Overload protection, components

Fig. 7.41 Components for detector overload protection HFAC-26 preamplifier, DCC-lOO detector controller card, and shutter assembly for R3809U MCP. Becker Hickl, Berlin...

Input overload hardening. Protection devices are placed at the input circuitry to prevent damage in the event of an accidental overvoltage. Fuses and semiconductor-based protection components are used. 

Overload protection It is a device which protects an electronic component from destruction by excess current. 

Drive Assemblies The drive assembly is the key component of a sedimentation unit. The drive assembly provides (1) the force to move the rakes through the thickened pulp and to move settled solids to the point of discharge, (2) the support for the mechanism which permits it to rotate, (3) adequate reserve capacity to withstand upsets andtem-poraiy overloads, and (4) a reliable control which protects the mechanism from damage when a major overload occurs. 

The principal components of a power distribution cable are the conductors and the insulators. The cable is completed by the provision of armoring, overloads and other features designed to protect the cable within its installed environment. 

In the literature dangerous for brain neurons effect of ROS was traditionally underestimated — one can believe that multi-step antioxidant system should provide reliable protection. Actually, antioxidants are able to remove toxic component of glutamate overloading and keep neurons viable. However, this point of view is under serious doubt because of both a multiple role of antioxidants in brain metabolism [1,38,52] and apparent absence of therapeutic effect of antioxidant protection [42]. 

The LDL receptor is a key component in the feedback-regulated maintenance of cholesterol homeostasis [1]. In fact, as an active interface between extracellular and intracellular cholesterol pools, it is itself subject to regulation at the cellular level (Fig. 2). LDL-derived cholesterol (generated by hydrolysis of LDL-bome cholesteryl esters) and its intracellularly generated oxidized derivatives mediate a complex series of feedback control mechanisms that protect the cell from over-accumulation of cholesterol. First, (oxy)sterols suppress the activities of key enzymes that determine the rate of cellular cholesterol biosynthesis. Second, the cholesterol activates the cytoplasmic enzyme acyl-CoA cholesterol acyltransferase, which allows the cells to store excess cholesterol in re-esterified form. Third, the synthesis of new LDL receptors is suppressed, preventing further cellular entry of LDL and thus cholesterol overloading. The coordinated regulation of LDL receptors and cholesterol synthetic enzymes relies on the sterol-modulated proteolysis of a membrane-bound transcription factor, SREBP, as described in Chapter 14. 

Circuit protective devices, such as fuses, circuit breakers, and GFCIs, automatically hmit or shut off current flow during a ground fault, overload, or short circuit in a wiring system. Fuses and circuit breakers protect conductors and equipment. They prevent overheating of wires and components that could create hazards. They also open the circuit under certain hazardous ground fault conditions. 

Pressure control valves have the primary task of limiting pressure in the system and thus protecting individual components and lines from rupturing or overloading. The valve opens when a predetermined pressure is reached and conveys the pump s excess delivery flow back into the tank. A pressure control valve is shown in Figure 5.9. 

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