Design and implementation of a sinusoidal flux controller for core loss measurements

In this paper, design and implementation of a sinusoidal flux controller has been proposed for a core loss tester for eliminating the higher order harmonics from the flux passing through the core. The core loss test is performed with a toroidal transformer that consists of a main and sense windings wound on a toroidal core. The flux through the core is calculated with the numerical integration of the sense coil voltage. The controller commands the voltage applied to the main winding to keep the sense coil voltage thus the flux waveform sinusoidal. A single-phase SiC inverter operating at 150 kHz has been developed to generate the waveforms, an LC filter is used between the converter and the toroidal transformer to smooth the pulsating inverter output voltages. To be able to achieve zero steady state error and fast tracking as well as being robust to the periodic errors, a new controller is proposed. The proposed controller includes the periodic, conventional feedback and feedforward controllers and coordinates them. The designed controller has been simulated and it has been found that the flux waveform tracks the reference fast enough with a satisfactory steady state error. The system has been tested through experiments and experimental results are in good agreement with the simulation results.