The development of power electronic devices offers the production of high-power current-source inverter-based coreless induction melting furnaces (CSI-CIMFs) for steel scrap melting process. These high-power CSI-CIMFs introduce many advantages in melting processes for low production rate steel mill and foundries. Besides the advantages of CSI-CIMF, it has unfamiliar time-varying harmonic and interharmonic characteristic. In this paper, operating principle and cause of time-varying harmonic and interharmonic characteristic of CSI-CIMF is clearly presented. The time-varying harmonic and interharmonic characteristic of CSI-CIMF is studied by simulation and field measurements of a real 10 MVA CSI-CIMF. The effect of time-varying harmonics and interharmonics of CSI-CIMF on power system is presented by harmonic analysis. The simulation model of CSI-CIMF is developed in PSCAD/EMTDC by using nameplate parameters and field measurements of a real 10 MVA CSI-CIMF in a steel mill which is located in Iskenderun, Turkey.