Showing papers on "Isolation transformer published in 1977"

DC signaling circuit for use in conjunction with isolation transformers

Abstract: The present invention relates to a DC signaling circuit operatively associated with a communication system having an isolation transformer interconnected between a central communication exchange center and a station site such as a power substation or generating plant where high voltage potential exists. The isolation transformer provides protection from fault conditions that could apply hazardous voltage to a cable pair entering the station. Because of the presence of the isolation transformer, there is no direct path for DC signal functions to pass from the station to the central communication exchange center. Thus, the DC signaling circuit of the present invention is designed to simulate and transfer the simulated DC signals across the isolation transformer to a line side of the communication system leading to the central communication exchange center. DC signals and logic information generated by a signal source such as a telephone on the station side of the isolation transformer can thusly be effectively transferred across the isolation transformer exactly as generated and in a clear and undistorted manner due, at least in part, to provisions in the DC circuit that shunt the windings of the isolation transformer during time intervals when DC signals are generated and communicated to the line side of said communication system.

Transformer coupled pass element

Abstract: A programmable negative resistance circuit, transformer coupled to the low-voltage high-current output conductors of the center-tapped secondary winding of a switching power supply transformer, maintains a constant voltage output irrespective of large load current variations.

Explosive magnetic field compression generator transformer power supply for high resistive loads

Abstract: An explosive flux compression generator is coupled to a high resistance load by a pulse transformer. Chemical energy is converted to electromagnetic energy and is transferred by means of the transformer to the high resistance load. The transformer allows coupling to a higher resistive load than is achieved with a transformerless-generator system having a current gain greater than unity.

Ferroresonant voltage regulating circuit

Abstract: A ferroresonant voltage regulator circuit includes a non-saturating transformer, a linear reactor in series with the input, and a capacitor across the non-saturating transformer. Voltage sensing and referencing circuits are inserted in the output. A synchronous switch -- usually a saturable reactor, a magnetic amplifier, a triac or back-to-back SCR's -- is connected in shunt across at least a portion of the non-saturating transformer, and is controlled by its control coil in a manner such that the non-saturating transformer is loaded by the shunt loop at no-load conditions of the regulator. The control coil of the synchronous switch is connected in the voltage sensing and referencing circuits, and acts so that the amount of loading on the non-saturating transformer from the synchronous switch varies substantially inversely as the amount of loading because of the load on the voltage regulator circuit. A linear reactor may be series connected with the synchronous switch in the shunt loop. The non-saturating transformer has an air gap in its iron core so that it has a considerably more linear volt-ampere vs. flux density characteristic of the core and the air gap than that of a similarly rated and constructed saturating transformer.

Automatic current overload protection circuit for electrostatic precipitator power supplies

Abstract: An automatic current overload protection circuit for electrostatic precipitator power supplies of the type utilizing a ferroresonant transformer. A low voltage tertiary winding in association with the transformer provides an output voltage to a sensing circuit for inhibiting current flow into the primary of the transformer when the tertiary voltage falls below a predetermined threshold. Another output voltage developed in association with the high voltage secondary winding of the transformer is also utilized to independently inhibit current flow into the primary of the transformer when the secondary voltage falls below a predetermined threshold. A time delay may be provided to permit operation of the overload protection circuit only in the event of a sustained overload current condition.

Oil burner ignition and control package

Abstract: The high voltage transformer for the ignition system of an oil burner and the control system for the oil burner are packaged together in a single housing. The duty cycle of the transformer is discontinuous. The transformer core is of symmetric U-I configuration but the coil arrangement is asymmetric with a single primary coil being provided. The transformer is not potted, the core ends are free of coils, and one core end overlaps a circuit board for the control system to thereby foreshorten the overall package. Although the transformer is not potted, tight constraints against shorting of the high voltage secondary leads are maintained by provision of an insulator bushing means which is positioned in apposition to the transformer secondary coils by means of a bracket which also provides a mounting for the transformer core, the high voltage leads being drawn through the insulator bushing means and secured at terminal contacts at the lower ends of the bushing means. The entire package is hinged for movement into and out of working association with the ignition leads of an oil burner.

Low cost, high efficiency radio frequency transformer

Abstract: Especially simple structure for an electrical transformer device provides cost effective fabrication thereof and offers improved operating performance particularly in a radio transmitter circuit for coupling high levels of radio frequency energy from the output of a radio frequency amplifier to an antenna system. One winding of the transformer is formed from a single, unitary, tubular member arranged into a U-shaped configuration which includes a pair of spaced sets of openings therein for the two-fold purpose of allowing efficient threading of a secondary winding therewithin and to improve air cooling characteristics of the device. A second winding comprises a wire passed through the interior of the tubular member, and a number of cylindrically shaped magnetic elements are sleeved over the tubular member to enhance the mutual inductive coupling between the windings. A circuit board having a cut-out zone therethrough is especially adapted to have the transformer device mounted thereon in an essentially flat position juxtaposed over the cut-out zone to provide maximum convection and conduction cooling of the transformer and thereby significantly increase the power handling capabilities of the device.

Transient voltage distribution improving line shield for layer wound power transformer

Abstract: An improved electrostatic shield assembly for power transformer windings provides a decreased shield to winding insulation spacing. The decreased spacing substantially improves the capacitive coupling between the windings and shield, reducing transient voltage oscillations within the windings caused by external lighting surges.

Shunt circuit for an insulation type current transformer to adapt to a wide-band of frequency

Abstract: A current transformer for large currents having an inductive element, such as a large DC current transformer; a universal current transformer or a wide-band high fidelity current transformer, is improved by providing a shunt circuit which comprises a series connection of a first line comprising a first resistive element and a first inductive element and a second line comprising a series connection of a second resistive element, a second inductive element and the current transformer, wherein the first line is connected in parallel with the second line.

Flyback type switching power source device

Abstract: A flyback type switching power source device alternately having a time during which energy is stored in a transformer and a time during which the stored energy is taken out. A current flowing into the primary winding of the transformer or out of the secondary winding thereof is detected, and the current thus detected is converted into a DC voltage proportional to the magnitude thereof. Furthermore, a voltage resulting from superimposition of the DC voltage upon a reference voltage is compared with a DC voltage resulting from conversion of a voltage induced in a tertiary winding of the transformer during the time for taking out the energy stored in the transformer to control the time during which energy is stored in the transformer.

Electronic transformers using amorphous material

Abstract: An electronic current transformer uses an amorphous material core transformer which operates into a virtually zero ohm load by use of feedback type operational amplifiers. The output voltage is directly proportional to the primary current of the transformer. Due to the very low flux density created by virtually short circuiting the CT, the nonlinear effects and core losses are reduced substantially. An advantage of the electronic transformer is, among others, that a current transformer of reduced size may be used. Application of the amorphous alloys in small electronic current transformers and other devices appear to be justified where the design optimization can make use of (1) the lower cost expected from the amorphous alloys, or (2) their lower losses and higher permeabilities compared to the crystalline Fe-Co and Fe-Si alloys. Test results have shown that the amorphous material core transformer using an active load has somewhat lower performance than Fe-Ni (HyMu 80)Rcore transformer of the same size but the amorphous core transformer is significantly superior to the Fe-Si core transformer.

Voltage control circuit for a DC-to-DC convertor

Abstract: A DC voltage convertor utilizes a switching transistor for switching the primary of a power transformer inserted in the emitter-collector circuit of the transistor, the base of the transistor is connected to the secondary of a control transformer which has its primary connected in series with the primary of the power transformer. A further secondary winding on the control transformer is connected to a transistor control circuit, which is controlled by a voltage dependent on the output voltage of the converter, provides voltage stabilization without galvanic connection between the primary and secondary sides.

Ferroresonant transformer power supply

Abstract: An electrical power supply for providing an electrical power signal of substantially constant voltage when the current level of the power signal is less than a predetermined value and for reducing the voltage of the power signal below said predetermined level when the power signal current level exceeds the predetermined value includes a ferroresonant transformer. A saturable reactor provides a current responsive impedance connected to the primary of the ferroresonant transformer for reducing the voltage supplied to the primary winding. The maximum current level in the secondary circuit of the ferroresonant transformer is adjusted by adjusting the effective impedance of the saturable reactor. A rectifier may be connected in the secondary circuit of the ferroresonant transformer to provide direct current electrical power signal. Three phase power may be used as a power supply input with six ferroresonant transformers having three primary windings connected in delta and three primary windings connected in wye electrical configuration.

High-voltage apparatus for skin therapy

Abstract: An apparatus for skin therapy employs a circuitry for generating a high voltage that is connected to an electrode. The circuitry to step up voltage from a power supply includes a transistor, transformer and rectifier; and the means to control application of the stepped up voltage to an electrode coil or transformer includes a silicon controlled rectifier in series with a capacitor and an output transformer's primary. Pulsing means, having voltage supplied from a power source on a separate circuit, to control the rate of silicon controlled rectifier firing and therefore discharge of the capacitor includes a unijunction oscillator and transistor. The output transformer's secondary powers the electrode.

Isolation voltage test apparatus

Abstract: Disclosed is an apparatus for providing non-destructive isolation voltage testing of circuit elements which includes a controllable full wave rectifier in series with the primary winding of a high voltage transformer, the secondary winding of which is connected to the circuit element under test. A current detector is responsive to a predetermined threshold current in the tested circuit element for providing a signal to control the rectifier to open-circuit the transformer primary winding prior to destructive breakdown of the tested circuit element. Opto-electronic elements are utilized in the rectifier to provide for the virtually instantaneous open-circuiting of the high voltage transformer primary winding.

Minimizing lamp flicker and blower speed variation in a microwave oven employing duty cycle power level control

Abstract: A microwave oven circuit includes a magnetron power transformer and a duty cycle controlled switching element connected to periodically energize the power transformer from an AC power source. Due to the effects of power source loading, the available AC voltage drops during those intervals when the power transformer is energized. This undesirably causes cyclical variation in the operation of certain constantly energized load devices such as the oven lamp and the motor for the blower which provides cooling air for the magnetron. To minimize the undesirable voltage variation, a low voltage secondary winding on the magnetron power transformer is connected in series with the constantly energized load device and properly phased to provide a voltage boost upon energization of the power transformer. Preferably, the low voltage secondary winding is an otherwise unused winding originally intended to be a magnetron filament winding. As a result, very little additional cost is involved.

Power transistor switching with a controlled regenerative current mode transformer

Abstract: A controlled regenerative current mode transformer provides nearly ideal characteristics as the control and driving means for power switching transistors. Guaranteed transistor gain, elimination of crossover current, and positive on/off control with a minimun of control power are some of the advantages when used as the interstage transformer. Design criteria are discussed utilizing DC to DC converter/regulator circuits to illustrate and analyze the transformer's performance characteristics.

Power supply for screened equipment enclosure - incorporates low pass filter on isolating transformer secondary side and overvoltage discharge elements on primary side

Abstract: The equipment components in a screened enclosure are fed from an AC source itself in a screened case. On the primary side of the isolating transformer discharge elements are connected to each input lead, to divert over-voltages to earth. A screen lead may be similarly protected. On the secondary side a low pass filter to eliminate electromagnetic impulses is connected to each lead. In single phase one end of the secondary winding is earthed to give voltage equalisation and the filter connected to the unearthed line. The filter typically provide damping of the order of 60 db in the range 10 to 10 Hz.

Multi-Stage-Singular Flyback Transformer

Abstract: A new flyback transformer has been developed with a secondary coil that is divided into several windings which are connected alternately in series with the same number of high-heat resistant, glass-molded diodes has been developed. This new design results in improved voltage enduring properties, facilitates transformer insulation and permits efficient high voltage regulation in dc voltage generation. Overall transformer size and weight are also reduced, which saves space in television receiver sets.

Switching circuit for TV receiver - derives setting value from pulse voltage of isolating transformer primary in amplitude rectifier for protection of output voltage rise

Abstract: The circuit has an isolating transformer (6), a periodically conductive switch, a feedback path (7, 16) derived from the transformer primary for the switch control, and a stabilising circuit (12) for output voltages. The circuit provides protection against heavy rise of output voltages (U1, U2). The protection is obtained by deriving a setting value (U5) from the pulse voltage on the primary side of the isolating transformer in an amplitude rectifier (14). If a threshold value has been exceeded, the setting value blocks the feedback path via an electronic switch (16) in series with the feedback path. The rectifier is preferably coupled to a coil (11), supplying the stabilising circuit.

Furnace transformer having a low-voltage internally-connected delta winding

Abstract: A high current furnace transformer is provided having the low-voltage windings arranged in a closed delta configuration within the transformer enclosure. Bus bar terminals are mounted exterior to the enclosure for providing electrical connection with the low-voltage windings.

Behavior of transformer insulation under short-time overvoltage

Abstract: This paper reports on a series of tests made on transformer insulation samples with automatically applied short-time a.c. overvoltages above the corona inception level to determine the conditions under which damaging corona occurs. Modified dielectric tests for power transformers are discussed.

The isolation amplifier, an interface between EEG recorder and data processor.

Abstract: An isolation amplifier is presented which is intended as an interface between electrophysiological recorders and standard data processing equipment. Due to its floating input and output, differences in ground potentials do not disturb the transmitted signal. Hence, recorder and data processors can be grounded according to the manufacturer's recommendation. Powerline leakage currents are also prevented from loading the ground of the electrophysiological recorder. Compared to the isolation transformer this device saves space, while polarity restorations can be made and no modifications are needed in any piece of equipment.

Horizontal deflection circuit

Abstract: The application relates to a thyristor-controlled horizontal deflection circuit of a television receiver with mains isolation Input inductor, communtating inductor, and isolation transformer are united in one component In the transformer used for this component, the open-circuit inductance performs the function of the input inductor of a conventional thyristor horizontal deflection circuit, and the short-circuit inductance that of the commutating inductor

Control circuit for transistor pushpull inverter - has saturation transformer for feedback control with core windings carrying DC equal to half period flow

Abstract: The saturation transformer primary is connected through a resistor in parallel with the invertor transformer primary winding. Its secondary winding is directly connected to control junctions of switching transistors. Two further windings (III1,III2) are provided on the saturation transformer (U1) core. They carry a current equal to the mean direct current flowing in each half-period, but flowing in the opposite direction. The series resistor in the saturation transformer (U1) primary circuit is replaced with a constant current circuit. Another embodiment utilises a circuit with the input voltage connected to an opposite diagonal of the main bridge.

Transducer servicing and isolation circuit - modulates HF oscillator feeding transformer whose output is full wave rectified and filtered, producing digitised output

Abstract: The transducer servicing circuit produces a standard voltage digitized output and electrically isolates the transducer from its associated transmission line. The circuit is for use with transducers on gas turbine engines, boilers and the like, and is insensitive to heat and other disturbances. A transducer (1) with a digital output modulates a relatively H.F oscillator consisting of a diac (7) and resistance capacitance circuit, and this signal is fed to an isolating transformer (3). The output of this is full wave rectified (10, 11) and filtered to produce a standard voltage digitized output suitable for transmission down a line to a logic receiver network.