Abstract: A method for predicting zero crossings of fault currents in a multi-phase power system includes sensing a fault current in each respective phase, estimating parameters of a model of each respective fault current, and independently using the estimated parameters for each respective fault current to predict a zero crossing of the respective fault current.

Abstract: A high power motor drive converter comprises: a three level neutral point clamped (NPC) output power conversion stage including switches for supplying power to an AC drive motor; a split series connected DC capacitor bank coupled in parallel with the NPC output power conversion stage; and a controller for selecting switch positions for controlling the NPC output power conversion stage and compensating for a neutral point voltage imbalance of the DC capacitor bank by adjusting amplitudes of carrier voltages according to an amount of voltage imbalance in the split series connected DC capacitor bank.

Abstract: A high power motor drive converter comprises: a three level neutral point clamped (NPC) output power conversion stage including switches for supplying power to an AC drive motor; a split series connected DC capacitor bank coupled in parallel with the NPC output power conversion stage; and a controller for selecting switch positions for controlling the NPC output power conversion stage and compensating for a neutral point voltage imbalance of the DC capacitor bank by adjusting amplitudes of carrier voltages according to an amount of voltage imbalance in the split series connected DC capacitor bank.

Abstract: An X-ray tube assembly includes a hermetically-sealed annular frame, spaced apart cathode and anode rings and an electron excitation device. The frame surrounds an exterior central passage for receiving a patient therethrough and has an interior chamber with a vacuum and an X-ray transparent window ring surrounding the central passage. The cathode and anode rings are stationarily mounted to the frame and disposed within the interior chamber. The cathode ring has circumferentially arranged side-by-side filaments each separately excitable by the electron excitation device to cause flow of electrons in an e-beam to a target portion of the anode ring such that an X-ray beam is produced that exits the interior chamber passing through the transparent window ring and that can be moved around the patient disposed within the central passage.

Abstract: An optimal phase-shifted control for a series resonant converter involves instantaneous monitoring of state variables (resonant capacitor voltage resonant inductor current and output voltage) and implementation of a control law for providing a quasi-squarewave-with-maximum-coasting (QSWMC) mode of operation. The control law uses the instantaneous resonant inductor current, the instantaneous resonant capacitor voltage and the output voltage to determine the optimal time to perform switching events in order to operate on a desired control trajectory. The QSWMC converter operates at a minimized frequency in a super-resonant mode with zero-voltage switching, minimized electrical stresses, and reduced electromagnetic interference due to nearly sinusoidal resonant tank currents.

Abstract: A high power motor drive converter includes: a five level hybrid NPC output power conversion stage including three NPC phase bridges having switches and coupled in a wye configuration through a converter neutral point, each NPC phase bridge receiving power on a respective direct current bus; three isolated split series-connected DC capacitor banks each coupled in parallel to a respective one of the three NPC phase bridges; and a controller for selecting switch positions with active control of neutral voltages. The controller is adapted to select switch positions using feedforward sine-triangle modulation with third harmonic injection, zero sequence injection, and/or discontinuous modulation injection.

Abstract: A three-level NPC converter includes at least one phase leg including four series coupled electrical switches having a first pair junction between the first two switches and a second pair junction between the second two switches. First and second inner switch snubber capacitors are coupled in series at a neutral junction. First and second inner switch snubber diodes are respectively coupled to the first and second pair junctions and respectively coupled at first and second inner diode-capacitor junctions to the first and second inner switch snubber capacitors. First and second inner switch snubber resistors are respectively coupled between the first and second inner diode-capacitor junctions and respective portions of a DC bus. In one embodiment, the NPC converter further includes first and second outer switch snubber diodes coupled between respective first and second inner diode-capacitor junctions and respective portions of the DC bus.

Abstract: A high power motor drive converter includes a three level neutral point clamped (NPC) output power conversion stage including switches; a split series connected DC capacitor bank coupled in parallel with the NPC output power conversion stage; and a controller for selecting switch positions for controlling the NPC output power conversion stage and controlling a neutral voltage balance of the DC capacitor bank by using space vector modulation and predictive charge calculations.

Abstract: Low-power auxiliary circuitry is added to a resonant converter for providing high efficiency operation, low EMI, and tight output voltage control over a wide load range. There is an auxiliary circuit corresponding to each half-bridge connection of main switching devices, each auxiliary circuit including a half-bridge connection of auxiliary switching devices with the junction therebetween coupled to the junction between the main switching devices of the corresponding half-bridge. Under heavy load conditions, sufficient energy is stored in the main resonant inductor to commutate the junctions joining the main switching devices in the resonant converter, resulting in zero-voltage switching for the main switching devices.

Abstract: An active damping circuit for an electromagnetic interference (EMI) filter for power factor correction (PFC) circuit is provided which simulates a line damping impedance which actively varies according to sensed line current. The active damping circuit comprises an nth-order, Cauer-Chebyshev, low-pass filter having input series damping impedance (Z.sub.d) simulated with a power operational amplifier and high-frequency isolation transformer. The simulated damping impedance offers greatly reduced size and power dissipation as compared to prior art passive schemes which typically require large impedance components for damping. A passive damping circuit is also shown which involves providing an alternate inductive current path in parallel with a damping resistor whereby lower frequency currents are diverted through the alternate current path and higher frequency currents continue to flow through the damping resistor.

Abstract: A novel switching rectifier circuit that combines the conventional three-phase, 6-stepped PWM rectifier/inverter circuit with a simple, low-power switch commutation circuit to provide zero-voltage turn-on for the switches, and soft turn-off for the diodes. The main features of the new circuit include elimination of switching losses on the power switches and reverse recovery problems on the diodes, elimination of the need for any snubbers in the three-phase bridge, possibility of use of slower diodes in the power bridge, constant frequency operation, and no increase in component current and voltage stresses over the conventional PWM rectifier.

Abstract: A three-phase, pulse-width-modulated, switching rectifier, with zero-voltage-switching.