Evaluation of motor power cables for PWM AC drives

Three-phase power cables installed between the inverter and motor of AC motor drive systems have been mostly ignored in the years since AC drives have become widely accepted in industrial applications. However, power cable characteristics have become quite critical with the advent of faster inverter switching times, which have decreased by a factor of perhaps 20:1 in the last ten years. This paper describes the present areas of concern with regard to power cabling, as well as a test program to quantitatively evaluate power cable-related remedies for these problematic areas. A relative ranking of test results is developed comparing the eight power cable types tested. Cable connector considerations are examined, together with interconnection of the cable shield, or sheath, and the NEC ground circuits are discussed in light of the test results and recommendations presented. Power cable voltage ratings are discussed and recommendations made. A final cable total performance comparison, including installation factors, summarizes the paper.