Real world ASD interference case study with modeled solutions

The installation of adjustable speed drives (ASDs) has been known to cause many types of radiated and conducted emissions-related electromagnetic interference (EMI) problems. Solutions to resolve these problems are often not straightforward and involve the correction application of filtering and shielding devices. The process of identifying effective solutions is also not straightforward. This paper describes a real-world case study where the use of several high horsepower ASDs caused EMI problems with a cable tester in an industrial plant. Included are the approaches for investigating the problem and mitigating the problem. It is shown that the correction application of an isolation transformer combined with the application of a custom power-line filter designed for mitigation of ASD-related conducted emissions resolved the problem. Modeling is also used to show the effects of adding a shield and a filter on the motor drive cables, and then a ground noise filter between the ASD system ground and the chassis ground.