Motor lead length issues for IGBT PWM drives

As PWM variable frequency technology advances in the use of IGBT power transistors, concerns have arisen over the amount of conductor located between the controller and the low voltage induction motor, several technical papers have been presented on the subject of dv/dt from these controllers and the effects on motor insulation. This paper builds on these previous papers while detailing application of transmission theory, drive current feedback design impact, proper modeling techniques of conductor distributed impedance, and motor design considerations, theoretical and experimental test data are included to support the findings. Although the focus of this paper is on applications below 5 HP, some theories and tests presented should be considered in larger systems. Chipping, de-barking, washing, and coating applications in the industry sometimes do not lend themselves well to close proximity location of motors and controllers. IGBT PWM design, motor design, and installation guidelines are discussed as solutions with several options presented to the engineer.<>