ABSTRACT

With the increasing focus on energy efficiency Variable Frequency Drives (VSD) usage have increased rapidly in last few years. VFD penetration in the industrial domain has shot up for attaining energy efficiency, process optimization or control over process paramters. VFD’s are becoming an integral part of the industries and commercial establishments too. Whether a VFD is installed on chiller water pump, or boiler feed water pump or on a dosing pump motor in chemical industries, all these applications are critical applications. Any problem in the VFD will cause tripping of these critical equipments affecting productivity, quality and reliability of the system.

As VFD’s are basically power electrocnics equipment, they are susceptible to fail or trip in any deviation on power quality. Apart from being susceptible to power quality deviations, VFD’s also generate harmonics themselves which can cause problems in other equipments installed in the premises. In order to protect VFD’s from power quality issues such as rapid voltage variations (high dv/dt) or reducing harmonics generated by the VFD, many industries are installing line reactors at the input of VFD. Like in medicine, all medicine has some kind of side effect, so as with line reactors. In fact, if line reactor is not properly selected or designed, instead of solving problems, it can generate problems. If a reactor is not properly sized, it can have additional energy losses. This will add up to operating cost of the line reactor in addition to initial purchase cost. This additional operating cost could go in substantial amount if not well thought of.

This case study presents a situation where one plant installed line reactor without understanding its purpose, and suffered subsequently. Poor selection and wrong design led to substantial financial loss.

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