Circular Winding Research Articles

A Novel Brushless PM-Assisted DC Motor with Compound-Excited Circular Winding

A novel compound-excited brushless DC motor with polygonal circular winding is proposed in this paper. The key is that DC excitation is effectively coupled with PM excitation, significantly improving the torque density per PM volume and improving the machine flux weakening performance in the proposed design. This proposed design provides simplified control characteristics similar to a compound-excited DC motor. Further, the flux weakening of the proposed machine can be smoothly achieved using polygonal closed-loop circular winding and a lagging slot winding shifting method.

An ergonomic evaluation of workers in the winding section of the pump manufacturing industry.

Work-related musculoskeletal disorders (WMSDs) are prevalent and have an impact across occupations. However, there are very few studies that document the prevalence of WMSDs in the pump industry. In manufacturing industries, the common issue for WMSDs and physiological stress among the workers is caused by poor working posture. To investigate the occupational risks at the winding station in the pump manufacturing industry. In addition, this study examined the influence of work-study on mitigating occupational risks. Workers who were involved in circular coil winding and insulation testing were considered for the study. Awkward postures adopted while performing these tasks cause fatigue, injuries and WMSDs. Tasks were evaluated as per the National Institute for Occupational Safety and Health (NIOSH) standards. A work-study was conducted to better understand the workflow. Virtual ergonomic postural evaluation (Rapid Upper Limb Assessment, RULA) was used to identify the occupational risks. Time taken for making circular windings and insulation testing (7.5 Hp submersible motor) was found to be 4.04 minutes and 0.95 minutes, respectively. A CAD model was used for ergonomic evaluation in the virtual environment. The RULA final score of 2 and 3 is attributed to coil winding and insulation testing. For further studies, the whole pump manufacturing process should be taken into account. The ergonomic tools used in this study will considerably reduce the occupation risks at the winding station in the pump manufacturing industry.

Improving the main indicators of transformers with twisted one-piece magnetic cores by changing the technology of circular winding turns formation

Introduction. With the adoption of standards to reduce losses in transformers it is necessary to change the design of transformers that remain unchanged. Further energy saving is possible with the use of non-traditional technical solutions for the improvement of transformers. Problem. In order to reduce idle losses, the curved magnetic circuits of power transformers are carried out in the form of low-volume circuits. Windings are injected into assembled magnetic conductors by shuttle machines. The shuttle of windings provides technological gaps in winding windows, which results in an increase in size, metal capacity and losses. Goal. Rationale for transformer performance improvement by excluding process gaps in winding windows. Methodology. The definition of the change in transformer indicators is performed using optimization functions of the dimensionless indicators of the technological level. The adequacy of the functions is confirmed by the calculation of the mass of the electromagnetic system and the losses of the transformer. The figures of the compact analogue are calculated from the named serial analogue. Results. The result is a reduction in mass and a loss in the compactness of the transformer. Originality. The improvement of the indicators and the simplification of the winding technology are provided by a change in the design of insulating frames of winding coils. Winding on the rods is ensured by rotating the outer part of the composite insulating frame. Practical significance. Replacement the design of the windings of transformer with power of 40 kVA of 1000 V voltage class with a spatially twisted, small-dimensional magnetic conductor on a compact analogue leads to a reduction in mass and overall dimensions by 15 % and (17-18) %. Efficiency increases by 0.3 %.

Experience in the use of tissue flossing for the prevention and treatment of muscle cramps

Introduction. Cramps are sudden, involuntary, painful tonic muscle spasms of individual muscles or muscle groups lasting from several seconds to several minutes. It occurs in patients of different age categories with a frequency of up to 37 %. Tissue flossing (flossing, voodoo flossing) is an effect on the musculature, tendons, fascia (myofascial structures) of the extremities with the help of a special elastic band circularly wound on the limb, and subsequent physical exercises in this condition in order to improve blood circulation in the limb segment, increase tissue mobility, elasticity and extensibility of muscle-fascial structures. Tissue flossing can help to increase the volume of movements in the joints, reduce pain and increase flexibility.The aim to study the effects of tissue flossing on the frequency and intensity of manifestations of cramps. Materials and methods. The publication was based on the materials obtained during the observation of 7 patients with cramps. The aggressive nature of the muscle spasms forced them to seek medical help. In order to assess the effect on the frequency and intensity of cramps, patients underwent circular winding of an elastic band on a limb segment (tissue flossing) in which cramps occurred, followed by physical exercises (mainly flexion and extension at a pace of one movement per second) without additional load (with their weight) for 1 minute. Then the elastic band was removed and the patient continued to perform the same movements also for a minute with a frequency of one movement per second. Patients performed exercises 1-2 times a day for 5-14 days.Results. In five out of seven patients, cramps did not resume after the first use of tissue flossing. In two of the seven patients, cramps stopped after 7 days of exercise use. At follow-up in one (out of seven) patients, cramps resumed 2 months after the use of tissue flossing, but with a lower intensity. In the other six (out of seven) patients in the subsequent follow-up period (from 14 days to 6 months), cramps did not resume.Conclusion. According to the preliminary results of observations, it can be assumed that the tissue flossing method is effective for preventing cramps of various genesis as an independent and additional method of treatment.

A Sensorless Control Algorithm for the Circular Winding Brushless DC Motor Based on Phase Voltages and DC Current Detection

Circular winding brushless dc (CWBLdc) motor is a novel square-wave multiphase permanent magnet motor with high torque density and excellent vibration performance. It has good prospect in high power and performance applications. However, the control of CWBLdc motor depends on a precise rotor position. Consequently, its application is restricted in some situations where it is difficult to install position sensors. In view of the fact that the existing sensorless control methods are not suitable for the novel CWBLdc motor, a sensorless control algorithm based on the phase voltages and dc current detection is proposed to obtain a continuous and precise rotor position. The fundamental harmonic amplitude of the phase current is estimated based on the dc current, which eliminates the process of phase currents detection and reduces the complexity of the circuit. The error of the algorithm is derived in detail and its accuracy is analyzed theoretically in the paper. The experimental results show that the performance of the proposed sensorless control algorithm is equivalent to that of control with position sensor.

Novel semi‐analytical method for mutual inductance calculation of the thin spiral disk coils

Accurate and fast calculation of the self and mutual inductance of coils is an important factor in system design and optimization for many applications. The methods of calculation mutual inductance between two spiral disk coils include elliptic integral solutions and coefficients in literature. In this study, a new semi-analytical method is proposed to calculate the mutual inductance between two thin disk coils without any coefficient and complex integral solutions. For this purpose, the circular winding is treated as polygonal winding with multiple edges. Unlike Grover's average diameter approach, the gaps between the turns of the coils and the diameter of the wire are included in the calculation. To observe the reliability of the method developed here, the mutual inductance between identical disk coils with an inner diameter of 10 and 20 cm were calculated using both methods. To confirm the accuracy of the proposed method, the experimental results are compared with two methods using the same coils. It is observed that the new method gives acceptable results (maximum error of 2.83%) especially at the distances equals to the inner radius. Consequently; this method is useful for the design of loosely coupled systems, such as wireless power transfer and pressure sensors.

Analysis and Calculation of Radial Electromagnetic Force of Circular Winding Brushless DC Motor

The circular winding brushless direct current (CWBLDC) motor is a special type of multiphase permanent magnet motors with nonsinusoidal electromotive forces and circularly connected phase windings. The motor does not rely on conventional pulsewidth-modulation inverters and has high torque density and low torque ripple, making it a promising choice for high-power and high-performance applications, such as marine propulsions. This paper studies the radial electromagnetic force of CWBLDC motors. The effect of slot-pole combinations on harmonic contents of the radial force density is analytically derived. Moreover, two computationally efficient numerical methods to calculate the radial electromagnetic force density distribution are proposed based on the space-time symmetry of CWBLDC motors and the superposition principle of the magnetic field, respectively. In order to validate the analysis, vibration testing of a 10-kW CWBLDC prototype is performed.

Control of the output voltage of a controlled rectifier based on a transformer with rotating magnetic field

A new control method for a rectifier based on a transformer with a rotating magnetic field (TRMF) containing an even number of sections of circular winding (CW), which makes it possible to double the number of ripples of rectified voltage in the supply-voltage period, is considered. It leads to a reduction in the ripple amplitude and improves the quality of rectified voltage. The geometrical similarity of the CW of a TRMF making it possible to implement the new control method is analyzed. Switching algorithms of power switches for the classical and new control methods for any quantity of an even number of CW sections are presented. As an example, a switching queue of power switches for a CW with ten sections is considered. The output-voltage shapes for different depths of control are shown. The calculating procedure of the control characteristic for the classical and new control methods, as well as corresponding diagrams, are presented. For the presented example with ten sections of CW, the efficiency of the new control method was evaluated and the dependences of the voltage-ripple ratio on the RMS of rectified voltage are presented. A comparative analysis of the number of ripples for different quantity of CW sections was conducted, and the harmonic composition of output voltage spectrum for the example under consideration is determined. It has been concluded that, in the case of using the new control method for achieving the desired quality of rectified voltage, the number of CW sections may be halved compared with the classical control method, which will simplify the manufacture of a transformer magnetic conductor, halve the number of pairs of power switches switching the CW taps, and decrease the mass, dimension, and cost factors of a semiconductor switch and the TRFM itself as a whole. Using the new control method makes it possible to make a controlled rectifier with an even number of sections of a CW transformer almost as efficient as using a transformer with an uneven number of CW sections and the classical control method. The new control method ensures the fulfillment of the requirements for the available value of the ripple ratio of the output voltage of a controlled rectifier based on a transformer with a rotating magnetic field set out by State Standard YuST 13109-97 at a lower RMS of rectified voltage.

Multi-objective Design Optimization of High-Power Circular Winding Brushless DC Motor

This paper proposes a novel circular winding brushless dc (CWBLDC) motor, which offers high torque density as BLDC motors and low-torque ripple as permanent-magnet synchronous machines (PMSMs). The novelty of the proposed machine is the circularly connected windings and its way of commutation, which make it suitable for high-power high-performance marine propulsion applications. First, the structure and the operation principle of CWBLDC are described. The method for calculating phase current of CWBLDC is subsequently introduced and validated by prototype experiment. Then, the multiobjective optimization problem for designing a high-power low-speed CWBLDC is formulated. Through large-scale design parameter sweeping, the best type of slot–pole combination and the best design scheme is selected and validated by finite element method (FEM) simulation. Finally, a multifactor regression analysis is performed to establish the relationship between performance objectives and design variables.

Algebraic curves for long folded and circular winding strings in AdS 5 × S 5

For the homogeneous configuration given by the long string limit of the folded string with a spin in AdS3 and a spin and a winding number in S1, we solve the auxiliary linear problem in the finite-gap method and construct the Lax operator to obtain an algebraic curve. We show that the long spiky string in AdS_3 has the same algebraic curve as the null cusp Wilson loop. The algebraic curve for the circular winding string in AdS3xS1 is evaluated. The Virasoro constraint is discussed to characterize the branch points of each curve.

Three-point correlator of heavy vertex operators for circular winding strings in [formula omitted

We consider an extremal three-point correlator of three heavy vertex operators for the circular winding string state with one large spin and one winding number in AdS5 and one large spin and one winding number in S5. We use a Schwarz–Christoffel transformation to compute semiclassically the extremal three-point correlator on a stationary string trajectory which is mapped to the complex plane with three punctures. It becomes a 4d conformal invariant three-point correlator on the boundary. We discuss the marginality condition of vertex operator.

Output voltage quality of a rectifier designed on the basis of a transformer with rotating magnetic fields at even and odd number of circular winding sections

On the basis of a geometrical analogy between a circular winding and regular polygon, the dependences of the rectified voltage ripple factor on the number of sections of circular winding for rectifiers designed on the basis of transformers with rotating magnetic fields have been ascertained.

A light-cone approach to three-point functions in AdS5 × S5

We consider worldsheet correlation functions for strings in AdS_5 x S^5 using a light-cone gauge for the worldsheet theory. We compute the saddle-point approximation to three-point functions of BMN vertex operators, all with large charges, by explicitly finding the intersection of three euclidean BMN strings. We repeat this calculation for non-BPS circular winding strings extended along a great circle of the S^5, though in this case the appropriate form of the vertex operator is uncertain. Furthermore, we compute the spectrum of fluctuations about euclidean BMN strings for generic boundary conditions, and show that the spectrum depends only on the total charge and not the details of the string configuration. We extend our considerations to include near-BMN vertex operators and through the evaluation of the string path integral make contact with the light-cone string field theory calculations of gauge theory three-point structure constants.

Extremal correlator of three vertex operators for circular winding strings in AdS 5 × S 5

We study a three-point correlator of the three heavy vertex operators representing the circular winding string states which are point-like in AdS_5 and rotating with two spins and two winding numbers in S^5. We restrict ourselves to the case that two of the three vertex operators are located at the same point. We evaluate semiclassically the specific three-point correlator on a stationary splitting string trajectory which is mapped to the complex plane with three punctures. It becomes an extremal and 4d conformal invariant three-point correlator on the boundary. The marginality condition of the vertex operator is discussed.

Square Helmholtz coil with homogeneous field for magnetic measurement of longer HTS tapes

Magnetic ac loss measurement of HTS tapes and films at various magnetic field orientations becomes a crucial issue from the view point of measurement precision. In principle, due to tiny loss component and anisotropic properties, longer HTS sample subjected to very good homogeneous field could facilitate the accuracy of this kind of measurement. We investigated field profile of Helmholtz coils with square winding as a magnetizer for HTS tape and films. It is found that square winding exhibits better field-homogeneity than that of conventional circular winding with the similar coil dimensions for ideal condition. Being apart from ideal condition, we investigated field profile of square Helmholtz coil with various combinations of coil parameters and made a conclusion for the best combination based on the field homogeneity and field intensity. The design also provides noise reduction facilities by allowing compact and identical pick up-compensation coil arrangement. In addition, we optimized the final design of Helmholtz coil to compensate the influence of difficulties in square winding on the field distribution. Finally, as small as 0.5% field variation was estimated for 50 mm long sample to be magnetized under a proper combination of fabrication parameters. Investigation of field homogeneity, noise effect and a practical design of square Helmholtz coil as a pick-up coil based magnetizer will be reported.

経皮信号伝送用組合せコイルの形状と受信特性について

Combined coils are proposed for transmitting signals to implanted medical devices. Figure-of-eight coils, which have been widely used in the field of magnetostimulation,are also useful for signal transmission, owing to their noisecancelling ability and low flux leakage. However, transmission characteristics are inevitably dependent on the angular misalignment of the transmitting and detecting coils owing to the asymmetrical flux distribution produced by the transmitting coil. We propose combined-hoop coils,which are hoop coils with another inverse circular winding inside. Because of their cylindrically symmetric structure,they allow angular misalignment and still cancel noise coming from around them.

An instrument for the determination of drill hole geometry

At the Geological Survey of Sweden an equipment has been constructed for determination of the inclination and declination of diamond drill holes. The indicator probe, of 35 mm diameter, contains a clinometer wheel and a compass, each having a circular resistance winding, which by means of sliding contact devices are coupled through a 3-conductor cable to a Wheatstone bridge. The resistance measured is a linear function ot the inclination respectively declination angle of the drill hole.