Showing papers on "Isolation transformer published in 1975"

Power supply for power line carrier communication systems

Abstract: Apparatus for powering a signal amplifier or repeater connected to the primary or high-voltage portion of a power distribution system. Oscillator and amplifier circuits are energized by power from the secondary or low-voltage portion of the power distribution system. The oscillator and amplifier circuits are connected to the primary winding of an air-core transformer. A capacitor is also connected to the primary winding to make the primary circuit of the air-core transformer resonant at the frequency of the oscillator. The secondary winding of the air-core transformer is connected to a resonating capacitor and to transformer and rectifier circuits which convert the AC voltage into DC voltage for powering the signal amplifier. Electrical isolation between the high-voltage and low-voltage portions of the distribution system is provided by the separation distance between the primary and secondary windings of the air-core transformer. Sufficient electrical energy is transferred between the primary and secondary windings of the air-core transformer by energizing the primary winding with a high-frequency voltage from the oscillator and amplifier circuits. The mutual inductance between the primary and secondary windings of the air-core transformer is low enough to permit reasonably efficient power transfer when the oscillator and amplifier circuits operate at high frequencies.

Repeater coupler for power line communication systems

Abstract: Apparatus for connecting separate transmitters of a carrier communication system to the same location on a power distribution line. A low-power transmitter is connected to the primary winding of an interconnecting transformer. The secondary winding of the interconnecting transformer is connected between a high-power transmitter and, through the primary winding of a coupling transformer, to ground potential. The secondary winding of the coupling transformer is coupled to the power distribution line. A voltage limiting device is connected across the secondary winding of the interconnecting transformer. The output of the high-power transmitter is directed across the voltage limiting device to the coupling transformer where it is applied to the distribution line. When the low-power transmitter is turned on and the drive signal to the high-power transmitter is turned off, the power from the low-power transmitter is transferred to the secondary winding of the interconnecting transformer and to the coupling transformer where it is applied to the distribution line. The high-power transmitter represents a virtual ground potential when it is not transmitting, thereby providing a closed circuit path for the power delivered by the low-power transmitter.

Ac to dc power supply circuit

Abstract: An electrical power supply circuit for converting alternating circuit power into a direct current output comprises a transformer and rectifier, a filter capacitor across the output terminals and a phase control switching device and a non-saturating inductor in the primary circuit. The circuit arrangement reduces the volt-time integral of the transformer and allows its core to be made of a smaller size, in comparison to the transformer cores of previously known power supplies, without danger of saturation. Other advantages such as low RFI, reduced transformer wire size and overload current protection are obtained. A commutator circuit may also be provided for turning off the phase control switching device before the end of the associated half cycle of input voltage to further reduce the transformer volt-time integral and to accordingly allow a further reduction in its core size.

A Tesla transformer high−voltage generator

Abstract: A Tesla transformer similar to that suggested for transformer−type pulsed accelerators is described. The theory is outlined and computational results presented for representative losses under various conditions of tuning and coupling. The behaviour of an experimental transformer housed in an SF6−filled pressure vessel is discussed. The device has a tuning ratio of 1.1, a voltage coefficient of 0.85, and a coupling coefficient of 0.37. The influence of eddy currents induced in the pressure vessel wall on the coupling coefficient and tuning ratio is noted. The particular transformer described can provide a 2.5 MV peak at the third half cycle of the secondary output voltage.

Controlled power supply for a television receiver equipped with remote control

Abstract: A single isolation transformer supplies both the remote control receiver and the television receiver. A pulse generator such as a blocking oscillator which energizes the primary winding of the isolation transformer has its pulse width controlled in response to the loading of the circuit of the secondary winding of the isolation transformer, as measured by the voltage across a resistor in the circuit of a primary winding. This measuring resistor is interposed between the emitter of the switching transistor of the blocking oscillator and the receiver chassis. A transistor switching circuit for cutting off the low voltage supply to the scanning circuit oscillators of the television receiver is responsive to the output of the remote control receiver, to a signal from an operating control of the television receiver, and to an indication of overcurrent in the picture tube, independently.

Converter utilizing leakage inductance to control energy flow and improve signal waveforms

Abstract: A single-ended converter circuit combines a magnetic energy storage medium with an energy discharge path to simplify transformer design, improve transformer operating characteristics, and reduce induced electromagnetic interference. The concept is extended to self-oscillating, single-ended converters and a double-ended type is achieved by combining two single-ended converters with a single power transformer structure.

Electrical apparatus and method for reducing power consumption of a fluorescent lamp system

Abstract: An attachment is provided for inclusion in a two-lamp rapid-start type fluorescent lamp and encapsulated ballast transformer combination to reduce the electrical power consumption thereof, comprising an isolation transformer and a capacitor. The isolation transformer is connected in circuit between the secondary heater winding at the electrical leads that extend from the encapsulated ballast and the first heater terminals of the first lamp, and the capacitor is connected in circuit between the primary and secondary of the isolation transformer.

Chopper and chopper-multiplexer circuitry for measurement of remote low-level signals

Abstract: A balanced bridge chopper circuit including four metal oxide semiconductor field effect transistors (MOSFETs) is driven by a remote oscillator connected through an isolator to modulate low-voltage low-frequency input signals at their remote source into a square wave A.C. output signal that can be conducted to a common point where it is amplified and demodulated for better linear measurement of said low-voltage signals. The oscillator is connected through the isolator to the bridge circuit in such a manner that opposing pairs of the bridge transistors are simultaneously conducting. The isolator may comprise a novel photovoltaic isolation device or it may consist of an isolation transformer or of other types of electrical isolation devices. The transistors and input and output terminals for the bridge circuit are shielded and are mounted on a heat sink consisting of a thermally conducting metal plate and/or a metal oxide single crystal which is in common with the shield and/or one terminal of the low-voltage source such that all leads and terminals are maintained at a constant temperature and preferably at the same temperature as the low-voltage source. Air currents are prevented from causing thermally induced voltages within the bridge circuit by the circuit shield and in some extreme cases by the use of a hermetically sealed shield for the critical circuit elements and connections. For accurately balancing out interelectrode capacitance-coupled gate drive to low-level channel signals, a pair of variable capacitors are connected between one output terminal of the bridge circuit and the gate of each of its two adjacent transistors. The balanced bridge chopper may be produced as a monolithic planar-silicon integrated circuit in which gate-to-channel capacitance balancing is accomplished during manufacturing in place of the variable capacitors. A novel balanced input filter and trimmer capacitors between the bridge output terminals and local ground greatly reduce 60 Hz. common mode noise. In a hybrid circuit embodiment of the bridge circuit, the individual MOSFET chips forming the bridge circuit are bonded and interconnected within a hermetically sealed and magnetically transparent metal oxide single crystalline container. Multiplexing circuitry is also disclosed for driving several chopper circuits from a single oscillator and for connecting the outputs from the chopper circuits to a single amplifier and demodulator at a remote location.

Power switching control circuit with enhanced turn-off drive

Abstract: A transformer-coupled power switching device control arrangement utilizes an active feedback energy source connected to the primary of the coupling transformer to enhance the turn-off drive to the power switching device. The active feedback energy source produces an output directly dependent upon the magnitude of the power switching device output current and independent of the duration of said output current. When the output current drops to zero, the active feedback source is disabled, and a bias network is connected to the transformer primary. The bias network maintains a reverse voltage at the control electrode of the power switching device and establishes a bias current through the primary suitable for resetting the transformer core flux.

High efficiency power supply having a reactive buck automatic d.c. voltage regulator

Abstract: D.C. power supply having a reactive buck automatic D.C. voltage regulator which directly controls the rectified D.C. output of a loosely coupled transformer thereby providing load regulation from an unregulated alternating current source. The load current passes through the secondary winding of an auxiliary buck transformer and is stepped down to a much lower value in the primary winding of the auxiliary buck transformer. The primary winding of the auxiliary buck transformer is coupled to an isolated winding on the core of a ferroresonant C.V.T. transformer which receives the unregulated alternating current input signal, and the coupling between the isolated winding and the primary winding of the buck transformer effects a bilateral energy transfer between the two transformers which effects a real time reactive compensation which regulates the D.C. output of the power supply for changes in the input voltage and in the load while conserving the energy which would normally be wasted in achieving regulation by transferring it back to the resonant circuit via the bilateral energy transfer between the two transformers. The control system is set up so that the auxiliary buck transformer is normally bucking under all line and load conditions when the frequency is precisely at the resonant frequency of the saturable inductor and capacitor. A frequency shift either above or below resonance simply changes the amount of bucking that takes place in a complimentary manner. It should be noted that little power is consumed during the buck process as the power is returned from the auxiliary buck transformer to the loosely coupled ferroresonant transformer. The operating point of a negative feedback system which determines the point about which the bilateral energy transfer occurs, may be fine-tuned by an error-sensing feedback circuit for altering the voltage level which the coupling network operates to hold constant by controlling the bilateral energy transfer. A capacitor is provided across the primary of the auxiliary buck transformer to reflect capacitance into the secondary winding during conditions of little or no bucking action in order to enhance the stability of the regulator.

Isolating transformer used as pulse transformer - is for use with high speed pulses and has two annular cores covered in windings

Abstract: The system comprises a pair of annular cores (10, 11), each of which carries a winding (12, 13) consisting of a number of turns. There is a winding (14) which is common for both cores and which consists of a single insulated wire passing through both cores. The two cores (10, 11) and their windings (12, 13) are at a distance from each other in order to prevent insulation breakdown between the windings (12, 13). An insulating barrier sheet may be installed between the two coils (10, 11), having a central opening just large enough to admit the single insulated wire.

The operation of a parametric transformer between two busbars

Abstract: This paper deals with the operation of a parametric transformer when both the input and output windings are connected to live busbars. The relationship between each core flux and the MMF's of the two windings is explained. Based on this relationship, the voltage equations of the device are integrated numerically to obtain the input and output currents and the power-angle characteristics. The effects of the phase angle "δ" between the two busbar voltages on the power flow, efficiency, power factor and harmonic currents are examined. A comparison between the experimental results on a small unit and those obtained from the numerical solution of the equations is also given.

Voltage protection circuit

Abstract: In a protection circuit for a device such as a motor, the unused half or a dedicated half of an AC signal on the secondary of an isolation transformer is sensed to disconnect the AC line from the device if the line voltage is abnormal, such as being too low. Conveniently the protection circuit is employed in a complete motor protection system which may include a thermal protection circuit, a low oil pressure protection circuit, and/or a time delay circuit to prevent start-up too soon after shut-down.

Nuclear reactor fail-safe unit having the function of control relay and current regulation

Abstract: An electronic unit for controlling the safety absorbers of a nuclear reactor comprises a self-supplied AND1 circuit for performing logical multiplication of input signals each capable of assuming one out of two values, series-connected modules each constituted by a dc/ac converter, the output of the last module being coupled to the first converter and to a regulator input at which is obtained a logical ac signal whose value corresponds to the result of multiplication of the different input signals, a static intensity regulator with negative current feedback for modulating the width of the square waves delivered by an isolation transformer, a rectifier for delivering a constant current to a load impedance

Direct current measuring system for rectifiers

Abstract: A dc measuring circuit for power rectifiers is described wherein primary line current is utilized to measure direct current output. In the measuring circuit, line current transformers are connected to a multiphase instrument rectifier through a phase shifting current transformer which is adjustable to compensate for differences between the primary and secondary line current phase shift characteristics of the power transformer and any phase shift in the line current transformer. By such compensation, the average value of rectified primary line current in the measuring circuit is maintained independent of the commutating angle of the rectified power current. The dc measuring circuit includes means for providing unity current transformation through the phase shifting current transformer. The dc measuring circuit also includes means for handling the presence of zero sequence current without causing measurement error or circuit damage. The dc measuring circuit also includes means for indicating the blowing of a fuse associated with the power rectifier circuit. In one embodiment, the phase shifting current transformer comprises a double extended wye connected autotransformer. In another embodiment, the phase shifting current transformer comprises a truncated delta autotransformer.

Low-Frequency One-Step Inductive Voltage Divider with Ratio up to 1: 1000

Abstract: The advantages and disadvantages of one-step and multidecade inductive voltage dividers at low frequencies, i.e., frequencies below 10 Hz, are discussed. By electronically decreasing the magnetizing current of one-step dividers and by use of a special design, errors become very small. The construction and the calibration of such dividers is described. Preliminary test results of dividers of the autotransformer and the isolating transformer type show in-phase errors of 10-8 (ratio 10-2) and 10-7 (ratio 10-3) of output. Output resistances are in the 10-3 ? range. The input resistances are about 109 ? at 81/3 Hz.

Method to protect the stationary type frequency transformer

Abstract: PURPOSE: When the A-C power of the stationary type frequency transformer that transforms the direct current in the middle is not obtained due to the power failure, the reactor of the direct current circuit is short circuited and the striking pulse of each transformer is obstructed to prevent the failure of current branching and prevent the accedent of overflowing current when the A-C power is restored. COPYRIGHT: (C)1977,JPO&Japio

Select the Right Transformer Winding Connection for Industrial Power Systems

Abstract: The importance of selecting the proper transformer winding connections because of its influence on power system operation and relaying is emphasized. The delta-wye connection is recommended.

Transformer for d-c signals

Abstract: In the d-c transformer of the present invention a current changing between two maximum values of opposite polarity is impressed on the secondary winding of the transformer. One input of a multiplier is coupled in parallel across the secondary winding and the other input coupled to a current value measuring device in the circuit of the secondary winding with the multiplier providing output signals which are proportional to the d-c signals at the input of the primary side of the transformer.

Method of measuring analog input voltages through isolation transformers and apparatus for the same

Abstract: In measuring analog input voltages through isolation transformers, an analog input voltage V in is applied across a primary winding of the isolation transformer, voltages V A and V B developing across the secondary winding of lapses of time T A and T B (T A < T B ) from application of the analog input voltage are detected, and by using measured times T A and T B and secondary winding voltages V A and V B , the analog input voltage V in is calculated in accordance with an expression ##EQU1## whereby influence of sag due to the isolation transformer is compensated for.

Dry-type instrument transformer with potential tap and connector therefor

Abstract: A dry-type instrument transformer having a potential tap in the form of a well molded into the body of the transformer. A female conductor terminal is provided inside the well connected to the high voltage winding of the transformer. A connector in the form of an elbow module fits within the well and has a male conductor member which mates with the female member. A ground coating is provided on the exterior surface of the transformer and is in conductive relation to a ground coating on the elbow module. A metering system having a potential transformer and a current transformer each with a potential tap and connected together by a pair of interconnected elbow modules.

Self-regulating line output stage

Abstract: Disclosed is a circuit powered from an unregulated voltage which generates television line scan deflection signals and a regulated voltage to power other circuits comprising a transistor with its input fed by variable width input pulses and its output transformer coupled to feed a storage capacitor for the regulated voltage resonant circuit including the deflection coils for scan generation, the transformer primary being connected to the collector of the transistor through a diode poled to block direct connection between the primary and secondary. Picture tube high voltage may be generated by an additional transformer secondary from the transistor or by inclusion of a transformer as part of the resonant circuit.

Supply and braking circuit for DC motor - has thyristors in rectifier shorting back-EMF and braking rotor when motor supply fails

Abstract: The supply and braking circuit, for a d.c. motor, has thyristors in the motor rectifier to short-circuit the back-e.m.f. and brake the motor when the supply fails. When the motor supply fails firing pulses are generated by a control circuit and applied to the thyristors. The rectifier unit contains an isolation transformer whose centre-tapped secondary winding is connected across the rectifier bridge input. The tapping point is earthed. The firing pulses for the thyristors are generated by an oscillator that supplies a pulse amplifier. The advantages of the circuit are its simplicity and cheapness.

Electrical leakage measurement apparatus - applies high voltage across component and measures current using opto-electronic threshold detection circuit

Abstract: The device measures electrical leakage, using an input isolating transformer (2) whose primary has a cut-out (4) in series and is supplied by the mains. A switchable supply unit (6) is fed from the secondary of the isolating transformer (2) and provides a high voltage of either polarity to the terminals of an electrical component (8) whose leakage is to be measured. One or more current measuring circuits (10, 14, 16) are connected in series with the component (8), as is a detection resistor (32). A detection circuit (36, 34, 42, 44) controlled by the voltage across the detection resistor (32), triggers the cut-out (4) when this voltage exceeds a variable threshold. The detection circuit includes a light source (34) and a photoelectric detector (42).

I.R. gas burner control - pulse generator in parallel with isolation transformer improves safety

Abstract: The pulse generator is parallel to both the primary of isolation transformer and a solenoid valve with contacts controlling the primary of ignition transformer of the gas burner The delay controlling relay is connected to the ac supply via a temperature sensor which checks the heating and is in series with a generator while the no contacts are in series with the nc contacts of the relly Burner control unit is espec suitable for multi-room heating, where eg continuous opening of doors, (creating a draught) is counteracted, by the delay controlling unit, preventing blow back etc

Ink droplet frequency control for ink jet printer - has sensing unit for detecting charge displacements and amplifier for controlling the pressure

Abstract: A control cct. incorporates a sensing unit with which the frequency dependent charge displacements occurring during the emission of droplets are detected at the nozzle. The circuit also includes a series connected amplifier system with a desired-value setting device and an adjusting unit which controls the pressure of the liquid via a pump. The average value from the droplet series is measured using an isolating transformer as a coupling element in conjunction with an operational amplifier. The natural resonance of the transformer corresponds to the droplet frequency.

Temperature sensing transformer primary switch

Abstract: A temperature sensing transformer primary switch for a distribution transformer, the switch being mounted within the distribution transformer below the level of the dielectric fluid and being manually operable externally of the transformer for opening the primary circuit and deenergizing the transformer, the switch including a temperature sensing device mounted on the internal end of the transformer below the level of the dielectric fluid to open the primary switch in response to overload temperatures produced on the transformer's secondary circuit. The temperature sensing device includes a compression spring and a wax motor for releasing the energy stored in the compression spring as the temperature of the dielectric fluid reaches a predetermined maximum temperature. The spring is preloaded sufficiently by a manual operation to actuate the switch at the maximum temperature. A pressure responsive switch assembly is provided for opening the primary switch.

FM digital transmission of analogue measurement signals - allows many different transmitters and receivers to be attached to same transmission line

Abstract: A method of transmitting and receiving essentially analogue measurement signals in a digital pulse coded modulated form, in which many different transmitters and receivers can use the same transmission line simultaneously, is presented. The method is more efficient than similar existing methods but maintains high accuracy. Each transmitting unit consists of an amplifier (1), an A/D converter (2), logic network (3), carrier frequency signal generator (5), modulator (4) and transformer (6). A frequency divider (5a) is used in a feedback arrangement of these units to present a pulse code modulated signal representing the input analogue signal to the isolating transformer (6), which feeds it to the transmission line. Each transmitting unit supplies its own characteristic carrier frequency. The receiving units each consist of a band post filter suited to one particular carrier frequency, a demodulator a digital storage unit and a display.

Floating measurement amplifier

Abstract: A floating measurement amplifier comprising an emitter and a receiver ferromagnetically coupled but totally separated from each other galvanically, the emitter comprising a modulator feeding the primary winding of a signal transformer and a feed device feeding the primary winding of a feed transformer, and the receiver comprising a demodulator, identical to the modulator controlling the feed of the secondary winding of the signal transformer and an oscillator connected to the secondary winding of the feed transformer, said modulator and demodulator being formed of transistors controlled by their bases, the modulator being connected to the primary winding of the signal transformer and, through a capacitor, to the primary winding of the feed transformer, and the demodulator being connected to the secondary winding of the signal transformer and, through a capacitor, to the secondary winding of said feed transformer.

A Digital Model of a Current Transformer - Distance Relay Combination

Abstract: A quantitative technique is developed which simulates the operation of a current transformer supplying a resistive - inductive burden and calculates the instantaneous value of the secondary output current. Only parameters normally available to the current transformer user are required as input data. Diagrams showing the current transformer output waveforms obtained for a range held direct current circuit breakers and then reviews the application of current transformer burdens and remanence conditions are included. The representation of typical high speed distance protection relays system is discussed and the dynamic performance of these relays when supplied by a current transformer operating in either the unsaturated or saturated state is analysed. Diagrams showing the relay output obtained are included.