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Technical Paper

Excitation Strategies for a Wound Rotor Synchronous Machine Drive

2014-09-16
2014-01-2138
In this research, excitation strategies for a salient-pole wound rotor synchronous machine are explored using a magnetic equivalent circuit model that includes core loss. It is shown that the excitation obtained is considerably different than would be obtained using traditional qd-based models. However, through evaluation of the resulting ‘optimal’ excitation, a relatively straightforward field-oriented type control is developed that is consistent with a desire for efficiency yet control simplicity. Validation is achieved through hardware experiment. The usefulness/applicability of the simplified control to variable speed applications is then considered.
Technical Paper

Digital Electrohydraulic Control for Constant-Deceleration Emergency Braking

2002-03-19
2002-01-1464
A digital electrohydraulic control system for emergency braking is designed, simulated, built, and tested. First, a dynamic model of the system was developed with Matlab Simulink. The parameters are obtained experimentally. Feedback gains are obtained by tuning the model. Then, the digital controller is implemented on an industrial personal computer programmed in Turbo C++. The control strategy is an improved digital version of the PID control. The key element in the control of the brake was an electro-hydraulic proportional pressure valve. Experiments show that the control system successfully realizes constant-deceleration emergency brake within mine safety rules. The same hardware can be reprogrammed for various hoists, different load conditions, and different control objectives. Although the test was conducted on a mine hoist brake, the control system can be applied to most vehicles.
Technical Paper

A Detailed Synchronous Machine Model

2002-10-29
2002-01-3205
A synchronous machine model is set forth that simultaneously incorporates magnetizing path saturation, leakage saturation, and transfer function representations of the rotor circuits. A parameter identification procedure consisting of voltage step tests as well as standstill frequency response tests is described. The model's predictions are validated using the Naval Combat Survivability Generation and Propulsion test bed.
Journal Article

The Utility of Wide-Bandwidth Emulation to Evaluate Aircraft Power System Performance

2016-09-20
2016-01-1982
The cost and complexity of aircraft power systems limit the number of integrated system evaluations that can be performed in hardware. As a result, evaluations are often performed using emulators to mimic components or subsystems. As an example, aircraft generation systems are often tested using an emulator that consists of a bank of resistors that are switched to represent the power draw of one or more actuators. In this research, consideration is given to modern wide bandwidth emulators (WBEs) that use power electronics and digital controls to obtain wide bandwidth control of power, current, or voltage. Specifically, this paper first looks at how well a WBE can emulate the impedance of a load when coupled to a real-time model. Capturing the impedance of loads and sources is important for accurately assessing the small-signal stability of a system.
Technical Paper

THE EFFECT OF PROPLETS AND BI-BLADES ON THE PERFORMANCE AND NOISE OF PROPELLERS

1981-02-01
810600
A analytical technique for predicting the aerodynamic performance of propellers with tip devices (proplets) using vortex lattice method shows that the ideal efficiency of a fixed diameter propeller can be improved by 1-5%. By suitable orientation and sweep of the proplet, the noise analysis method presented predicts that propellers with tip devices will have approximately the same noise as propellers without tip devices. Therefore proplets can be added to a fixed diameter propeller to improve the efficiency with no increase in noise or the noise may be reduced by decreasing the diameter with no loss in aerodynamic efficiency.
Technical Paper

The Analysis of Counter-Rotating Propeller Systems

1985-04-01
850869
A vortex lattice method for the aerodynamic analysis of counter-rotation propellers was developed. This model along with an unsteady Sears analysis for correcting the quasi-steady loadings that are obtained from the vortex lattice model were used to predict the performance of counter-rotation propeller systems. The method developed shows good correlation with experimental results. The investigation into the unsteady loadings on each of the propellers indicates that significant variations in loading occur due to the unsteady flow and due to the propeller blade passage. These variations were found to be as high as 17 percent of the mean value. The parametric studies that were performed indicate that reducing the rear propeller's diameter or rotational speed results in a loss of efficiency.
Technical Paper

A Dynamic Two-Phase Component Model Library for High Heat Flux Applications

2019-03-19
2019-01-1386
Pumped two-phase systems using mini or microchannel heat sink evaporators are prime candidates for high heat flux applications due to relatively low pumping power requirements and efficient heat removal in compact designs. A number of challenges exist in the implementation of these systems including: ensuring subcooled liquid to the pump to avoid cavitation, avoiding dry out conditions in heat exchangers that can lead to failures of the components under cooling, and avoiding flow instabilities that can damage components in an integrated system. To reduce risk and cost, modeling and simulation can be employed in the design and development of these complex systems, but such modeling must include the relevant behavior necessary to capture the above dynamic effects.
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