Iron loss estimation for highly distorted currents in inverter output chokes

Abstract

In drive applications with long cable fed electrical machines, inverters and machines need to be protected from high charging currents and overshoot voltages, respectively. This protection is often performed using inverter output chokes with laminated cores to smooth the output current waveform and limit charging currents. As cable and choke reactor form an LC-circuit, they do support oscillations of current and voltage especially at the inverter terminal with unpredictable effect on the core loss of the output choke. The research presented in this paper is an attempt to quantify the core loss in laminated iron cores for highly distorted current waveforms. In a laboratory setup, a scale model of a choke inductor is integrated into an LC-circuit and supplied with inverter feed in order to imitate the current signal found in real world applications. The measured current waveforms are fed into a loss model based on a magnetic equivalent circuit and the equivalent elliptical loop model to compare simulated losses with the measured values. A good agreement is achieved.