Oxford Magnet Technology Limited

Siemens Corporation

Kevin Jonathan Hickman

Anthony John Salloway

A coil energizing apparatus has a superconducting energization power supply having an output port. The power supply is arranged to generate, when in use, a pulsed output current signal at the output port.

Coil energization apparatus and method of energizing a superconductive coil

A method of measuring a level of liquid cryogen, comprising the steps of immersing a liquid cryogen level probe in a liquid cryogen, applying a propagation current to the heater () to induce quench in at least an adjacent part of the superconductive material (); removing the propagation current from the heater; applying a measurement current to the superconductive material; and measuring () a voltage across the superconductive material thereby to determine the level of the liquid cryogen. In articular, the method comprises the steps of monitoring () the voltage across the superconductive material while the propagation current is being applied; and ceasing application of the propagation current in response to the detection of a voltage across the superconductive material which exceeds a certain threshold level.

Method for measuring liquid cryogen level using a level probe

There is disclosed a parallel loaded series resonant converter suitable for supplying DC to a three axis gradient amplifier in an MRI system. In conventional resonant circuits, output voltage is regulated by controlling the switching frequency of an H-bridge or half bridge switching arrangement and the resonant circuit ( ) is under more stress at no load than at full load. The voltage across the resonant capacitor ( ) is a function of the switching frequency, the load and the voltage applied across the resonant circuit (V -V ). In the present invention, the peak current at no load is reduced to lower than the peak current at full load by controlling the voltage applied to the resonant circuit (V -V ) rather than controlling the switching frequency.

Regulated resonant converter

A regulated resonant converter comprises a series resonant circuit through which current is switched alternately in opposite directions by a pair of switching transistors, a rectifier via which the switching transistors are fed with d.c. current from an a.c. mains supply input, operation of the switching transistors being controlled by signals generated in a control circuit, in dependence upon a fed-back sample of a convertor output developed in the resonant circuit in accordance with the amplitude of which regulation is effected, and a cross-over voltage associated with current reversal in an inductor which forms a part of the resonant circuit, which cross-over voltage is fed to the control circuit via a differentiator whereby switch operation is effectively enhanced.

A resonant converter arrangement comprises two resonant converters, each having a resonant circuit through which current is switched alternately in opposite directs by respective switch elements. The outputs of the two resonant converters are combined to provide an output of the arrangement which has an amplitude that is dependent upon the relative phase of the outputs of the two resonant converter. For the later purpose, switch controller controls the switch element for one of the two resonant converters, in accordance with such relative phase of the two resonant converters.

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Witney, United Kingdom

Kevin Jonathan Hickman