Case study: To eliminate major root causes of failures with VSDs installations

VSD´s are often judged as much less reliable compared to DOL operation of motors. This paper discusses that most failures that contribute to the (bad) image of VSD´s are related to specification and engineering, rather than to the drive itself. As a matter of fact, the usage rate of drives in chemical industry is far below the usage rate of drives in other industries (3% vs. >8%). Because failures with high voltage frequency controlled drives also contribute to the image of low voltage drives, an overview is given on all types of failures and their possible prevention for low voltage as well as high voltage. The rate of possible improvement is given, based on a split in failures caused by design vs. the drive itself and expressed in MTBF values.