A low-loss "RL-plus-C" filter for overvoltage suppression in inverter-fed drive system with long motor cable

Inverter-fed drive systems have been widely used in residential, commercial, and industrial applications. Special emphasis is placed on avoiding overvoltage spikes traveling along the cable and inside the motor, when a long motor cable is used. Such phenomenon would cause premature failure of the motor and cable insulation. Many passive and active overvoltage suppression techniques have been proposed to tackle this issue. Among them, passive overvoltage filters are dominant solutions, as their implementation is simple, cost effective, and robust. However, they have the main drawback of high power dissipation. This paper gives a new perspective on this subject. A generalized model for characterizing the inverter-cable-motor system with the filter included will be formulated to describe the interactions between the filter and the drive system. Then, the characteristics of an ideal overvoltage filter will be derived. Furthermore, a low-loss filter, named as "RL-plus-C" filter that exhibits near ideal characteristics will be proposed. Its performance will be compared with that of the commonly adopted RC and RLC filters, theoretically and experimentally on a 1-hp motor drive system. Results reveal that the proposed filter has the lowest power dissipation.