Reduction of Cogging Torque in Surface Mounted Permanent Magnet Brushless DC Motor by Adapting Rotor Magnetic Displacement

Cogging torque is a critical dilemma in Permanent Magnet Brushless DC (PMBLDC) motors. In medium-low power PMBLDC motors, redundant vibrations and forbidding noises arise as a result of the harmonic magnetic forces created by cogging torque. This paper introduces a simple approach for minimizing cogging torque in PMBLDC motors by applying placement irregularities in rotor magnets. An angle shift in the rotor magnets in surface-mounted PMBLDC motors helps to attain magnet displacement. This displacement imparts an asymmetrical magnet structure to the rotor. Maintaining pole arc to pole pitch ratio (L/τ) of between 0.6 and 0.8, shifting angles from 1° to 8° were considered in order to analyze the effect of the angle shift on the rotor magnets. An analytical expression was also derived for finding the shifting angle with the minimum cogging torque in the PMBLDC motor by using the Virtual Work Method (VWM). The optimization of the shifting angle with minimum cogging torque was investigated using 3D Finite Element Analysis (FEA). A comparison of the simulation and analytical results of cogging torque was carried out. It was determined that the reduction of cogging torque in the analytical results showed good agreement with the FEA analysis.

Polypyrrole-Chitosan-CaFe2O4 Layer Sensor for Detection of Anionic and Cationic Dye Using Surface Plasmon Resonance

A polypyrrole-chitosan-calcium ferrite nanocomposite was prepared using the electrodeposition method. The prepared layer was characterized by using Fourier transform infrared spectroscopy, the X-ray diffraction technique, and field emission electron microscopy. The thickness of the thin layers was in the range of 2.8 nm to 59.5 nm, and the refractive index of the composite layer was in the range of 1.66131+0.156i to 1.62734+0.167i. Detection and removal of cationic and anionic dyes, such as methylene blue and methylene orange, are subject of great interest for protecting environmental water. The layer composite was used to detect methylene orange and methylene blue using the surface plasmon resonance technique. Consequently, the polypyrrole-chitosan-calcium-ferrite composite layer interacted with the anionic and cationic dyes. The resonance angle shift for the detection of the cationic dye was larger than the resonance angle shift for the anionic dye. The sensor limit was achieved from a sensogram at about 0.01 ppm.

An Operation Data-Based Method for the Diagnosis of Zero-Point Shift of Wind Turbines Yaw Angle

The alignment of the wind turbine yaw to the wind direction is an important topic for wind turbine technology by several points of view. For example, the negative impact on power production of an undesired non-optimal yaw alignment can be impressive. The diagnosis of zero-point shifting of the yaw angle is commonly performed by adopting supplementary measurement sources, as for example, light detection and ranging (LIDAR) anemometers. The drawback is that these measurement campaigns have a certain cost against an uncertain diagnosis outcome. There is therefore an increasing interest from wind turbine practitioners in the formulation of zero-point yaw angle shift diagnosis techniques through the use of nacelle anemometer data. This work is devoted to this task and is organized as a test case discussion: a wind farm featuring six multi-megawatt wind turbines is considered. The study of the power factor Cp as function of the yaw error (estimated through nacelle anemometer data) is addressed. The proposed method has been validated through the detection of a 8 deg zero-point shift of the yaw angle of one wind turbine in the test case wind farm. After the correction of this offset, the performance of the wind turbine of interest is shown to be comparable with the nominal. The results of this work therefore support that an appropriate analysis of nacelle anemometer and operation data can be effective for the diagnosis of zero-point shift of the yaw angle of wind turbines.

The impact of supply phase shift on the three phase induction motor operation

The performance of a three-phase induction motor operating under supply unbalance conditions has been the focus of many research works using various methods. Most of the studies have focused majorly on voltage magnitude unbalance without due analysis to determine the effect of deviations in the supply phase angle from the 120° phase to phase displacement. This research investigates the significance of supply phase shift on the performance of a three-phase induction motor by applying a novel phase shift unbalance definition to the zero, negative and positive sequence components model of the motor. The test results reveal that when both phase angle shift and voltage magnitude unbalance occur simultaneously during motor operation the effect of the phase shift dominates over the effects of the voltage magnitude unbalance. This study shows that phase angle unbalance has a severe consequence on three phase motor performance.

Efficiency of object identification for binary images

In this paper, a comparative analysis of the correlation-extreme method, the method of contour analysis and the method of stochastic gradient identification in the objects identification for a binary image is carried out. The results are obtained for a situation where possible deformations of an identified object with respect to a pattern can be reduced to a similarity model, that is, the pattern and the object may differ in scale, orientation angle, shift along the base axes, and additive noise. The identification of an object is understood as the recognition of its image with an estimate of the strain parameters relative to the template.