Abstract: A magnetic resonance apparatus has a basic field magnet for providing a uniform magnetic basic field, a gradient coil system for coding within the basic field as well as a passive shim system for homogenizing the magnetic basic field. This passive shim system is composed of shim iron plates that are placed in the magnetic basic field. A device is provided with which the temperature of these shim iron plates is controlled.

Abstract: A magnetic resonance apparatus has a basic field magnet for providing a uniform magnetic basic field, a gradient coil system for coding within the basic field as well as a passive shim system for homogenizing the magnetic basic field. This passive shim system is composed of shim iron plates that are placed in the magnetic basic field. A device is provided with which the temperature of these shim iron plates is controlled.

Abstract: A power amplifier has an amplifier module and a pole changer module connected to the amplifier module, and during the operation of the power amplifier an amplifier current flows in a single current direction between the amplifier module and the pole changer module. The pole changer module optionally provides the amplifier current with unchanged current direction or with reversed current direction, as output current of the power amplifier. A nuclear spin tomography apparatus contains at least one such power amplifier. Such a power amplifier exhibits the required efficiency quantitatively and qualitatively, with low outlay and low cost.

Abstract: A power amplifier has a supply assembly for offering an intermediate circuit voltage and an output stage connected to the supply assembly for generating an output voltage from the intermediate circuit voltage. The supply assembly contains at least two voltage sources that can be optionally connected in parallel or in series via at least one switch stage. A nuclear magnetic resonance tomography apparatus can be equipped with such a power amplifier. The power amplifier exhibits the required high performance capability in quantitative and qualitative terms, with low losses.

Abstract: A thermally conductive, electrically insulating connection, which is not sensitive to air moisture comprises a ceramic layer formed by thermal spraying on a surface of the workpiece, which layer is either impregnated or sealed with electrically insulating material and is joined to another workpiece which may be a ceramic layer which has been either impregnated or sealed and attached to another member. The connection is particularly useful in power assemblies with at least one power component for conducting away lost heat from the component with a sufficient electrical insulation of the component from the cooling body or heat sink.

Abstract: A glued connection suitable for attaching high power electronic components to a mounting location, such as on a cooling element, has an electrically insulating base layer of unfilled adhesive applied onto at least one surface of the parts to be glued. An adhesive filled with an electrically insulating powder that has good thermal conductivity is applied onto at least one part surface. Grains of the powder puncture the base layer, and the thickness of the glued connection thus essentially corresponds to the size of the grains.

Abstract: A cooling unit for a number of power semiconductors is formed by a quadrangular tube to which the power semiconductors are secured at an exterior with good thermal conductivity, in an equipping region of the tube. The quadrangular tube has a coolant inlet and a coolant outlet. The quadrangular tube contains a laminarization unit disposed in a region following the coolant inlet, this region overlapping the equipping region. The laminarization unit produces a substantially laminar flow of the coolant in the tube within the aforementioned region. In a region between the laminarization unit and the coolant outlet, the quadrangular tube contains a number of turbulence-producing elements for introducing turbulence into the coolant flow.

Abstract: Power amplifier for the feed of an inductive load having switched transistors is composed of a bridge circuit, wherein a plurality of series circuits of transistors with free running diodes are connected parallel in each bridge arm. An inductor is arranged in the connection of each series circuit to the inductive load, this inductor being current-compensated such that it has an effective inductance only when a non-uniform division of current occurs in a bridge arm. The transistors and diodes are linearly arranged.