Effect Of Winding Research Articles

Influence of Extension Length of Rotor End Windings on the Three-Dimensional Electromagnetic Field and Temperature Rise in the Large Turbine Generator End Zone With Magnetic Screen

Leakage magnetic field from the rotor end windings affects obviously the electromagnetic losses and temperature of end components in the turbine generator end zone with magnetic screen. As the capacity of turbine generator increases, this effect of rotor end windings has become more prominent. To investigate influence of the extension length of rotor end windings on the electromagnetic and thermal fields in the turbine generator end zone with magnetic screen, three-dimensional transient electromagnetic field model of 1250 MW turbine generator end zone is given. Leakage magnetic field and losses of end components are compared and studied in the end zone under the different extension lengths of rotor end windings. Based on the calculation results of electromagnetic losses (heat sources) and flow network (boundary conditions), three-dimensional fluid-thermal coupling field is calculated in the turbine generator end zone with magnetic screen. Distribution of complex fluid velocity in the end zone is obtained. Influence of the different extension lengths of rotor end windings on the stator-end copper coil, screen plate, finger plate, press plate, magnetic screen, and stator end core is researched in the turbine generator end zone. The accuracy of calculation results is validated by experimental values.

Effect of end windings on the shaft voltage of a high power alternator using FE analysis

Effect of end windings on the shaft voltage of a high power alternator using FE analysis

Optimal Winding Selection for Wound-Rotor Resolvers

Wound-rotor (WR) resolvers are the most commercially used resolvers in industrial applications. In this paper, the effect of different winding arrangements on the accuracy of WR resolvers is discussed. Three windings are proposed for the stator of the resolver that are involved on-tooth overlapping winding, distributed lap winding and distributed concentric winding. Those windings are also applied to the rotor. All the rotor windings are assumed to be single phase and two-phase. Therefore, the effect of damper winding is also studied in the paper. The analysis is done using time stepping finite element method and the most accurate resolver is built and tested. Close agreement between the experimental measurements and the finite element results confirms the obtained results.

Taper Tension Profile in Roll-to-Roll Rewinder: Improving Adhesive Force of Pressure-Sensitive Adhesive Film

The roll-to-roll adhesive film manufacturing process has been widely used in the field of composite film manufacture. Thus far, many research groups have reported on the variation in characteristics of pressure sensitive adhesive film according to application environment characteristics, such as temperature and external forces, failure mechanism, and structures that improve the adhesive force of the film. However, there are few studies that analyze the effects of the manufacturing process conditions on the quality of the adhesive film. In this study, we find that hoop stresses due to winding tension may cause a decrease in the quality of the adhesive layer by generating wear on its surface. Moreover, radial and hoop stresses in the wound film affect the degree of wear. This suggests that the operating conditions of the film manufacturing machine affect the quality of the pressure sensitive adhesive (PSA) film, as do the properties of the film and the environment. To improve the adhesive force of PSA film, we applied two taper tension profiles that determine the distribution of the tension applied to the winding PSA film with respect to the wound ratio, followed by experimental verification of the effects of winding.

A robust differential protection technique for single core delta-hexagonal phase-shifting transformers

This paper presents an advanced technique for the differential protection of single core phase shifting transformers. The proposed technique is based on sensing electrical signals without sensing tap position. Only terminals currents are sensed by using two current transformers (CTs) per phase unlike other methods that need more CTs. Other methods use at least four transducers per phase and, in addition, sense the tap changer position, which increases the cost of the protection system. The proposed technique is based on the analysis of magnetically coupled and metallically connected circuits. The excitation winding currents are calculated to represent input currents to the differential protection relay. Tap changer position is estimated according to the phase shift between sources currents. The technique is checked for various types of shunt faults inside and outside the protection zone. The results prove the relay sensitivity and stability for internal and external faults, respectively. The effects of inrush current, series winding and CTs saturation are taken into consideration.

Effects of damper winding, eddy current, and leakage flux on magnetic field distortion and stator electrical quantity research of nuclear power turbo‐generator under external asymmetry

One phase overload or lightload condition is a very common condition in nuclear power turbo‐generators, and magnetic field distortion and current asymmetrical degree concern the safe operation of turbo‐generators. Damper and wedge windings are the special parts that distinguish the nuclear power generators from other smaller generators. Therefore, it is extremely important to investigate magnetic field distortion and stator electrical quantity. At the beginning, taking saturation and slot effects into account, the finite element model of a 1400MVA nuclear power generator is built up. And through comparison between the finite element simulation and the experimental results of no‐load characteristics and short‐circuit characteristics, the effectiveness of the finite element model was fully tested. Then, with or without damper and wedge windings, and leakage flux, the negative sequence equivalent circuit is employed to explain the law of magnetic field distortion under stator negative current, which is also verified by finite element simulation. Based on a novel theory proposed in this article, the law of the stator positive and negative sequence current, and the current asymmetrical degree with alteration of one‐phase load under steady state are given in detail. Additionally, the finite element method is developed to test the correctness of the novel theory. The influence of damper and wedge windings, leakage flux at coil ends, and eddy current on the solid magnetic‐pole of rotors on stator electrical quantity is also discussed in detail. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Axial‐flux permanent‐magnet synchronous generator with coreless armature and non‐integral coil–pole ratio

This article presents a study on an axial-flux permanent-magnet synchronous generator (AFPMSG) with a double-sided rotor, coreless armature. The armature winding consists of non-overlapping concentrated coils and has a non-integral coil-pole ratio. It is shown that, with an appropriate choice of armature coil number to pole number, the fundamental winding factor of the AFPMSG can be made close to that of a full-pitched integral slot winding. The field distribution and load performance are computed for a prototype machine based on a two-dimensional, time-stepping finite element method. A study of the armature reaction effect of the coreless armature winding and the origin of torque ripple is also carried out. The computed voltage and current waveforms, as well as the load characteristics, are verified by practical experiments.

Investigation about the effects of metal-clad winding on the electromagnetic characteristics of the GdBCO racetrack coils in a time-varying magnetic field

Abstract In this study, the electromagnetic characteristics of the insulated (INS), non-insulated (NI), and metal-clad (MC) racetrack coils are examined in a time-varying magnetic field. The delay in the generation of induced current and the amount of induced current when the coils are exposed to the time-varying magnetic field have been thoroughly examined. Additionally, the electromagnetic stability of each test coil was investigated under an overcurrent condition in the presence of an external magnetic ripple field. We also performed an AC loss test to investigate the effects of an MC layer on the magnitude of the AC loss. Based on the test results, the feasibility of using an MC winding technique for developing a highly stable high-temperature superconducting wind turbine generator with an enhanced electromagnetic response was thoroughly examined

The effect of winding arrangements on measurement accuracy of sinusoidal rotor resolver under fault conditions

Variable reluctance (VR) resolvers are proposed for industrial applications due to their simple structure. In this paper the effect of different stator windings on position accuracy of the sinusoidal rotor VR resolver under different fault conditions is studied. The effect of pole numbers and winding configuration (concentric or distributed winding) are discussed. The studied faults are static and dynamic eccentricities, run out and short circuit on excitation or signal windings. The analyses are carried out using 3-D time stepping finite element method. Then, the prototype of the sensor as well as its test set up is constructed. Good agreement between simulation and experimental results validate the success of analysis.

Effect of damper winding on accuracy of wound‐rotor resolver under static‐, dynamic‐, and mixed‐eccentricities

Most of the resolvers used in high precision servomechanism are two-pole, wound-rotor ones. The configuration of their stator winding is based on variable-turn, on-tooth method. However, there is different opportunity for their rotor: using distributed winding or on-tooth one. Furthermore, based on the operating principle of the resolver its rotor needs a single phase winding. While, in many practical cases a two-phase winding that one of them is short-circuited (damper winding) is employed for rotor. In this study, the effect of different configurations for rotor winding on the resolver performance in terms of the average of absolute position error, maximum position error, and total harmonic distortion of induced voltages envelopes is investigated. Then, the effect of damper winding on the performance of the resolver under static-, dynamic-, and mixed-eccentricities are studied. In this study, all simulations are performed using three-dimensional time stepping finite-element method and finally, the experimental tests on the studied sensor using a precision test setup are employed to approve the simulation results.

Analysis on the Amplitude and Frequency Characteristics of the Rotor Unbalanced Magnetic Pull of a Multi-Pole Synchronous Generator with Inter-Turn Short Circuit of Field Windings

Inter-turn short circuit of field windings (ISCFW) is a common generator fault which can result in serious safety accidents for power systems, if the fault is not eliminated in time. Taking advantage of the electrical and mechanical characteristics of the generator after a fault as a fault criterion is a new idea for fault monitoring, so finding out the frequency and amplitude frequency characteristics of rotor unbalanced magnetic pull (UMP)—the vibration excitation source of the fault—is the basis and key of the research. Taking a six-pole generator as an example, the effects of harmonic magnetic motive force (MMF) interaction on rotor UMP, as well as the frequency characteristics of rotor UMP after generator faults in different stator windings, are obtained based on the analysis of the air-gap MMF of the generator after a fault, and the results of theoretical analysis are verified by simulation. Based on the above results, the simulation calculation on rotor UMP of generators with three stator winding forms under different operating conditions has been achieved, to get the relation between rotor UMP amplitude and active power and field current, and to find out the mechanism of rotor UMP amplitude change along with operating conditions and effect of stator winding forms on UMP amplitude by theoretical analysis. The conclusions are of important significance for studying fault mechanical characteristics of generators and lay a foundation for online monitoring on ISCFW by integrating mechanical and electrical information.

Three-D Numerical Thermal Analysis of Electric Motor with Cooling Jacket

The need of a sustainable clean future has paved the way for environmental friendly electric vehicle technology. In electric vehicles, overloading is limited by the maximum temperature rise in the electric motor. Although an improved cooling jacket design is of vital importance in lowering the maximum temperature of the motor, there has not been as much study in the thermal analysis of motors compared to electromagnetic design studies. In this study, a three-dimensional steady state numerical method is used to investigate the performance of a cooling jacket using water as the primary coolant of a three-phase induction motor with special emphasis on the maximum temperature and the required pumping power. The effective thermal conductivity approach is employed to model the stator winding, stator yoke, rotor winding and rotor yoke. Heat transfer by induced air is treated as forced convection at the motor ends and effective conductivity is obtained for air in the stator-rotor gap. Motor power losses, i.e., copper and iron losses, are treated as heat generation sources. The effect of bearings and end windings is not considered in the current model. Pressure and temperature distributions under various coolant flow rates, number of flow passes and different cooling jacket configurations are obtained. The study is successful in identifying the hot spots and understanding the critical parameters that affect the temperature profile. The cooling jacket configuration affects the region of maximum temperature inside the motor. Increasing the number of flow passes and coolant flow rate decreases maximum motor temperature but results in an increase in the pumping power. Of the cooling jacket configurations and operating conditions investigated, a cooling jacket with six passes at a flow rate of 10 LPM with two-port configuration was found to be optimal for a 90-kW induction motor for safe operation at the maximum output.

The effect of winding and core support material on the thermal gain dependence of a fluxgate magnetometer sensor

Abstract. Fluxgate magnetometers are an important tool in geophysics and space physics but are typically sensitive to variations in sensor temperature. Changes in instrumental gain with temperature, thermal gain dependence, are thought to be predominantly due to changes in the geometry of the wire coils that sense the magnetic field and/or provide magnetic feedback. Scientific fluxgate magnetometers typically employ some form of temperature compensation and support and constrain wire sense coils with bobbins constructed from materials such as MACOR machinable ceramic (Corning Inc.) which are selected for their ultra-low thermal deformation rather than for robustness, cost, or ease of manufacturing. We present laboratory results comparing the performance of six geometrically and electrically matched fluxgate sensors in which the material used to support the windings and for the base of the sensor is varied. We use a novel, low-cost thermal calibration procedure based on a controlled sinusoidal magnetic source and quantitative spectral analysis to measure the thermal gain dependence of fluxgate magnetometer sensors at the ppm°C−1 level in a typical magnetically noisy university laboratory environment. We compare the thermal gain dependence of sensors built from MACOR, polyetheretherketone (PEEK) engineering plastic (virgin, 30 % glass filled and 30 % carbon filled), and acetal to examine the trade between the thermal properties of the material, the impact on the thermal gain dependence of the fluxgate, and the cost and ease of manufacture. We find that thermal gain dependence of the sensor varies as one half of the material properties of the bobbin supporting the wire sense coils rather than being directly related as has been historically thought. An experimental sensor constructed from 30 % glass-filled PEEK (21.6 ppm°C−1) had a thermal gain dependence within 5 ppm°C−1 of a traditional sensor constructed from MACOR ceramic (8.1 ppm°C−1). If a modest increase in thermal dependence can be tolerated or compensated, then 30 % glass-filled PEEK is a good candidate for future fluxgate sensors as it is more economical, easier to machine, lighter, and more robust than MACOR.

New high frequency multi-conductor transmission line detailed model of transformer winding for PD study

The first step of partial discharge (PD) detection is to obtain a model through which the winding behavior is monitored precisely in high frequencies. The multi-conductor transmission line (MTL) model is one of the best models conducting the PD studies. It is worth to say that one of the main problems of the MTL model is that it considers the windings in a parallel way as well as equal length. Solving the mentioned problem can decrease the simulation error relating to the PD detection. This paper presents an accurate approach in order to solve the problem. This modified MTL model uses the circular effect of windings. Considering the windings circular is one of the important parameters which should be evaluated with respect to PD signal propagation. This method has been applied on a 20 kV transformer winding. The simulation and experimental results show the powerful performance of circular multi-conductor transmission line (CMTL) model in comparison with the MTL model.

Improvement of Current Limiting and Recovery Characteristics of Flux-Lock Type SFCL with Series Connection of Two Coils Using Its Third Coil

In this work, the current limiting and recovery characteristics of a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils were effectively improved by adding a third winding into the conventional flux-lock type SFCL with series connection of two coils. To confirm the contribution of the third winding to the current limiting and recovery characteristics of this type of the SFCL, short-circuit testing was carried out with consideration of the third winding, and the effect of the third winding on the current limiting and recovery characteristics was examined by comparative analysis of the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising the SFCL. Through the analysis of both the limiting impedance and the operational current as the main design parameter of the SFCL, the improved current limiting and recovery characteristics of the flux-lock type SFCL using the third winding could be verified.

Modulation signal bispectrum analysis of electric signals for the detection and diagnosis of compound faults in induction motors with sensorless drives

ABSTRACTAs a prime driver, induction motor is the most electric energy consuming component in industry. The exposure of the motor to stator winding asymmetry, combined with broken rotor bar fault significantly increases the temperature and reduces the efficiency and life of the motor. Accurate and timely diagnosis of these faults will help to maintain motors operating under optimal status and avoid excessive energy consumption and severe damages to systems. This paper examines the performance of diagnosing the effect of asymmetry stator winding on broken rotor bar (BRB) faults under closed loop operation modes. It examines the effectiveness of conventional diagnostic features in both motor current and voltage signals using spectrum and modulation signal bispectrum analysis (MSBA). Evaluation results show that the combined faults cause an additional increase in the sideband amplitude and this increase in sideband can be observed in both the current and voltage signals under the sensorless control mode. MSB analysis has a good noise reduction capability and produces a more accurate and reliable diagnosis in that it gives a more correct indication of the fault severity and its location for all operating conditions.

Effect of combined stator winding on reduction of higher spatial harmonics in induction machine

The paper introduces the possibility to eliminate certain groups of spatial harmonics of the current layer, magnetic flux density in the air gap and flux in the yoke of the induction machine with the aim to increase the efficiency. The content of higher spatial harmonics is reduced by means of the so-called combined winding. It is shown how this winding must be arranged in stator slots so that the selected groups of spatial harmonics mutually reduce themselves. The results of the theoretical analysis were validated by the measurements on the experimental machine with the implemented combined winding. Eventually these results were compared with those of the machine with the classical three-phase winding.

Waves and null congruences in a draining bathtub

We study wave propagation in a draining bathtub: a black hole analogue in fluid mechanics whose perturbations are governed by a Klein–Gordon equation on an effective Lorentzian geometry. Like the Kerr spacetime, the draining bathtub geometry possesses an (effective) horizon, an ergosphere and null circular orbits. We propose here that a ‘pulse’ disturbance may be used to map out the light-cone of the effective geometry. First, we apply the eikonal approximation to elucidate the link between wavefronts, null geodesic congruences and the Raychaudhuri equation. Next, we solve the wave equation numerically in the time domain using the method of lines. Starting with Gaussian initial data, we demonstrate that a pulse will propagate along a null congruence and thus trace out the light-cone of the effective geometry. Our new results reveal features, such as wavefront intersections, frame-dragging, winding and interference effects, that are closely associated with the presence of null circular orbits and the ergosphere.

Oscillation effect of auxiliary winding in primary side regulated flyback converter

In the operation of a primary‐side‐regulated (PSR) flyback converter, oscillation of the auxiliary winding would degrade the system reliability, as this winding plays an important role. In previous works, the oscillation of the auxiliary winding was thought to be related to the oscillation of the primary winding when the switch is turned off. However, a comprehensive explanation has not been given for this phenomenon. Meanwhile, the oscillation of the auxiliary winding depends not only on the oscillation of the primary winding but also on the conducting size and the layer distribution. Based on a multi‐winding model obtained from the physical dimensions, this paper derives a mathematical expression to calculate the relation, in the time domain, between the ringing of the auxiliary winding and primary winding. The analytical results would allow the magnetic windings to be analyzed and optimized because the oscillation of the auxiliary winding is expressed as a function of the winding geometry and position. Besides, the skin and proximity effects as well as the nonlinear core properties are considered in the multi‐winding model. An application example is also included. Simulation and experimental results of a single‐stage, 16‐W PSR flyback converter are given to validate the proposed analysis. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Torsional vibrations of helically buckled drill-strings: experiments and FE modelling

This paper presents investigations of a complex drill-string vibrations on a novel experimental rig, developed by the Centre for Applied Dynamics Research at the University of Aberdeen. The rig is capable of exhibiting of all major types of drill-string vibrations, including torsional, axial and lateral modes. The importance of this work lies in the fact, that the experimental rig utilizes real industrial drill-bits and rock samples, which after careful identification of Torque On Bit (TOB) speed curves, allows to use an equivalent friction model to accommodate for both frictional and cutting components of the bit-rock interactions. Moreover, the proposed Finite Element model, after a careful calibration, is capable of replicating experimental results, for the prebuckled configuration of the drill-string. This allows us to observe the effect of winding and unwinding of the helical deformation during stick-slip motion.