Abstract: A high voltage step-up power transformer includes at least one module which defines a lower voltage primary side and a higher voltage secondary side and which includes at least one primary winding and at least one secondary winding, wound concentrically around a ferromagnetic core body, the primary winding(s) being situated outwardly, and at least one shielding and/or insulating surface structure being arranged between the primary and secondary windings. The transformer (1) is characterized in that the outer primary winding (2) or winding parts is (are) made of at least one insulated high voltage cable and in that the at least one conductive intermediate surface structure (5) and/or the core body (4) are set at a referential potential which is a fraction of the output voltage or potential difference on the secondary side.

Abstract: A high voltage step-up power transformer includes at least one module which defines a lower voltage primary side and a higher voltage secondary side and which includes at least one primary winding and at least one secondary winding, wound concentrically around a ferromagnetic core body, the primary winding(s) being situated outwardly, and at least one shielding and/or insulating surface structure being arranged between the primary and secondary windings. The transformer (1) is characterized in that the outer primary winding (2) or winding parts is (are) made of at least one insulated high voltage cable and in that the at least one conductive intermediate surface structure (5) and/or the core body (4) are set at a referential potential which is a fraction of the output voltage or potential difference on the secondary side.

Abstract: Commutation device to connect and disconnect a current or voltage generator and a coil adapted to create a gradient of magnetic field in a measurement chamber of an NMR apparatus. The device comprises a switch (1) mounted in the supply circuit (2) of the coil (3), actuated by a control signal and adapted, in open position, to isolate totally the coil (3) from the generator (4). The switch is a double switch (1) adapted to separate, upon opening, the supply circuit (2) into a portion (5) connected to the generator (4) and a portion (6) connected to the coil (3), independently of each other. Alternatively the switch can be a high speed switch comprising at least one field effect transistor.