Showing papers on "Isolation transformer published in 2006"

Auto-Calibrating DC Link Current Sensing Technique for Transformerless, Grid Connected, H-Bridge Inverter Systems

Abstract: Power electronic inverters are commonly used for the interfacing of distributed generation systems to the electrical power network. These electronic inverters operate in a current controlled mode to inject unity power factor sinusoidal current into the network. To prevent possible dc current injection, a mains frequency isolation transformer is often employed at the inverter output. This isolation transformer is a costly component. An alternative approach is to use current sensing and control techniques to eliminate the dc current component. One method is to use a current controller to force the output dc current to zero. Current controllers are prone to errors associated with nonlinearity and offsets in the current transducers. This paper considers a novel auto-calibrating dc link current sensing technique that eliminates the errors associated with the current transducer, and helps avoid dc current injection into the grid when using a transformerless grid connect inverter system

Method and Apparatus of Providing Power to Ignite and Sustain a Plasma in a Reactive Gas Generator

Abstract: According to a first aspect, a power supply and a method of providing power for igniting a plasma in a reactive gas generator is provided that includes (i) coupling a series resonant circuit (100) that comprises a resonant inductor (110) and a resonant capacitor (120) between a switching power source (60) and a transformer (30), the transformer having a transformer primary (32) and a plasma secondary (36); (ii) providing a substantially resonant AC voltage from the resonant capacitor across the transformer primary, thereby inducing a substantially resonant current within the transformer primary to generate the plasma secondary; and (iii) upon generation of the plasma secondary, the resonant inductor limiting current flowing to the switching power supply. According to another aspect, bipolar high voltage ignition electrodes can be used in conjunction with inductive energy coupling to aid in plasma ignition.

Planar transformer power supply

Abstract: A planar transformer power supply for an electrosurgical device to minimize stray capacitance comprising a step down/step-up isolation transformer and circuitry to limit the effects of a short circuit in the output of the planar transformer power supply on the input to the planar transformer power supply to enhance power capacity at a low load impedance as low as from about 5 ohms to about 10 ohms and to operate at resonance at the output of the planar transformer power supply.

Design of High-density Transformers for High-frequency High-power Converters

Abstract: Moore’s Law has been used to describe and predict the blossom of IC industries, so increasing the data density is clearly the ultimate goal of all technological development. If the power density of power electronics converters can be analogized to the data density of IC’s, then power density is a critical indicator and inherent driving force to the development of power electronics. Increasing the power density while reducing or keeping the cost would allow power electronics to be used in more applications. One of the design challenges of the high-density power converter design is to have high-density magnetic components which are usually the most bulky parts in a converter. Increasing the switching frequency to shrink the passive component size is the biggest contribution towards increasing power density. However, two factors, losses and parasitics, loom and compromise the effect. Losses of high-frequency magnetic components are complicated due to the eddy current effect in magnetic cores and copper windings. Parasitics of magnetic components, including leakage inductances and winding capacitances, can significantly change converter behavior. Therefore, modeling loss and parasitic mechanism and control them for certain design are major challenges and need to be explored extensively. In this dissertation, the abovementioned issues of high-frequency transformers are explored, particularly in regards to high-power converter applications. Loss calculations accommodating resonant operating waveform and Litz wire windings are explored. Leakage inductance modeling for large-number-of-stand Litz wire windings is proposed. The optimal design procedure based on the models is developed.

Partial discharge investigation of a power transformer using wireless wideband radio-frequency measurements

Abstract: The remote detection of a transformer internal partial discharge (PD) has been demonstrated using mobile wideband radio-frequency receiving equipment. The PD is externally detectable due to coupling within the transformer tank, causing impulsive signals to be radiated from external connections. A wideband direction-finding technique using a four-antenna array has shown the source of the radiation to be the tertiary winding connections; the radiated impulse has characteristics typical of this method of emission. No other external site of radiation from the transformer was detected. Due to the lack of coupling to the primary and secondary windings, it is believed that the PD is present between the tertiary windings and the core.

Acoustic data coupling system and method

Abstract: A data coupler includes an acoustic isolation transformer operable to develop an isolated output signal in response to an input signal. A transmitter is coupled to the acoustic isolation transformer and generates the input signal responsive to a data input signal. A receiver is coupled to the acoustic isolation transformer to receive the isolated output signal and generates a data output signal responsive to the isolated output signal.

Comparison of z-source and boost-buck inverter topologies as a single phase transformer-less photovoltaic grid-connected power conditioner

Abstract: In PV grid connected power conditioners; usually is required to step up the PV array voltage, and to step down the dc bus voltage for injection of a sinusoidal current to the grid. In this paper, the design procedure of the traditional double stage boost-buck inverter and single stage Z-source converter, as a single phase PV grid connected transformer-less power conditioner is presented. The reduction of the component cost is a research goal in PV grid connected systems. The omission of the isolation transformer, and the usage of a single-stage Z-source inverter, helps to develop a cost-effective PV-PCU. In addition, the optimum modulation method for each converter is proposed. The performances of both topologies are investigated. The energy storage elements and the efficiency of the converters are compared.

Assessing and limiting impact of transformer inrush current on power quality

Abstract: Transformers are essential elements, which facilitate the transmission of electric power at high voltages over long distances and transformer energization is a common occurrence. The energization can lead to excessive transient inrush current, especially when the transformer core has remnant flux that adds to the flux build-up after switching. Inrush current sags the system voltage, thereby affecting the power quality of the network in proximity of the transformer. The extent to which power quality is degraded depends on short circuit MVA at the source bus, and the magnitude and decay time constant of the transient current. Present day thyristor-controlled machinery used in mining, pulp and paper industries and semiconductor manufacturing require high quality power. Some of these industries even pay a premium price for high quality power. It is, therefore, necessary to first assess the impact of energizing a large transformer on power quality and then develop a technique to limit this impact. This paper presents results from field tests and simulations using Electromagnetic Transients Program a 138 kV 315 MVA transformer energization in the BC Hydro system. The transformer is situated close to a pulp and paper mill with voltage sensitive loads. Methods to assess and to limit the voltage sags during energization are discussed.

High-Efficiency Transformerless Single-phase Photovoltaic Inverter

Abstract: Grid-connected photovoltaic (PV) systems usually include a line transformer in their power conversion stage. This transformer guarantees galvanic isolation between the grid and the PV system, thus providing personal protection and avoiding leakage currents between the PV system and the ground. Furthermore, it also ensures that no continuous current is injected into the grid. However, because of its low frequency (50 Hz), the transformer is big, heavy and expensive. As an alternative to the grid-connected PV systems with line transformer, new transformerless inverter topologies are being studied. If no transformer is used, a galvanic connection between the grid and the PV array exists. In these conditions, leakage currents due to the capacitance between the photovoltaic array and earth could occur and increase the electromagnetic emissions. To avoid these leakage currents, it is necessary to use inverter topologies that avoid commonmode voltages. In this paper, a new transformerless singlephase PV inverter with six IGBTs and one diode is proposed. This topology generates no common-mode voltage and has a higher efficiency than the existing topologies. The topology has been validated by simulation.

High frequency power transformer modeling for Power Line Communication applications

Abstract: This paper deals with the modeling of distribution power transformer with the frequency up to 10 MHz for power line communication (PLC) applications. For this purpose, a new approach to model the transformer is proposed. Then, the elaboration of the model from the impedance measurement in frequency domain is presented. For the determination of the parameters of model, the necessary methods are introduced. The simulation is carried out with ATP/EMTP to compare the characteristic of the measured impedance and the model. In order to verify the model, the small signal transfer through the transformer is measured and compared with the simulation

A high-power active filtering system with fundamental magnetic flux compensation

Abstract: In this paper, a novel transformer structure is proposed in order to manufacture a high-power active filtering device. The novel transformer structure contains one primary and multiple secondary windings. The system configuration and compensation principle are addressed in detail. The fundamental magnetic flux compensation in the case of the transformer with multiple secondary windings is fulfilled. In addition, a three-phase active power filter topology consisting of three independent transformers with multiple secondary windings is presented so that the filter can run under unbalanced loads. The parameters of hysteresis current control are also analyzed in detail. A simple and practical fundamental detecting approach is discussed. Transient response and fault protection schemes are explained. A set of automatic three-phase active power filtering devices has been constructed and operated in the field. The field test results verify the validity of the novel transformer structure and the active power filtering system.

Non-contact power supply unit

Abstract: PROBLEM TO BE SOLVED: To provide a non-contact power supply unit that can obtain a stable DC output of high electric power which is of low noise and highly-efficient and that can reduce the cost and size of an entire system by miniaturizing a transformer with the reduction of the number of circuit elements and the use of high frequency. SOLUTION: A power transmission side circuit is made up of a half-bridge switching circuit 2, a series resonance capacitor C2, and a power-transmission transformer T1. The capacitor C2 performs current resonance between the transformer T1 and inductances L1, L2. A receiving side circuit is structured with a receiving transformer T2 and a voltage-doubler rectifier circuit 3. A capacitor C3 works for rectification and the current resonance. COPYRIGHT: (C)2008,JPO&INPIT

A device and a method for control of power flow in a transmission line

Abstract: A device (2) for control of a power flow in a three-phase ac transmission line (L2, La, Lb, Lc) has, for each of its phases (a, b, c), a transformer (12a, 12b, 12c) with a primary winding (121c) and a secondary winding (122c). The secondary winding is serially connected into the respective phase of the transmission line. A voltage dependent on a controllable part of the voltage between the other two phases of the transmission line is applied to the primary winding of the transformer.

CMOS compatible transformer power combiner

Abstract: A new approach for power combining several low-voltage CMOS amplifiers using a new on-chip transformer architecture is presented. The transformer utilises lateral coupling and thus the layout only requires one relatively thick metal layer. Full-wave electromagnetic simulation confirms the operation and low insertion loss of the transformer.

Space Vector Modulation for High Power Five Level Current Source Inverters

Abstract: A 5-level current source inverter (CSI) is proposed in this paper for high-power applications. The converter topology consists of two full-bridge current source inverters whose outputs are connected in parallel for a large induction motor. The two inverters are fed by two isolation transformers to the elimination of possible circulating currents. A space vector modulation scheme is developed for the inverters to generate the desirable output current. The inverter current harmonics are investigated at different amplitude modulation index and fundamental frequencies. The developed scheme for multilevel CSI can produce adjustable output current with limited switching frequencies, which are very desirable features for high dynamic performance large motor drives.

Electrosurgical generator and method for simulating output signals

Abstract: Voltage and current of an electrosurgical output signal which is conducted by a transformer are accurately simulated by executing a simulation algorithm to compensate for inherent distortion in the values of the current and voltage induced between primary and secondary windings of the transformer. The simulation algorithm is executed in response to voltage and current signals from a primary winding of the transformer, which may be a power output transformer or part of an electrosurgical output signal sensor.

Method and system for enhancing computer peripheral safety

Abstract: A method and system for enhancing computer peripheral safety is provided. In accordance with various aspects of the present invention, the exemplary method and system are configured to monitor and/or isolate alternating current (A.C.) supplies with and/or from any peripheral subsystems or devices. An exemplary method and system comprises an A.C. supply, a host computer system, and a peripheral subsystem or device connected to the host computer system, such as an ultrasound imaging and/or therapy peripheral, and an isolation subsystem configured for monitoring and/or isolating the A.C. supply from the peripheral subsystem or device. In accordance with an exemplary embodiment, an isolation subsystem comprises application software and associated modules and functions that when executed continuously monitors and/or polls the host computer's hardware and/or operating system for the presence of an isolated source, such as a battery, or an unisolated power source, such as through a battery charger and/or other connection path to the A.C. main supply. In accordance with other exemplary embodiments, an isolation subsystem can comprises a wireless or other safe/isolated electrical link for connecting a patient contact device, and/or a verification link or other verification mechanisms configured between an isolation transformer and host computer to monitor or observe usage to power the host computer and peripheral subsystem.

Transformer And Method Of Winding Same

Abstract: A component having a core, a first multi-wire bundle having primary and secondary windings wound about the core and a second multi-wire bundle having primary and secondary windings wound about the same core. In one form, the first and second bundles are wound in parallel with one another in a bifilar manner about the core. The method of winding the component allows the component to handle high current, high frequency data applications. An isolation transformer and filter circuit are also shown using the transformer and/or method of winding same.

Supplementary transformer cooling in a reactive power compensation system

Abstract: A reactive power compensation system includes a reactive power compensation device and a transformer electrically connected to the reactive power compensation device and having a cooling unit. The reactive power compensation device has an enclosure housing power electronics and at least one fan which provides an airflow for cooling the power electronics. The enclosure further includes an air outlet through which the airflow exits the enclosure after cooling the power electronics. The air outlet and the airflow are directed toward the cooling unit of the transformer to provide supplementary cooling to the transformer. The transformer cooling unit comprises external cooling fins in a liquid-filled transformer embodiment and comprises an air inlet of the transformer housing in a dry-type transformer embodiment. An optional duct may be provided between the enclosure and the transformer cooling unit.

Control Power Self-Generation and Sensors Integration in Emitter Turn-off (ETO) Thyristor

Abstract: This paper highlights the design and demonstration of control power self-generation and integration in the emerging new power semiconductor switch emitter turn-off (ETO). It also discusses a method that is utilized to achieve complete sensor integrations in the ETO. Conventional high-power devices require dedicated external power supplies with isolation capability to operate. An isolation transformer lowers the system reliability and increases the cost of the power converter. At the same time, conventional converters rely on expensive external sensors to gather the voltage, current, and temperature information. The emerging ETO is a fully optically controlled power switch: The internal control power is self-generated; voltage, current, and temperature sensors are also integrated in the device.

Isolated switched maintain power signature (MPS) and fault monitoring for power over Ethernet

Abstract: One embodiment monitors a line-side electrical current provided by a power sourcing equipment (PSE) port to a powered device (PD), the PSE port having a power-isolation transformer with a primary coil on an isolated side and a secondary coil on a line side. A switching signal having a switching period and a duty cycle is applied to the primary coil of the power-isolation transformer. A value is determined for an electrical current on the isolated side of the power-isolation transformer, conversion is performed between a line-side electrical current value I out and a corresponding isolated-side peak-current value I peak , and the line-side electrical current is indirectly monitored based on the determined isolated-side current value.

Synchronous rectification circuit for power converters

Abstract: A synchronous rectification circuit for power converters operable under fixed and/or variable frequencies where no current sense circuit or phase-lock circuit are needed is provided. It has a power switch coupled to a transformer for the rectification. A signal-generation circuit is used for generating a control signal in response to a magnetized voltage of the transformer, a demagnetized voltage of the transformer, and a magnetization period of the transformer. The control signal is coupled to turn on the power switch. The enable period of the control signal is correlated to a demagnetization period of the transformer.

A transformerless single phase on-line UPS with 110 V/220 V input output voltage

Abstract: In this paper, it is proposed a new nonisolated UPS system configuration that allows the bypass circuit operation even if the input voltage is different from the output voltage. The UPS system is composed by an AC-DC/DC-DC three level boost rectifier/converter combined with a double half bridge inverter. This topology allows the reduction of some parameters that are commonly discussed in the nonisolated UPS systems such as size and cost, compared with others isolated UPS configurations for the same purpose. Also, the efficiency are improved due to reduced number of switches and batteries, as well as no low frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate in high frequency, using a passive nondissipative snubber circuit in the boost converter and IGBTs switches in the double half bridge inverter, with low conduction losses, low tail current and low switching losses. A simple and well-known control strategy is used. Principle of operation and experimental results for a 2.6 kVA laboratory prototype are presented to demonstrate UPS performance.

A New High-Frequency AC Link Three-Phase Four-Wire Power Electronic Transformer

Abstract: In this paper, a new three-phase four-wire high-frequency AC link matrix converter is discussed, and the topology of conventional matrix converter is modified with an additional transformer for three-phase four-wire electronic power distribution application. The proposed approach accomplishes high output voltage transfer ratio which is more than unity, galvanic isolation between both voltage sources and higher power density by employing a high-frequency transformer into the intermediate stage of the dual bridge matrix converter. It has a bidirectional power flow capability, controllable input source displacement power factor and lower harmonic distortion on both input and output sides. Furthermore, with three dimensional space vector PWM (3D SVPWM) and modified control strategy, the input and output currents may keep low harmonic distortion under unbalanced input voltage or variable three-phase four-wire unbalanced loads. The proposed approach is a competitive solution to the electronic power transformer. Experimental results of a three-phase four-wire 220/380 V 5 KVA 50 Hz electronic power transformer system based on DSP controller are presented and shown to demonstrate the advantages of the proposed system

Multilayer planar balun transformer, mixers and amplifiers

Abstract: A surface mountable transformer integratable into a printed circuit board. In one aspect, the transformer (300) comprises two broadside vertically coupled transmission lines (304,308,312,316). In another aspect, the transformer may comprise two broadside vertically partially coupled transmission lines. The layout of the transformer is adaptable for use in microwave modules where transformers are integrated into the printed circuit board and the active components are mounted in the cavity. The layout preferably requires only two signal areas. In addition, an aspect of the present invention allows the differential or unbalanced ports to lie on the same surface as the balanced port.

Errata - High power universal piezoelectric transformer

Abstract: This study describes a multilayer piezoelectric voltage and power transformer that has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed isolation gap. The electrode pattern is a ring/dot structure such that it uses radial mode for both input and output part that are built-in on the same ceramic disk. A prototype transformer was fabricated of size 15 2 78 mm2 having mass of 3.8 gm. In the step-down configuration at the constant output power of 6 W, the transformer characteristics across a 100 Ω load were found to be efficiency = 92%, gain = 0.21 input voltage = 110 Vrms, and temperature rise = 20 C from the room temperature. In the step-up configuration at the constant output power of 5 W, the transformer characteristics across a 5 kΩ load were found to be efficiency = 97%, gain = 9.5, input voltage = 16 Vrms, and temperature rise = 8 C from the room temperature. A detailed equivalent circuit analysis of the transformer was done, and the results were found to be in excellent agreement with the experimental results.

Analysis of resonance in transformer windings under very fast transient overvoltages

Abstract: To study the resonance in transformer windings, under very fast transient overvoltages (VFTOs) generated by switching operations in gas insulated substation (GIS), a single input and multiple output circuit model is presented in this paper which is based on multi-conductor transmission line (MTL) model of transformer windings. The procedure to determine the transfer function is deduced. The resonant frequencies and the location of resonance are determined by the analysis of amplitude frequency response characteristics. For validation, the calculated results are compared with the measurements on a transformer winding model and the result is satisfactory.

Current-mode resonant inverter circuit

Abstract: A high conversion efficiency inverter circuit by providing the current-mode resonant type efficient in using a power source. A current-mode resonant inverter circuit comprises a step-up transformer; the secondary winding side of the step-up transformer is composed of a resonant circuit between leakage inductance of the step-up transformer secondary winding and a capacitive component present in the secondary side circuit; one end of the step-up transformer primary winding is connected to the power source side; the other end of the primary winding is connected to a switched snubber circuit through the primary winding of a current transformer; the switched-snubber circuit comprises a pair of transistors different from each other in polarity; bases or gate of the pair of transistors, connected to each other, are connected to the secondary winding of the current transformer; either collector of the pair of transistors is connected to the primary winding of the current transformer; the other collector of the transistor is connected to the current transformer primary winding through a capacitor.

Analysis of the Contactless Power Transfer System Using Modelling and Analysis of the Contactless Transformer

Abstract: In this paper, the electrical characteristics of the contactless transformer is presented using the conventional coupled inductor theory. Compared with the conventional transformer, the contactless transformer has a large airgap, long primary wire and multi-secondary wire. As such, the contactless transformer has a large leakage inductance, small magnetizing inductance and poor coupling coefficient. Therefore, large magnetizing currents flow through the entire primary system due to small magnetizing inductance, resulting in low overall system efficiency. In high power applications, the contactless transformer is so bulky and heavy that it needs to be split by some light and small transformers. So, the contactless transformer needs several small transformer modules that are connected in series or parallel to transfer the primary power to the secondary one. This paper shows the analysis and measurement results of each contactless transformer module and comparison results between the series- and parallel-connection of the con tactless transformer. The results are verified on the simulation based on the theoretical analysis and the 30㎾ experimental prototype.