Other considerations: the motor cable, voltage stresses, and bearing currents

• Published in: Electrical Machine Drives Control pp. 469 - 498
• Main Authors: Hrabovcova, Valeria, Pyrhonen, Juha, Semken, R. Scott
• Format: Book Chapter
• Language: English
• Published: United Kingdom John Wiley & Sons, Incorporated 2016; John Wiley & Sons Ltd
• Subjects: direct current link voltage; electromechanical drive components; motor cable; motor overvoltage; pulse width modulation; radio frequency shield; voltage stresses
• ISBN: 1119260450; 9781119260455
• DOI: 10.1002/9781119260479.ch13

Basic electrical engineering often assumes that voltage pulses travel with infinite speed. Pulse width modulation produces high du/dt differential mode and common‐mode voltage pulses by sequentially switching the direct current (DC)‐link voltage to the motor windings. In many high‐power applications, the electromechanical drive components are separated from the converter by a motor supply cable that runs between them. Voltage doubling can only occur if the cable length is above the critical cable length, that is, long enough to keep the negative wave returning from the inverter from suppressing the overvoltage. Overvoltages can be reduced by filtering or by inverter programming. The most common way to implement filtering is to add du/dt chokes to the motor cable. Low induction connection methods must be used to attach the supply cable armour and radio frequency (RF) shield to the motor frame.