J. N. Nderu

Possible application of amorphous wire as a sensor of angle of rotation, direction of rotation and torque

Stress changes the domain structure in magnetostrictive materials and consequently changes the magnetization. From this, one can imagine possible sensor applications based on the stress-magnetic effect of the wires. In this work, the authors have studied the stress-magnetic characteristics of amorphous wires and subsequently proposed possible applications for the wires based on the stress-magnetic effect. The proposed possible applications are, for instance, sensing of angle of rotation, direction of rotation and sensing of magnitude of torque.

MPPT of a standalone wind energy conversion system using magnetostrictive amorphous wire speed sensor and fuzzy logic

This paper details the design and implementation of a Fuzzy Logic based controller for Maximum Power Point Tracking (MPPT) of a case study standalone wind energy conversion system(WECS). A magnetostrictive amorphous wire speed sensor is used for rotational speed measurement to provide an inexpensive, fast and robust solution to speed measurement. The designed MPPT algorithm includes a peak detection feature and a self-tuning capability which makes it intelligent and generic. The designed fuzzy logic controller determines the appropriate duty cycle D that yields optimum speed for maximum power extraction from the WECS for various wind speeds. It then applies this D to the DC-DC boost converter to control the speed of rotation of the PMSG to track maximum power point curve. The designed system was implemented on a real case study wind turbine under controlled conditions. Experimental results show that the designed system was able to significantly increase the maximum electrical power extracted for varying wind speeds.

Lightning protection of HV substations at coastal region and enhanced earthing system — Case study

In every HV substations, protection from the direct lightning stroke is paramount. However, substations protected from direct lightning stroke using shielding wires at coastal region are found to be more susceptible to failure. This is because of accidental snapping of the earth wires after attacked by severely corrosion causing a short circuit within the substation. In this regards, use of lightning masts was proposed to mitigate this menaces. Despite low keraunic level at coast region, approximately 25 thunderstorms days per year, lightning is known to be capricious, unpredictable and probabilistic event hence cannot be ignored. This paper explores use of empirical curves to obtain the height of the masts and position within the substation. By use of empirical curves of <0.1% protection lightning exposure, 1.8×10−5 number of lightning expected to penetrate the substation, SP was obtained. In addition, integrating earth wire inside the masts was devised hence deterring the vandals from accessing the earthing system.

Age clustering approach to metabolic syndrome using spherical and torus SOM

One of the threatening trends of human health in recent years has been metabolic syndrome. Metabolic syndrome is a cluster of conditions that occur together resulting in simultaneous disorders related to ones metabolism. This paper analyses the effect age clustering has on the syndrome trends using SOM. It gives an analysis and visualization of the contributing parameter(s) to the syndrome in each cluster and then projects the overall effect the clustered SOM analysis has on the entire group of examinees. Inter-relation of the input parameters and the severity of their contribution to the syndrome risks are investigated.

Effect of motor-cage temperature on motor speed sensing characteristics of magnetostrictive amorphous wire

Magnetostsrictive amorphous wires have been shown to possess various important sensing characteristics. Previously we presented results of speed sensing of induction motor using the amorphous wire, in which the speed sensing capability was seen to match that of conventional speed sensors such as tachometer. However, one concern was the fact that the properties of amorphous wire change when exposed to certain temperature ranges for a long time (as would be expected to occur inside the motor cage) in a process termed relaxation. In the present work we have shown that the amorphous wire sensing characteristics are completely lost when the wire is exposed to elevated motor-cage temperatures. Furthermore, we have suggested and tested a simple, but effective remedy to this problem.

Magnetization properties of amorphous ribbon due to heat treatment

Magnetization properties of an amorphous ribbon, Co-based Fe-Ni-Mo-B-Si, have been investigated. The hysteresis curves of the heat-treated amorphous ribbon showed a very unique behavior under applied tensile strain. For example, a Co-based amorphous ribbon, which has a negative magnetostriction constant, showed a tensile insensitive magnetization. The magnetization does not decreases despite applied tensile stress.