Application of finite-element modeling tools for analysis and design of AC drive power bus structures

AC motor drives contain several power bus structures, which include the DC bus structure between the capacitor bank and inverter, IGBT power module internal bus structure to parallel several chips to obtain high current rating, and bus structures between low power AC drive units that are paralleled to obtain a high power AC drive. It is necessary to model these bus structures to perform circuit simulations for optimum drive design, to minimize voltage overshoot on the power module during transient conditions, which eliminates the need for snubber circuits, and to ensure that paralleled drives share load current, thus increasing the reliability of the drive. Commercial finite-element tools are available to model three-dimensional bus structures and extract equivalent circuit parameters. In this paper, some examples of application of these tools to AC drive bus structure design and optimization will be provided, supported with experimental results.