Core Slot Research Articles

Novel Winding and Core Slot Structures - More Sustainability for Electric Motors

Novel Winding and Core Slot Structures - More Sustainability for Electric Motors

Creation of Efficient Pathology Research Pipelines for Discovery: Tissue Microarray Construction Coupled with Digital Image Analysis

Pathology translational research pipelines are complex, as many studies rely on analyses of tissue immunohistochemistry. High-throughput methodologies such as tissue microarrays (TMAs) have been critical for many recent advancements as large datasets are necessary to make detailed disease and biologic discoveries. Currently, TMA molds can be purchased from online vendors or constructed in house with complex machinery. However, there are certain limitations to these molds, such as cost per mold and inability for selection of core slot patterns. Thus, we propose a practical and cost-effective method for constructing a silicone-based rubber TMA mold that can be used to create a paraffin template block. Our results show that these self-manufactured molds are durable, effective and easy to customize, reducing operating costs and creating flexibility for users. Furthermore, in leveraging this technique, we describe coupling TMA-prepared slides with a rapid research-focused digital analytic pipeline that allows for a streamlined method of quantitative and qualitative companion discovery.

Large group-index bandwidth product empty core slow light photonic crystal waveguides for hybrid silicon photonics

This paper investigates the slow light propagation in silicon on insulator wide slot photonic crystal waveguides (PCWs). Two design schemes are presented, relying on the dispersion engineering of hole lattice and slot, respectively. Mode patterns and band diagrams are calculated by 3D-plane wave expansion method. Then, coupling and slow light propagations are modeled using finite difference time domain method in a full Mach-Zehnder interferometer (MZI). Results show high amplitudes interference fringes and high coupling efficiencies. Fabrication and measurement of devices lead to slow light propagation with group indices above 50, while multiple scattering and localized modes near the band edge also observed. This study provides insights for losses in hollow core slot high group index waveguides.

Effects of accelerated repetitive impulse voltage aging on performance of model stator insulation of wind turbine generator

A high reliability is essential for the insulation system of wind turbine generator because of its high repairing cost. In this paper, three experimental methods based on accelerated aging under repetitive impulse voltage and multi-environmental factors are established to (i) investigate the failure or degradation mechanism during the aging, and (ii) make recommendations on how to assess the functional life and reliability of insulation systems for wind turbine generator. Repetitive impulse voltage stress combined with thermal stress, change of temperature, steady damp heat and salt mist was, in turn, applied to model specimens with different length and section sizes. Some of non-destructive characteristic parameters such as dissipation factor, insulation resistance, and partial discharge inception voltage were measured periodically during the aging. In addition to the residual breakdown voltage, the appearance features and infrared spectrum analysis of specimens were carried out after aging. It has been found that the surface partial discharge generated under repetitive impulse voltage resulted in the degradation of surface insulating material near the slot end. The change of temperature also caused the delaminating of stator insulation from the core slot especially when massimpregnated insulation used in long slot of practical stator. The increase of dissipation factor of insulation system was largely contributed by salt mist and moisture factors especially when the surface or interface of insulation material was damaged. The electrically accelerated aging under about triple maximum repetitive impulse voltage for 1000 h was an effective and feasible method to assess the insulation system of wind turbine generator.

Slot discharge pattern of 10 kV induction motor stator coils under condition of insulation degradation

In the manufacturing process of the 10 kV induction motors, a semi-conductive layer with certain resistance covering the linear part of the stator coil is often used to suppress the partial discharges (PDs) happened in the slot. However, due to electromagnetic force while the motor is running, slot discharge is still one of the main causes of stator insulation degradation. In this paper, an adjustable width mockup core slot is designed using silicon steel sheet. Several 10 kV real machine stator coils subjected to varying aging degrees are adopted as test coils. The phase resolved partial discharge (PRPD) patterns of slot discharge are analyzed using a PRPD analyzer and the variation law of slot discharge patterns with voltage variation is illustrated. The investigation result has been applied to the online monitoring and pattern recognition of the insulation for a 10 kV induction motor in a coal mine and it has great application significance.

6.6 kV 전동기 고정자 권선의 절연진단과 절연파괴 특성

To assess the condition of stator insulation, nondestructive and overpotential tests were performed on four high voltage motors. The stator windings under these tests have nominal ratings of 6.6 kV. After completing nondestructive tests, the AC overvoltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No. 1, No. 2, No. 3 and No. 4 of 6.6 kV motors failed near rated voltage of 18.4 kV, 19.8 kV, 19.7 kV and 21.7 kV, respectively. The breakdown voltage of four motors was higher that expected for good quality coils(14.2 kV) in 6.6 kV motors. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor(<TEX>$tan{\delta}$</TEX>) and partial discharge magnitude.

Fuser Roller Core and Drive Collar Assembly Design for High Speed Printer

Very high speed electrophotographic printers often use a fusing system consisting of a fuser roller and associated drive mechanisms which employ a coupled drive hub assembly. The fuser roller typically includes a metal core onto or into which a mating drive hub and collar assembly are connected. Rotating at high rotational speed, and at high temperature, with extremely fast start/stop conditions, instabilities create issues between the contacting surfaces causing micro machining issues which eventually develop failure modes of the apparatus. Such is the case in the drive system employed in printers using a drive key and drive slot configuration. The thermal expansion of the aluminum core differs significantly from the thermal expansion of the steel drive hub causing loss of contact between the mating surfaces. Micro machining occurring between the steel drive key and the aluminum core slot, widens and weakens the drive slot causing eventual failure of the roller and drive hub, sometimes catastrophic.The design of the fuser core and the drive collar assembly has undergone development that takes into account the differing thermal expansion of the aluminum fuser core and the steel drive hub. The development has been furthered by a unique design which incorporates a self locking and self centering drive mechanism, along with a rubber interface design, again taking into account for the thermal expansion of aluminum and elimination of the drive key and slot, to address the failure mechanism of the previous designs. This mechanism absorbs the shock energy of the fast start &#x2013; stop motion, dissipating the energy over the full surface diameter of the drive hub. This paper describes the design history, the associated failure modes, and the new and novel solution.

AC Loss Evaluation of MgB2 Superconducting Windings Located in a Stator Core Slot with a Finite-Element Method

AC losses in stator windings of fully superconducting motors with an MgB2 wire are numerically evaluated by means of a finite-element method using edge elements for a self-magnetic field. The physical properties of the MgB2 wire for numerical calculations are obtained from the corresponding experiments with an existing wire. It is assumed that the voltage–current characteristics of the MgB2 wire are given by Bean’s critical-state model, in which the critical current density is independent of the local magnetic field. The influences of core slot size and turn number of windings on the AC losses are discussed quantitatively toward the optimum design of the stator winding with the MgB2 wire.

Stator Insulation Quality Assessment for High Voltage Motors Based on Probability Distributions

Stator insulation quality assessment for high voltage motors is a major issue for the reliable maintenance of industrial and power plants. To assess the condition of stator insulation, nondestructive tests were performed on the sixty coil groups of twelve motors. After completing the nondestructive tests, the AC voltage applied to the stator winding was gradually increased until insulation failure in order to obtain the breakdown voltage. The stator winding of each motor was classified into five coil groups; one group with healthy insulation and four groups with four different types of artificial defects. To analyze the breakdown voltage statistically, Weibull distribution was employed for the tests on the fifty coil groups of ten motors. The 50th percentile values of the measured breakdown voltages based on the statistical data of the five coil groups of ten motors were 26.1kV, 25.0kV, 24.4kV, 26.7kV and 30.5kV, respectively. Almost all of the failures were located in the line-end coil at the exit of the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of dissipation factor and ac current. It is shown that the condition of the motor insulation can be determined from the relationship between the probability of failure and the type of defect.

Failure-Analysis Case History—Shorted Winding in Motor

Abstract A large dc motor in a servo positioning system began behaving erratically whenever the rotor was in certain positions. This article describes the examinations and tests that were conducted to determine the root cause of failure, which turned out to be a shorted motor winding stemming form damage most likely caused by the tool used to pack the conductors into the core slot.

견인전동기 고정자 권선의 절연상태 분석

Diagnostic, surge and ac breakdown tests are widely used to evaluate the insulation condition of stator winding in traction motor. Diagnostic test included ac current, tan delta and maximum partial discharge. The result of diagnostic test indicates that five kinds of stator windings are good condition. Surge test was peformed to confirm the healthy of turn insulation in stator windings. This test is very easy to detect the turn insulation failure between normal and defect stator windings. After completing the diagnostic test, ac breakdown test has conducted gradually increasing ac voltage, until the stator winding punctured. No. 5 stator windings failed near rated voltage of 18.9 kV The breakdown voltage of No. 1 stator windings was 13.0 kV The ac breakdown voltage of normal winding is about 1.45 times higher than that of defect windings. The failure was located in a line-end coil at the exit from the core slot.

6.6 kV급 고압전동기 고정자 권선의 절연열화 평가

Prior to destructive testing, diagnostic tests were performed in ten high voltage motors. Diagnostic tests included polarization infer, ac current, dissipation factor<TEX>$(tan{\delta})$</TEX> and partial discharge magnitude. The rewind of motet slater insulation at rated voltage is assessed by the results of these tests. After completing the diagnostic tests, the stator windings of motors were subjected to gradually increasing ac voltage, until the insulation punctured. No. 8 motor failed near rated voltage of 19.0 kV. The breakdown voltage of No. 4 motet was 7.0 kV which is lower that expected for good quality coils in 6.6 kV class motors. The failure was located in a line-end coil at the exit from the core slot. These two motors began operation in 1994. While testing No. 7 motor, flashover occurred between the stator winding and the stator frame at 15 kV. The relationship between the diagnostic test and the drop in insulation breakdown voltage was analyzed.

Fundamental Electromagnetic Characteristics of Magnetically Anisotropic Damper-Wedges.

A magnetically anisotropic conductor was applied to the damper-wedge which acts as a slot wedge and damper bar in electrical rotating machinery. This conductor is composed of copper clad steel wires of 1.6mm diameter, which are aligned in the same radial direction. This means permeability in the direction of the wires, i.e. the thickness direction of the damper-wedge, is larger than the permeability perpendicular to this direction, and electrical conductivity is good. In order to evaluate the electromagnetic characteristics, a trial damper-wedge, 1.2m in length and with a steel space factor of 40% to total volume, was manufactured and mountained in a stand-still model iron core. Test results were as follows when the magnetically anisotropic damper-wedge was employed.(1) As the magnetic flux flowed well in the radial direction, the flux distribution at the core slot portion was flattened. Consequently, the ripple amplitude became small and the average flux density increased compared with cases when the non-magnetic or magnetic isotropic conductor are used.(2) The damper-wedge had a smaller skin effect for AC current than a conventional copper damper bar. The losses concentration for the damper system was relieved, so that better machine performance under heavy load condition would be obtained.

Fundamental electromagnetic characteristics of magnetically anisotropic damper‐wedges

AbstractA magnetically anisotropic conductor was applied to the damper‐wedge which acts as a slot wedge and damper bar in electrical rotating machinery. This conductor is composed of copper‐clad steel wires of 1.6 mm diameter aligned in the same radial direction. This means permeability in the direction of the wires, i.e., the thickness direction of the damper‐wedge, is larger than the permeability perpendicular to this direction, and electrical conductivity is good.To evaluate the electromagnetic characteristics, a trial damper‐wedge, 1.2 m in length and with a steel space factor of 40 percent to total volume, was manufactured and maintained in a standstill model iron core. Test results were as follows when the magnetically anisotropic damper‐wedge was employed.(1) As the magnetic flux flowed well in the radial direction, the flux distribution at the core slot portion was flattened. Consequently, the ripple amplitude became small and the average flux density increased compared with cases when the nonmagnetic or magnetic isotropic conductor is used.(2) The damper‐wedge had a smaller skin effect for ac current than a conventional copper damper bar. The losses concentration for the damper system was relieved so that better machine performance under heavy load condition would be obtained.