Stator Coils Research Articles

Design generator of magnetic power (Based on gap rotor-stator motor magnet)

The paper discusses magnetic power generators; if a conductor moves across the magnetic field, a voltage difference will occur at the ends of the conductors. The voltage rises as it approaches the area and vice versa, so electricity arises in cycles: positive - zero - negative - zero. In this study utilizing the rotation of a magnetic motor caused by the unbalance repulsive force between magnets. The design of the tool starts with designing a generator model that will be made. The design of generators is based on calculations obtained through the reference of generator design. The generator design uses magnets instead of anchor coils on the rotor (source of magnetic flux) and copper wire coils as anchor coils on the stator. This design considers rotor and stator parameters, including the distance between magnets, rotor diameter, rotor plate thickness, area of a magnetic area, number of stator coils, number of stator windings, and stator coil dimensions, and calculate generator output power. Tool testing is done to obtain data from tools that have been made. In testing the comparison of the results obtained from the study of the target to be achieved, if the results have not yet reached the target, then improvements are made to the results obtained as expected. Tests were carried out with no load and burden. The results showed that the rotor speed in the generator design could be achieved by determining the number of rotor poles, the generator voltage is influenced by the flux density produced by permanent magnets and the number of stator windings.

Use of Bulk Superconductors in the Excitation System of Low-Speed Synchronous Generators

This work focuses on implementing HTS bulks in the excitation circuit of low-speed synchronous generators as permanent magnets. In addition to the implementation study, it is also addressed to remagnetize HTS bulks in electric generators. To reduce the maintenance costs and time required for the magnetization process, an in-loco remagnetization is used. The HTS bulks are magnetized in their position inside the machine's magnetic circuit. A pulse-field magnetization (PFM) technique is used, using the stator coils of a linear generator. YBCO and GdBCO samples are tested. The experimental procedure starts with the in-loco PFM to magnetize the HTS bulks and, by applying an oscillatory movement to the linear generator's moving part, measuring the magnetic flux density induced voltage is done. Experimental tests show that, for the FeSi core used in the generator, the YBCO material is most suitable for the excitation circuit.

Influence of the Number of Coil on the Accelerated-Type Wave Energy Generation System

This paper proposed a pulley-buoy accelerated type linear wave power generation system, and verifies its feasibility and effectiveness through experiments. Compared with traditional three-phase wave energy converter, the process of energy transfer was cancelled in the pulley-buoy accelerated type linear wave power generation system, wave energy was converted into electrical energy through the movement of float directly. In the system, the pulley assembly increased the velocity of the float and the generating capacity of the linear generation system, thereby increasing its conversion efficiency. In the experiment, an undersized pulley-buoy accelerated type linear wave power generation system and a swing wave-making system were built in the laboratory. The experiment explored the influence of the number of the stator coil on the power generation performance of the system, and results showed that within the scope of this research, increasing the stator coils to a certain extent could effectively raise the efficiency of wave energy conversion and improve the generation performance of the pulley-buoy accelerated type linear wave power generation system. This research provides valuable experience for the actual application and effective operation of wave energy conversion system.

Effect of deep cryogenic treatment on C93700 bearing bush material used in submersible pumps

Bearing bush is an essential part of a rotating machine. It is inserted in a housing to support the motor shaft of a submersible pump with a radial clearance of 40 μm. This plain bearing is made of high lead tin Bronze, C93700. In the working condition the submersible pump stacked with series of impellers is assumed to be an overhanging structure as the fluid flow through the impellers is not uniform in the beginning. This imbalance leads to the misalignment between pump and motor shafts resulting in the contact of bearing bush with motor shaft, as the shaft material AISI 420 stainless steel is harder than the bearing material, wear out of latter is inevitable. Due to the continuous running of motor in this condition for long hours, the shaft comes in contact with the stator and the stator coils begin to burn implying the breakdown of pump set within 6–12 months of installation. This paper aims to improve the hardness and wear resistance of C93700 bronze through deep cryogenic treatment. The test samples of the material were treated with liquid Nitrogen at −196℃ temperature and tested for tensile strength, hardness and wear resistance. Microstructure of the samples have been examined using SEM and chemical analysis was done through EDS.

Transient Test and AC Loss Study of a Cryogenic Propulsion Unit for All Electric Aircraft

This paper reports a pioneering demonstration platform of a cryogenic propulsion unit at liquid nitrogen temperature. A high temperature superconducting (HTS) machine is connected with a cryogenic power rectifier in a generator mode to prove the feasibility of a cryogenic propulsion unit for electric aircraft propulsion applications. Machine operation was carried out with a special focus on the total heat dissipation inside the HTS AC windings. Different types of 2G HTS tapes were tested to provided data for stator coils’ design. The transient operation was carried out to represent a short-circuit failure in one of the power electronic devices. The test shows AC loss performance of the HTS windings using calorimetric method during the short circuit event, indicating the importance of developing protection schemes for the cryogenic propulsion units to prevent damage to the HTS components. The paper provides initial insights into the interaction between superconducting machines and cryogenic power electronics within a cryogenic propulsion unit. It is an important first step to understand and further develop cryogenic propulsion technology for future electric aircraft.

A Mathematical Model of a Three-Phase Induction Motor with a Phase Rotor

A mathematical model of an induction motor (IM) with a phase rotor is developed on the basis of the usual assumptions that does not use the supposition that there is an annular rotating field in its air gap and various transformations of coordinates. The model is valid for both transient and steady-state modes and with various ways of control by changing the parameters of the three-phase feeding voltage system of the IM stator coil. It is shown that the desired stationary operation mode that exists in the developed nonlinear IM model at a constant feeding voltage of the stator and load torque corresponds to the constant electromagnetic torque and spinning frequency of the rotor at sine-wave rotor and stator currents. A digital IM model is developed in the MATLAB system. An analytical solution is derived for the system of linear differential equations that describes the IM with a retarded rotor and allows evaluating the nonlinear digital model for correctness. Examples of applying the IM model in analyzing transient and steady-state operation modes of this motor are provided.

Comparative Analysis of Permanent Magnet Synchronous Generators with Mechanical Energy Storage according to Machine Types

This paper deals with the comparative investigation on the performance of various permanent magnet wind power generators according to magnetization patterns and stator coil winding typ ...

Lattice Boltzmann simulation of liquid falling on horizontal rectangular pillar arrays

Stator coils of automobiles in operation generate heat and are cooled by a coolant poured from above. Since the behavior characteristic of the coolant poured on the coils is not clarified yet due to its complexity, the three-dimensional two-phase flow simulation is conducted. In this study, as a steppingstone to the simulation of the liquid falling on the actual coils, the coils are modelled with horizontal rectangular pillar arrays whose governing parameters can be easily changed. The two-phase flows are simulated using the lattice Boltzmann method and the phase-field model, and the effects of the governing parameters, such as the physical properties of the cooling liquid, the wettability, and the gap between the pillars, on the wetting area are investigated. The results show that the oil tends to spread across the pillars because of its high viscosity. Moreover, the liquid spreads quickly when the contact angle is small. In the case that the pillars are stacked, the wetting area of the inner pillars is larger than that of the exposed pillars.

Effect of chording on the efficiency of induction motor supplied by PWM inverter

The increasing usage of theinverter fed three-phase induction motor due to latest technological innovations in the industry demands for designing a high efficiency motor. Three-phase induction motor stator coils were short pitched and tested with pulsewidth modulation (PWM) inverter voltage supply at various switching frequencies. Various loads were varied using eddy current brake and torque is measured using torque gauge. The effect of short pitching on the efficiency of novel winding designed motor were quantified and found that the shortest pitched coil radically improves the efficiency of the motor due to attenuation of lower order harmonics and reduced copper losses.

Use of current sheet coupled to an analytical tool to analyze by FEM the harmonic content of armature winding ditribution

PurposeFor a given rotor, the study of the impact of stator MMF from different winding distributions is usually carried out using analytical model under some simplifying hypotheses to limit time computation. To get more accurate results, finite element model is thus more suitable. However, testing different combinations of stator windings with the same rotor can be tedious when considering the stator slots. Indeed, this introduces mesh constraint, reluctance variation of the air gap and possibly taking into account of the connection between stator coils. To avoid this, a current sheet supplied such to represent the stator MMF and spread all around the inner slotless stator surface can be used. In addition, such an approach can be very useful to didactically assess the effect of each winding space harmonic on machine performance separately. The purpose of this paper is to use a current sheet coupled to an external analytical tool in order to easily test different windings or to quantify the effect of a given spatial harmonic of the winding.Design/methodology/approachIn the proposed approach, the current sheet supply is obtained from an analytical tool that allows determining the spatiotemporal stator MMF of any winding considered. Moreover, stator teeth height is not modelled, and only the thickness of the stator yoke is considered along with the same air gap thickness. Results with the proposed approach are compared to the real stator modelling for two different winding configurations. Last, linear and non-linear magnetic material behaviours are investigated to validate the proposed approach in term of magnetic distribution.FindingsFor both studied cases, results in term of local and global physical quantities show good agreement between the real stator modelling and the proposed approach.Originality/valueCurrent sheet is used with finite element model to study the inherent effect of different winding configurations on local and global physical quantities of an AC electrical machine. The proposed approach avoids the constraints in terms of stator slot geometry and electrical circuit definition. This is very useful to quickly test different winding configurations or to isolate a specific winding space harmonic to quantify its effect on the electrical performances. This cannot be performed using classical modelling as all space harmonics are taken into account.

Evaluation of the Correlation Coefficient as a Prognostic Indicator for Electromechanical Servomechanism Failures

In order to identify incipient failures due to a progressive wear of a primary flight command electromechanical actuator, several approaches could be employed; the choice of the best ones is driven by the efficacy shown in fault detection/identification, since not all the algorithms might be useful for the proposed purpose. In other words, some of them could be suitable only for certain applications while they could not give useful results for others. Developing a fault detection algorithm able to identify the precursors of the abovementioned electromechanical actuator (EMA) failure and its degradation pattern is thus beneficial for anticipating the incoming malfunction and alerting the maintenance crew such to properly schedule the servomechanism replacement. The research presented in the paper was focused to develop a fault detection/identification technique, able to identify symptoms alerting that an EMA component is degrading and will eventually exhibit an anomalous behavior, and to evaluate its potential use as prognostic indicator for the considered progressive faults (i.e. frictions and mechanical backlash acting on transmission, stator coil short circuit, rotor static eccentricity). To this purpose, an innovative model based fault detection technique has been developed merging several information achieved by means of Fast Fourier Transform (FFT) analysis and proper "failure precursors" (calculated by comparing the actual EMA responses with the expected ones). To assess the performance of the proposed technique, an appropriate simulation test environment was developed: the results showed an adequaterobustness and confidence was gained in the ability to early identify an eventual EMA malfunctioning with low risk of false alarms or missed failures.

Perfection of the equipment of electromagnetic stirring in moulds of billet and bloom CCM

To avoid defects of continuously casted billets, such as core porosity, shrink liquation, ingot developed dendrite structure and others, various methods of external physical impact on the crystallizing billet are used. One of the most technological and effective of them is the electromagnetic stirring (EMS) of the liquid melt of the crystallizing billet. An analysis of the experience of industrial EMS systems application at steel plants of Russia was accomplished. It was noted, that operating in Russia industrial CCM, intended for production of high quality billets, are equipped mainly by EMS systems of foreign production. The stator of the EMS is located outside a mould body and the bodies of the stator and the mould are manufactured of nonmagnetic steel of austenite class. Such systems are characterized by low reliability and high energy consumption because of their design features (location outside a mould body and necessity to use for them a separate circuit of cooling by a “boiler” water). Bessides, most of the EMS stators of foreign manufacturing are made in nonseparable bodies, hence in case of a failure the expensive rrepair of the stators should be carried out at the foreign plants-manufacturers. At present in Russia the EMS systems are being elaboorrated by specialists of AKKH “VNIIMETMASH”, Moscow. VNIIMETMASH within the frame of import substitution program elaboorated both built-in and external variants of EMS systems for moulds of billet and bloom CCM, the stator coil poles being cooled bby the water of the mould and its winding is made of immersible into water wire with a double insulation. Based on the results of thee study it was determined, that location of the elaborated EMS systems in a mould results in improving of the surface quality, as welll as quality of the subsurface layer and the billet macro-structure, decreasing of the point unevenness and decreasing of number of thee subshell bubbles.

Frequency Occurrence Plot-Based Convolutional Neural Network for Motor Fault Diagnosis

A novel motor fault diagnosis using only motor current signature is developed using a frequency occurrence plot-based convolutional neural network (FOP-CNN). In this study, a healthy motor and four identical motors with synthetically applied fault conditions—bearing axis deviation, stator coil inter-turn short circuiting, a broken rotor strip, and outer bearing ring damage—are tested. A set of 150 three-second sampling stator current signals from each motor fault condition are taken under five artificial coupling loads (0, 25%, 50%, 75% and 100%). The sampling signals are collected and processed into frequency occurrence plots (FOPs) which later serve as CNN inputs. This is done first by transforming the time series signals into its frequency spectra then convert these into two-dimensional FOPs. Fivefold stratified sampling cross-validation is performed. When motor load variations are considered as input labels, FOP-CNN predicts motor fault conditions with a 92.37% classification accuracy. It precisely classifies and recalls bearing axis deviation fault and healthy conditions with 99.92% and 96.13% f-scores, respectively. When motor loading variations are not used as input data labels, FOP-CNN still satisfactorily predicts motor condition with an 80.25% overall accuracy. FOP-CNN serves as a new feature extraction technique for time series input signals such as vibration sensors, thermocouples, and acoustics.

Analysis of coil pitch in induction machines for electric vehicle applications

This study investigates the influence of stator coil pitch on the electromagnetic performance of squirrel-cage induction machine (IM) with emphasis on the flux-weakening (FW) capability for electric vehicle applications. Three different winding topologies, obtained by changing the coil pitch, namely integer-slot distributed winding (ISDW), integer-slot concentrated winding, and fractional-slot concentrated winding (FSCW), are studied. Their merits and demerits are revealed by comparing their performances characteristics, including winding harmonic index, total axial length, average torque, torque ripple, power losses, efficiency, and FW capability. It is revealed that due to the very high Magnetomotive force (MMF) harmonics induced in the bar current, the bar copper loss of the IM with FSCW is significant. It is also revealed that the parasitic effects of the double-layer winding configurations are lower than those of the single-layer (SL) winding configurations. It is also demonstrated that for the slot/pole/phase combinations lower than two , the higher the coil pitch, the lower the parasitic effects and the higher the efficiency. Moreover, it is found that the combinations , especially those having longer coil pitch and higher stator slot number, and the SL combinations offer better FW capability. Finally, the Finite-element analysis (FEA) results of IM with long-pitch ISDWs are validated by experimental measurements.

Torque Modelling and Validation for a Spherical Motor with Stepped Permanent Magnets

A spherical motor is an electromagnetic device with multi-degree-of-freedom motion. Three-dimensional (3-D) magnetic field analysis and torque analysis are needed for the design, optimization and control of the motor. Presently, these analyses are carried out by the finite-element method (FEM) with a large amount of calculation and time consumption. An analytical method (AM) can reduced the computational burden of the FEM without sacrifice of the accuracy. A stepped permanent magnet (PM) can obtain a large range of the magnetic field while effectively saving PM materials. However, its special structure causes difficulties in analytical modelling. This paper presents an AM for the 3-D magnetic field and torque of a permanent magnet spherical motor with stepped PMs. The analytical model of the 3-D magnetic field of the stepped PM is derived based on the loop current method, and the electromagnetic force of the stator coil is calculated based on the Lorentz force method. Thus the 3-D magnetic field and torque can be calculated efficiently with reasonable accuracy. The analytical model is verified by the FEM and experimental tests. The test results confirm the high accuracy of the developed model.

Phased-resolved partial discharge patterns of 10 kV stator coils under different experimental conditions

The most five common types of partial discharge (PD) activities involving 10 kV motors, namely internal discharge, slot discharge, corona discharge, surface tracking and bar-to-bar discharge, were researched in this paper. PD was induced on some 10 kV coils with modern epoxy-mica insulation system through off-line experiment under different conditions. The phased-resolved partial discharge (PRPD) patterns of different types of PDs were recorded to characterize different PDs. This research can provide a reference in off-line fault diagnosis and be useful for the PD online monitoring of high voltage motors.

Modeling and Analysis of Permanent Magnet Spherical Motors by a Multitask Gaussian Process Method and Finite Element Method for Output Torque

Permanent magnet spherical motors (PMSMs) operate on the principle of the dc excitation of stator coils and three freedom of motion in the rotor. Each coil generates the torque in a specific direction, collectively they move the rotor to a direction of motion. Modeling and analysis of the output torque are of critical importance for precise position control applications. The control of these motors requires precise output torques by all coils at a specific rotor position, which is difficult to achieve in the three-dimension space. This article is the first to apply the Gaussian process to establish the relationship of the rotor position and the output torque for PMSMs. Traditional methods are difficult to resolve such a complex three-dimensional problem with a reasonable computational accuracy and time. This article utilizes a data-driven method using only input and output data validated by experiments. The multitask Gaussian process is developed to calculate the total torque produced by multiple coils at the full operational range. The training data and test data are obtained by the finite-element method. The effectiveness of the proposed method is validated and compared with existing data-driven approaches. The results exhibit superior performance of accuracy.

Analytic Optimization of the Halbach Array Slotless Motor Considering Stator Yoke Saturation

Hybrid subdomain analysis is utilized to optimize the design of a high-speed compressor motor. Permanent magnets (PMs) are arranged in Halbach array and bounded by a carbon fiber sleeve. The stator core does not have a slot structure, so that it is advantageous in reducing the iron loss. Since the core saturation takes place, magnetic equivalent circuit (MEC) is used to find the permeability depending on the flux density of stator yoke. Furthermore, since the core is not infinitely permeable in the subdomain analysis, the solution is obtained in the whole subdomain regions: shaft, PM, air gap, coil, and stator yoke. The results of hybrid analysis are compared with those of finite-element analysis (FEA). Very close matching results are obtained in the flux density and torque even under yoke saturation. The stator yoke height is optimized against the rotor outer radius so that torque, power density, and efficiency are maximized, while stator outer radius, stack length, and coil area are fixed.

Superconductor fault current limiter effect on the performance of doubly-fed induction generators

<span>Between different wind turbine-generator configurations, one of the most accepted and highly regarded structures in the industry is the wind turbine with doubly-fed induction generator. The DFIG wind turbines are very sensitive to grid disturbances especially to voltage drop during grid faults due to relatively low power of the power converters. Fault in a power system causes voltage drop, current increase in stator and rotor coils, and over voltage in the DC shin. Several control methods have been proposed so far. A model based on power electronic instruments and superconductor theory, superconductor fault current limiter (SCFCL), has been proposed in this paper to improve domain and the attenuation time of the parameters under control such as voltage, current, and speed and voltage of the DC link against various types of faults (single-phase, two-phase, and three-phase). In addition to this, in order to compare the results with convectional models (crowbar) and study the innovation of the proposed model, a simulation of the system under two-phase fault and use of crowbar method to control the fault has been conducted using MATLAB-SIMULINK and also, the performance of the proposed method has been assessed. </span>

Surface modified nano-SiO2 enhances dielectric properties of stator coil insulation for HV motors

Nano-SiO 2 particles were doped into epoxy resin (EP) to fabricate the main insulation used for high voltage (HV) motors. The EP-based nanocomposite with different mass ratios of nano-SiO 2 particles (0.5, 1, 2.5, and 5 wt%) were prepared. Surface morphology and conductivity of samples were tested, and AC breakdown strength was measured at different temperatures. The mechanisms for the tailoring of dielectric properties of EP were discussed. The optimal doping scheme (0.5 wt%) was selected and used as the base material in preparation of a stator coil insulation for 6 kV motors. The dielectric properties, including dielectric loss and leakage current as well as partial discharge, were tested, and the potential application of nano-SiO 2 particles in the stator coil insulation of HV motors was discussed. The test results showed that the doped nano-SiO 2 particle into dielectric composite used as the main insulation material for HV motors can be an optimal candidate to improve the above mentioned properties especially dielectric losses and electrical breakdown strengths. The results in this paper offer references and a guiding significance for the application of nano-SiO 2 in the insulation of HV motors.