Abstract: An electromagnetic drive system includes a motor having a first motor section movable relative to a second motor section along a motion axis. The second motor section has three excitation coils. The first motor section includes a magnetic circuit generating a magnetic field in the excitation coils. The first motor section also includes a short-circuit winding for only high-frequency induction currents. This short-circuit winding is magnetically coupled to the excitation coils. The degree of electromagnetic coupling of at least one excitation coil depends on the position of the first motor section relative to the second motor section. The short-circuit winding provides a position-dependent electromagnetic coupling between the center excitation coil and the two outer excitation coils.

Abstract: The invention relates to a circuit arrangement suitable for high-frequency operation of a discharge lamp, provided withinput terminals (1, 2) for connection to a low-frequency supply voltage source,a rectifier circuit (G) coupled to the input terminals for rectifying a low-frequency supply voltage supplied by the low-frequency supply voltage source,a DC-AC converter,a branch (22) of which a first end is connected to a point of the DC-AC converter at which a high-frequency voltage is present during lamp operation and of which a further end is coupled to the rectifier circuit,the branch being conductive at least for alternating current in both directions, and the further end of the branch being connected to a first input terminal,where by the amount of interference caused by the circuit arrangement is considerably reduced, while the circuit arrangement can be realized with a comparatively small number of components.

Abstract: An extremely efficient magnet system having a comparatively large angle of aperture can be obtained for magnetic resonance imaging by a reduction of fields of all orders in a common approach affecting active and passive as well as positive and negative oriented coil elements. Passive soft-magnetic ring segments are arranged in two pairs and located within a plurality of larger diameter active magnetic coils. The active coils include a central coil and outer coils wherein the outer coils are smaller than the central coil. The coils are in a helium Dewar vessel and arranged such that the system has an aperture of about 90.degree.. The central active coil may have a larger radius than the smaller outer coils.

Abstract: A power control circuit for at least two ohmic loads includes power semiconductors, switching elements and a control unit for adjusting the power consumption of the loads. In order to comply with international standards to avoid disturbances in mains supply systems when higher loads are switched, a simple and cheap circuit is described which is also suitable for smaller domestic appliances such as light cookers, flat-irons, cooking vessels etc. A control unit controls a switchable power semiconductor unit which can pass current in two directions and connects one or both loads to the single power semiconductor unit via the switching elements in a variety of circuit configurations so as to adjust the power to the loads as required.

Abstract: A fluorescent lamp ballast having improved power factor by providing high frequency signals fed back to the a.c. side of the ballast rectifier. The feedback signal is regulated by limiting or reducing the voltage gain of the feedback signal based on the level of the unregulated feedback signal or rectified signal, respectively.

Abstract: A phantom which simulates the electric load in a magnetic resonance apparatus includes a loop which can be inductively coupled to the RF coil of the MRI apparatus and which has a predetermined electric resistance. The phantom has a simple, rugged and light construction in that the loop includes a member having a shape that corresponds mainly to the shape of the RF coil and which is made of a solid material having a specific electric resistance and a thickness chosen so that the square resistance measured on a surface of the member is between predetermined limits. The member is preferably formed as a layer of an electric resistive material provided on an electrically insulating support having a suitably shaped surface.

Abstract: A driving scheme for a high intensity discharge lamp. The driving scheme eliminates the need for a level shifter by requiring only one reference level in determining the level of current to be produced by the down converter. The down converter has a substantially constant D.C. voltage input and consumes a relatively low amount of fixed power relative to the load attached across the output of the down converter.

Abstract: A transformer having a plastics coil former on whose hollow winding tube (7) between flanges (3, 5) windings (11, 13) of different potentials are wound with one winding wound on top of the other. The flanges (3, 5) are provided with spacers (17, 19, 23) to keep the windings (11a, 13a) axially spaced from the flanges (3, 5). An insulating layer (21), which extends from flange to flange, is interposed between the windings (11, 13). The winding (11) nearer the coil-former axis is spaced from the flanges (3, 5) by fixed spacers or stepped portions (17, 19) provided on the winding tube (7). The winding (13) arranged on the insulating layer (21) is spaced from the flanges (3, 5) by spacing blocks (23) which are connected to the flange areas (24) of the coil former by integral hinges (25). The spacing blocks are operable for swinging down onto the insulating layer (21).

Abstract: An electrical connecting device having a receptacle and a two part plug inserted into the receptacle. The two part plug includes an inner part for holding a plurality of zero gap insulation displacement connectors and an outer part for receiving a corresponding plurality of insulated wires. The inner part of the plug can be inserted partially or fully within the outer part of the plug. When the inner plug part is in its partially assembled position, the insulated wires can be easily inserted into the outer part of the plug. When in its fully assembled position, the plurality of connectors within the inner part of the plug are in electrical contact with the insulated wires.

Abstract: A starting capacitor disconnect scheme for a fluorescent lamp system in which each starting capacitor shunts one or more series connected fluorescent lamps until all of the fluorescent lamps are ignited. Following ignition of all fluorescent lamps, each starting capacitor is effectively removed from the ballast. Preconditioning of the fluorescent lamp filaments can be limited to the period of time that one or more lamp loads are shunted by the starting capacitor.

Abstract: A circuit arrangement for commutating a reluctance motor including a current generator which produces first and second cyclic sequences of current pulses. In response to the first cyclic sequence applied to the stator windings of the motor, a rotor travels a predetermined distance along a motion coordinate path. Application of the second sequence to the stator windings results in the rotor traveling at least twice the predetermined distance along the motion coordinate path. The second sequence, which is applied when rotor speed exceeds a predetermined level, is formed by omitting predetermined current pulses from the first cyclic sequence.

Abstract: A transformer having a core of soft magnetic material around which a first winding and a second winding are wound and a leakage inductance based on the magnetic coupling between these windings. The effective leakage reactance is minimized by adding a third transformer winding serially connected to a capacitor, the latter of which is varied to reduce the leakage reactance over a broad frequency range.

Abstract: An ignition scheme for a high intensity discharge ballast. The ballast includes a down converter for producing a varying level of current during the glow stage of the lamp. The level of current available at the time of lamp ignition is equal to or greater than any other level of current produced during at least takeover of the lamp. The need for building up the level of current during at least takeover is eliminated thereby minimizing the need for re-ignition of the lamp.

Abstract: A compact fluorescent lamp in combination with a high frequency DC-AC converter includes a rectifier circuit and a buffer capacitor coupled between a source of low frequency AC voltage and the converter. A feedback capacitor couples a high frequency feedback signal corresponding to the converter output signal to the buffer capacitor via the rectifier circuit so as to improve the power factor of the combination.

Abstract: In a magnetic resonance imaging apparatus comprising an array consisting of several rf coil elements, a bandpass filter is coupled to corresponding individual coils of the array, the outputs of the bandpass filters being connected to form a signal summing device. As a result, a substantial part of the imaging is sequentially performed, so that the construction of the image processing device may be simpler and the risk of image artefacts is reduced. The array forms a linear series of surface coils, a common axis of which coincides with the measurement gradient field direction.

Abstract: The winding support comprises a first cylindrical portion (1) which comprises a winding space for a coil winding which is situated between a first wire fastener unit (7) and a wire guide (5), and a second portion (3) which is situated in the prolongation thereof and which is shaped as a semi-cylinder with a flat supporting face (17) for mounting an electronic component (23) which comprises contact pads (25, 27). The component (23) is mounted in a recess (19) at the area of the lacking cylinder half, which recess is axially bounded by the wire guide (5) on the one side and by a second wire fastener unit (21) on the other side. Lead-out wires (31, 41) of the coil winding are guided by way of the wire guide (5), across the contact pads (25, 27) to the second wire fastener unit (21) whereto they are fastened. Subsequently, soldered or welded joints (43, 45) are formed between the lead-out wires (31, 41) and the contact pads (25, 27) by way of a thermal treatment.

Abstract: The invention relates to a dimming circuit arrangement for operating a high-pressure sodium lamp L with controllable color temperature. The lamp is supplied with current pulses having a controllable duty cycle D. A change in the color temperature can be achieved through a change .DELTA.D in the duty cycle D and a simultaneous change .DELTA.P in the power supplied to the lamp, while the relation .DELTA.D/.DELTA.P>0 is satisfied.

Abstract: A lighting system having a primary light source and an emergency lamp. The emergency lamp is turned on and remains on upon failure or removal from the system of the primary light source. The system also includes a control device for sensing when the voltage across the primary light source rises above a predetermined level in determining when to turn on the emergency lamp.

Abstract: A fluorescent lamp system including a ballast with primary and secondary windings and a switch for each of the plurality of electrodes of the lamp system. Each switch is operable in response to the voltage across its associated lamp after its associated lamp turns on to interrupt the connection of an associated electrode to its associated heater winding, and wherein at least two of the plurality of switches conduct current which flows through a semiconductor conducting device before the lamps turn on.

Abstract: A fluorescent lamp lighting arrangement controlled by both a motion detector and a light sensing detector operable when said motion detector senses motion.