Resonant Link PFN Charger and Modulator Power Supply

For PFN chargers and large power modulator 50/60/400 Hz utility power must be drawn from the grid with acceptable total harmonic distortions and without large inrush currents. The standard twelve or eighteen-pulse rectification require large utility power transformers and large harmonic filtering with high capital cost. SAIC has developed a Resonant Link (also known as AC-Link) electronic transformer that draws controlled harmonic power from the utility grid with less than 1.5 % total harmonic distortion. The active rectification is performed with the "soft switching" Resonant Link inverter at a switching frequency of 15 to 20 kHz using commercial IGBTs or other available solid state devices. To step up or step down the power to the required voltage, a small high frequency and efficient nanocrystalline transformer, operating at the inverter frequency, uses the transformer leakage inductance as part of the inverter resonant output circuit. The secondary rectified output DC has no 360 Hz components and can be regulated to better than 1% with minimum passive filtering, or can be used to charge up a capacitor bank in a controlled manner. Such a system has a power density in the range of 2 to 6 MW/m with a small fraction of the standard equipment weight and substantially reduced cost. In addition the soft switching topology yields an efficiency in excess of 97%.