Simulation of three-phase short-circuit at the terminals of synchronous machine
Three-phase sudden short-circuit at the terminals of a synchronous machine under open circuit condition is simulated. The standard parameters are calculated by using the known parameters, and substituted into the analytical expression for computing short-circuit current. The curve of the relationship between the maximal armature momentary current and the rotor angle is plot. It is concluded that the armature momentary current is maximal when short-circuit occurring at the time of the terminal voltage wave is going through zero. Furthermore, a simulation model in SIMULINK environment is constructed, thus the oscillograms of the armature short-circuit currents in the three phases and the field short-circuit current are plot.
Dynamics of a Turbo-generator Driven by DC Motors During Off-line Three-phase Sudden Short Circuit
Abstract This article reports the responses of a turbo-generator driven by separately excited DC motors when the former is subjected to a sudden short-circuit test. Such setups are usually arranged in test rigs of generator manufacturers and electrical machines laboratories, where DC motors are used as the prime mover. Sudden short-circuit tests on turbine generators offer a short-circuit current spectrum that can be used to extract operational impedances and time constants of the generator. The sets of differential equations representing the DC motors, coupling system, and generator are appropriately solved together to obtain the responses. The results show the machine and system dynamics under damped and undamped shaft coupling. Transient parameters of the generator are extracted in each case and compared. The influence of speed departures on shaft torques and current waveforms are also studied. These results suggest that short-circuit tests can be performed at rated voltages if the couplings can be designed so as to absorb the high short-circuit torques developed during sudden short-circuit tests.
Drugged Driving Expert Panel Report: A Consensus Protocol for Assessing the Potential of Drugs to Impair Driving
In November 2008 and again in March 2009, an expert panel was convened by the National Highway Traffic Safety Administration with the goal of determining whether a list could be developed to indicate which medications or classes of medications may pose a hazard to driving. There was particular interest in having the panel develop a list of “safe” medications that do not impair driving. The value of the list would be to better inform patients and physicians regarding the likely effects of a drug on driving. This information could lead to better-informed prescribing practices and to more rational selection of medications by patients. The panel was composed of an international group of behavioral scientists, epidemiologists, pharmacologists, toxicologists, and traffic safety professionals to provide a broad-based perspective on the issue. Discussions included prescription (Rx) medications as well as over-the-counter (OTC) medications and illicit drugs. Although illicit drugs are best known for their impairing effects, Rx and OTC medications are also known to be capable of producing impairment and many are frequently encountered in impaired driver populations. The panel agreed that one of the barriers to categorizing drugs with respect to driving impairment risk is the lack of a common, standardized protocol for assessing the impairing potential of drugs. The panel recognized the need for a structured, standardized protocol for assessing the driving impairment risk of drugs that would lead to better classification of drugs in terms of driving impairment risk. The approach could be useful in providing more meaningful precautions for users and prescribers regarding the impact of drugs on driving. This report provides the background for the project and assembly of the expert panel, a description of the proposed protocol, and offers examples of how the protocol could be useful in evaluating a drug.