Application of the magnetic ear for flux balancing of a 160kW/20kHz DC-DC converter transformer

The non-ideal behavior of semiconductor devices used in power electronic circuits exciting a transformer can cause DC voltage components applied to the transformer terminals. This DC voltage in turn generates a DC current and/or DC flux density component only limited by the parasitic resistance of the windings and semiconductors. The biased flux density operation deteriorates the performance of the converter, since the core can be driven into saturation, generating higher currents and hence higher temperatures in the circuit. In order to overcome this problem, the previously reported “Magnetic Ear”, a non-invasive flux density transducer concept, is used in this paper. The design, placement and all implementation issues for this flux density transducer are described. For verifying the theoretical considerations, the transducer is used to perform a closed loop control over the DC component of the flux density in the 166kW/20kHz transformer, therefore ensuring its unbiased magnetic flux density operation.