Abstract: A multistep inverter uses multiple inverter H-bridges connected in series to piecewise approximate a sine wave. The inverter H-bridges are bypassed or switched into service as required for sinewave synthesis. After a step is switched in, it creates its portion of the sine wave. Each step is further smoothed using pulse width modulation which leads to a smoother sine wave with the consequent advantages of lower distortion, smaller and lighter filtering circuits, and lower conversion losses during transistor switching.

Abstract: A shuntable low loss variable current vapor cooled lead (VCVCL) configuration delivers current to and from a superconductive load, such as a superconductive magnet, immersed in a cryogenic liquid in a way that minimizes the boil-off rate of the cryogenic liquid. The VCVCL configuration includes superconductive lead assemblies containing superconductive segments. The assemblies are connected in parallel between the superconductive load and an output current source or sink. Each assembly is controlled so that its superconducting segment is either superconducting or non-superconducting.

Abstract: High-voltage, solid-state switches that are capable of interrupting current, offer relatively low on-state losses (low forward voltage drop) and provide for high current densities. Low-voltage transistors and silicon-controlled rectifiers are employed to achieve low power losses at high current densities. One embodiment of the present invention relates to a solid-state switch for controlling a source of direct current. The switch includes four switching elements. Each element has a first terminal, a second terminal and a control signal input terminal. The switching elements provide a high resistance to the flow of electrical current in response to a first control signal. A second control signal causes the switching elements to offer a low resistance to the flow of electrical current. The first and second switching elements are connected in series, as are the third and fourth switching elements.