Showing papers on "Magnetic circuit published in 1969"

Soft ferrites: properties and applications

Abstract: Ferrites - their nature, preparation and processing the expression of electrical and magnetic properties properties of some manganese zinc and nickel zinc ferrites magnetic circuit theory inductors high frequency inductors wide band transformers pulse transformers and inductors power transformers and inductors ferrite antennas properties of windings.

Electrical induction apparatus

Abstract: An electrical induction apparatus, adaptable for use as a transformer or a reactor which contains a magnetic circuit and an electrical circuit. The active portions of the magnetic circuit are formed of electrically isolated segments, each segment being electrically connected to a distinct portion of the electrical circuit such that when a voltage is impressed on the electrical circuit a systematic and uniform progression of voltage is imposed on the magnetic circuit. The electrical isolation appearing between each segment of the magnetic circuit is coated with a material adapted to establish electric field boundaries between the segments and prevent the creation of high electrical stress points while also preventing excessive eddy current loses.

Saturated leakage reactances of cage induction motors

Abstract: The paper presents a method of predicting the saturation of the leakage reactances of cage induction motors. It commences with a discussion of leakage fluxes and reactances and the manner in which they are affected by magnetic saturation. The calculation of the components of leakage reactance under unsaturated conditions is described. The theory then progresses to the calculation of the magnitude and phase of the leakage-flux components likely to be affected by saturation, and to the determination of the leakage-flux paths. A general method is given for computing reduction factors, or saturation factors, to be applied to those components of leakage reactance with saturable associated fluxes. A logical system for dealing with complex magnetic circuits which contain combinations of fluxes in a number of saturable areas is described and explained by the use of examples. Saturable areas in the magnetic circuits of induction motors are defined for a number of alternative slot shapes. The variation of skew-leakage flux, and therefore of the saturation, as a function of axial position is treated by subdividing the core length into short sections and summing their reactances. Results of computations are compared with test results on 18 medium and large motors, and good correlations are shown for both unsaturated and saturated locked-rotor impedances.

Eddy-current and hysteresis effects in rotating machines

Abstract: Hysteresis in the magnetic circuit of a rotating machine is represented by an approximate method which neglects harmonics and enables the hysteresis motor to be analysed by the equivalent Kron primitive machine. The method is extended to hysteresis and eddy-current effects in hysteresis, induction and synchronous machines; steady-state equivalent circuits are derived for the hysteresis motor and induction machine.

Magnetic Forces for Medical Applications

Abstract: The force that a magnetic field gradient can exert on a ferromagnetic material can be utilized in a number of medical applications. This force is proportional to the spatial gradient of the ambient magnetic field times the magnetic moment of the material; the magnetic moment is a function of the magnitude of the ambient field and the geometry and material used. This paper discusses the importance of each of these factors and discusses methods for calculating magnetic fields and gradients produced by permanent magnets, electromagnets, and superconducting magnets. Examples of an electromagnet and a superconducting magnet for medical applications are presented.

Core losses in magnetic materials at very high flux densities when the flux is not sinusoidal

Abstract: Presently, insufficient material data is available to predict core losses at high flux densities with complex flux waveforms. A steel tester is described whereby this data can be obtained from electrical steel at densities in excess of 20 kG. The flux wave-form can be selected and controlled to study the influence of harmonics and to simulate actual flux conditions existing in magnetic circuits. An electromechanical waveform generator is capable of synthesizing waveforms of 30 to 90 Hz fundamental with phase and amplitude selected odd harmonics up to the eleventh. This signal is amplified to excite Epstein sample strips placed in a water-cooled test yoke up to 140 kA/m. Feedback technique is applied to keep total distortion between input signal and flux waveform below 4 percent at peak excitation. The flux density is measured with air-flux compensated search coils. A calorimetric method is used to measure core losses by recording the temperature rise of thermistors placed between sample strips. Some test results are presented to demonstrate the flexibility and usefulness of the steel tester.

Ferroresonant transformer with controllable flux

Abstract: A ferroresonant transformer with means for varying saturation flux capacity for controlling the transformer output. A ferroresonant transformer with at least a portion of the core structure carrying the secondary winding having two separate sections providing parallel magnetic paths for the secondary and resonant flux, with a control winding on one of the sections and a switching circuit for opening and closing the control winding. A low frequency version utilizing E and I laminations with the control winding on one of the outer legs of the E. Another low frequency version utilizing E and I laminations with the control winding encircling a portion of the secondary magnetic circuit. A high frequency version utilizing a plurality of toroid cores with the control winding on one of the cores.

Permanent magnet applications

Abstract: The main uses of permanent magnets are covered either by the range of cast and magnetically treated alnico alloys or by the several grades of sintered barium/strontium hexaferrite, but minority materials have their special applications and continue to develop. Three different technical classes of permanent magnet applications can be distinguished. Firstly, magnets working in a magnetic circuit of static reluctance, e.g., speakers, moving-coil measuring instruments, microwave devices, separators, etc. Secondly, those working in a varying self-demagnetizing field due to change of circuit reluctance, such as clamping and holding magnets which range from planning-board indicators to large chucks for machine-tools. Thirdly, magnets which work in both a self-demagnetizing field and a varying externally produced field, as in motors, generators, the several types of magnetic couplings, and magnetic suspensions. For each of these three classes the basic design principles are indicated and typical applications are described. Additionally, there are uses for high-hysteresis permanent magnet materials without premagnetization, as in hysteresis motors.

Electromagnetic valve means for tapping molten metal

Abstract: Valve means for ladles or furnaces, preferably of channel type, provided with at least one bottom tap hole. This means comprises a magnetic circuit with an "air gap" in the hole and with a flux direction straight across the flow direction in said hole. Current conductors are also arranged to conduct electric current straight across the stream, perpendicular to the flux, and a force is thus produced in the melt in the hole directed upwards or downwards and depending on the law of magnetic force. The invention also includes an embodiment with similar means in a channel type furnace, but used for circulating molten metal in the channels of the furnace.

An unorthodox transformer for free-running parallel inverters

Abstract: Limitations imposed on free-running parallel inverters by the interdependence of critical characteristics of the networks, transformers, and switching elements of these inverters are identified. The transformer's role within these networks with abruptly changing circuit configurations is related to the network's functional mechanism. Special attention is devoted to forms of "volatile" returnable energy stored within the intended paths of magnetic flux and to magnetic saturation effects in pertinent transformer cores that cause harmful current spikes at the termination of individual cycles of operation. Returnable magnetic energies stored in representative "square loop" iron and ferrite transformer cores per unit of volume, and in related air gaps are calculated and tabulated for comparison and reference. A method for mitigation of storage of unwanted magnetic energy and for the prevention of magnetic saturation in inverter transformer cores is presented; it is reinforced with quantitative relations and a report on experimental work.

Computation of magnetic field produced by two plane-parallel keepered current straps

Abstract: An integral/matrix-equation formulation is utilized to calculate the two-dimensional magnetic field produced by two plane and parallel keepered current straps. The mathematical formulation of the problem and its numerical solution are discussed in detail. Results are presented for the magnetic field inside and outside the permeable keepers, assuming different values for the thickness, width, and relative permeability of the keepers.

Electromagnetically driven tuning fork

Abstract: THERE IS DISCLOSED AN ELECTROMAGNETICALLY DRIVEN TUNING FORK STRUCTURE WITH A DRIVE COIL AND A PICKUP COIL DISPOSED NEAR THE END OF THE TUNING FORK TINES AND ON OPPOSITE SIDES THEREOF, THE MAGNETIC BIAS PROVIDED BY THE CORES OF THE COILS IS SYMMETRIC WITH RESPECT TO THE TUNING FORK AXIS. A LOW RELUCTANCE MAGNETIC CIRCUIT IS PROVIDED INCLUDING THE BASE OF THE STRUCTURE WHICH TENDS TO LIMIT THE MAGNETIC FLUX FROM THE DRIVE COIL TO THE SIDE OF THE STRUCTURE OCCUPIED BY THE DRIVE COIL AND THUS LIMIT THE INFLUENCE OF TRAY FIELDS IN THE PICKUP COIL.

Apparatus for correcting electron beam deflection

Abstract: AN APPARATUS FOR CORRECTING ELECTRON BEAM DEFLECTION IN ELECTRON MICROSCOPES CAUSED BY ASYMMETRICAL LEAKAGE FLUX COMPRISING A SMALL MAGNETIC CIRCUIT WHICH GENERATES A MAGNETIC FIELD OPPOSITE TO THE DEFLECTING COMPONENT OF SAID LEAKAGE FLUX, THE MAGNETIC CIRCUIT BEING SMALL AS COMPARED WITH THE MAGNETIC CIRCUITS OF THE ELECTRON LENS, BEING MADE OF THE SAME MATERIAL AS THE LENSES AND BEING ENERGIZED BY A CURRENT PROPORTIONAL TO THE CURRENT ENERGIZING THE MAGNETIC CIRCUITS OF THE LENSES.

Fuel injection arrangement for internal combustion engines

Abstract: A fuel injection arrangement for internal combustion engines in which the duration is varied as a function of an operating characteristic of the engine The timing of a monostable multivibrator is varied by varying the resistance values of magnetically-sensitive resistors mounted within a magnetic field which is varied as a function of a desired operating characteristic A function sensor coupled to either the rotational speed, intake manifold pressure or throttle of the engine, varies the reluctance of the magnetic flux through a magnetic circuit path The magnetically-sensitive resistors are mounted within the magnetic path so that the resistance values become varied through the function sensor

Overcurrent relay circuit

Abstract: An overcurrent relay circuit, the pickup value of which is substantially independent of the DC-component in an asymmetrical alternating current, has an input transformer, the magnetic circuit of which is provided with air gaps while the secondary load of this transformer is high-resistive To the secondary winding of the transformer is connected a rectifier with a smoothing device connected to level-sensing circuit and an output magnetic relay in the output circuit of the level-sensing circuit

Ingnitor for internal combustion engines

Abstract: An ignition device for internal-combustion engines, wherein a spark gap is, energized by a voltage pulse, has a transformer having primary and secondary windings, the secondary winding being connectable to the spark gap. An amplifier is connected to the primary winding and a magnetic circuit provides a magnetic field having an intensity which changes between determined values thereof. A galvanomagnetic sensing element is disposed in the magnetic field and is responsive to the changes in the field intensity. The sensing element is connected to the amplifier for controlling the flow of current through the primary winding so as to develop voltage pulses across the secondary winding for energizing the spark gap.

Improvements in and relating to means for measuring the direct current in direct current carrying rotor windings of dynamo electric machines

Abstract: 1,146,343 Measuring DC in rotor windings CA PARSONS & CO Ltd July 19, 1967 [Sept28, 1966], No43254/66 Heading G1U The DC current in the rotor winding of a dynamo-electric machine is monitored by measuring the voltage of a Hall plate 4 located in the magnetic circuit of a U-shaped magnetic core 3 inductively coupled to a current loop 1a carrying the rotor current and located around the axis of rotation of the rotor To compensate for error voltages introduced by axial or transverse movement of the rotor shaft, two diametrically opposed and axially displaced magnetic cores are used, Fig 3 (not shown) and the outputs of the Hall plates are added together Instead of forming a single loop, as shown, the conductor 1 may branch off to form two half-loops, Fig4 (not shown) and the loop may be mounted in a diode carrier forming part of a rotating rectifier arrangement, Fig6 (not shown)

Improvements relating to thermally sensitive magnetic devices

Abstract: 1,149,060. Temperature alarms. E. H. TAYLOR. 18 Dec., 1967 [16 Dec., 1966], No. 56516/66. Heading G4N. [Also in Division H1] A temperature sensitive alarm comprises a thermally sensitive magnetic device including a permanent magnet mounted in a surrounding housing, the housing or part thereof being formed of a material having a Curie temperature below the temperature at which the magnetic properties of the permanent magnet are affected, the device being arranged to actuate a warning device by induction of an electric current in the warning device at temperatures either above or below the Curie temperature. The arrangement of the permanent magnet and the housing is such that either below or above the Curie temperature of the material a locally intense magnetic field is produced by the device. A cylindrical permanent magnet 1 is mounted in a pot 2 of " Curie material " and surrounded by an aluminium spacer 3. This device acts as a normal pot magnet until the Curie temperature is passed whereupon the magnetic circuit through 2 is broken and the annular magnetic field no longer exists. In another embodiment (Fig. 2, not shown) a polepiece (4) of " Curie material " is provided on the magnet 1 to give a device working in the same way. Another series of devices is disclosed which work in the opposite way, i.e. they have no effective magnetic field at room temperature but exhibit a magnetic field once the Curie temperature is passed. In one embodiment (Fig. 3, not shown) the device is identical in shape with that shown in Fig. 1, but the spacer 3 is made of the " Curie material ". In other embodiments (Figs. 4 to 8, not shown) combinations of aluminium spacers, polepieces and " Curie material " keepers are employed to give pot magnets and shallow-pot magnets, some having bolted keepers. The pot magnets may be used to form temperature sensitive electric switches or fluid valves, whilst auxiliary heating coils may be used to heat the magnets. The " Curie materials " may be nickel/iron, copper/nickel, pure nickel, "Nilo" (RTM) or Ferroxcube Mn-Zn ferrite whilst the permanent magnet may be Alcomax III (RTM).

Magnetic recording head

Abstract: 1,179,251. Magnetic recording heads. EPSYLON RESEARCH & DEVELOPMENT CO. Ltd. 25 April, 1967 [29 April, 1966], No. 18933/66. Heading G5R. A head comprises a primary magnetic circuit 45, having a winding 47 and a recording gap 48, and a secondary magnetic circuit 49 having two spaced limbs 50, 51 and a winding 52, the secondary circuit 49 being located with one limb 50 facing the. gap 48 and the parts of the primary circuit on either side thereof and the other limb 51 facing the surface of one limb 52 of the primary circuit, the tape (not shown) passing through a gap between the circuits and the signals to be recorded being fed to both windings. The effect is that the effective recording flux is concentrated in a narrow portion 61 of the gap between the two circuits.

Magnetic wheel with rotor position sensor

Abstract: A unique magnetic circuit in a magnetic rotor position sensor couples the change of the periodically generated DC magnetic flux in a command coil to an interrogating coil.

A magnetic recording head

Abstract: 1,141,726. Electromagnetic printing. STANDARD TELEPHONES & CABLES Ltd. 2 June, 1967, No. 25608/67. Heading B6C. [Also in Division G5] Recordings are made on a magnetic medium by an effectively moving gap in a stationary recording head produced by applying to the head a gradually decaying A.C. bias signal to provide a flux which follows a path whose reluctance reduces gradually from one end of the head to the other. As shown, an offset bias winding 1 is arranged between saturable flanges 5 attached to polepieces 6, 7 so that the reluctance path reduces from end A to end G. The signal "winding" comprises a single wire 8 in a gap 16 and the materials of the polepieces and medium 9 are chosen so that the magnetic circuit between them has a rectangular hysteresis loop (Fig. 3). When the A.C. bias is applied in the absence of a record signal, successive regions across the head are demagnetized. When a record signal is present and when the bias amplitude at a particular region is just insufficient to take that region through a complete cycle and thereby change its state of magnetisation, that part of the record signal prevailing adds a relatively D.C. component to the bias so as to record that part of the signal 15 (Fig. 3) at that region, the amplitude ΠH1 of the record signal being insufficient by itself for recording. Transverse tracks may thus be recorded across a magnetic tape for video recording, the tape being driven either continuoulsy or stepwise, the signal being recorded while the tape is stationary. In either case, a sync. pulse is interposed between successive signals. In modified constructions, the signal winding 8 is disposed in a slot in one of the pole pieces (Figs. 4A, 4B, not shown), or in a separate core member on the opposite side of the tape from the biasing core (Figs. 6A, 6B, not shown), or a generally U-shaped core may have the winding 8 in one limb with the tape passing between the limbs (Figs. 5A, 5B, not shown). The head may be used in non-percussive printing in which a signal is recorded across the width of a drum or band, made visible with magnetic powder which is then transferred to a sheet under pressure, and finally "fixed" by heating.

Solid-state hour meter

Abstract: The following specification describes an hour meter assembly utilizing a solid-state circuit applying appropriately timed pulses to a coil capable of driving the meter dials with portions of the coil magnetic circuit and terminals supplying electrical power to the circuit serving to locate and secure an assembly of the solid-state circuit and dials in a meter case.

Contact-free electrical pulse generator utilizing galvanomagnetic semiconductor body

Abstract: A permanent magnetic circuit directs a control magnetic field during operation to a galvanomagnetic semiconductor body. A first magnet in the circuit has a rectangular hysteresis loop. An outside magnet outside the magnetic circuit provides a magnetic field for abruptly switching the first magnet from one remanent state to the other whereby the total magnetic induction which results at the semiconductor body changes abruptly from one magnitude to another. A second magnet is connected in the magnetic circuit in magnetic parallel with the first magnet relative to the semiconductor body.

Electrical isolating transformer

Abstract: An isolating transformer is described for transmitting AC electrical power from a power-supply circuit at ground potential to a load circuit which is at DC high voltage; the transformer comprises a single transfer loop equipped with insulation which withstands the DC voltage, which loop is inductively coupled to a first of said electrical circuits by way of a magnetic circuit completely surrounding the said turn, and inductively coupled to the other of said electrical circuits and at DC potential thereof.

Magnetic analog memory device

Abstract: A magnetic analog memory device comprising a core with control windings and a variable induction transducer or sensing means, in which a higher stability is achieved by making up the core of two open parts, each part carrying a control winding and forming a magnetic circuit with two poles, the first poles of the magnetic circuits being combined, the second poles being separated by a gap accommodating the variable induction transducer.