Reflected waves and their associated current

Reflected wave transient voltages that result from fast IGBT voltage source inverters have received considerable investigation. The modeling and simulation of these transients requires sophisticated motor and cable models. Most voltage source PWM adjustable speed drive suppliers now provide combinations of passive and active control techniques to mitigate the adverse effects of overvoltage stress, however, the cost of the passive fixes often exceed the cost of the drive. Another aspect of low rise time devices, heretofore not examined to the extent of the overvoltage problem, is the resulting current from traveling waves. In this paper a historical perspective of the overvoltage problem is presented. Models of system components are reviewed and simulation results are compared with experimental results. These models are then employed to predict the peak currents from voltage source inverters as the cable, load, and IGBT rise time are altered. The paper then examines the consequences of reflected wave currents on current sensing, drive control, and device performance. From these results, a minimum rise time is established.