Power transformers are facing different stress factors during service. Usually, the effects of DC components superimposing AC phase currents are not taken into consideration. Nevertheless, DC can occur in transmission grids due to different sources. This contribution presents ongoing field measurements which show DC in the range of serval Amperes. Different superimposing DC sources are identifi...

The use of buck-derived topologies for unity power factor ac-to-dc applications is limited by their inherent inability to draw current from the line in those intervals, during the line half period, in which the input voltage is lower than the output one. This drawback is overcome in the proposed high-quality rectifier based on the forward topology with secondary-side resonant reset. The employe...

In case of low voltage (12 to 24V) solar and battery powered sinus inverter applications a special converter topology for managing the high input current rating is required. Conventional solutions uses paralleled power MOSFETs to realize high current (several 100A) switches. In this paper a synchronized multi phase PWM concept was chosen to rise the over all efficiency of the inverter. In gener...

The purpose of this study is to generate a highly stable DC current by using a superconducting transformer. For the first trial stage, a 100 A class superconducting transformer was designed and fabricated for operation at the temperature of liquid nitrogen. The secondary coil of the transformer was wound with a superconducting Bi-2223 tape, and the turn ratio of the primary and secondary windin...

This paper proposes a method to obtain a protected voltage gain by employing a protection circuit for the voltage doubler or multiplier circuit in an isolated tyde DC-DC Converter. The entire set up consists of a phase shift converter with a protected bridge/voltage doubler rectifier on the output side. The operating frequency of the phase shift converter is 20-25kHz (depending on the requireme...

The high frequency transformer in single-phase full-bridge DC-DC converter is prone to saturation because of the asymmetry circuit parameters. Transformer will increase power consumption, accelerate aging winding insulation, and even damage switches. In order prevent this risk, a DC bias suppression strategy presented article, main advantage that problem can be completely eliminated. firstly, m...

In applications for high-Tc superconducting DC-SQUIDs such as biomagnetism, nondestructive evaluation and the relaxation of magnetic nanoparticles, it is important to maintain reliable sensor performance over an extended time period. We designed and produced DC-SQUID gradiometers based on YBa2Cu3O7−x (YBCO) thin films which are inductively coupled to a flux transformer to achieve a higher sensi...