Conducted emission tests are always performed by the use of LISNs in laboratories in accordance with CISPR22, CISPR11 and other similar standards. However, it is not always possible to use LISNs because of some limitations. If the EUT (Equipment Under Test) has large dimensions or high currents, it is not, most of the time, possible to send it to an EMC laboratory or to use LISNs during the test. As a consequence, usage or development of alternative conducted emission test methods are inevitable in industry. In this paper, we establish the fundamentals of alternative conducted emission tests based on the impedance measurements of the EUT, supply and used cables. We also establish the correlation between this alternative conducted emission test method based on the impedance measurements and the reference conducted emission test method based on LISN. In addition, we also investigated the use of impedance boxes parallel to the LISN as another alternative method in order to reduce the mains current on one LISN and allow LISNs to be used also for high current applications.
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