Showing papers on "Isolation transformer published in 1984"

High voltage isolation transformer

Abstract: A high voltage power supply is formed by three discrete circuits (12, 14, 16) energized by a battery (18) to provide a plurality of concurrent output signals floating at a high output voltage on the order of several tens of kilovolts. Each circuit has a regulator stage (20, 28, 36). In the firsttwo circuits, the regulator stages are pulse width modulated and include adjustable resistances (R1, R2) for varying the duty cycles of pulse trains provided to corresponding oscillator stages while the third regulator stage includes an adjustable resistance (R3) for varying the amplitude of a steady signal provided to a third oscillator stage. In the first circuit, the oscillator (22), formed by a constant current drive network and a tuned resonant network including a step-up transformer (46), is coupled to a second step-up transformer (24) which, in turn, supplies an amplified sinusoidal signal to a parallel pair of complementary poled rectifying, voltage multiplier stages (76, 76') to generate the high output voltage. Each of the other two circuits include oscillator drive stages (30, 38) which, together with isolation transformers (32, 40) provide output signals floating at the high output voltage.

Parallel-resonant bridge-inverter fluorescent lamp ballast

Abstract: Center-tapped DC power to a self-oscillating full-bridge inverter-type fluorescent lamp ballast is obtained from a regular power line by way of a voltage doubler. The DC power is supplied to the inverter through an inductor means having two separate windings on a common magnetic core--with one winding being positioned in each leg of the DC power supply. The full-bridge inverter, which comprises four switching transistors connected in usual full-bridge fashion, comprises a center-tapped parallel-tuned L-C circuit connected across its AC output, thereby providing a center-tapped sinusoidal voltage to its load, which consists of a fluorescent lamp connected in series with a current-limiting capacitor. Due to the effect of the inductor means, the current provided to the bridge is substantially constant during a complete period of the inverter's oscillation. The arrangement is symmetrical and provides for the center-tap of the DC voltage source to be at the same potential as the center-tap of the inverter's AC output; which means that the center-tap of this inverter or ballast output may be grounded without the need for using an isolation transformer.

Current sensing transformer assembly

Abstract: A current sensing transformer useful for sensing overload current with static trip units is fabricated from an inexpensive array of transformer core laminations and a conventional secondary transformer winding. The transformer primary strap is arranged about the secondary winding for improved flux transfer.

Three-phase ac to dc power converter with power factor correction

Abstract: A system for converting three-phase AC to DC voltage employs three separate converter circuits having their outputs connected in parallel to reduce current harmonics. Each converter circuit includes a full wave rectifier feeding a pulse width current modulator which modulates the DC current flow to the load in a manner to maintain the magnitude of the DC current proportional to the instantaneous magnitude of the DC voltage. The current modulators act as substantially resistive loads to reduce source current harmonics and correct the power factor. The modulators include a pair of transistors connected in a push-pull circuit which are controlled by an oscillator circuit to modulate the DC current at a frequency which is many orders of magnitude greater than the line frequency of the AC source. The DC current outputs of the modulators are coupled through DC/DC isolation transformers to the load.

AC transducers, methods and systems

Abstract: A position and motion transducer is described comprising means for providing a permanent magnetic field adjacent an appropriately oriented toroidal transformer, which can be either an isolation transformer or an autotransformer. The means for providing a permanent magnetic field, in an especially useful embodiment is a permanent magnet cobalt disk magnet with its surface pole facing generally radially in the plane of the torus or generally perpendicular the axis thereof. Appropriate excitation of one winding of the toroidal transformer enables readout equipment connected with the other winding to indicate the position and movement of the magnet relative the toroid. Appropriate mounting of the magnet enables various measurands to be indicated. For example, mounting the magnet on or for movement with a diaphragm enables fluid pressures applied thereto to be measured while mounting the magnet on a spring support force plate or piston/cylinder enables the force or weight applied thereto to be measured.

Switch current sensing with snubber current suppression in a push-pull converter.

Abstract: A push-pull converter has transistor power switches which conduct alternately to connect a DC source with the primary windings of an output transformer. A turn-off snubber circuit is connected with each power switch. When a power switch is turned on, snubber current pulses flow in the circuits connected with both switches. A switch current sensor circuit has a current transformer with an output winding inductively coupled with each of the conductors connected between the power switches and the primary windings of the output transformer. The snubber current pulses through the conductors are 180° out of phase and are suppressed in the current transformer output. The switch current signal from the secondary of the current transformer is free of snubber current pulses and is used in a flux balance circuit and in a pulse-by-pulse current limiter.

Oil and fuel contamination monitoring system

Abstract: A contamination monitoring system is disclosed wherein a low frequency alternating current signal is applied to a remotely mounted probe in the liquid being monitored for contamination. A fixed resistor located at the probe is electrically in parallel with the resistance of the liquid being monitored. The resistor is isolated from the liquid and allows a signal to be transmitted through an interconnecting cable even though the liquid resistance is very high. A signal is returned to signal processing electronics via the interconnecting cable to a high input impedance amplifier which drives an isolation transformer. The isolated electrical signal induced on the secondary winding of the isolation transformer drives a two stage amplifier circuit the output of which is representative of the amplitude of the isolated electrical signal which in turn is representative of the resistance of a path between the alternating current signal generating means and the high input impedance amplifier that drives the isolation transformer. The representative resistance is applied to three comparator circuits that indicate and alarm the three conditions; (a) an increase in conductivity in a normally nonconductive liquid, (b) an abnormally high conductive condition indicative of a short circuit and (c) unusual increases in nonconductive measurments which would indicate open circuit conditions in the cable.

Fault protection system for power supplies that use ferro-resonant transformers

Abstract: A fault detection system for use in power supply systems using ferro-resonant transformers is presented. Current sensing means are used to sense the current flowing in the ferro-resonant circuit associated with operation of the ferro-resonant transformer. A fault detection circuit, powered by its own power supply connected to the primary source of power, monitors the sensed current and signals any significant change therein. A fault condition in any of the secondary circuits of the transformer causes the ferro-resonant current to change, and upon sensing this change, the fault detection circuit disconnects the primary of the transformer from the source of power.

Audio amplifying apparatus and method

Abstract: An audio amplifier operatively connected to the secondary winding of a power transformer. The primary winding of the transformer is connected through a control circuit which has switch means that is turned on and off during selected portions of half cycles of the voltage imposed upon the primary winding of the transformer. By turning the switch on and off at appropriate intervals, the proper amounts of electrical energy can be delivered to supply the power requirements for amplification, while substantially reducing problems of idling currents in the primary winding of the transformer. Thus, the transformer can be made much smaller than in power supplies of conventional amplifiers.

Transformer built of coupled flux shuttles

Abstract: A D.C. isolation transformer consisting of a primary group of one or more flux shuttles coupled, preferably inductively coupled but alternatively capacitively or resistively coupled, to a secondary group of one or more additional flux shuttles is capable of transforming, and transmitting, power at both alternating and direct currents. A flux shuttle is a plurality, n, of Josephson junctions interconnected in parallel one to the next by like plurality minus one, n-1, of inductors. When the Josephson junctions and the inductors are equivalent within and between the flux shuttles as comprise both the primary and the secondary of the transformer then the transformer device will have a voltage gain of exactly an integer number, i.e. 2, 3, 4 etc. The transformer is preferably implemented in planar thin film technology, the Josephson junctions being created with the Selective Non-Anodizing Process (SNAP) while the inductors are superconducting stripline.

DC-DC converter with galvanically isolated feedback voltage regulation

Abstract: A switched mode power supply has a sense transformer (TX2) with three windings. A first (primary) winding (WD) is in series with the primary winding (WP1) of the power transformer (TX1). Current regulation of the output is provided via a second (sense) winding (WS). Voltage regulation of the output is provided by a further (third) winding (WC) being connected in parallel with the secondary winding (WP2) of the power transformer for producing isolated feedback of an output voltage error signal using the sense transformer (TX2) as a current summing transformer.

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 overheated 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.

Magnetically modulated d-c to d-c forward converter power supply

Abstract: A d-c to d-c forward converter power supply has a magnetic modulator in the timing circuit which operates between its residual magnetic flux density and its saturation flux density to deliver a fixed number of volt seconds during sequential clock interval periods. The clock period is fixed so that the output voltage averaged over each clock period will be constant and independent of input voltage over a given design range. A bias current is applied to the magnetic modulating transformer to controllably modify volt second capability of the device. In one embodiment, two transformers are employed, one of which is non-saturating and the other of which is a control transformer and saturates during its operation. In a second embodiment of the invention, only a single transformer, which is a saturating transformer, is employed.

Power supply circuit utilizing transformer winding voltage integration for indirect primary current sensing

Abstract: In a power supply having transformer coupling for regulation of voltage by a pulsing of primary current, a control circuit integrates the output voltage to obtain a measure of flux and primary current. A comparator monitors the integrated voltage to terminate a pulse of primary current prior to saturation of a core of the transformer. This insures linear operation and efficient transfer of energy from the primary to the secondary windings of the transformer. A sensor of secondary current initiates a new pulse of primary current when the secondary current has decayed to a fractional value of the peak secondary current.

Symmetrical load power reduction device for lighting fixtures

Abstract: A device to reduce power consumption in a rapid-start fluorescent lighting fixture having one or more lamps and a conventional ballast. The device includes a step-up isolation transformer, a capacitor connected in parallel with a bleed resistor and in series with a protective fuse all across the transformer. The device being mounted external of the ballast and wired in series between the ballast and the filament of a lamp to present a symmetrical load to the ballast circuit. In one embodiment the capacitor of the device is connected between the primary and secondary windings of the transformer by taps intermediate of the windings with an optimum connection at the center taps of the windings. In a second embodiment the capacitor is connected between either lead of the primary winding of the transformer and the center tap of the secondary winding. In a third embodiment the connection of the capacitor is made between either input lead of the transformer's primary winding and the electrically opposite lead of the transformer's secondary winding.

Power switching circuit

Abstract: @ A power switching circuit for switching power repetitively to a load at a relatively low frequency employs a power switching device (14) which is driven across an isolating transformer interface (60). The drive signals are high frequency pulse signals which are modulated with the low frequency switching information, the modulations being detected in the secondary circuit (62) of the transformer. Such an arrangement affords isolated driving with fast switching edges and requires only a small transformer. Power for the detection circuit is derived by rectification (120-124) of the high frequency signals induced in the transformer secondary.

Power modulator provided with a transformer

Abstract: The invention concerns a power modulator provided with a transformer. This transformer having a high transformation ratio receives a low voltage impulse and transforms it into a high voltage impulse directly applicable on a high frequency or hyperfrequency tube in order to create a powerful impulse magnetic field. The transformer is particularized by the realization of its primary composed of a plurality of primary windings, all of which are connected in parallel and which, put end to end, extend along the entire lengths of the secondary. They are wound furthermore around the secondary and not inside it.

Switching power supply unit for a device with stand-by operation, especially a television receiver.

Abstract: of EP00978841. Switch mode power supply having an isolating transformer (1) for an apparatus having a stand-by condition, especially a television receiver, having a first rectifier (15) for producing a first high drive voltage (U1) and a second rectifier (16) for producing a second low drive voltage (U2), which is also effective in the stand-by condition, whereby the first drive voltage (U1) is reduced in the stand-by condition via a primary side control circuit (11) by a voltage (22) appearing at the secondary side to such a degree that the stages connected to the first drive voltage (U1) no longer function, characterized in that the voltage (22) arising at the secondary side is applied to the primary side control circuit (11) via a galvanic isolating element (23) distinct from the isolating transformer (1), and the first drive voltage (U1) is utilised with its reduced value (15 V) as the second drive voltage.

A new variable-voltage parametric transformer using bridge-connected magnetic circuit

Abstract: This paper describes operating characteristics of a new parametric transformer with variable output voltage. The parametric transformer is constructed with two of a bridge-connected magnetic circuit, and the value of the parametrically-generated output voltage is easily controlled by dc current. An application of the parametric transformer to a dc power stabilizer with high performance is presented in this paper.

High voltage D-C transmission power station with a generator transformer

Abstract: In the high voltage d-c transmission (HGU) power station in a block circuit, a three-phase generator feeds a 12-pulse high voltage d-c transmission (HGU) short coupler through at least one shifting transformer which serves for forming voltages of two three-phase voltage systems phase-shifted relative to each other by 30° el. As compared to a full transformer, the shifting transformer can be constructed for substantially less power, which reduces the cost and the losses of the station. While the voltages of the two phase-shifted voltage systems can be taken off at the external terminals of the secondary windings of the shifting transformer, the center taps of the secondary windings are acted upon by the generator voltage. Advantageously, the high voltage d-c transmission short coupler is formed of a multiplicity of parallel, electrically separate d-c circuits which can be fed by separate shifting transformers.

Power modulator having a transformer

Abstract: The invention relates to a power modulator provided with a transformer (5). This high turns ratio transformer receives a low voltage pulse and converts it into a high voltage pulse applied directly to a high-frequency or microwave tube to create a strong pulse magnetic field. The transformer is particularized by the achievement of its primary composed of a plurality of primary windings (51, 52, 53, 54) all connected in parallel and which, placed end to end, extends over the entire length of the secondary ( 57). They are wound around the more secondary and not inside it.

Development of a Prototype UHV Transformer and its Application to 500 kV Transformers

Abstract: Development principles of an insulation structure for a prototype UHV transformer are presented. New interleaved windings having gradual apportionment of series capacitances were developed, and shown to have approximately uniform voltage distribution for lightning impulse and high reliabaility in their dielectric characteristics. The insulation structure developed for the UHV transformer was applied to a 500 kV transforrner, which allowed its floor space, weight and loss to be reduced about 20 % compared to a conventional 500 kV transformer.

Very high frequency power transformer and method of manufacturing

Abstract: A transformer assembly suitable for use in very high frequency (VHF) switching power supplies that maintains a low leakage inductance between critical transformer windings while complying with the physical and electrical requirements imposed by standards for primary to secondary isolation. The transformer includes a telescopic bobbin assembly (99, 112) with an inner (99) and an outer (112) section that telescope together to form an interior clearance space or chamber between the two sections. The interior chamber has a narrow conduit (108) exiting to the exterior of the bobbin assembly (99, 112). Described are two embodiments for a transformer used in a forward-averaging type converter and a third embodiment for a transformer used in a frequency modulated converter.

Auxiliary voltage source for supplying electrical circuits which are at a high-voltage potential

Abstract: The invention relates to an auxiliary voltage source for supplying electrical circuits which are at a high-voltage potential, and is used in the case of electron beam guns which are supplied with high voltage. Their cathode is connected to a heating current circuit which has a controllable voltage supply device and an AC region. In order to achieve the object of saving an isolating transformer and nevertheless making available an auxiliary voltage at high potential, it is provided according to the invention that the primary winding (24) of a current transformer (25, 25a) be located in the AC region (23) of the heating current circuit (9) of the cathode (8). The at least one secondary winding (26) of said current transformer (25, 25a) is connected via a rectifier (27) to a parallel controller (28) whose output (29) provides the auxiliary voltage.

Interface of process controller

Abstract: PURPOSE:To ensure sufficient accuracy by providing a power supply means which supplies selectively a driving power and a signal power to an analog interface section from a power supply section selecting a low and a high impedance via an isolation transformer so as to decrease modulating power. CONSTITUTION:A rectangular wave pulse is outputted from the 1st power supply section 16 of an analog input interface of a process controller in synchronizing with a clock of a controller 1 for computer or the like. The 2nd power supply section having a higher impedance than that of the power supply section 16 is constituted by the power supply section 16 and resistors 7a-17d, and the pulsive power of the 1st and 2nd power supply sections is applied respectively to the 1st and 2nd isolation transformers 18a-18d, 19a-19d. An output of the transformers 18a-18d is applied to the analog interface sections 21a-21d via rectifier sections 21a-21d, so as to process an analog signal from the filters 4a-4d and to reduce the modulating output and to ensure sufficient accuracy.

Stand-alone protective device for multi-phase AC energy set.

Abstract: The device of the invention comprises a six-phase bridge 4 and, looped to this bridge, a circuit breaker control resistor 6 for two-phase and three-phase faults, a Zener diode 10 and a Darlington transistor 36 to create energy for supplying the striker of the circuit breaker, energy stored in a capacitor 11. The control signal for the resistor 6 is amplified by an amplifier 18 and detected by an amplifier 21, in order to control a thyristor 26 actuating the circuit breaker. In the case of a homopolar fault, there is provision for a separate processing unit 29 with a control resistor and a same threshold detection, at the output of an isolating transformer 28 looped to the bridge 4.

Single-ended transformer drive circuit

Abstract: A single-ended transformer drive circuit includes a transformer having a primary winding and a secondary winding and a switching transistor connected to the primary winding of the transformer and adapted to turn on and drive the transformer in the forward direction along its hysteresis curve, whereby an output voltage is generated in the secondary circuit of the transformer. An auxiliary transistor circuit is coupled to the transformer for driving it in the reverse direction along its hysteresis curve when the switching transistor turns off, whereby the transformer is reset and prepared for the next cycle of operation when the switching transistor turns on again.

Direct current converter for switched mode power supply

Abstract: The converter comprises an output transformer (T1) through which pass trapezoidal current waves. The primary winding (A0) is supplied under the control of two control circuits (P1, P2), each comprising a transistor (Q1, Q2) and a diode (D1, D2) which are connected in anti-parallel. The two transistors are controlled by two oppositely-poled secondary windings (W1, W2) of a second transformer (T2), the primary winding (W3) of which is controlled by the first transformer (T1). Associated with each control circuit (P1, P2) is a capacitor (C1, C2) such as to accumulate energy during one phase of operation and to discharge it during a subsequent phase. Another winding (Wc) of the second transformer (T2) permits the latter to be biased, stabilizing the output voltages by means of closed-loop feedback control of one thereof.

Power supply circuit of television receiver

Abstract: PURPOSE:To attain an inexpensive circuit by rectifying a voltage at the secondary side of a flyback transformer, and supplying the oscillating output of a horizontal oscillating circuit by the resulted rectified voltage to a horizontal driving transistor (TR) via an isolation transformer, and separating the circuit into a charging part and a non-charging part by both the said transformers. CONSTITUTION:A DC voltage is outputted from a stabilizing circuit 11 to the charging part 25, and a bias is applied to a base to the horizontal drive TR6 by a start circuit 29, and the TR6 is made conductive. Then, a charging capacitor 31 is charged. A pulse voltage is generated in a secondary winding 8b of a driving transformer 8 in this case, a horizontal output TR16 is turned on and off, thereby causing a pulse voltage in the primary winding of the flyback transformer 12. A pulse voltage generated in the ternary winding 12c is rectified in this case to activate the horizontal oscillating circuit 5. The oscillated output is applied to the TR6 via the isolation transformer 33 to turn on and off the TR6 and to bring the TR16 into the steady state. Since the rectified voltage being a tap voltage at the primary side of the transformer 12 is low voltage in steady state, a low dielectric strength TR is enough for the TR6.

Broad band transmitting transformer for high frequency telecommunication.

Abstract: The transformer is an air-gap transformer the winding (10-12, 11-13) of which is chosen to be as long as possible in order to favour the low frequencies whilst letting through the upper frequency of the working frequency band. In order to improve the characteristics of the transformer at low frequencies an open magnetic circuit, consisting of ferrite bars (b1,b4) parallel to one another, is used. Application, in particular, to H.F. telecommunications in the 2-30 MHz band.