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A novel four-port circulator is presented which uses an inline ferromagnetic element to allow for transmission or reflection depending on the sense of the incident circularly polarized wave. This configuration has been shown to reduce the dependency on ferrite anisotropy and support higher power, low rf loss, operation. An analytic analysis of this device is presented alongside corroborating cold test data of the first prototype. High-power operation was performed at 2.856 GHz, with input power levels up to 8 MW for $3.5~\mu \text{s}$ in a pressurized nitrogen environment. The results from this research not only demonstrate ability to eliminate the use of greenhouse insulators, such as SF6, but also provide conceptual groundwork for a new class of ultrahigh power (50 MW+) nonreciprocal networks including circulators, isolators, phase shifters, and rf switches. [ABSTRACT FROM AUTHOR]

The reliability of conventional photovoltaic (PV) structure in shaded situations can undergo different issues related to internal and external conditions. The internal condition accounts for the inhomogeneity of the properties of electrothermal cells, while the external conditions connote optimal power maximum tracking techniques and protection circuit limitations. This article proposes a new technique to improve the reliability of shaded panels, considering the internal and the external issues. Our study begins with an extensive analysis to assess the vulnerability of PV cells to second-quadrant thermal stress and operational limits of bypass diode protection against hot spot. Consequently, we proposed a new system that concurrently operates with the maximum power extraction process to assist bypass diodes with hot-spot protection. This proposition results in a reconfigured panel with both a local detection circuit that defines the conduction states of bypass diodes and additional mosfets that switch shaded subgroups. In this article, an algorithm was developed that is capable of controlling the optimal maximum operation point tracking with an on-demand deployment of the protection mosfets, using the signals provided by the local detection circuit. A set of experiments were carried out in order to demonstrate the capability of the proposed method to prevent hot-spot damages over all shading rates and operating points. The novelty of the proposed approach is its low cost of implementation as well as its simple and efficient design. Therefore, it has the potential to be easily integrated along side existing infrastructure and maximum power point tracking algorithms. [ABSTRACT FROM AUTHOR]

In electrical power systems, cords and extension cords are exposed to mechanical damage and other insulation stresses. Mechanical damage to stranded conductors can reduce locally their cross section or break them and cause anomalous local conditions of overheating or arcing. The ordinary protective devices cannot detect the series faults that persist, so the fault point remains energized and is subject to electric shock and fire hazards. Effective protection can be accomplished by implementing active and passive measures: installing arc-fault circuit interrupters or arc-fault detection devices, able to detect arcing faults, or wiring the circuits with a grounding protection conductor to involve the ground in every fault. In this way, residual current protective devices (residual current devices or ground fault protective devices) quickly protect the series faults not only with arc, but also without it. Ground-fault-forced cables facilitate by design the conversion of any kind of cable fault to a ground fault. They are particularly recommended for cords and extension cords, internal circuits to grounded equipment, uninterruptible power system continuity circuits, aircraft circuits, road tunnels, data centers, refrigerated containers parks, residences, and hospitals. [ABSTRACT FROM AUTHOR]

In electrical power systems, all the wiring exposed to mechanical damages and other insulation stresses, such as flexible cords, can be involved in overheating, arcing, and burning. Mechanical damages of the stranded bare conductors can locally degrade the effective sizing of the cross section and cause anomalous local conditions. The circuit protective devices (PDs) can be unfit to detect the faults of cords that remain so energized and available to electric shock and fire hazards. Some fire ignitions result from these types of special unprotected faults. To highlight the local incident energy in case of fault, this paper introduces the parameters steady and transient current densities that assist in analyzing these fault events. Efficient protection can be achieved by the integration of active and passive techniques: adopting arc-fault circuit interrupters or detection devices, recognizing arcing faults, and wiring circuits with a grounding protection conductor to involve the ground in every fault that, in ac systems, is rapidly protected by residual current PDs (or ground-fault PDs). At this aim, the use of special cables, namely, ground-fault-forced cables, is recommended, particularly for cords and extension cords also supplying Class II equipment. The dc system protection requires special care. [ABSTRACT FROM AUTHOR]

With increased opportunities for the exploitation (i.e., reverse engineering) of vulnerable electronic components and systems, circuit protection has become a critical issue. Circuit protection techniques are generally software-based and include cryptography (encryption/decryption), obfuscation of codes, and software guards. Examples of hardware-based circuit protection include protective coatings on integrated circuits, trusted foundries, and macro-sized components that self-destruct, thus destroying critical components. This paper is the first to investigate the use of microelectromechanical systems (MEMS) to provide hardware-based protection of critical electronic components to prevent reverse engineering or other exploitation attempts. Specifically, surface-micromachined polycrystalline silicon to be used as meandering resistive heaters were designed analytically and fabricated using a commercially available MEMS prototyping service (i.e., PolyMUMPs), and integrated with representative components potentially at risk for exploitation, in this case pseudomorphic high-electron mobility transistors (pHEMTs). The MEMS heaters were initiated to self-destruct, destroying a critical circuit component and thwart a reverse engineering attempt. Tests revealed reliable self-destruction of the MEMS heaters with approximately 25 V applied, resulting in either complete operational failure or severely altering the pHEMT device physics. The prevalent failure mechanism was metallurgical, in that the material on the surface of the device was changed, and the specific failure mode was the creation of a short-circuit. Another failure mode was degraded device operation due to permanently altered device physics related to either dopant diffusion or ohmic contact degradation. The results, in terms of the failure of a targeted electronic component, demonstrate the utility of using MEMS devices to protect critical components which are otherwise vulnerable to exploitation. [ABSTRACT FROM PUBLISHER]

The objective of this work is the development of a methodology for experimentally characterizing a polymeric thermistor used as an over current and temperature protection device. Uncertainty of measurements of parameters, such as temperature, voltage, current and ohmic resistance is also estimated. The tested thermistor has a Positive Temperature Coefficient (PTC), which means that its ohmic resistance increases with temperature. In order to measure the thermistor characteristics, an electric circuit was mounted and placed in a dry oven; the circuit consists of a stable voltage source and a variable resistance, both in series with the thermistor. A K type thermocouple was attached to it. so that its temperature could be measured and controlled. By gradually decreasing the circulating current through the circuit, the Joule effect could be neglected, and the thermistor resistance is only a function of temperature, which is easier to measure. The acquired dates were used to build several characteristics curves, which were analyzed and compared to the available ones from the manufacturer data. Finally, this work proposes the development of a systematic procedure to obtain the thermistor performance data, so that the manufacturer data can be verified, together with its uncertainty, providing at the same lime information not presently available in the market for system design. [ABSTRACT FROM AUTHOR]

Electromechanical circuit breakers based on micro-electromechanical systems (MEMS) structures are proposed, and initial prototypes are demonstrated. The devices use laterally moving thermal actuators to set and trip low resistance contacts. The actuators are fabricated from electroplated Ni, on Si substrates, with Au-Co contact layers. Trip currents of 300 mA are obtained, with contact resistances below 1 Ω. Rapid tripping (below 50 ms) is achieved, even for modest over-current levels, and sensitivity to ambient temperature is much less than for positive temperature coefficient (PTC) devices typically used for over-current protection in electronics applications. These MEMS devices offer an ultra-miniature, potentially low cost solution for circuit protection applications at low currents, where a high degree of system control is desired. [ABSTRACT FROM AUTHOR]

This paper presents an area-efficient multiple circular layout cells that provide an excellent electrostatic discharge (ESD) robustness for CMOS output buffers. Experimental results using a 0.35 μm nonsilicided CMOS process from the Institute of Microelectronics (IME) has demonstrated that the ESD robustness of the proposed layout design based on the human body model (HBM) is enhanced when compared to the traditional finger-type layout approach. The pMOS and nMOS output transistors achieve higher driving/sinking current by using the proposed layout design. In the meantime, the layout area requirement is reduced and hence producing a lower drain-to-bulk parasitic capacitance. These attributes of the new circle-type layout design make it judiciously suitable for utilization in high-density and high-speed applications. [Copyright &y& Elsevier]