Search results for " Limit"
showing 10 items of 1716 documents
Reducing DC Link Voltage Unbalance in a Fault-Tolerant Inverter
2014
Today, continuous working of power inverter drives is mandatory for several applications. Damages to materials, machines or even risks to human life have to be absolutely avoided. In the literature, fault-tolerant algorithms and architectures to achieve a successful fault handling are investigated. Researchers aim at reducing the number and cost of additional components, improving at the same time the inverter performances under postfault conditions. Cost, post-fault power derating and increasing distortion are usually conflicting requirements. In this paper, a fault-tolerant three phase inverter is presented. A reconfigurable architecture and a novel fault-tolerant algorithm is designed to…
Dimensionless analysis of RC rectangular sections under axial load and biaxial bending
2012
This paper proposes a numerical procedure able to provide ultimate curvature and moment domains of rectangular RC sections subjected to combined axial load and biaxial bending. The formulation is carried out in dimensionless terms in order to give results that are valid for classes of sections characterized by the same values of the geometric and mechanical parameters governing the section response. The role of some of these parameters is investigated here. The results show possible correlations linking the actual values of moment and curvature to the values corresponding to two cases of uniaxial bending to be considered separately. © 2012 Elsevier Ltd.
Proposal for a more accurate physically based S–N curve for welded steel joints
2009
Abstract The present article proposes a more accurate S–N curve in the high cycle fatigue regime for fillet welded joints in steel subjected to constant amplitude loading. The S–N curves are constructed based on a physical model of the fatigue damage evolution. It is a two phase model where the crack initiation is treated by a local weld notch approach. The subsequent growth is based on the concept of the stress intensity factor at the crack front by applying the Paris law. According to the proposed model, the time to crack initiation becomes the dominant part of the fatigue life at low stress range levels. The resulting S–N curves are non-linear for a log–log scale and they do not predict …
Occupational hygiene in a waste incineration plant
2003
Abstract The Turku incineration plant was renovated in 1995 to meet the emission requirements of modern waste combustion facilities. It treats presorted municipal waste from 170,000 residents in the Turku area. In the plant, the incineration process produces several types of by-products having importance in terms of occupational hygiene. Although not obligated by the law, the management of the plant has a keen interest in occupational hygiene at the plant, which was studied from 1998 to 2001. Concentrations of microbes, endotoxins, and dust and the noise level were investigated in three different working areas. Microbe measurements were conducted with a six-stage impactor and using the CAMN…
Control of solid-state fault current limiter for DG-integrated distribution systems
2017
Fault current limier (FCL) is a device that limits the system current under fault conditions without disconnecting the system and affecting the power system protection components such as circuit breakers. Many types of FCLs have been proposed to limit the magnitude of the fault current. Solid-state fault current limiters (SSFCLs) can limit the peak value of the fault current by applying several methods, such as controlling the system impedance or controlling the voltage that appears across the fault. In this paper, a new control scheme for the SSFCL circuit is presented. The control method is based on controlling the duty cycle of solid state switches to control the rms value of the system …
Current and Voltage Behaviour During a Fault in a HV/MV System: Methods and Measurements
2015
When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighbouring substations. In this paper the problem of fault current distribution is introduced, the te…
A Fisher–Kolmogorov equation with finite speed of propagation
2010
Abstract In this paper we study a Fisher–Kolmogorov type equation with a flux limited diffusion term and we prove the existence and uniqueness of finite speed moving fronts and the existence of some explicit solutions in a particular regime of the equation.
Comparing analytical methods to detect SARS-CoV-2 in wastewater
2021
Wastewater based epidemiology (WBE) has emerged as a reliable strategy to assess the coronavirus disease 2019 (COVID-19) pandemic. Recent publications suggest that SARS-CoV-2 detection in wastewater is technically feasible; however, many different protocols are available and most of the methods applied have not been properly validated. To this end, different procedures to concentrate and extract inactivated SARS-CoV-2 and surrogates were initially evaluated. Urban wastewater seeded with gamma-irradiated SARS-CoV-2, porcine epidemic diarrhea virus (PEDV), and mengovirus (MgV) was used to test the concentration efficiency of an aluminum-based adsorption-precipitation method and a polyethylene…
A method for measuring low-weight carboxylic acids from biosolid compost
2006
Concentration of low-weight carboxylic acids (LWCA) is one of the important parameters that should be taken into consideration when compost is applied as soil improver for plant cultivation, because high amounts of LWCA can be toxic to plants. The present work describes a method for analysis of LWCA in compost as a useful tool for monitoring compost quality and safety. The method was tested on compost samples of two different ages: 3 (immature) and 6 (mature) months old. Acids from compost samples were extracted at high pH, filtered, and freeze-dried. The dried sodium salts were derivatized with a sulfuric acid–methanol mixture and concentrations of 11 low-weight fatty acids (C1–C10) were a…
Transient response of a TLP-type floating offshore wind turbine under tendon failure conditions
2021
Abstract Among various types of floating offshore wind turbines (FOWTs), the tension leg platform (TLP) floating wind turbines have relatively small motions due to stiff tendons. Similar to TLP applications in the offshore industry, tendon failure may lead to deteriorated stability and large transient responses, which should be considered as part of accidental limit state (ALS) checks at the design stage of the TLP FOWTs. This paper takes the WindStar TLP system as a representative and investigates the transient effects of one-tendon failure on the system responses. A coupled numerical model is first established using the aero-hydro-servo-elastic simulation tool FAST. Subsequent numerical s…