Input power quality issues and how to specify variable frequency drive for weak input line conditions

The vast majority of input power quality problems experienced by industrial customers can be attributed to voltage sags, harmonics, and transients. Frequently they result in process interruptions. Variable frequency drives are commonly used in the industry due to their energy savings benefits but when properly specified they can withstand and resolve most equipment issues caused by input power disturbances. Although there are many papers written on topic of power quality, this paper provides a holistic overview of the most common input power quality issues, and a synopsis of their impact on industrial process and equipment. The first purpose of this paper is to provide support to engineers when specifying drives for weak input line conditions, and then to identify various mitigation techniques required for low voltage and medium voltage drives.