Showing papers on "Isolation transformer published in 1982"

Method of manufacture of miniaturized transformer

Abstract: A miniaturized thick-film isolation transformer comprising two rectangular substrates each carrying successive screen-printed thick-film layers of dielectric with spiral planar windings embedded therein. The spiral windings comprise conductors formed of fused conductive particles embedded within a layer of dielectric insulating means solidified by firing at high temperature to form a rigid structure with the windings hermetically sealed within the dielectric and conductively isolated from each other within the transformer. The substrates are formed at opposite ends thereof with closely adjacent connection pads all located at a single level to accommodate automated connection making. Connections between the pads and the windings are effected by conductors formed of fused conductive particles. The substrates and the dielectric layers are formed with a central opening in which is positioned the central leg of a three-legged solid magnetic core. The remaining portions of the core surround the two substrates to form a compact rugged construction especially suitable for assembly with hybrid integrated circuit components.

Coupling power line communications signals around distribution transformers

Abstract: A circuit is described for bi-directionally coupling a communication signal around a distribution transformer. The circuit includes a single-phase coupling transformer with a primary to secondary voltage ratio approximately equal to that of the distribution transformer. A capacitor is connected to one of the secondary terminals of the coupling transformer. The capacitor is chosen so that the series circuit including the capacitor, the self inductance of the coupling transformer and, possibly, the series inductance of interconnecting lines is resonant at the carrier frequency of the communications signal. The series combination of the capacitor and the secondary of the coupling transformer can be connected between two of the conductors on the secondary side of the distribution transformer which are selected for communication signal propagation.

Power line communications bypass around delta-wye transformer

Abstract: Circuits for bi-directionally bypassing a delta-wye transformer with a balanced phase-to-neutral power line communication signal, using passive components. The circuits include a set of three capacitors connected in a wye configuration, each having one side connected to one of the three-phase power lines on the delta side of the transformer. The circuit further includes a network connected from the node of the wye configuration of capacitors to neutral, the network including an inductive reactor with one side connected to neutral and the other connected to the node of the wye windings of the transformer. Component values are selected so that the circuit is resonant from the three phase lines on the delta side of the transformer to neutral. Further, the voltage transformation ratio of the communication signal from the delta side to the wye side is made the same as the corresponding power voltage ratio of the transformer.

Communications signal bypass around power line transformer

Abstract: A circuit for bi-directionally bypassing a delta-wye transformer with a balanced phase-to-neutral power line communications signal, using passive components. The circuit includes a set of three capacitors connected in a wye configuration, each having one side connected to one of the three phase power lines on the delta side of the transformer. The circuit further includes a network connected from the node of the wye configuration of capacitors to the neutral conductor or conductors associated with the power lines on the two sides of the delta-wye transformer. The network includes a single phase transformer, as well as a capacitance connected from the secondary of this transformer to the node of the wye of the delta-wye transformer. The network further includes an inductive reactor connected from the neutral on the wye side of the delta-wye transformer to the node of the wye transformer. Component values of the network are selected so that the network is resonant from the three phase lines on the delta side of the transformer to the node on the wye side of the delta-wye transformer. Further, by selection of the voltage ratio of the single phase transformer, the voltage transformation ratio of the communications signal from the delta side to the wye side is made the same as the corresponding power voltage ratio of the delta-wye transformer.

High voltage, low power transformer for efficiently firing a gas discharge luminous display

Abstract: A power system comprising a high voltage, low power transformer that utilizes self-resonance parameters and pulse control techniques for efficiently firing a gas discharge lamp of the type commonly used to form a luminous advertising display. The transformer is fabricated from a material, such that the transformer will have a characteristic self-resonating frequency. The transformer is driven by Direct Current pulses from a source of supply thereof. The widths of the current pulses are controlled so as not to exceed one fourth the wavelength of the self-resonating frequency of the transformer. Performance is optimized when the repetition rate of the current pulses is directly controlled according to the self-resonating frequency of the transformer. By virtue of the present invention, an efficient transformer of relatively low weight, size, and cost is provided by which to fire the lamp of the display and thereby produce an apparent optical intensity that is approximately equal to that available from a conventional gas discharge power transformer. However, the energy consumed by the present transformer is substantially less than that expended by presently available transformers.

Constant power switching power supply

Abstract: A power supply for a gaseous discharge lamp in which power adjustments are made automatically to insure that rated lamp power is delivered regardless of changes in lamp impedance or line voltage which may occur. A high D.C. voltage is delivered to a step down low hysteresis transformer and electronic switching is provided to obtain a high frequency pulsed flow to the primary of the transformer. Sawtooth waves are generated and peak current is utilized to regulate closely power input to the transformer. A feature is the use of a programming resistor to select the desired power level for the particular gas discharge lamp.

Electrosurgical generator with improved rapid start capability

Abstract: An electrosurgical generator, having particular utility in arthroscopic surgical procedures, is provided with a rapid start capability in its pure cut mode by inhibiting secondary modulation for an initial starting interval during which an uninterrupted high frequency cutting signal is applied to the output terminals. Upon expiration of the starting interval, the secondary modulation takes effect to modulate the cutting signal with a low frequency repetitive signal having a predetermined duty cycle. In addition, the generator output isolation transformer is arranged to provide an output impedance of at least 1,000 Ohms to match the impedance of human joints on which arthroscopic surgery is performed.

Transformer apparatus with -superimposed insulated switch and transformer units

Abstract: This invention relates to improvements in a transformer apparatus in which a transformer unit insulated with insulating oil and a switch unit insulated with insulating gas are combined. The transformer unit is accommodated in a transformer tank filled with the insulating oil. The switch unit is accommodated in a switch tank filled with the insulating gas. The switch tank is disposed on the top of the transformer unit and made integral therewith such that these tanks are communicated with each other in the interior of the communicated tanks.

Ground fault detector and shutdown system

Abstract: A ground fault detection and shutoff system for underwater power transmisn provides protection to divers from swimming into electric fields. This system uses DC power to monitor the true resistance of the load system rather than the AC power to the load. The system comprises DC power supply, ground fault monitor, circuit breaker and isolation transformer which monitors the system's DC resistance to ground and shuts off the power system if the resistance falls below a preset value.

DC to DC switching regulator with temperature compensated isolated feedback circuitry

Abstract: A DC to DC switching regulator includes a first pulse width modulator (PWM) (26) and two switching transistors (48) and (50) that are coupled to a transformer (18) to generate an output signal that has pulse widths variable in response to the PWM (26). The output of the transformer (18) is rectified to provide a regulated DC output. A second PWM (78) is provided to convert the amplitude of the regulated DC output to a stream of pulses that are input to an isolation transformer (112) by a push-pull arrangement of transistors (118) and (120). The pulse width of the pulses input to the isolation transformer (112) is variable as a function of the level of the regulated DC and the amplitude thereof is a constant referenced to the internal reference of the PWM (78). The output of the isolation transformer (112) is rectified and filtered to provide an error signal that varies in response to the pulse width of the output pulses from the PWM (78). The constant amplitude, variable width pulses output by the PWM (78) provides a signal that does not vary in response to noise on the regulated DC output and the error signal derived therefrom is input to the PWM (26) to vary the pulse width thereof to maintain regulation on the regulated DC output.

Method and apparatus for balancing flux in a power transformer circuit

Abstract: Method and apparatus are disclosed for use with switching power transformer circuits for balancing and compensating for core flux caused by unswitched D.C. current flowing in the transformer. A method and apparatus for adjusting the duty cycle of the switching portion of the power transformer circuit serves to balance the flux present in the transformer core during each half cycle of the operation of the circuit.

Power converter symmetry correction circuit

Abstract: A pulse width modulated power converter having a single time multiplexed symmetry correction circuit operative to vary the pulse width of output drive pulses applied to an output transformer. As a result, the average current and thus the volt second product seen by each half of the transformer primary winding will be equal under steady state conditions. The transformer drive remains balanced over the entire dynamic range to prevent unwanted saturation of the transformer core.

Multiple input output electrical isolation for use with electronic integrated circuits

Abstract: A plurality of electrical isolation devices are provided on a monolithic integrated circuit. Each of the isolation devices includes a current strap and a magnetic field sensor. The current strap is adapted to carry an electrical current representative of a signal to be transferred through that isolation device. The strength of the magnetic field produced by that current is measured by the magnetic field sensor.

Method and device for evaluating the secondary current of a current transformer primary connected to an electric power supply line

Abstract: Die Erfindung betrifft ein Verfahren sowie eine Einrichtung zur Auswertung des Sekundarstromes (J 2 ) eines primarseitig in eine Leitung (10) eines elektrischen Energieversorgungsnetzes geschalteten Stromwandlers (20). The invention relates to a method and a device for evaluating the secondary current (J 2) of a primary side into a conduit (10) of an electrical power supply system switched current converter (20). Bei Sattigung des Stromwandlers (20) infolge eines Kurzschlusses auf der Leitung (10) wird ein diese Sattigung anzeigendes Sattigungssignal (X) sowie ein die Polaritat der Verlagerung des Kurzschlusstromes (J,) anzeigendes Polaritatssignal (P) erzeugt. At saturation of the current transformer (20) as a result of a short circuit on the line (10) this saturation indicating saturation signal (X) and the polarity of the displacement of the short-circuit current (J,) indicative of the polarity signal (P) is generated. Mit beiden Signalen (X, P) werden der Polaritat der Verlagerung des Kurzschlusstromes (J 1 ) entsprechende Nulldurchgange des Sekundarstromes (J 2 ) ausgewahlt. With two signals (X, P) are of the polarity of the displacement of the short-circuit current (J 1) corresponding zero crossings of the secondary current (J 2) is selected. Nach ausgewahlten Nulldurchgangen wird der Sekundarstrom (J 2 ) durch ein Stromsignal (C) entsprechend seinem sattigungsfreien Verlauf extrapoliert. According to selected zero crossings of the secondary current is extrapolated according to its saturation-free course (J 2) a current signal (C). Das Stromsignal (C) wird schlieslich Schutzeinrichtungen anstelle des Sekundarstromes (J 2 ) zugeschaltet. Instead of the secondary current (J 2) are switched on the current signal (C) eventually protection devices.

Current spike protection circuit for switch-mode power supplies

Abstract: A circuit which prevents the flow of excess spikes of magnetization current in the primary windings of a transformer used in a switch mode power supply is disclosed. The circuit comprises an AC coupled, peak detecting, negative feedback path from a current sensing resistor in the primary windings of the transformer to the input of the voltage regulator so that as excess primary winding current spikes begins to flow the driving switches on the transformer primary are rapidly turned off thereby preventing any further rise in transformer primary current.

Oil Additives for the Evaluation of Hot Spot Temperature in Power Transformers During Overload Tests

Abstract: An oil additive of the blowing-agent type, which decomposes rapidly above 132°C with accelerated gas evolution at a concentration of 1000 ppm in oil, has been used to determine the hot-spot temperature during overload tests on a 16 MVA power transformer. The formation of gas in the Buchholz relay indicates that this e ottest-oil temperature of 132 ± 2°C has just been reached somewhere in the transformer during the overload test. The method is simple and does not require the hot-spot location to be known in advance as in the case of acoustic or pressure transducer devices. Used during heat-run tests, when voltage is relatively low and gas formation not harmful to the transformer, it can bring useful information about the actual overload ecapability of the transformer. The hot-spot temperature obtained by this method with the 16 MVA power transformer was substantially higher than that deduced from the ANSI and IEC loading guides.

Analog-to-digital converter

Abstract: PURPOSE:To avoid the effect of switching noise, by converting an analog signal into a digital signal, when the operation is stable without noise at switching. CONSTITUTION:To isolate an analog data input with a transformer, a DC signal is converted into an AC signal, which is inputted to an isolation transformer, and the analog data transformed into AC is inputted to an A/D conversion circuit 4 through a synchronizing rectifying circuit 3 for DC, to make signal conversion of the analog data through an amplifier 2 and a digital data corresponding to the analog input is obtained. In this case, when a switching pulse of a switching power supply 6 is generated from a timing generating circuit 5, a high frequency switching noise is generated. But, the effect of high frequency switching noise can be omitted by generating a DC/AC conversion pulse at a stable region without this high frequency noise.

Base drive circuit for power transistors

Abstract: A base drive circuit for power transistors uses a base drive transformer in a dual mode, as a voltage transformer when it is driven to switch on or off, and as a circuit transformer when the transistor is conducting. Particularly a single base drive is used to drive a plurality of base drive transformer, each base drive transformer acting in the dual mode. This isolates the power transistors from each other and avoids differences in switching characteristics of the power transistors from affecting each other.

Low leakage filtered power supply

Abstract: An AC power supply system having transformer and filter structures. The electrical center of the filter section, which is normally connected to system ground, floats with respect to system ground and is connected to a center tap on the secondary winding of the transformer structure.

Transformer coupled amplifier circuit

Abstract: A transformer coupled amplifier circuit that eliminates transformer induced non-linearities by way of a dual feedback path without sacrificing any of the inherent attributes of general transformer coupled amplifiers

DC current transformer

Abstract: A general purpose, magnetically isolated current sensor is described. Based upon the flux nulling technique, this sensor uses a novel flux detector, instead of a Hall effect device, to achieve improved performance at lower cost.

Transformer coupled up-down converter

Abstract: A transformer coupled DC-to-DC converter provides a regulated output with only one active switch. The converter includes a switch, a diode and an inductor coupled to the primary of a transformer in a way which provides symmetry to the transformer as the duty cycle of the switch changes for regulation. The circuit may be current-fed by supplying an input voltage higher than the transformer ratio would indicate, or may be voltage-fed by providing an input voltage lower than the transformer ratio would indicate. The circuit is operated to charge an inductor through the switch and half the primary of a transformer and discharge the inductor through the other half of the primary so that equal energy is provided through the transformer during charging and discharging, thereby providing a symmetrical signal without the need for more than one switch.

Intrinsic safety power supply with a controlled semiconductor disposed in the primary circuit of a transformer

Abstract: We will describe a power supply device that works according to the principle of a clocked power supply unit. For this purpose a controllable semiconductor (3) is arranged in the primary circuit of a transformer (5), which is driven periodically by a clock generator (18). The duty cycle of the clock generator is influenced via an optocoupler (17) by a voltage regulator (16), on the one hand a reference value and on the other hand, the outputs of the power supply device (1) to be entered. In the secondary circuit of the transformer (5), a Short-circuiting Device (10) to which a throttle (14) and a voltage limiter (19) is connected upstream lie. A current limiting regulator (11) operates in such a manner that a decreasing current-voltage characteristic is obtained. A control switch (20) applies the voltage regulator (16), the Ausgangssgrosse of the current limiting regulator (11) and switches to the input variable, when the current limiting controller (11) limits the current.

Starting and operating apparatus for fluorescent lamps

Abstract: Lightweight, transistorized, inverter circuit is particularly adapted for starting and operating screw-in compact flurorescent lamp intended for incandescent lamp replacement. Household-type AC is converted to DC with one terminal connected to the center tap of a transformer primary through a choke which constitutes a high impedance at the operating frequency. A tuned circuit capacitor is connected across the transformer primary and a current-limiting capacitor and the lamp to be operated are connected in series across the transformer primary. A pair of transistors are connected in push-pull arrangement between the end portions of the transformer primary and the other terminal of the DC source, with the base members of the transistors connected to the transformer secondary winding so that the push-pull connected transistors oscillate at the tuned circuit resonant frequency which is determined by the inductance of the transformer primary winding and the total capacitance of the connected capacitor means. A potential is applied to the midpoint of the transformer secondary upon energization of the apparatus in order to initiate transistor conduction.

Simulation of a transformer/rectifier unit for aircraft power-supply systems

Abstract: A mathematical model for the type of transformer/rectifier unit used in aircraft power-supply systems is described. The model is suitable for investigating both the effects of variations in the transformer parameters on the unit performance and the interaction of the unit with other items of plant in the supply system. The experimental unit on which the model was validated exhibits a marked imbalance between the two diode bridges fed from the transformer secondary windings, and this is satisfactorily predicted by the model. Introducing even a moderate harmonic content into the supply voltage to the transfer increases considerably the imbalance, which under full-load conditions could result in overloading and possible failure of the diodes of one of the bridges.

Pulse transformer having conductive shield around magnetic core material

Abstract: A pulse transformer is used in a radar transmitter to transform a high current pulse at relatively low voltage into a very high voltage pulse which can be used to directly drive a magnetron oscillator. The potential of the output pulse can be of the order of 30 kV and since the transformer is required to operate at very high peak powers of the order of two megawatts, it must be very carefully designed to avoid excessive electrical losses and voltage breakdown. The core material of the transformer consists of a closely wound reel of magnetic material in the form of an elongate tape, which is mechanically fragile. The magnetic core is loosely mounted within a sealed container so that the primary and secondary windings surround it. A conductive shield is placed around the magnetic material so as to protect it from the very large electric fields generated within the transformer. This prevents the ionization of gases which could lead to the rapid deterioration of the magnetic core material.

Electrically heated soldering tool

Abstract: 1. Electrically heated soldering tool comprising a heating element (8) fed via a transformer (4) for heating a soldering tip (6) and a temperature sensor (7) with following evaluation circuit (9, 10) for supplying the power fed to the heating element, characterized in that the transformer (4) is a high-frequency transformer which forms the oscillation transformer of a voltage transformer (3, 4), that the secondary voltage of the transformer (4) feeds the heating element and via a rectifier circuit (5) the evaluating circuit (9, 10) for the output signal of the temperature sensor (7), and that the output signal of the evaluating circuit (9, 10) via a coupling element (11, 12) with dc disconnection of the input and output circuits controls the operating state of the voltage transformer.

Optically-Coupled Floating Double Probe for Local Electric Field Measurements in Pinch Discharge Plasmas

Abstract: Local electric field signals from a floating double probe immersed in a pinch discharge plasma are transmitted via a pair of fiber optic cables in order to achieve electrical insulation between the probe circuit and an oscilloscope. This optical coupling scheme has a higher electrical insulation voltage and a wider frequency response than the commonly-used isolation transformer methods and commercially-available photocoupler devices. The measuring system consists of a transmitter with light-emitting diodes and a receiver with PIN diodes and responds in the frequency range up to 3 MHz. Transient noise, which disturbs the probe measurements in the implosion phases of pinch discharges, has been eliminated.

Neutral-Deriving Transformers for Grounding Low Voltage Systems with Delta-Connected Source Transformers

Abstract: Recommendations are developed for selecting and connecting three single-phase transformers as a neutral-deriving transformer bank to ground a 480 V low-voltage power system supplied from a delta-connected source transformer. Assumptions made are that the system has no 277 V loads, and that the bank is used solely as a source of ground fault current.

Active frame antenna with transformer coupling

Abstract: An amplifying, electronic three-pole network is coupled to a single-winding frame antenna with the aid of a transformer. In this case, it is intended to exceed a required signal-to-noise ratio over a broad band within a specified frequency range, with frame dimensions which are as small as possible. Furthermore, it is intended that the effective height of the active frame antenna be largely frequency-independent and that the antenna amplifier have linearity properties which are as good as possible. The invention is based on the use of a low-capacity transformer to whose secondary winding an active, electronic three-pole network is connected in a base or in a gate circuit, and the primary side of the transformer is supplied from the single-winding frame. An optimum signal-to-noise ratio is achieved by selecting an optimum transformation ratio for the transformer. Such active frame antennas are preferably suitable for reception in the HF and VHF bands.