Showing papers on "Isolation transformer published in 1986"

Flat matrix transformer

Abstract: A flat matrix transformer or inductor is made of a plurality of interdependant magnetic circuits, arranged in a matrix, between and among which electrical conductors are interwired, the whole cooperating to behave as a transformer or inductor. The flat matrix transformer or inductor has several advantageous features, among them compact size, good heat dissipation and high current capability. A flat matrix transformer or inductor can be very flat indeed, nearly planar, and can be built using printed circuit board techniques. A flat matrix transformer can insure current sharing between parallel power sources, and/or between parallel loads. The flat matrix transformer can be configured to have a variable equivalent turns ratio.

Forceless non-contacting power transformer

Abstract: A transformer for coupling electrical power from a stationary location to a moving location with a minimum of disturbance forces between the stationary and moveable components. The transformer is particularly adapted to coupling power to a magnetically suspended platform. The transformer includes an enclosed core housing two windings, a stationary primary coil, and a secondary coil free to move linearly and angularly over a limited displacement, where the secondary coil is affixed to the moveable platform, thereby enabling energy to be extracted for powering apparatus mounted within the platform.

Transformer Computer Design Aid for Higher Frequency Switching Power Supplies

Abstract: A transformer computer design aid is presented that was developed for use at switching frequencies above 100 kHz where the classical method of using the saturation constraint results in an over-heated transformer due to excessive core loss. Flux density is selected instead by an optimization procedure that minimizes total transformer losses. Key equations used in the design procedure are developed. Emphasis is placed on the algorithm used in the transformer design procedure.

Isolation amplifier with T-type modulator

Abstract: An isolation amplifier including a full-wave modulator which applies to the primary winding of an isolation transformer an attenuated version of the input signal, to reduce the flux density in the transformer without the need for a complicated flux-nulling feedback arrangement. This is a wide-band modulator with means for protection against the adverse effects of thermal drift in the attenuator. Two or more resistors create a resistive divider across the signal and ground terminals of the isolator's input port. A tap on the resistive divider is connected to the input of a first buffer amplifier whose output is connected in series with a capacitor to one lead of the primary winding of the transformer. The signal input is supplied to one throw of an SPDT analog voltage switch, the other throw of which is connected to ground. The pole of the switch is connected to the input of a second buffer amplifier and the output of that buffer is connected to the other lead of the transformer primary. A carrier signal from a carrier source controls the opening and closing of this switch to "chop" the input signal and provide a modulated input to the transformer. A synchronous demodulator connected to the transformer secondary demodulates the chopped input signal.

Power reducer for fluorescent lamps

Abstract: An attachment is provided for connection in fluorescent lamp circuits for reducing power consumption. The attachment is particularly designed for use with fluorescent lamp circuits having an encapsulated ballast including a transformer and capacitance. The attachment includes an isolation transformer with a capacitor and a resistor connected across the transformer, and an inductance connected in line with the primary of the ballast transformer with a resettable thermal switch connected to shut down the ballast transformer in response to high current overload conditions, and a surge voltage protection circuit connected through the thermal switch to shut down the ballast in response to a ballast power factor capacitor failure. The ballast and power reducer cooperate to produce a substantially square wave output resulting in increased system efficacy, reduced lamp lumen depreciation, and increased lamp life.

High voltage measurement transformer for suspension from a high voltage switching apparatus

Abstract: The current converter or transformer component of a high voltage measurement transformer comprises a primary lead or conductor which is surrounded by secondary windings or optical conducting elements. The primary and secondary components of the current converter or transformer component are housed in a casing having an integrally formed entry duct for the secondary leads. The secondary components of the current converter or transformer component are surrounded by plastic or synthetic insulation material. This insulation material or insulation also surrounds a channel for the secondary leads extending completely through the entry duct. The primary lead or conductor is provided with connecting flanges at both ends for mechanically or electrically connecting the high voltage measurement transformer to a high voltage or high power circuit breaker or similar device. The high voltage measurement transformer is suspended from the circuit breaker by this connection such that no further support is necessary for the high voltage measurement transformer.

Transformer protection system

Abstract: In a transformer protection system, data of voltages and currents detected at individual terminals of a transformer connected to an electric power system are supplied to a computer. The computer computes driving point admittances or shunt admittances of the transformer on the basis of the voltage and current data and predetermined transfer admittances of the transformer and decides that an internal fault has occurred in the transformer when the values of the driving point admittances or shunt admittances deviate from pre-set reference values, thereby disconnecting the transformer from the electric power system.

Power supply operable on varying inputs

Abstract: A power supply provides the stable DC voltages needed for a computer terminal from a wide range of line voltages and frequencies. The line is rectified and fed to a flyback transformer wherein primary current is controlled in duration for providing the desired energy transfer to the secondary winding. The outputs from the flyback transformer are rectified and filtered. A separate start-up circuit uses a transformer across the line voltage, and a positive coefficient resistor provides a time limit to allow the use of a small transformer even though the line voltage may be high. The start-up circuit must produce a minimum voltage for the switching transistor in the flyback arrangement to allow operation of the power supply, and the start-up transformer is disconnected from the circuit after operation to prevent electromagnetic interference within the terminal. The output from the power supply is used in the control of the switching transistor so that, once the start-up circuit has achieved the needed voltage level, the power supply can assist in maintaining the operation.

System of transformers for a welding apparatus

Abstract: A transformer system for resistance welding intended for installation on robotic devices comprises an auto transformer having a tap selection switch connected through electrical conductors to an isolation welding transformer located at the end of the robotic arm. The auto transformer is uniquely selected for the maximum efficiency thereof and the optimum reduction in the size of the conductors between the transformers. The isolation welding transformer is also optimally sized due to the reduction permissable by the previous interposition of the auto transformer in the welding system. Moreover, the isolation welding transformer comprises primary and secondary coils formed from tubular members each of which is cooled by a fluid coolant. Utilization of refrigerated coolant permits further reduction in size and mass, and increases electrical efficiency because of the unique design of the isolation welding transformer in which both primary and secondary windings are cooled by such fluid coolant.

Circuit arrangement with differential transformer

Abstract: A circuit arrangement with a differential transformer is proposed, the transformer core (8) of which is used as a distance sensor. To eliminate temperature influences and other influences impairing the measurement result, it is provided that the aggregate voltage of the two secondary coils (4, 5) is kept constant by regulating the primary voltage (Up). This, at the same time, results in a linearisation of the distance signal.

Method for attenuating at least one electric harmonic of the system frequency in a multi-phase alternating-current system

Abstract: A method for attenuating at least one unwanted harmonic, particularly the second harmonic, with respect to the system frequency in a multi-phase alternating current system, wherein an additional stabilizing circuit is installed into a conventional current/voltage controller including a current/voltage controller and a three-phase firing pulse generator in a reactive-power compensator connected via a reactive-power transformer and a current transformer to a 50 Hz three-phase system. The reactive power compensator has for each phase of the three-phase current at least one air choke, which is connected via a current transformer and via an alternating-current switch via another sum-current transformer to a secondary winding of the reactive-power transformer. In addition, the reactive-power compensator has for each phase of the three-phase current at least one capacitor bank or a capacitor, which is connected via a current transformer and an alternating-current switch (13) to the sum-current transformer (20). The stabilizing circuit measures a harmonic-containing magnetising current as the difference between compensator current (iK) and sum current (iSu) on the primary and secondary side of the reactive-power transformer, and by means of a voltage transformer a system-frequency voltage signal, which is proportional to the system frequency. These two three-phase current and voltage signals are converted into a single direct-voltage signal in a reactive-power meter. An input harmonic of 100 Hz occurs on the output side as a 50 Hz signal which is filtered out in a bandpass filter and, after a +90° phase shift, is added in an adding section to the conventional output signal of the current/voltage controller via a double-sided limiter.

Adjustable light base and transformer housing

Abstract: An adustable light base and transformer housing to house an isolation transformer and to be used as a mounting base for in pavement airport navigational lights comprising an adjustable upper portion adapted to receive said light fixture and maintain and position it at the proper elevation with respect to the surface of the airport runway.

Power supply for a.c. corotrons

Abstract: A circuit for supplying power to the a.c. corotrons of copying or printing machines using a high leakage inductance type transformer both as a power transformer and as a low pass filter; a d.c. power source coupled to the transformer primary winding center tap; a push-pull amplifier having a MOSFET gate pair controlling energization of the transformer primary winding halves by the d.c. power source; a pulse width modulator for supplying alternating signal pulses to the MOSFET pair at a fixed frequency; a voltage doubler network for monitoring corotron current, the modulator adjusting the pulse width of the signal pulses in response to the network control signal to thereby adjust the power output of the circuit and maintain a constant corotron current; and a capacitor at the transformer output cooperable with the transformer to form said low pass filter.

High voltage resonant DC/DC converter

Abstract: A high voltage DC/DC converter including a voltage resonance switching circuit formed by a coreless transformer, a GTO thyristor switching element connected between the primary winding of the transformer and a D.C. source, and a voltage resonance capacitor connected in parallel to the switching element. A rectifier circuit is connected to the secondary winding of the transformer to rectify an output current from the transformer circuit. The resonance frequency of the parallel resonance circuit made of the resonance capacitor and the coreless transformer is selected to be the frequency of that component of the current supplied to the circuit through the switching element, which has a greater amplitude than any other component of the current (including the fundamental frequency and other harmonic).

Low-loss voltage limiting network for isolating transformers or flux converters

Abstract: A circuit arrangement for low-loss limiting of the maximum blocking voltage of the switch element of an isolating transformer or flux converter, having a converter transformer whose primary winding is connected in series with the switch element, and having a discharge capacitor, an additional winding of the converter transformer being provided as a demagnetisation winding which is connected by means of two series-connected diodes to the input terminals of the converter, and the discharge capacitor being arranged between that connection of the switch element which is on the primary winding side and the junction of the two series-connected diodes.

Switched-mode power supply for an apparatus having a standby mode, especially a television receiver

Abstract: A switched-mode power supply for an apparatus having a standby mode, especially a television set. A line-frequency switching voltage (9) in normal operation controls the switching transistor (12) on the primary side. As a result of the disconnection of the switching voltage in the standby mode, the primary side changes over to a regulated, self-oscillating circuit which causes the power for the standby mode to be transmitted via the transformer (24). A separate isolating transformer for the standby mode is saved, stabilisation with respect to mains-voltage fluctuations of 100-270 volts in the standby mode is achieved and a soft changeover to normal operation (soft starting) is made possible without interrupting the operating voltage for a television set (49).

Small transformer with shield

Abstract: A transformer of small installed volume which affords, besides electrical separation, also an effective static protective shield between the power supply side and the user side, along with simple production and assembly. To accomplish this, a two-chamber transformer with a coil form for the primary winding and a coil form for the secondary winding, both plugged one behind the other onto the transformer core in the direction of the coil axes and a stamped metal foil frame as the shielding wall between the adjacent face flanges of the coil forms are used. The transformer is particularly well suited for application in equipment of the entertainment, communications and medical technologies.

Transformer system and direct current power supply

Abstract: The present invention relates to a transformer system and a direct current power supply for obtaining a dc current including a luminous body disposed on the primary side for converting a electric power into a light and a solar cell unit disposed on the secondary side, opposing the luminous body, for receiving light emitted from the luminous body and for converting the light into electric power, thereby constituting a transformer which is further provided with an input control circuit and an output control circuit so as to configure a dc power supply According to this apparatus, a stable dc current can be obtained without generating the magnetic field and noise problems of typical wound core transformers

Ac current sensing circuit

Abstract: An alternating current sensing circuit for sensing the current supplied by a power supply of an electronic instrument includes an isolation transformer and at least one transistor connected across the secondary winding of the transformer. The isolation transformer provides galvanic isolation between the power supply and internal feedback circuitry that controls the power supply located within the instrument. The transistor clamps the secondary voltage on the transformer to a constant magnitude when the base-emitter junction is forward biased. In response to the sensed current, the secondary current of the transformer flows through the transistor when the base-emitter junction is forward biased to produce the constant secondary voltage. The secondary current provides a current sensing signal which is transmitted to the feedback circuitry. The low, constant secondary voltage enables the transformer to maintain its range of frequency response and thereby accurately transform the sensed current to a secondary current that provides the current sensing signal to the feedback circuitry.

Current transformer circuit tester

Abstract: Apparatus for determining the size adequacy of a current transformer in an electrical power distribution system. The apparatus includes a voltage generating source for connection in series with a current transformer secondary circuit, which source saturates the current transformer. A first signal is provided which is indicative of the voltage required to cause the current transformer to enter saturation. A second signal is provided which is indicative of the resistance of the secondary circuit of the current transformer after saturation. A third signal is then provided which is responsive to the product of the second signal and predetermined constant value. A ratio of the first to the third signals which exceeds unity indicates adequacy of the current transformer for a given system.

Energy storage transformer power conditioning systems for Megajoule class flux compression generators

Abstract: Circuit and energy storage transformer configurations are developed to match high impedance loads to low impedance sources. With the secondary open, a large di/dt is produced in the primary circuit by inserting a resistance, characteristic of an opening switch, and the load circuit is connected using a preset spark gap. Transformer design concepts using a foil-MYLAR ''sandwich'' for the secondary winding are described, permitting close primary-secondary coupling. Transformer experiments driven by a 0.25 MJ capacitor bank support the overall system concepts. A compact flux compression generator-transformer system is described.

Low-noise transformer

Abstract: A low-noise transformer, particularly for the use as an output transformer of an inverter, comprising a sound-proof envelope surrounding at least one of the windings for absorbing or screening noise originating from vibration due to electromagnetic force.

Regulated voltage converter which has substantially fewer parts than prior art devices

Abstract: An improved switching power source in which the output of the DC input power source is switched off and on under control of switching elements of an oscillating drive circuit which is supplied to the primary side of a power source transformer and from which a constant voltage output is supplied from the secondary of the transformer. A saturable reactor transformer supplies an input to the control terminals of the switching elements of the oscillating drive circuit and the inductance of the saturable reactor transformer is controlled with the output voltage from the secondary of the power source transformer so as to control the oscillating frequency of the oscillating drive circuit and, thus, stabilize the output voltage at the secondary of the power source transformer so as to obtain an increased conversion efficiency, reduce the size and weight of the transformer, reduce the leakage flux, improve the control range and reduce the cost of production.

Fluorescent lamp brightness control

Abstract: A load side phase control circuit is used in conjunction with a conventional fluorescent light ballast (step-up autotransformer) and an isolation transformer to achieve fluorescent lamp brightness control. A resistor and capacitor connected in series shunt the phase control circuit to maintain low level illumination even when the phase control circuit is nonconducting and also provide a transient suppression when the phase control circuit switches to a conducting state. The circuit is especially suited to printed circuit board preassembly and subsequent connection to the lamp and ballast by a one step crimping operation. The resulting fluorescent lamp system--of the rapid start type--is well suited for use as a task light where the lamp is mounted relatively close to an underlying work area and receives power from a conventional outlet.

A modulator/demodulator and a portable digital computer incorporating the same

Abstract: A modem has a LINE terminal (310) which is connected to telephone line terminals TIP (402) and RING (403) by way of an isolating transformer (401). The LINE terminal is connected to the receive and transmit lines within the modem. These lines are preferably also connected to terminals for an acoustic coupler. The modem is very lightweight so that it may be incorporated in a portable computer. In particular the transformer (401) is very small. This renders it liable to damage from power surges on the telephone line but the transformer is protected by varactors (404,405) connected across the telephone line.

Starlan coded data transceiver collision detection circuit

Abstract: A daisy chain collision detection circuit for use with a StarLAN coded data transceiver includes a voltage comparator having an inverting input, a non-inverting input and an output. The inverting input of the voltage comparator is responsive to differential output voltages from a differential line drive and transient spike voltages from the primary of an isolation transformer. A charging capacitor is connected to the non-inverting input of the voltage comparator. The capacitor is charged to a reference voltage which is directly proportional to the peak voltage of the differential output voltages. The output of the voltage comparator provides an internal collision detection signal which is switched from a high logic level to a low logic level upon the occurrence of a daisy chain collision.

Transient voltage protection for toroidal transformer

Abstract: An apparatus and method for protecting a toroidal transformer from damage due to voltage oscillations and dielectric stresses caused by applied voltage transients is disclosed. Two conductive sheilds are each electrically coupled to a line lead of the primary windings of the toroidal transformer and are disposed around and insulated from the periphery of one semitoroidal segment of the primary windings. A conductive grounding plate is strapped to the outside of the transformer adjacent to and insulated from each conductive shield.

Television camera device

Abstract: PURPOSE:To separate electrically a television camera part and a power source part by means of a low-priced isolation transformer without fail by superimposing an output signal from the television camera part on a carrier at the prescribed frequency higher than that of a video signal component CONSTITUTION:The oscillation frequency f0 of an oscillator 24 is set to a far higher frequency than the frequency hand of the video signal of the output signal of a CCD 14 A multiplier 22 AM-modulates (carrier suppression modulation) the output signal from the CCD 14 with the signal from the oscillator 24 as a carrier signal Since the compared frequency width (=frequency width/ central frequency) of the output signal of the multiplier 22 is small, the isolation transformer 26 passes the output signal of the multiplier 22 without distortion Thus the low-priced isolation transformer 26 can electrically separate the tip of an endoscope which is liable to contact a human body from a power source without fail, and a pressure proofing value and a leakage current value can lie within a safe range

Partial-discharge measurement of a high-voltage transformer

Abstract: For measuring the partial discharge, the low-voltage winding (NW) of a flyback transformer (T) to be tested is excited with flyback pulses for a short time in order to charge the transformer (T) to the specified high voltage. During the charging process, a partial-discharge detector (D) is decoupled from a measuring impedance (Zm) connected in series to the high-voltage winding (HW) of the transformer (T). The partial discharge is measured during the direct-voltage state existing after the charging process, in which state the coupling between measuring impedance (Zm) and partial-discharge detector (D) is restored. To calibrate the partial-discharge measuring device by means of a calibration pulse of known charge quantity, diodes (D1...Dn) connected into the high-voltage winding and moulded together with the transformer are biased in the forward direction.