Variation Of Self-inductance Research Articles

Design Recommendations Considering Charging Pads’ Self-Inductance Variation With LCC–S and LCC–LCC Compensation Based IPT Chargers in Low Clearance EVs

Inductive Power Transfer (IPT) based Electric Vehicle (EV) charging systems practically experience self-inductance variation in charging pads with air-gap, especially for low ground-clearances. Conventional design model ignores these variations, resulting in poor sizing and performance. This paper presents a comprehensive theoretical modelling and evaluation of system’s performance considering self-inductance variation for LCC-Series (LCC-S) and LCC-LCC type compensation. The work begins by examining various types of charging-pads with similar design-specifications, and finds circular-pad to exhibit least self-inductance variation. Subsequently, through extensive theoretical analysis, several contour-plots are derived, depicting variation of output voltage/current, output power, input Volt-Ampere (VA), input power-factor, and VA of compensation elements with various load and coupling-coefficient, for both the conventional and proposed models systematically. It is shown that proposed model provides accurate design recommendations over conventional model on various critical parameters, including optimal load, charging-time, dc-link voltage, maximum gain of secondary-side dc-dc converter, and VA ratings of the input and compensation elements. For example, proposed model predicts that a 7% increase in self-inductance with LCC-S type compensation (designed for 5kW) leads to 36.4% reduction in maximum output power, requiring compensatory increases in dc-bus voltage by 25.3% and input VA rating by 34.47%. The proposed model is validated experimentally.

Measurement of conductivity and diameter of metallic rods using eddy current testing

The conductivity and radius are significant parameters for metallic rods, which are associated with metal composition, hardness and microstructure. Accurate conductivity and radius measurement can reflect internal structure status of metallic rod, so as to prevent accidents. The method in this paper aims at simultaneously estimating the conductivity and diameter using sweep-frequency eddy current testing (ECT). This method is an extension of the analytical solution we proposed previously. Specifically, the peak frequency of the imaginary part of the self-inductance variation has the inverse relationship with conductivity. However, the peak frequency is also affected by rod diameter. In order to decouple the conductivity and diameter of metallic, the real part of self-inductance variation have been proved to be only related to the diameter of the metallic rod under high frequency. Combining the peak frequency and real part of self-inductance variation under high frequency, the conductivity and radius can be simultaneously obtained. The experiments using standard specimen are implemented to- verify the feasibility of the method. Results illustrate the average relative errors are within 1.4%.

Variable Inductor Control for Misalignment Tolerance and Constant Current/Voltage Charging in Inductive Power Transfer System

In wireless power transfer system, not only the mutual inductance variation but also the self-inductance variation can be occurred under the misalignment condition. In light of the Unmanned Aerial Vehicles, the variation of the secondary self-inductance and mutual inductance are significantly under the misalignment condition. In order to stabilize the output voltage and current and achieve near-ZPA (near-zero phase angle) of the input impedance. A variable inductor control is presented in this paper, which regulate the inductance of the secondary side by adjusting the dc bias current under large <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> variation. The proposed control method does not need any auxiliary circuit, and constant current-constant voltage (CC-CV) charging can be achieved by controlling the duty cycle of the boost converter. To verify the proposed control method, a 500-W prototype was set up in the laboratory, and the variable inductor control method ensures a stable output voltage and current with horizontal and vertical offsets of 200 mm and 92 mm, respectively. Additionally, communication is not need between primary and secondary side, and the results show that the maximum efficiency is 92.9%, which is 2.3% higher than the conventional dc-dc regulation method.

Mutual and Self-Inductance Variation in Misaligned Coupler of Inductive Power Transfer System: Mechanism, Influence, and Solutions

Mutual and Self-Inductance Variation in Misaligned Coupler of Inductive Power Transfer System: Mechanism, Influence, and Solutions

A Novel Parallel-Excited Dual-PM Reluctance Machine With Enhanced Torque and Efficiency Performance

This paper presents a novel parallel-excited dual-PM reluctance machine (DPM-RM) with enhanced torque and efficiency performance. The key is to build an integrated magnetic field with two sets of PM excitation sources in both stator yoke and slot openings. Two excitation sources produce a parallel magnetic field, which contributes to a superimposed magnetic flux in the airgap, thus leading to strengthened flux variation, improved back-EMF and torque. Additionally, with a special slot&#x002F;pole combination, biased component and even order harmonics in the phase magnetic flux are eliminated to make the phase flux linkage more sinusoidal. In the meantime, self-inductance variation is greatly suppressed with odd order harmonics of self-inductance removed, resulting in suppressed torque ripple. The prototype is manufactured, and experiments are carried out to verify the effectiveness of the machine design.

A metal object detection system for electric vehicle wireless charging with quadrupole detection coils

In the practical application of magnetic coupling wireless charging technology, the absence of direct contact between the receiver and transmitter usually leads to metal objects (MOs) entering the charging area. The strong magnetic field between the receiver and transmitter causes eddy current effects and generates large amounts of heat in MOs, which may lead to serious hazards such as fires, so it is necessary to detect accidental entry of MOs. In this paper, a novel detection coil layout suitable for wireless charging of electric vehicles (EVs) has been proposed, which consists of multiple quadrupole coils arranged to achieve decoupling from the receiver and the transmitter to minimize the effect on the system efficiency. The influence of the presence of MOs on the equivalent inductance and equivalent resistance of the quadrupole detection coil has been deduced. The simulation results show that the maximum self-inductance change rate of the proposed detection coil reaches 28.11%, and a high self-inductance variation rate is also achieved at the edge of the detection coil.

A Self-Tuning LCC/LCC System Based on Switch-Controlled Capacitors for Constant-Power Wireless Electric Vehicle Charging

In this article, a self-tuning <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> wireless power transfer system based on switch-controlled capacitors is proposed to maintain a high power factor on the primary inverter side and fixed output power on the secondary side against self or mutual inductance variation of the magnetic coupler. The PI control on the primary side and the method of gradient descent on the secondary side are proposed based on the proposed normalized mistuned <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> circuit model. Only two switch-controlled capacitors on each primary and secondary side are used to implement the control scheme without the Wi-Fi communication or parameter identification. A 3 kW experiment setup was built in the lab and two different magnetic shields, namely ferrite and nanocrystalline, were tested on the secondary pad. According to the experiment results, the proposed system is proven to be able to maintain a high power factor (>0.9) and the desired dc output power against 52% mutual inductance variation and 12% self-inductance variation of the secondary pad. The proposed system can be applied as a wireless charger for electric vehicles or a high-power wireless charger test bench.

A Self-Tuning LCC/SP System for Electric Vehicle Wireless Charging against Large Self- and Mutual Inductance Variations

An LCC/SP self-tuning wireless charging system is proposed herein for use in a wireless charging test bench. With different dislocations in addition to changes in the coil self-inductance and mutual inductance caused by different secondary magnetic shielding materials, the system can ensure that the high power factor of the primary side remains unchanged without changing the circuit topology. Based on this normalized detuning LCC/SP circuit model, a switch-controlled capacitor (SCC) self-tuning method based on PI control is proposed. The control scheme employs only two MOSFETs and capacitors, without WIFI communication or parameter identification. A 2 kW experimental device was set up in the laboratory, and experimental verification was carried out with large-scale dislocations and different secondary magnetic shielding materials. The experimental results confirm that the system can maintain a high power factor (&gt;0.9) under a system mutual inductance variation of 47.7% and secondary coil self-inductance variation of 12%, and that it can be applied in electric vehicle wireless chargers or high-power wireless charger test benches.

A novel doubly‐fed doubly‐salient machine with DC‐saturation‐relieving structure for wind power generation

This paper presents a novel doubly-fed doubly-salient machine (DF-DSM) with DC-saturation-relieving effect for wind power generation application, which possesses the advantages of enhanced torque density, reduced torque ripple and improved power density. The key is that PMs are introduced into the stator slot openings to mitigate the saturation effect in stator core caused by DC field excitation, and relatively large excitation current can be fed into stator field windings, which contributes to improved power density of machine. In addition, with the armature winding artificially connected, the reluctance of all magnetic paths is kept the same, and the variation of self-inductance is compensated, and the torque ripple is greatly suppressed. In this paper, the machine structure and DC-saturation-relieving working principle are introduced. The slot-pole combinations are analysed, and dimension parameters are optimized. By using time-stepping finite-element analysis, the electromagnetic performance of optimal machine is evaluated which verifies the validity of the proposed design.

Frequency and Phase-Shift Control of Inductive Power Transfer for EV Charger with LCCL-S Resonant Network Considering Misalignment

In inductive power transfer (IPT) systems for electric vehicle applications, the coupling coefficient k and self-inductances of the pads can vary depending on the misalignment and vertical distance due to the presence of loosely coupled pads. Furthermore, the operating frequencies of IPT systems are restricted by a Society of Automotive Engineers standard. These frequencies lead to increases in volt-ampere rating and switching losses. Therefore, this paper proposes a control method for operation in a zero voltage switching region close to the zero phase angle frequency for a low volt-ampere rating considering k and the self-inductance variation in a limited operating frequency range. A mathematical analysis is performed, and the critical coupling coefficients of the proposed control are derived. Simulation and experimental results using a 3.3 kW IPT prototype are presented so as to verify the numerical analysis.

Autotuning Control System by Variation of Self-Inductance for Dynamic Wireless EV Charging With Small Air Gap

In this paper, an autotuning control system (ACS), which utilizes the variation of self-inductance of a transmitter (Tx) coil caused by a ferrite core of a receiver (Rx), is newly proposed for the dynamic wireless electric vehicle (EV) charging. A Tx module consists of only passive elements that include a Tx coil, a partially compensated capacitor in series with the Tx coil, and a parallel compensation capacitor. All Tx modules share an ac bus line that passes the output filter of an inverter in parallel without any active switches. The current of the coupled Tx coil increases automatically without any manipulations such as controlling the power switches, sensing, or communication when the Rx module is approaching. Not only the system efficiency is increased by the reduction of the conduction losses from the uncoupled Tx modules, but control also becomes simpler because sensors are not required for detecting EVs, and the constant output voltage characteristics can be obtained. Through experiments, it was found that the proposed ACS is suitable for applications such as a tram that runs along an orbit with a small air gap, such as a train. The results showed that the current of a coupled Tx coil increased 11.6 times larger than that of an uncoupled Tx coil, at which time the dc–dc efficiency achieved was 88.4% for an output power of 766 W (10 Ω of load resistance) at the laboratory scale.

Mutually Coupled Switched Reluctance Motor: Fundamentals, Control, Modeling, State of the Art Review and Future Trends

Switched reluctance motor (SRM) is gaining more interest in the last decades due to its simple and robust structure. SRMs are classified into conventional SRMs (CSRMs) and mutually coupled SRMs (MCSRMs). CSRMs are based on single-phase excitation and torque is generated by the variation of self-inductance with rotor position. MCSRMs are based on multi-phase excitation and torque is produced by the rate of change of both self- and mutual inductances. MCSRM has the advantages of using the standard voltage source inverter at balanced current operation, when the sum of the phase currents is zero, while CSRM requires an asymmetrical converter. This paper presents the state-of-the-art review of MCSRMs, including operating concept, winding, and pole configurations, control methods by using different current waveforms, performance comparison of MCSRM configurations, modeling methods, and future work for improving MCSRM performance.

Self-Inductance-Based Metal Object Detection With Mistuned Resonant Circuits and Nullifying Induced Voltage for Wireless EV Chargers

In this paper, a metal object detection (MOD) system, a kind of foreign object detection (FOD), which is based on mistuned resonant circuits and utilizes the variation of self-inductance of a sensing pattern, is newly proposed for wireless electric vehicle (EV) chargers. The sensing pattern that consists of multiple loop coil sets is mounted on the transmitting (Tx) pad of an EV charger, where a loop coil set has two coils connected in series with the opposite polarity to cancel out the induced voltage generated by the Tx coil. Variation of self-inductance of the loop coil set is detected by a parallel-resonant circuit, driven by a current source and operating at near 1 MHz, in order to enhance the resolution of the proposed MOD system. To increase the detection sensitivity of the proposed MOD system, instead of an exact resonant frequency, a mistuned operating frequency near the –3 dB point is utilized for the parallel-resonant circuit. In this way, the proposed MOD system can detect very small metal objects regardless of their position and orientation on the Tx coil without any blind zone. Through simulations and experiments, it is found that the proposed MOD system detects not only horizontal but also standing upright metal objects. A prototype MOD system, operating at 85 kHz to satisfy the standard J2954, was fabricated to verify its feasibility. The results showed that output voltage change of the proposed MOD system becomes 22.7% for a piece of the aluminum foil of 3 × 3 cm2 and 40.9% for 100 Korean Won coin.

Design of Doubly Salient Permanent Magnet Motors With Minimum Torque Ripple

This paper presents a design approach for doubly salient permanent magnet (DSPM) motors, aiming to minimize the torque ripple. The key is to propose the design criteria that the reluctance of all magnetic paths is the same, and the armature windings can be artfully connected to compensate the variation of self-inductance. Based on these criteria, the magnetic characteristics become symmetric, and the variation of self inductance is suppressed. Thus, the resulting torque ripple can be minimized. By using the time-stepping finite element method, the proposed DSPM motor and the existing DSPM motor are quantitatively compared in terms of their back-EMFs, self-inductances, and torque ripples, hence confirming the validity of the proposed design approach.

Sensorless Control of Brushless DC Motor Based on Wavelet Theory

This article seeks to develop a sensorless drive technique for brushless machines based on wavelet theory that provides the advantages of separating low-frequency and commutation effects. The approach adopts two methods of position prediction. The first method employs self-inductance variation, as established with finite element analysis. The second is based on induced voltage and zero-crossing point estimation. The problem of starting is resolved by sensing inductance for the first method and by providing a look-up table for each direction of rotation for the second method. Both proportional-integral-derivative and fuzzy control algorithms are developed, and simulated current and speed-controlled performance predictions are obtained. Daubechies discrete wavelet analyses of experimental and simulated waveforms are obtained, with emphasis on commutation intervals. An algorithm is developed to predict commutation instants from wavelet results. The simulation model and its wavelet analysis match the experiments.

The measurement of the self-inductance of variable air condensers

Three methods are described by which the self-inductance of variable air condensers may be measured. In the first, a rectangular coil is connected to the condenser, and the total inductance of the circuit is found when the coil is short-circuited at a number of points along its length. The self-inductance of the condenser is found by extrapolating to zero length of the coil. The necessary correction to allow for the capacitance of the coil is discussed, and a method of finding it is described. The second method consists in short-circuiting the terminals of the condenser under test, and finding the frequency of resonance of the circuit so formed. The inductance of the air condenser can then be calculated from the capacitance and the frequency of resonance. In the third method, the effective capacitance of the condenser under test is compared at two frequencies, one low and the other high, with the effective capacitance of a special air condenser of negligible inductance. From the change of effective capacitance with frequency the self-inductance may be deduced. The results obtained by the three methods are shown to be in good agreement. The effect of various sizes of wire as short-circuiting link in the second method is shown, and some results are given on the variation of self-inductance with setting of variable air condensers.