Steady-state Operation Modes Research Articles

Improved performance of polyphase hysteresis-reluctance motors fed from single-phase supplies

The balanced operation of a three-phase hysteresis-reluctance motor connected to a single-phase power supply was studied for both steady-state and dynamics modes of operation, and experimental tests were run to verify the analysis. Improved performance characteristics for balanced operation of a three-phase hysteresis-reluctance motor operated on a one-phase power supply are presented and optimum values of two-element balancers are shown for fast run-up as well as smooth synchronizing performances.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A flexible AGC algorithm for the Hellenic interconnected system

A flexible automatic generation control (AGC) algorithm is described that has been developed for the Hellenic interconnected system. The algorithm includes the three well-known load frequency control (LFC) types (flat frequency, flat tie-line, and tie-line bias) and introduces four operating modes that depend on the magnitude of the measured area control error (ACE). These modes are the steady-state operating mode, the normal operating mode, and two distinct emergency modes. The LFC stability margins are calculated for the case of slow-acting, flat frequency control. The effects of integral feedback are also considered and analyzed. An approximate economic dispatch algorithm is presented that makes use of a predetermined table of the economic loading of units. Simulation results are reported that demonstrate satisfactory operation of the AGC system. Detailed transient stability program simulations demonstrate that a number of ACE measurements per measuring period are necessary to avoid dangerous false emergencies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Cathode erosion studies on MPD thrusters

The fundamental processes occurring at the cathode interphase of magnetoplasma dynamic (MPD) arcs and their consequences on material erosion are by no means fully understood, despite the great many publications in this field on various different arc types of similar conditions. This paper presents the results of a cathode erosion study on an MPD arc thruster under pulsed and steady-state operating modes and, moreover, gives an explanation of the cathode attachment mechanisms for both operating modes.

Tokamak Fusion Test Reactor gas injection control system design and operation

Magnetic fusion devices require fast‐responding, versatile, and accurate gas injection systems in order to initiate and modulate the plasma density. We describe the gas injection control system (GICS), which regulates the gas injected into the torus of Princeton’s Tokamak Fusion Test Reactor (TFTR). Synchronized with each TFTR discharge, a PDP 11/23 microcomputer provides real‐time control for one to six fast injection valves, each allocated to feedback or open loop operation. Up to four feedback sources, including torus pressure gauges and plasma density measurements, are checked once each cycle for 1000 cycles; the cycle duration can be set to any multiple of 2 ms up to 16 ms. Detection of various fault conditions can cause automatic shutdown or modification of GICS operation. Data is archived after each TFTR discharge, and subsequently used for particle fueling studies and analysis of system drifts. A steady state mode of operation is used for vacuum vessel discharge cleaning. The system also provides for valve calibration and torus pumping speed measurements.

Steady-state performance of PWM inverter drives

It is predicted that, with the increasing availability of digital computing facilities, computer-aided design will play an increasingly important and cost-effective role in the design of variable-speed drives (VSD). This paper describes the detailed development of an extremely versatile PWM VSD package which has the potential for investigating a wide range of steady-state operational modes. The capabilities of the package are demonstrated, using a number of examples of typical operational modes of PWM inverter-machine systems, which serve to highlight the potential uses of the package. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter-drive system.

COMPUTATION OF STEADY-STATE OPERATING CONDITIONS OF TURBOALTERNATORS TAKING SATURATION INTO ACCOUNT

ABSTRACT This paper describes a method for the determination of magnetic field distribution in the air gap of a saturated turboalternator at steady-state operating conditions. The magnetic field distribution along one pole-pitch is analyzed and used for direct determination of the machine characteristics. The generator steady-state load characteristics are determined without using the concept of synchronous reactances. These reactances may be determined as results of the main procedure. The associated numerical method is described and realized on a digital computer Owing to its high accuracy and relative simplicity, the method described provides efficient means for the determination of the steady-state modes of operation of a turboalternator at the design stage. Simulation and experimental results are given

A rate theory of swelling induced by helium and displacement damage in fusion reactor structural materials

The combination of helium gas and displacement damage production in fusion reactor structural materials is detrimental to their integrity. A simplified rate theory is presented to explain existing fission reactor swelling data. The theory is applied also to fusion reactor conditions in both the steady-state and pulsed modes of operation. In this time-dependent rate theory both the nucleation and growth phases of cavities are treated. The smooth transition from nucleation to growth is achieved by developing an approximate equation for the time-dependent nucleation current. This current decreases sharply after the formation of the majority of cavities. Cavity growth then controls the overall swelling. It is shown that the dynamic dispersion of helium atoms into the matrix by radiation (re-solution) plays an important role at low temperature. Radiation pulsing of the tokamak-type results in a higher effective mobility for helium. This is attributed to the annealing of helium vacancy traps in between pulses. Overall lower cavity concentrations are therefore expected in this particular situation.

Oscillations and control features in glycolysis: numerical analysis of a comprehensive model.

We present an analysis of glycolysis based on experimental findings and an interpretation based on concepts of efficiency, resonance response, and control features available in highly nonlinear reaction kinetics. We begin with a model for the glycolytic mechanism that is comprehensive, includes a large number of known activations and inhibitions of enzymes by metabolites, and couples the phosphofructokinase (PFKase) and the pyruvate kinase (PKase) reactions. The PFKase and PKase reactions and the coupling between them are modeled according to experimental information, but we do not attempt to model the glyceraldehyde-3-phosphate dehydrogenase-3-phosphoglycerate kinase reaction. We use experimental data to obtain the best estimates for the kinetic parameters and test the model by calculating the concentration variations of the intermediate metabolites. We confirm oscillatory behavior and calculate the ATP/ADP ratio and the free-energy dissipation for an extended range of the kinetic parameters as a function of the driving force for the glycolytic pathway, a measure of which is the total adenine nucleotide concentration. We find agreement of the calculated results with experimental findings except for the insufficiently represented reactions. Our model shows that the average ATP/ADP ratio is increased and the average free-energy dissipation is decreased in an oscillatory compared with a steady state mode of operation. The average values of the ATP/ADP ratio and of the free energy dissipation change abruptly past the onset of sustained oscillations.

STARFIRE, a commercial tokamak power plant design

STARFIRE is a design for a conceptual commercial tokamak electrical power plant based on the deuterium/tritium/lithium fuel cycle. In addition to the goal of being technologically credible, the design incorporates safety and environmental considerations. STARFIRE is considered to be the tenth in a series of commercial fusion power plants. STARFIRE has a 7-m major radius reactor producing 1200 MW of net electrical power from 4000 MW of thermal power, with an average neutron wall load of 3.6 MW/m 2. The aspect ratio is 3.6 and a D-shaped plasma with a height-to-width ratio of 1.6 and average toroidal beta of 0.067 is used. The maximum magnetic field is 11T. Availability goals have been set at 85% for the reactor and 75% for the complete plant including the reactor. The major features for STARFIRE include a steady-state operating mode based on a continuous rf lower-hybrid current drive and auxiliary heating, solid tritium breeder material, pressurized water cooling, limiter/vacuum for impurity control, most superconducting EF coils outside the TF superconducting coils, fully remote maintenance, and a low-activation shield.

Master Control System for the central receiver solar power plant

A Master Control System (MCS) is described in terms of its operation and evaluation role for the nation's first major solar thermal electric power venture. The specific application referred to is the 10 MWe solar thermal central receiver Pilot Plant being built at Barstow, California. Five subsystems have been defined for the Pilot Plant version of this concept. They are designated as the Collector Subsystem (CS; i.e., heliostats), the Receiver Subsystem (RS; i.e., absorber and tower), the Thermal Storage Subsystem (TSS; i.e., tank and fluid), the Electrical Power Generation Subsystem (EPGS; i.e., turbine, generator, and associated balance of plant), and the MCS. First, a brief history is provided of the Pilot Plant development which led to the adoption of the MCS configuration. Then, an overview of this configuration is presented, followed by a general discussion of subsystem control considerations. Next, functions of three primary MCS elements are described, followed by general definitions of associated software and steady-state operation modes. Finally, a summary and conclusions are presented pertaining to the overall MCS configuration and present/planned developments.

NMR images by the multiple sensitive point method: application to larger biological systems

With a view to applying the method to problems in medicine and biology, an NMR imaging system capable of examining objects to order 10 cm in size has been constructed and first examples of images obtained with this instrument are presented. Features of this system are its successful exploitation of a fast multisensitive point method, the use of a steady-state free precession NMR mode of operation to optimize sensitivity and the generation of truly three-dimensional images.

On estimating the performance of automatic optimization systems in steady-state operating modes

Using the example of the investigation of a relay difference automatic optimization system, the author discusses and approves a new procedure for estimating the performance of sample-data systems having constant-area control pulses in steady-state operating modes.

The use of difference equations for the investigation of the steady-state operating mode of a gradient extremal system having an inertial object

The use of difference equations for the investigation of the steady-state operating mode of a gradient extremal system having an inertial object

Performance characteristics of pulsed phototransistor structures under various conditions

Measurements are made on linear and area arrays of phototransistors operating in the steady-state and pulsed (integration) modes of operation. Description of the experimental setup is given. A simplified analysis of the pulsed mode of operation is presented. The heart of the study is concerned with measuring parameters critical to pulsed mode performance. The effects of temperature, readout voltage level, integration time, and device configuration on sensor operation are depicted. Increased leakage with temperature is found to change the proportionality constant between output and integration time. Both the saturation level and the dark response show a direct dependence on readout voltage. Varying the frame time (i.e., the integration time) is shown to be equivalent to changing the aperture setting of the optical system used to focus images onto the sensor. The relation between the steady-state photocurrent and the pulsed mode output has been established and is in agreement with analyses of the integration mode. The effects of collector pulse amplitude and temperature were found to match the relations derived from an extended analysis. An integration rate is extrapolated from the data. Images produced by a mechanically scanned line sensor and an area array are shown.

Method of Multiple Reference Frames Applied to the Analysis of Symmetrical Induction Machinery

A method of analyzing the constant-speed performance of a symmetrical induction machine with applied stator phase voltages of any periodic form is presented. Symmetrical components are not used in this analysis. Instead, it is shown that by employing a series of reference frames, dc circuit theory may be used to determine the performance of induction machines. Since phasor and complex impedance concepts are not incorporated, the theory of multiple reference frames permits a convenient and simple method of analyzing steady-state modes of unbalanced or nonsinusoidal operation which have heretofore been limited to analysis by the method of symmetrical components. Also, this method establishes a rigorous approach to the analysis of constant-speed electrical transients of induction machinery.