Tapped Transformer Research Articles

An L-coupling STATCOM integrated with primary tapped transformer for voltage compensation

An L-coupling STATCOM integrated with primary tapped transformer for voltage compensation

180° hybrid using a novel planar balun on suspended substrate for beam forming network applications

In this paper, a 180° hybrid consisting of a broadband balun and a T-junction in-phase power divider is proposed. The 180° hybrid is intended for operation in the C-band. The balun resembles a center tapped magnetic transformer where the coils are replaced by broadside-coupled lines. This new technique allows magnetic couplers to be realized by planar structures at microwave frequencies. The planar balun is broadband, and the size reduction is considerable. The broadside-coupled lines are on a suspended substrate. The proposed structure can be used in the beam forming networks of the multiple-beam antennas. It also prevents cross connections in the conventional beam forming networks. The planar balun is analyzed by the signal flow graph method. The scattering parameters of the 180° hybrid are calculated by the multiport connection method. Some design formulas for the construction of the balun are presented. The 3-dimensional model of the planar 180° hybrid is simulated by a full-wave simulator. Measurement results of the fabricated hybrid approve the simulation results. The 180° hybrid exhibits a relative bandwidth of 45% centered at 4.5 GHz. In the operating band, the amplitude and phase imbalance of the output ports are <0.6 dB and <10°, respectively.

Performances Evaluation of On-Chip Large-Size-Tapped Transformer for MEMS Applications

This article aims at providing a better behavior understanding and performance evaluation of a large-size passive on-chip tapped transformer when used as a transducer in low-frequency integrated microsystems [30–300 kHz]. Thus, a CMOS-based 1:1 transformer, consisting of 70 turns of 1.6- $\mu \text{m}$ -wide top-level metal spaced by 0.6 $\mu \text{m}$ and with a total length of 1.7 mm, has been investigated and tested. The spatial separation between the two transformer windings was set to 70 $\mu \text{m}$ . An electrical equivalent lumped model has been extracted through an exhaustive specific measurement procedure. The model is useful to simulate and evaluate the voltage transformation ratio (TR) between the two transformer windings. The effects of parasitics and imperfect coupling between transformer windings and through the silicon substrate are outlined from the circuit point of view. We report a magnetic coupling coefficient that does not exceed $k=0.15$ , with a voltage TR of about 0.39 around the resonance frequency of ~5.3 MHz, when the secondary is unloaded. It has been proven that the interwindings capacitance introduced by close conductors of each winding, evaluated to 13 pF, assures the most important role in the power transfer. This article has shown that by optimizing properly the transformer realization and limiting some parasitics elements, the inductive and capacitive links could both play a key role in MEMS transducers through tapped transformers operation around 100-kHz frequencies.

A Simple Harmonic Reduction Method in 20-Pulse AC–DC Converter

This paper proposes a simple and passive harmonic reduction method at dc link of 20-pulse rectifier. The 20-pulse topology is obtained via two paralleled 10-pulse ac–dc converters, each of them consisting of a five-phase (five-leg) diode bridge rectifier. For independent operation of the paralleled diode-bridge rectifiers, a zero sequence blocking transformer (ZSBT) is designed and implemented. Connection of a tapped inter-phase transformer (IPT) at the output of the ZSBT results in doubling the number of the output voltage pulses. The application of the pulse doubling technique with a low power rating (2% of the load power rating) results in a simpler and more economical configuration of the whole system and increased number of pulses. The design is suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The proposed structure is simulated using Matlab/Simulink software under different loading conditions. The simulation results confirm the significant improvement of the power quality indices (IEEE-519 standard requirements) at the point of common coupling (PCC). Experimental results are obtained using the designed and constructed laboratory prototype of the proposed converter to validate the design procedure and the simulation results. The VA rating of the magnetic circuit is calculated to confirm the savings in space, volume, weight and cost of the proposed configuration.

Consideration for Unbalanced Secondary Current of LLC resonant converter with Center Tapped Transformer

LLC resonant converter which have features as high power density, high efficiency and low noise is widely used for consumer and industrial applications. Recently, LLC resonant converter with center tapped transformer is applied to industrial application such as FA (Factory Automation), because wide-input voltage range and high power density is required in this application. Accordingly, a problem of unbalanced secondary current for each half cycle becomes apparent. In this paper, the influence of coupling coefficient of center tapped transformer between primary and secondary to the unbalanced secondary current is investigated. As a result, an offset of magnetizing current by difference of the coupling coefficient occurs then the unbalanced secondary current are generated to cancel the offset.

Comparison of Impulse Wave and Sweep Frequency Response Analysis Methods for Diagnosis of Transformer Winding Faults

Monitoring of winding faults is the most important item used to determine the maintenance status of a transformer. Commonly used methods for winding-fault diagnosis require the transformer to exit operation before testing and an external exciting signal, whether the transformer is malfunctioning or not. However, if an overvoltage signal can be regarded as a broadband excitation source for fault diagnosis, then the interference caused by signal injection can be eliminated without the need for additional pulse or impulse signals. In this paper, a tapped transformer is designed and test platforms are built to compare winding diagnoses using the impulse wave and sweep frequency response analysis methods by recording voltage responses on both the high- and low-voltage sides and calculating the respective transfer functions. Based on comparison of statistical indicators, it is found that the sensitivities of both methods are similar for detecting conditions of winding-ground and winding-interlayer short circuits. It is concluded that it is feasible to use a transient overvoltage monitoring system for winding-fault diagnosis.

A Galvanically Isolated DC–DC Converter Based on Current-Reuse Hybrid-Coupled Oscillators

This brief presents a fully integrated dc–dc converter consisting of only two CMOS chips, which are a power oscillator with an integrated transformer and a full-bridge rectifier. A thick inter-metal oxide layer guarantees a galvanic isolation rating as high as 5 kV. A current-reuse hybrid-coupled oscillator is proposed, which is based on a three-winding tapped isolation transformer and improves both output power and silicon area occupation with respect to previous works. The converter is operated at 5-V power supply and is able to deliver up to 300-mW dc power at 10-V output voltage while exhibiting a power density and a power efficiency of 36 mW/mm2 and 24%, respectively.

Inclusive Design and Implementation of Novel 40-Pulse AC–DC Converter for Retrofit Applications and Harmonic Mitigation

A novel 40-pulse ac–dc converter based on a 20-pulse converter is designed and implemented in this paper. Combining the outputs of two parallel 10-pulse diode bridges, consisting of five legs of diode rectifiers, results in a 20-pulse topology. A zero sequence blocking transformer (ZSBT) is designed and applied to the proposed scheme guarantying the independent operation of the two bridges. To achieve a 40-pulse output, a pulse doubling circuit is applied which is inherently a tapped inter-phase transformer. A T-connected autotransformer platform is designed and added to the converter, making the proposed scheme suitable for retrofit applications. The proposed solution is a tradeoff among the pulse number, the transformer platform, the complexity of the scheme and the cost. The proposed scheme has an optimized configuration in this regard. In this paper, the proposed scheme is simulated by MATLAB/SIMULINK considering different loading scenarios. The simulation results show that the proposed scheme improves the power quality indices and satisfies the IEEE-519 requirements at the point of common coupling (PCC). Also, a laboratory prototype is implemented using the proposed design and the experimental results confirm the simulation results under different loading conditions. The important aspect of the proposed scheme is a considerable reduction in the burdens of the magnetic parts with respect to the nominal load rating which is verified by kVA calculation. This fact indicates a significant improvement in the total cost and space of the proposed configuration in comparison with similar configurations.

Protected Object Models as the Basis of Distance Measuring Units Algorithms Synthesis

In the present study, the algorithms of distance protection (DP) for a high-voltage transmission line are considered. The single, parallel and tapped transformer lines can be as a protected object. The steady-state and transient modes in the model of protected objects are described by the node-voltage equations, which may be in simplified record either taking into account all parameters or not taking into account some mode parameters. DP efficiency depends on the record form of the node-voltage equations. The programmed distance measuring units algorithms synthesized based on the protected object model are analysed.

A fully integrated 10-Gb/s tapped delay Hilbert transformer for optical single sideband

A 10-Gb/s SiGe HBT tapped delay Hilbert transformer (HT) integrated circuit (IC) is described. The four tap filter uses an integrated LC transmission line with a total delay of 180ps, and the HT has a nominal group delay of 120ps. The circuit is fabricated in a 47-GHz f/sub T/ SiGe HBT process and consumes 112mW from a -3.3-V supply. Measured s-parameters and time domain waveforms are shown to agree with theory. Measurements of a 10-Gb/s optical single sideband system indicate that 7dB of broadband sideband suppression is obtainable using the IC.

Experimental study of integrated tunable transformer

A new tunable integrated transformer topology together with its tuning method is presented. The proposed tunable topology consists of a conventional tapped transformer and a coupled inductor. The phase shift between the input power into the primary winding and that into the coupled inductor was used to control the electrical characteristics such as maximum stable gain, input impedance and quality factor. The new tunable transformer achieved about 3dB higher maximum stable gain and 2.8 times higher quality factor compared to the conventional transformer.

Alternating-current magnetic measurements with a bridge network employing inductively coupled ratio arms

The paper describes the theory and use of a bridge network employing inductively coupled ratio arms for the measurements of core loss and permeability in magnetic materials subjected to alternating excitation. The bridge combines the inherent advantages of the parallel resonance bridge and the inductively coupled bridge, but it differs technically from the conventional forms of either of these bridges.In common with all bridge methods, the magnetic test coil (sample) forms one arm of this bridge, and its self inductance and effective resistance are found from the conditions at bridge balance. The core loss and the permeability are then easily calculated. A variable capacitor is used in this bridge as reactance standard.Selected experimental results are given to illustrate the use of the bridge for a.c. magnetic measurements over a frequency range of 50c/s–20kc/s under various conditions of excitations in the core.It has been shown that the bridge offers definite advantages and flexibility of measurements, in spite of operating with a very small number of components. A variable standard capacitor and a variable resistor are the only components used for the bridge arms in addition to the test coil and a tapped coupling transformer. Error due to earth capacitances of the components is also negligibly small.

A Cranial Radiographic Technic in the Living Rat

IN an earlier paper (1) a description was given of the radiographic technic then employed in the study of the rat cranium, the animal being sacrificed and the cranium cleaned of the soft tissues, sawn sagittally, and dried. The x-ray machine then used was an obsolete model of the portable type, modified for the purpose by the provision of a half voltage midpoint tap on the high voltage winding of the transformer, and addition of a tapped supply transformer to control input voltage to the machine. Using fine grain, single-coated 35 mm. film, exposures of the order of eight seconds were required with a voltage of 40 kv. and 15 ma., the anode film distance being 15 inches. It was realized that a much increased usefulness would be gained if such x-ray study could be extended to living rats at chosen periods of their life history, avoiding possible errors introduced by comparing treated animals with control animals. It was believed that with anesthetized rats exposures of about a tenth of a second would be nee...