Design of a Modified Three Phase Line Impedance Stabilization Network for Conducted Emission Test

The infiltration of power electronic devices in power system has led to high frequency noises being injected into the power grid, owing to the short turn-on and turn-off time of the semiconductor switches. This necessitates conducted emission (CE) tests to be carried out on devices which arc intended to be connected to the power supply. Line Impedance Stabilization Network (USN) is an apparatus recommended for conducted emission testing by standard setting organizations like Collate International Special des Perturbations Radioelectriques (CISPR). In this paper, a high precision and low cost LISN design is explained. The LISN components are designed to provide better decoupling of power supply noises from the measurement terminals, in addition to the other requirements such as providing low impedance path to high frequency disturbances introduced by the Equipment Under Test (EUT) and stabilizing the impedance across the measurement port. Conducted emission test has been carried out on 5kVA induction motor drive using modified LISN. Readings obtained from the LISN are compared with the conducted emission measured using a High Frequency Current Transformer (HFCT), for validating the effectiveness of the LISN component design.