM ASD systems against high-frequency overvoltage problems

This work presents a new tool for use in the design of long-cable adjustable-speed drive (ASD) systems. It allows coordination between the inverter, the motor and the cable type and length in order to protect the motor against overvoltages due to the reflected wave. Detailed mathematical formulas describing the transient voltage and current along the cable are first developed in the frequency domain. Then, by applying the boundary conditions at the cable ends and assuming a lossless cable, delay equations are developed in the time domain. Using these equations, an appropriate simulation scheme is built with the SimPowerSystems (SPS) and Simulink modules of the MATLAB software environment to compute the high-frequency overvoltages (and their associated currents) at the ends of the feeding cable. The proposed tool has been applied to a 5 kVA industrial ASD prototype using a four-wire shielded long cable. The paper includes simulation results and experimental validations.