Leakage Inductance Research Articles

An improved new transformer type arc suppression reactor

In this paper, to accurately compensate the arc suppression coil, the structure of the transformer is improved. Here, a fixed inductive element is connected in series with the short-circuit winding, which combines with the leakage inductance of the original transformer to form a new short circuit impedance. The improved transformer reduces the manufacturing cost and difficulty of the controllable inductor, reduces the requirements for the winding of the reactor, and makes the manufacturing easier.

Once again about the Steinmetz transformer model and the ongoing subdivision of its leakage inductance

PurposeDespite its well-founded criticism and lack of proper justification under core saturation conditions, the T-equivalent transformer model (Steinmetz scheme) is obviously championing in the literature. This educational paper aims to explain in a simple manner the limitations of the T-model of a low-frequency transformer and critically analyses some attempts to improve it.Design/methodology/approachUsing a simplified examination of magnetic fluxes in the core and windings and using the modeling in ATPDraw, it is shown that transient transformer models with the indivisible leakage inductance allow circumventing the drawbacks of the T-model.FindingsThe authors show the absence of valid grounds for subdividing the leakage inductance of a transformer between its primary and secondary windings. The connection between the use of individual leakage inductances and inaccurate prediction of inrush current peaks is outlined as an important example.Practical implicationsThe presented models can be used either as independent tools or serve as a reference for subsequent developments.Social implicationsOver generations, the habitual transformer T-equivalent is widely used by engineers and Electromagnetic Transients Program experts with no attention to its inadequacy under core saturation conditions. Having studied typical winding configurations, the authors have shown that neither of them has any relation to the T-equivalent.Originality/valueThis educational paper will contribute to the correct understanding of the transients occurring in a transformer under abnormal conditions such as inrush current or ferroresonance events, as well as during an out-of-phase synchronization of step-up generator transformers.

Application of the Sinusoidal Voltage for Detection of the Resonance in Inductive Voltage Transformers

In the case of the inductive voltage transformer (VT), the resonance phenomenon may be the main reason for its poor transformation accuracy of the non-sinusoidal voltage. This problem mainly results from the leakage inductance and the parasitic capacitance of its primary winding. The application of the sinusoidal voltage with a frequency from 20 Hz to 20 kHz presented in this study ensures proper identification of the resonance frequencies of the medium-voltage (MV) inductive VTs. The results are consistent with the values obtained in the reference condition at their nominal primary voltage. Therefore, it is proven that the proposed solution is effective in all cases. The influence of the main frequency variation of the non-sinusoidal primary voltage on the resonance properties of the inductive VT is also studied. Moreover, the tests indicate that the capacitance of the load of the secondary winding may cause a decrease in their resonance frequency.

Analysis of Inductive Displacement Sensors with Large Range and Nanoscale Resolution

With the advantages of high resolution, structural simplicity, reliability, compact size, and high sensitivity, inductive sensors have been widely used in nanopositioning systems. However, the measuring range of traditional inductive sensors are usually limited to 0.2 mm. A novel analysis and design methodology of the miniaturized inductive sensor with large measuring range and nanoscale resolution is proposed. Firstly, an accurate leakage inductance model is established. Secondly, a design rule of armature size is proposed by considering the fringing effect. Then, the error terms introduced by the measurement circuit of differential inductive sensors are analyzed and the corresponding error suppression methods are illustrated. Moreover, A design rule of selecting the optimal excitation frequency is proposed to meet the requirements of high Q value and high bandwidth, and to minimize the impact of core loss resistance on the performance of the sensor. Validated by the experiments, the proposed analysis and design method can effectively guide the design of the miniaturized inductive sensor with nanoscale resolution in the measuring range of ±0.5 mm. The overall size of the fabricated sensor prototypes is less than 6 mm × 6 mm × 3 mm. Combined with large range, high resolution and ideal miniaturization, this inductive sensor can be well suitable for compact and large stroke nanopositioning systems.

An interleaved high step‐up DC–DC converter with ZVS capability for renewable energy systems applications

In this paper, an interleaved zero voltage switching high step-up converter based on active clamp, coupled inductor (CI), built-in transformer (BIT), and switched capacitor (SC) is proposed. The main novelty of the proposed converter is that the secondary winding of the CI is inserted between the primary winding of the CI and the primary winding of the BIT. Therefore, the voltage gain can be achieved in proportionate to the multiplication of the turn ratios of the CIs and BIT. The configuration of the proposed converter not only increases the voltage gain, but also reduces the current and voltage stress of the power switches and restricts the input current ripple, which decreases the conduction losses and increases the lifetime of the input source. Also, zero voltage switching turn-ON and turn-OFF conditions for all switches are achieved by employing an active clamp configuration. The voltage across the diodes clamped to the output voltage and the reverse recovery problem is reduced due to the leakage inductors. Finally, a 600 W prototype with 24–400 V voltage conversion is built to verify the performance and theoretical analysis.

Challenges in Winding Design and Thermal Calculations: Physical Model of Permanent Magnet Synchronous Machine

Interest in multilayer windings is increasing with the application of the hairpin winding technology to the manufacturing of electrical machines. Therefore, the four-layer fractional slot concentrated winding is used for the initial design of the machine in this paper. The proposed physical model of the machine uses winding with a relatively high number of turns which is inappropriate to hairpin winding. Therefore the round-wire winding is created and the three-layer winding is derived and analyzed including the effect on the slot leakage inductance. The thermal analysis is then applied to the physical model of the machine to evaluate the slot-related thermal properties of the slot and the whole machine. The measurement is compared with the finite element analysis (FEA) and the equivalent slot thermal conductivity and heat transfer coefficients of the stator and rotor are obtained.

An improved high-voltage high-frequency multi-winding transformer structure for anode power supply in ECRH

An improved multi-winding transformer structure is proposed for high-voltage (tens of kV) high-frequency (hundreds of kHz) applications for anode power supply in ECRH. The relationship between the number of secondary winding layers and leakage inductance and parasitic capacitance is studied for the proposed structure. The results show that winding structure parameters has little effect on the leakage inductance and great effect on the parasitic capacitance. The parasitic capacitance of single-layer winding is the minimum and that of double-layer winding is the maximum. For multi-layer winding, the more layers, the smaller the parasitic capacitance is. The high-frequency multi-winding transformer is built and tested in the anode power supply, where the output is 0–30 kV, the switching frequency is 100 kHz, the maximum output power is 3 kW. The test results verify the analysis.

Operation and Design Consideration of an Ultrahigh Step-Up DC–DC Converter Featuring High Power Density

A new dual-coupled inductor (CI) single-switch high step-up dc–dc topology featuring high power density is proposed in this study. Various capacitive power transfer methods, as well as inductive power transfer techniques, are utilized to act as a more efficient power interface between the input and the load. Three ports in the output terminal are employed to distribute the overall output voltage, diminish the voltage ripple in high-voltage gain ratios, and decrease the voltage stress on the port component. In the proposed converter, first, the voltage gain is high in lower duty cycles of the switching. Second, the stored energy of magnetizing and leakage inductances is recycled in both Cls. Third, the switch voltage spikes are alleviated. Fourth, the operation is done with no circulating current. Fifth, low-size passive components are presented. Sixth, high power density is obtained, and the voltage range is widened. Finally, a simple pulsewidth modulation (PWM) utilizing a wide control range is provided. In this study, the steady-state operation is analyzed under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM), and the performance of the converter is evaluated using comparisons with similar works. In addition, the experimental results have been provided to justify the feasibility of the design.

An Explicit Discrete-Time Large- and Small-Signal Modeling of the Dual Active Bridge DC–DC Converter Based on the Time Scale Methodology

The conventional method to model a dc–dc converter is by averaging its state variable over a switching period. However, due to the dc–ac–dc structure of the dual active bridge converter (DABC), the average value of the inductor current over a switching cycle is zero. Therefore, the conventional methodology cannot be applied to the DABC. The time-scale discrete-time modeling of the DABC is proposed to mitigate the zero average state variable problem. The time-scale methodology simplifies the analysis of the DABC by segregating the fast state variable inductor current and slow state variable output voltage. The proposed model has the advantage of the explicit large signal in terms of the circuit parameter, like the average value model. The explicit steady-state circuit expression from the large-signal model helps in the study of the soft-switching range of the DABC. Moreover, the small-signal model from the proposed method results in an explicit small-signal model. The model incorporates semiconductor <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistance, inductor equivalent series resistance, transformer resistance, and leakage inductance. The effect of the converter net equivalent resistance on the small-signal model is thoroughly studied. Finally, the model accuracy in the steady-state, open-loop, and the small-signal are verified in both the switching simulation model and experimental setup.

A New High-Gain, High-Efficiency SEPIC-Based DC–DC Converter for Renewable Energy Applications

This article proposes a new configuration of quasi-resonant high-gain high-efficiency single-ended primary inductor converter (QRHGHE-SEPIC)-based dc–dc converter with continuous input current. The presented single-switch topology uses a coupled-inductor (CI), a voltage multiplier integrated with a regenerative passive lossless clamp circuit to enhance the voltage conversion ratio. In the proposed converter, the main power switch turns <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> at zero current switching. Moreover, by adopting a quasi-resonance (QR) operation between the leakage inductor of the CI and the middle capacitors, the current value of the main switch at turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> moment is alleviated. In addition, the leakage inductance slows down the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> slope of all diodes and hence there is no reverse recovery problem in the proposed converter. Due to soft-switching operation in all switching components, the power dissipations in the converter are significantly alleviated. Thus, the proposed QRHGHE-SEPIC can provide high voltage gain while achieving a high efficiency. Steady-state analysis, comprehensive comparisons with other related converters, and design considerations are discussed in detail. Finally, to verify the validity of the theoretical analysis, a 160 W/200 V sample prototype is demonstrated at the switching frequency of 60 kHz and with voltage gain of 10.

Isolated DC–DC Boost Converter for Wide Input Voltage Range and Wide Load Range Applications

A current-fed dual-inductor resonant full-bridge dc–dc isolated boost converter is proposed. The converter is most suitable for applications that demand wide input voltage and load ranges. It can be used as a front-end dc–dc converter that can boost variable low voltage from a power source [battery (home/industrial inverter/industrial UPS application), fuel-cell, or solar-PV] and interface it to a high-voltage dc-link, which typically feeds an inverter. It removes all major drawbacks of conventional current-fed isolated dc–dc converters, namely high-voltage spikes across the switches due to transformer leakage inductance, need for additional start-up circuit, and difficulty in converter tripping in case of faults. Soft-switching of rectifier didoes and clamping power switches is load independent leading to good efficiency over entire load range. Converter can be operated with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> < 0.5, making it suitable for wide input voltage range applications. A detailed comparative analysis with state-of-the-art converters for wide input voltage range applications considering the major important factors, such as power device utilization, transformer utilization, inductive energy requirement, and dc capacitors utilization, confirms the superiority of the proposed converter. Experimental results for a 2.5 kVA inverter application with an input dc voltage range of 90–160 V and output ac voltage of 230 V are provided.

Numerical simulation of a squirrel cage motor including magnetic wedges and radial vents

This work is a proposal of a finite element model to obtain the electromagnetic performance of a squirrel cage motor considering the magnetic wedges and radial vents. To analyze the electromagnetic performance at the design stage, without the need to build a prototype, the paper proposes a simple two dimensions finite element model, which includes components as magnetic wedges used to hold the windings in the stator slots, radial vents in the core, which are part of motor cooling system, and edge effects to improve the model. The stator and rotor cores are modeled with an equivalent homogeneous permeability, obtained from the combination of the radial air vents of rotor and stator and the magnetic core material. The permeability of magnetic wedges is also considered. Edge effects considered are the end winding leakage inductance, representing the leakage flux in the end coils of the stator, and an equivalent impedance between rotor bars due to conductivity and leakage flux in the rings of the squirrel cage. The results obtained are compared with experimental tests performed in steady state to validate the model. Furthermore, no-load, and blocked-rotor tests are simulated to estimate the equivalent circuit parameters and draw the typical induction motor torque-speed curve, which is compared with the obtained curve by means of Thevenin’s theorem. With this proposed model, the results are close to the ones obtained experimentally. The implementation of a 3D model is complex, and the computational cost can be much higher, compared to the 2D model developed here.

Implementation of Snubber Circuits in a PV-Based Off-Grid Electric Vehicle Charging Station—Comparative Case Studies

With the penetration of electric vehicles (EVs), there have been paradigm shifts in the transportation sector. EVs are ideally considered to be clean and eco-friendly, but they can overload the existing grid infrastructure and significantly contribute towards carbon emissions depending on the source of charging. The ideal solution is to develop a charging infrastructure for EVs that is integrated with solar energy technology. This paper presents the design of a zero-voltage switching snubber-based bidirectional converter for an off-grid charging station for EVs. The proposed system includes a solar array with a boost converter, a bidirectional converter with snubber circuits and an energy storage unit. A comprehensive comparison between various types of snubbers, such as the resistive capacitive diode snubber, active clamp snubber and flyback snubber, is presented. This type of system configuration clamps the rail voltage, due to the difference in current between leakage inductance and low voltage side-fed inductor currents, resulting in reduced current spikes at the converter’s switches. Such a converter, therefore, leads to higher efficiency of the charging station for EVs. The design of a snubber-based off-grid charging station for EVs is formulated and validated in the MATLAB/Simulink environment.

Design Method of Differential Cascading for Dual-Stator Brushless Doubly-Fed Induction Wind Generator With Staggered Dual Cage Rotor

This article proposes a new differential-cascading-based dual-stator brushless doubly-fed induction machine with a staggered dual cage rotor. Conventional differential mode of the brushless doubly-fed machine with cage rotor suffers from the low number of rotor bars because of the low equivalent synchronous pole pairs of |p1-p2|, and thus, severe rotor flux leakage, low capacity of magnetic field conversion of the rotor and low efficiency. To overcome the obstacle of the excessive harmonics of the rotor, a design method based on the differential cascading is proposed which enables the cage rotor with a high number of conductor bars even in the case of low pole pairs of |p1-p2|, hence the greatly reduced rotor leakage inductance and enhanced performance of the machine. The rotating magneto-motive force theory is applied to derive the interconnection rule of the staggered dual cage rotor, and meanwhile, the corresponding examples are illustrated. The performance comparisons between the differential cascading and the sum cascading based on the proposed machine are carried out. The results show that the proposed machine based on the differential cascading obtains higher power densities comparing to the sum cascading at the region of sub-natural synchronous speed, while its drawback is the increment of the loss due to the high rotor frequency, gaining lower efficiencies at the region of super-natural synchronous speed.

Soft‐switching non‐isolated high step‐up three‐level boost converter using single magnetic element

Here, a soft switched three-level boost converter with high voltage gain is proposed which is suitable for high step-up applications with wide output power range. In this converter, a ZVT auxiliary circuit is used which provides soft switching in a wide range of output power independent of load variation. Utilizing coupled-inductors with one magnetic core removes extra auxiliary core in the soft switching circuit and provides high voltage gain in conjunction with size reduction. Also, the secondary and tertiary leakage inductances of the coupled-inductors minimize the reverse recovery problem of the output diodes. Due to its three-level structure, it has very low voltage stress over semiconductor elements in comparison to the existing interleaved structures, resulting in using MOSFETs with low on-resistance and thus lower conduction losses and cost. Operating modes as well as analytical analysis of the proposed converter are discussed. Finally, in order to validate the proposed converter performance, experimental results from a 200-W laboratory prototype are presented.

Full Soft-Switching Ultra-High Gain DC/DC Converter Using Three-Winding Coupled-Inductor with Modular Scalability for Renewable Energy Applications

This paper proposes a new non-isolated single-switch DC/DC converter with an ultra-high voltage gain, low input current ripple, low voltage stress, soft-switching operation, and modular scalability for renewable sources applications. Here, with the help of a Three-Winding Coupled-Inductor (TWCI) and Voltage Multipliers circuits, ultra-high voltage gains can be achieved without needing a large duty cycle. A regenerative clamp capacitor recycles the energy stored in the leakage inductor; thus, the maximum voltage across the single power switch is restricted. Moreover, at the turn-on instant of the power switch, a Zero Current Switching (ZCS) condition is achieved. By designing a resonant tank, the switched current value of the main switch at the turn-off instant is reduced significantly. Also, the leakage inductor of the TWCI helps all converter diodes to operate under the ZCS condition. Due to full soft-switching performance, the introduced topology can provide a wide output voltage range under a high conversion efficiency. The steady-state analysis and comprehensive comparisons are provided in this paper. A 160 W prototype with 24 V input and 250 V output voltage is developed to validate the theoretical analysis. Due to ZCS operation and low voltage stress (VDS ≈ 40 V), the power loss portion of the MOSFET is low. Moreover, the maximum voltage stresses of the diodes are measured 40 V, 60 V, 90 V, and 110 V that are well below the output voltage. Furthermore, at the full-load condition, the input current ripple is about 20 % and the measured efficiency is about 96.3%.

Design and Analysis of Planar Transformers in Modern Switching Mode Power Supply

This paper presents a development and calculated rating of high-frequency transformer connect with switch-mode power supplies. These power supplies are used in various devices such as power personal communications services, television, DVD players and charge mobile phones Thus, increasing power density and decreasing cost are still the main factors in designing a switch-mode power supply. Magnetic elements represent a great amount of size in switch-mode power supplies and therefore volume reduction and power density raise are beneficial. These switch-mode power supplies consist of two power stages separated by a power transformer with high frequency power. The transformer architecture, which can run at a high frequency, has since become a major challenge for the engineers. Lower component height and better thermal management are advantages with the planar core design. This paper provides a detailed summary of the operating principles of high-frequency transformers. Two transformers are compared in a dual active bridge converter: a wire wound, a planar. This paper discusses a comparison between the wire-wound transformer, high-frequency transformer, and structures in terms of winding loss, core loss, leakage inductance, parasitic capacitance the focus of this research is to find an optimal transform solution for the converter operating at a power level of 220 W. Furthermore, the power losses of a planar transformer are estimated.

Measures and Simulations of Induction Machines Flux Linkage Characteristics Based on Rotor Field Orientation

The focus of this work is on the experimental measurement and the proper finite-element prediction of stator and rotor flux linkages for induction machines. The purpose is to characterize the stator and rotor flux linkages adopting a rotor field-oriented reference frame. The proper basic set of equations is inspired by the direct field-oriented control approach, in order to indirectly derive the rotor flux linkage from the measurement of the stator flux. The proposed method requires a small set of preliminarily known parameters, such as the stator resistance and the overall leakage inductance. Moreover, the only measured quantities are voltages and currents, from which the flux linkages are derived. The adopted strategy also allows to estimate electromagnetic torque and rotor resistance, using the rotor field-oriented model equations. A complete finite-element validation reported for comparison.

Quasi-Y Source network: A design and analysis approach for a DC-DC application

This paper presents a detailed design methodology for a DC-DC converter based on the recent Quasi-Y Source impedance network, which has interesting characteristics for applications related to renewable energy sources. Despite the advantages of this particular impedance network, there is a lack in the current literature, of details regarding the design of the diode and coupled inductors, and a description of its leakage inductance impact on the performance of the Quasi-Y-Source based converter. Therefore, this work presents design guidelines for the coupled inductors including core material choice criteria and optimization of windings combinations. Several analyses are conducted, through computational simulation, with respect to voltage stresses on the converter switches. The simulations results are compared with experimental implementation considering different voltage gain B operational scenarios. The obtained results shows that the proposed approach is useful to design: (a) Quasi-Y Source DC-DC converter components; (b) Evaluate the best coupled inductors configuration; (c) Implement closed loop controllers and snubbers circuits. A discussion evaluating the converter characteristics is made, exploring possible solutions to problems related to real operation scenarios.

Standstill Identification of an Induction Motor Model Including Deep-Bar and Saturation Characteristics

This article deals with standstill identification of an induction motor drive for sensorless self-commissioning purposes. The proposed identification method is based on an advanced model of a squirrel-cage induction motor. The model includes the deep-bar effect and the magnetic saturation characteristics. The excitation signals are fed to the stator using a standard inverter without compensating for its nonlinearities. The saturable stator inductance is first identified by means of a robust flux-integration test, where unknown voltage disturbances are canceled with suitably selected current pulses. Then, the deep-bar characteristics are identified by means of a dc-biased sinusoidal excitation using different frequencies. Finally, the cross-saturation characteristics of the rotor leakage inductance are identified by altering the dc bias of the excitation signal. The identified characteristics are transformed to the parameters of the advanced motor model taking into account the interrelations of the aforementioned phenomena. Since the physical phenomena affecting the standstill identification process are properly included in the identified model, fewer approximations are needed and more accurate parameter estimates are obtained. The identification procedure is validated by means of experiments using two different induction motors (5.6 and 45 kW).