1182 results about "Field coil" patented technology

An improved interrogator for an inductively coupled identification system is disclosed. The interrogator provides a multidimensional electromagnetic field through a plurality of coils aligned relative to each other. The coils provide a rotating magnetic field having approximately constant amplitude regardless of orientation with respect to the transponder. An additional coil may be utilized to precess the multidimensional electromagnetic field. The interrogator may further provide an impedance matching network that includes a series drive capacitor to match the impedance of a capacitor in parallel with a coil to a driver load impedance.

A low inductance electrical machine which may be used as an alternator or motor with low armature inductance is disclosed. Arrangements of complementary armature windings are presented in which the fluxes induced by currents in the armature windings effectively cancel leading to low magnetic energy storage within the machine. This leads to low net flux levels, low core losses, low inductance and reduced tendency toward magnetic saturation. Separately excited field arrangements are disclosed that allow rotor motion to effect brushless alternator or brushless motor operation. An exemplary geometry includes a stator including two toroidal rings and a concentric field coil together with a rotor structure separated from the stator by four air gaps. An alternate embodiment allows for counter-rotation of two rotor elements for use as a flywheel energy storage system in which the external gyroscopic effects cancel.

A method and device for monitoring vascular access is described. A field coil is placed at a location on an extracorporeal circulation loop connected to the vascular system of a patient, and an induction coil is placed at another different location. A voltage is supplied to the field coil, inducing an electric current in the blood. The current induces a voltage in the induction coil. Monitoring the voltage in the induction coil reveals if vascular access is defective.

A probe instrument using room-temperature sensor(s) that can measure variations in magnetic susceptibilities. The instrument has sufficient resolution to monitor paramagnetic materials in a human body, such as iron in a human liver, by noninvasively examining patients with iron-overload diseases. The instrument includes room temperature magnetic sensors, and detects the sample, that is, the tissue response to an alternating current field applied by an applied field coil. The applied field coil dimensions are chosen so that the applied field is optimized for maximum response from the liver while minimizing the effects due to the overlying abdominal tissue and at the same time not unduly increasing the sensitivity of the instrument to the lung. To overcome variations in the sensor output due to fluctuations in the applied field, change in the ambient temperature and mechanical relaxation of the instrument, the sensor-sample distance is modulated. The detector assembly is oscillated while the examined patient remains stationary. An improved water-bag technique is employed to eliminate background tissue response. The detector assembly forms part of a probe instrument for performing noninvasively the paramagnetic concentration of a patient.

An electromagnetic vibrator has a movable magnet that can move linearly in an axial direction. A field coil surrounds the movable magnet. Magnetic bumpers are disposed on opposite ends of the vibrator, and are oriented to repel the movable magnet. When an alternating current is provided in the field coil, the movable magnet oscillates linearly in the axial direction, bumping against the magnetic field of the bumper magnets and thereby creating vibration. The movable magnet may have a toroidal shape and be disposed on an axial shaft to linearly constrain the motion of the movable magnet. Two field coils can be provided to simultaneously create push and pull forces on the movable magnet. The bumper magnets can be replaced with compression springs. The electromagnetic vibrator can be very small and energy efficient; it is well suited for use in portable electronic devices, cell phones, toys, industrial mixers, and massage devices.

An atomic clock having a physics package that includes a vacuum chamber cavity that holds atoms of Rb-87 under high vacuum conditions, an optical bench having a single laser light source, a local oscillator, a plurality of magnetic field coils, an antenna, at least one photo-detector and integrated control electronics. The single laser light source has a fold-retro-reflected design to create three retro-reflected optical beams that cross at 90° angles relative to one another in the vacuum chamber cavity. This design allows the single laser light source to make the required six trapping beams needed to trap and cool the atoms of Rb-87. The foregoing design makes possible atomic clocks having reduced size and power consumption and capable of maintaining an ultra-high vacuum without active pumping.

A homopolar machine produces an axial counter force on the rotating shaft to compensate for the load on the shaft's thrust bearing to reduce wear and noise and prolong bearing life. The counter force is produced through magnetic interaction between the shaft and the machine's field coils and is created by changing the current excitation of the field coils, which results in a magnetic flux asymmetry in an inner flux return coupled to the shaft. The homopolar machine may also have a configuration that uses current collectors that maintain substantially constant contact pressure in the presence of high magnetic fields to improve current collector performance. The current collectors are flexible and may be made from either electrically conductive fibers or stacked strips such that they bear up against the armature so that the pressure is maintained by the spring constant of the current collector material. The homopolar machine may also have a configuration where the brushes are oriented so that the current is aligned as much as is practical with the local magnetic field lines so as to reduce the lateral electromagnetic forces on the brushes.

A hand-held power tool (1) includes a linear motor (2) having a rotor (3) which is movable along a percussion axis (A) in an axially limited manner between two reversal points (W) and which can be driven by the striking piston (5) of the power tool with the intermediary of an air spring (4), sensors designed for determining the actual state of the rotor (3) and connected to a computer (9) connected via power electronics (33) to at least one field coil (10) of the linear motor (2), with the rotor (3) being displaced against a contact element (11a, 11b) at least at one reversal point (W) and being pressed against the contact element electromagnetically; and a control process for the hand-held power tool.

A brushless electrical machine, usable as a motor, generator, or alternator, has a rotor that is comprised of a rim portion and a substantially open center portion. The rim portion has a partially hollow core in which a stationary field coil is supported. Current to the field coil generates magnetic flux that circulates in a poloidal flux path in the rim, crossing a single magnetic air gap formed by the rim. Protrusions in the rim located around the circumference form poles all having the same polarity. As the rotor rotates, the flux exiting the poles passes through multiple stationary armature windings around the circumference that are located in the single air gap. An AC voltage is induced in the armature windings from rotation.

An engine-driven welder/generator is controlled by an integrated controller that is coupled to both the engine and to the welder/generator. The controller receives input signals for operational parameters of the engine, and additional signals indicative of electrical output by the welder/generator. Operation of the engine and welder/generator may thus be coordinated. The controller may control speed, timing, fuel injection, and so forth of the engine, and output of the welder/generator, such as by control of input to a field coil.

A belted-alternator starter system that continuously provides pre-flux when the vehicle ignition is on and the engine is off to provide a faster torque response when the engine is turned on. The alternator/starter device operates as an alternator for providing electrical energy to vehicle electrical devices and the battery when the ignition is on and the engine is running, and operates as a starter for providing engine torque to start the engine when the engine is off and the ignition is on. The system further includes an inverter/rectifier circuit to provide AC current to the armature coils when the alternator/starter device is operating as a starter. The system provides an operating field current to the field coil when the ignition and the engine are on and provides a pre-flux field current to the field coil when the vehicle ignition is on and the engine is off.

Methods and apparatuses for magnetic resonance imaging (MRI) and/or magnetic resonance spectroscopy comprising a superconducting main magnet operable to generate a uniform magnetic field in an examination region, at least one superconducting gradient field coil operable to apply a respective at least one magnetic field gradient within the examination region, and at least one RF coil that is operable to transmit and receive radio frequency signals to and from the examination region, and that is configured for cooling and comprises at least one of (i) a non-superconducting material that when cooled to a temperature below room temperature has a conductivity higher than that of copper at that temperature and (ii) a superconducting material. The main magnet, the gradient coils, and each of the at least one RF coil of a given system may each be implemented as high temperature superconductor materials.

The invention discloses a magnetorheological hydraulic engine mount based on an extrusion mode, which comprises a housing, a rubber main spring, a connecting rod and a rubber bottom membrane, wherein a decoupler is arranged between the rubber main spring and the rubber bottom membrane; a field pole plate is fixedly arranged on the connecting rod, close to the decoupler; a field coil is wound in the field pole plate; an extrusion pole plate is arranged on the decoupler, corresponding to the field pole plate; and an extrusion damping channel is formed between the extrusion pole plate and the field pole plate and fully filled with magnetorheological fluid. The magnetorheological hydraulic engine mount adopts the extrusion mode, and the field pole plate arranged on the connecting rod forms the extrusion damping channel with the extrusion pole plate on the decoupler, so that the vibration isolation capability of the mount is improved. In addition, the extrusion mode can satisfy a maximum output damping force and expand an adjustable range of the damping force.

A synchronous motor with low vibrations and an electric driving system using the motor. A field-coil synchronous motor comprises a stator and a rotor rotatably supported at the inner peripheral side of the stator with a gap left relative to the stator. The stator has a stator coil supplied with electric power while being controlled such that driving torque is reduced as a rotation speed of the rotor increases, and the rotor has a field coil supplied with a field current while being controlled such that the field current is reduced as the rotation speed of the rotor increases. The rotor is a tandem claw-pole rotor comprising plural pairs of N- and S-claw poles disposed side by side in an axial direction, and the plural pairs of claw poles of said tandem claw-pole rotor are relatively shifted from each other in a circumferential direction.

A synchronous electric machine having a fixed stator, a multi-phase stator winding and having a rotor which has poles, excited in a predefined sequence, over its circumference, the number of poles being changeable as a function of the intensity and the direction of a field current in at least one field coil of the rotor. For improving the efficiency of the machine and for reducing the number of field coils and the entire coil cross section it is provided that the rotor has a laminated core, laminated in the axial direction, which has grooves on the circumference for accommodating the at least one field coil and that the at least one field coil is situated on the circumference of the rotor with a step size which corresponds to the pole pitch of the lower number of poles.