Showing papers on "Isolation transformer published in 1973"

Dual battery electrical system for internal combustion engine

Abstract: In a dual battery system for an internal combustion engine, as used in a vehicle or the like, wherein an auxiliary battery is connected in series with a service battery to provide a high battery voltage for a starter circuit, a charging means is provided for charging both the service battery and the auxiliary battery without changing their series connection. This charging means comprises an alternator, rectifier and voltage regulator for charging the service battery and an additional rectifier connected to the alternator through an isolation transformer for charging the auxiliary battery.

Improved coupling arrangement for power line carrier systems

Abstract: A power line carrier system is coupled to two or more phase wires of an electrical power transmission line by transformers and coaxial transmission lines. Each phase wire to be used is provided with a coupling capacitor which is respectively coupled to one end of a coaxial line through an impedance matching transformer. The other ends of the coaxial lines are coupled to the carrier system through one or more isolation transformers. Use of this coupling arrangement eliminates the previously used, exposed unbalanced lines, and their inherent disadvantages. Where a plurality of phase wires are used, this arrangement permits the carrier to be coupled to the phase wires with various relative voltage magnitudes and various relative phases.

Sonobuoy receiver system, floating coupler

Abstract: A modulation-demodulation floating coupler for use in a Sonobuoy Receiver to perform the function of an isolation transformer operating over a wide frequency band with very little phase shift is disclosed. The coupler is responsive to a high frequency composite input signal having a carrier portion on which is modulated a baseband information portion which is to be coupled and includes a transformer for coupling the composite signal to a pair of demodulators, the first of which provides an output with no ground reference, and the second demodulator produces a local feedback signal for gain and distortion control.

Transformer-diode isolated circuits for high voltage power supplies

Abstract: An improved power supply having a single input stage which operates a plurality of output stages. The input stage includes an isolation transformer or a push-pull drive circuit. This input stage controls a plurality of regulated output stages. The output stages may include either series or shunt regulators, however, at least one of the output stages includes a series regulator. The series regulated output stage includes a center tap transformer having a transistor connected to the center tap. The output voltage or current is sensed and fed back to the base of the transistor to regulate and keep constant the output voltage or current. A pair of rectifiers are connected between the series regulated output stage and the other output stages to provide isolation between the series regulated output stage and the other output stages.

Current transformer with active load termination

Abstract: A current transformer and transresistance amplifier are combined; the secondary winding of the current transformer being connected to the input of the transresistance amplifier and being virtually short-circuited because of the very low input impedance of the transresistance amplifier. The transresistance amplifier, nevertheless, supplies an output voltage which is proportional to current in the primary winding of the current transformer. An output voltage is developed from the current in the secondary winding. An important advantage, among others, of the subject combination is that a current transformer having considerably lower volt-ampere capacity may be employed. A current transformer employed alone for the same purpose would have to have a much larger volt-ampere capacity.

Dynamic Response of Power Transformers Under Axial Short Circuit Forces Part II - Windings and Clamps as a Combined System

Abstract: This paper is in continuation of Part I. It discusses the dynamic axial risponse of the total transformer system made up of the windings and the clamping structure. The numerical solution presented here accounts for all nonlinearities in the system. The viscoelastic model for representing the dynamic stiffness of the oil-permeated insulation is investigated in detail. Good comparisons between the calculated values and the test values on a 10 MVA transformer support the models and methods developed here.

Remotely monitored and controlled transformer

Abstract: A power transformer adapted for remote monitoring and controlling, and system of providing same. The transformer contains a temperature sensor, a pressure sensor, and a deenergizing switch. Electrical signals from the sensors are transferred to a remote load management center which compares the signals to predetermined standards and originates a switching signal when a standard is exceeded. The switching signal opens the switch to de-energize the transformer. The load management center may utilize standards which are fixed or which are variable with other conditions in the power system.

Low leakage current electrical isolation system

Abstract: The disclosed invention presents an isolated electrical distribution system which includes at least a pair of power lines for providing a source of alternating voltage, one of the lines being connected to electrical ground, which are connected across the primary winding of an isolation power transformer, and at least a second pair of lines, neither of which is connected to said ground potential, wired to an electrical outlet or load and connected across the secondary winding of the transformer. The isolation transformer, housed in a metal enclosure, includes a magnetic core, a primary winding formed in a coil, a secondary winding formed in a separate coil with the coils mounted on the magnetic core on one side of the primary, with the turns of one coil wound in a clockwise direction relative to the core and the windings of the other coil wound in a counterclockwise direction relative to the core; another secondary winding formed in a separate coil and mounted on the core on the other side of the primary coil; and thin flat nonmagnetic metal shield members, each having a slot therethrough, are fitted over the magnetic core and sandwiched in between each of the two secondary coils and the primary coil. As described, leakage currents between the primary and secondary windings and between the secondary windings to ground is minimized with concurrent reduction in stray magnetic fields.

Compensated transformer circuit

Abstract: A circuit for reducing or eliminating the effect of the magnetizing inductance of a transformer on voice-frequency signals coupled through that transformer. Circuitry is provided to generate voltages and currents which simulate the presence of a negative inductance and to couple those voltages and currents to a transformer in cancelling relationship to the magnetizing inductance thereof. Circuitry is also provided to reduce or eliminate the effect of the equivalent shunt resistance of the transformer and thereby render the transformer virtually free of core losses. Finally, circuitry is provided to linearize the nonlinear magnetization characteristics of non-linear cores and thereby substantially reduce the distortion of signals coupled through the transformer.

Influence of core gap in design of current-limiting transformers

Abstract: Core gaps are used in the magnetic shunt paths of current-limiting transformers to limit secondary current under short-circuit conditions. It is shown here that for short-circuit current limited to twice normal a current limiting transformer has only 55% of the rating of a noncurrent-limiting transformer of the same physical size. Part of the reduction in rating stems from the space required for magnetic shunts, part from the greater space needed for winding insulation, and part from the increased loss due to the gaps. Reliability of a previously tested gap-loss equation is established, and design examples are given for both stamped laminations and strip-wound cores.

Ground fault interrupter with means protecting against a grounded neutral condition and with a test circuit for testing performance

Abstract: In a ground fault interrupter of the differential transformer type having a means for protection against a grounded neutral condition, which means is located on the supply side of the differential transformer, there is provided a test circuit branch connected between a first point on the load side of the differential transformer to the line conductor and on the supply side of the differential transformer to the neutral conductor. This arrangement provides the capability to test performance of the differential transformer and also the means for protection against the grounded neutral condition.

Current transformer terminated by active load elements for providing phase-inverted signals

Abstract: The secondary winding of a current transformer is terminated in a virtual short-circuit condition by a pair of active load elements, such as transresistance amplifiers, which provide, for example, a pair of phase-inverted output voltages proportional to current in the primary winding of the current transformer.

Grounded control circuit

Abstract: A material moisture sensing control includes a circuit connectable to a two-wire alternating current supply in either of two polarity postures. The circuit includes an earth grounding of one electrode and is operable for providing the desired consistent sensing and safe operation with either polarity posture while eliminating the need for either an isolation transformer or an auxiliary isolation resistor at the earth ground electrode.

Method and apparatus for generating electrical voltage of amplitude varying with time

Abstract: Voltage generators in which the primary winding of a superconductive transformer is excited by momentary connection to a source of direct current and is further energized responsively to voltage induced in the secondary winding by cyclic changing of primary winding current, for compensating losses internal to the transformer and associated circuitry. Control of such further energization and maintenance of transformer winding current below the current level at which the transformer windings are rendered normal are effected by superconductive current-interrupting devices.

Current transformer with active load termination for providing, inter alia, phase angle alteration

Abstract: The secondary winding of a current transformer is terminated in a virtual or near short circuit condition by an operational amplifier which has connected therewith Circuit means, such as passive circuit elements, are provided for shifting the phase angle between current in the primary, or the secondary, winding of the current transformer and an output voltage produced by said amplifier in response to current in the secondary winding The output voltage produced by the amplifier is proportional to the primary, or the secondary, current in the current transformer

Protective system for mobile electric power apparatus

Abstract: In a mobile electric power apparatus, such as a mining machine to which high voltage ac power is supplied from a remote substation through a flexible cable, the frame of the machine is grounded at the substation through a ground conductor in the cable. Integrity of the ground conductor is continuously monitored by means of a low voltage dc current derived from the power circuit at the machine end through a potential transformer having a wye-connected primary. The potential transformer supplies a rectifier through a zig-zag autotransformer. A neutral-to-neutral connection between the zig-zag transformer and the potential transformer primary enables balanced return of monitor current through the power conductors.

Fluid-cooled transformer having a temperature responsive indicating and controlling device

Abstract: Temperature responsive device suitable for use with air-cooled power transformers. The temperature responsive device indicates the temperature at a predetermined location within the transformer and controls the activation of fans, alarms, and circuit breakers associated with the transformer. Electrical isolation between a temperature sensing element and the controlled auxiliary apparatus is provided by light channels across which the control information is transmitted.

Voltage-limited deflection system for a television receiver

Abstract: A voltage-limited deflection transformer includes a tuning capacitance integrally formed therein. A portion of the transformer winding is in the form of two strips of insulated metallic foil arranged on the core such that the foil strips form the electrodes of the capacitance required to tune the transformer. An open circuit occurring in one foil results in no DC to the transformer whereas an open circuit in the other foil substantially disables the transformer. A short circuit in the foil capacitor detunes the transformer and lowers its output voltage.

Bonneville Power Administration Transformer Short Circuit Test Results - Comparison of Winding Inspection With Diagnostic Methods

Abstract: This paper summarizes Bonneville Power Administration's transformer short circuit test experience of three-phase units rated 115-kv Delta to 12.47-kv Wye; reviews BPA's diagnostic and low voltage impulse test results, and correlates them with factory inspection of damaged units. Special emphasis is on the low voltage impulse method of evaluating transformer damage.

D.c. to d.c. converter for connection across telephone lines

Abstract: D.C. supervisory signals control tones and audio signals appearing across a pair of balanced floating telephone lines are converted to permit processing by a single-ended grounded system. The converter circuit includes a high-impedance diode bridge full wave rectifier connected across the floating telephone lines and feeding a self-excited oscillator with an output signal amplitude substantially proportional to the D.C. voltage across the floating lines. The output signals from the rectifier and oscillator are passed through an isolation transformer to a single-ended detector which restores the supervisory signal D.C. level. The relatively high D.C. level of the supervisory signal acts to forward bias the rectifier and detector to pass the relatively low level audio signal and touch tones without distortion.

Retrofit emergency lighting system

Abstract: A retrofit emergency lighting system including a 60Hz AC ballast for operating at least one gaseous discharge lamp. There is provided a means for substantially electrically isolating the secondary side of the ballast transformer from ground thereby reducing the hazard of electrical shock during lamp replacement. The ballast transformer is an isolation transformer having the secondary winding connected across the lamp. A pair of filament windings are connected to the filaments of the lamp and are positioned laterally with respect to the primary winding and in a pancake form so as to provide low capacitance between the filament windings and primary winding. An inverter circuit, which is driven by a DC battery, is further connected across the lamp for operating the lamp during emergency conditions. The inverter circuit operates at such a frequency so as to minimize capacitive leakage and inductive shunt current losses.

Ground fault interrupter apparatus with means protecting against a grounded neutral condition

Abstract: Ground fault interrupter apparatus of the differential transformer type is provided with an additional output transformer, the primary of which is connected between a line conductor and the neutral conductor of an A.C. system with a current limiting resistor adjacent the primary winding. The secondary of the output transformer is the neutral conductor. THe saturation properties of the core of the output transformer are such that during each half cycle a voltage pulse is induced in the secondary. The voltage pulse is of no consequence in the system during normal conditions but if a grounded neutral condition exists a current is produced in the neutral conductor unbalancing the differential transformer and interrupting operation.

Fault protection circuit for an adjustable motorized hospital bed

Abstract: The electrical control system for an adjustable motorized hospital bed is energized by an AC power supply through an isolation transformer. Power to the transformer''s primary winding is interrupted in response to circuit component failure in the control system, which failure causes grounding of either terminal of the secondary winding to the conductive frame of the hospital bed. Each terminal of the secondary winding is coupled to the bed frame through a diode and a series-connected light emitting device. In the absence of component failure or fault, neither of the diodes conduct. However, when a failure or fault occurs and establishes a connection from one of the secondary terminals to the bed frame, the diode and light emitting device connected to the other secondary terminal conduct. The device illuminates and energizes a relay to open the primary winding circuit.

D.c. to d.c. converter with conductive isolation

Abstract: A d.c. isolation amplifier includes an isolating transformer one winding of which is driven by an a.c. source. A controlled load impedance is applied across a second winding of the transformer. The impedance of the load is controlled in accordance with the magnitude of a d.c. input signal. The current in all of the windings of the transformer is thus controlled as a function of the magnitude of the input signal.

Ground isolating circuit

Abstract: In a D.C. power supply circuit having two power leads and a secondary current path through ground, a transformer having very good inductive coupling between its windings is connected in series with the power leads and substantially reduces any pulsating components of the D.C. current passing through the secondary current path. The transformer equalizes the pulsating components of the D.C. currents in the two power leads and thereby reduces the coupling of noise from the D.C. power supply circuit to any signal circuits using the same ground.

Dc signal translator with a variable amplitude oscillator

Abstract: A DC signal translator having an output DC isolated from the input comprises a variable amplitude oscillator generating an oscillating output signal having an amplitude directly related to the magnitude of the DC supply voltage for the oscillator. A DC isolating transformer is associated with the oscillator. A feedback rectifying circuit is coupled between the DC isolating transformer and the input of an amplifier so that the oscillator''s DC supply voltage, and hence, AC amplitude, is continuously adjusted so as to maintain a portion of the rectified DC feedback signal very nearly equal to the input signal. An output rectifying circuit which is matched with the feedback rectifying circuit is coupled to the isolating transformer so as to produce a DC output signal corresponding to the DC input signal while maintaining DC isolation between the input and the output of the DC signal translator.

Recommended Practice for Voice-Frequency Electrical Noise Tests of Distribution Transformers

Abstract: The practice described herein provides instruction on the testing of distribution transformers as voice-frequency noise generators, to measure the degree to which they may contribute to electrical noise in communication circuits that are in parallel with the power supply circuits serving the transformers. Transformers have a characteristic common to other iron-core devices of causing harmonic currents at voice-frequencies to flow in supply circuits to the transformers. The magnitudes of these currents, and of interference that may result, vary according to design of the transformer as well as excitation voltage. The tests described in this practice provide a standard method for use by the transformer manufacturer, user and others in industry for the purpose of better evaluating the design choices available and moving toward industry objectives as to levels of harmonic exciting current expressed as I . T [current × telephone influence factor (TIF)].

Television receiver power supply

Abstract: A television receiver of transformerless type having primary and secondary voltage supply circuits which respectively supply ungrounded and grounded supply voltages to horizontal and vertical deflection circuits on the one hand and other remaining circuit components on the other hand. D.c. isolation is provided between the grounded and ungrounded components by an isolating transformer connected between sync signal amplifier means and the deflection circuits, the transformer however permitting a.c. signal transmission between the sync signal amplifier means and the deflection circuits.

Electrical isolation device and method

Abstract: A method and electrical device for transmitting information between isolated circuits through a transformer having windings tuned to resonate at a fixed frequency by exciting one of the windings of the transformer with an oscillating signal, of about the fixed frequency, and varying the amplitude of the oscillating signal by changing the electrical characteristics or loads associated with the transformer winding or windings not excited by the oscillating signal, the variation or modulation of the oscillating signal being opposite in sense than that conventionally expected from mutual inductance between windings of a transformer and advantageous for the transmission of digital or analogue information.

Four-lead tuning capacitor for television deflection system

Abstract: A voltage-limited deflection transformer system includes a fourlead tuning capacitor. The foil electrodes of the capacitor each include connecting leads at opposite ends thereof. The electrodes are connected in a series circuit with the DC source, the transformer and the transformer driving circuit. An open circuit occurring in either foil electrode interrupts the DC to the transformer and disables it. A short circuit in the capacitor detunes the transformer and lowers its output voltage.