Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Homopolar motor with high temperature superconductor field windings

Abstract: A superconducting field winding, assembled with discrete coils wound with bismuth 2223 high temperature superconducting (HTS) wire, has been successfully operated in an electric homopolar motor designed and built by the Naval Surface Warfare Center. The motor's field winding is composed of two HTS coils fabricated by American Superconductor Corporation and two HTS coils fabricated by Intermagnetics General Corporation. These field winding coils were produced for the Navy under contracts with the Naval Research Center. At a HTS field winding operating temperature of 4.2 K, the motor produced 125 kW (167 hp) of output power. At a temperature of 28 K the motor power developed was 91 kW (122 hp). In comparison to other motor types, a homopolar motor provides an ideal operating environment for a superconducting magnet. The design, construction, and operating characteristics of this machine are described. Information describing the HTS field winding and its superconducting capabilities is presented along with that for the laboratory test facility used to measure the performance of the machine. Motor measured performance results and those predicted by computer simulation are compared and presented. An assessment of the state of the engineering development of HTS superconductors for magnet applications and recommendations for future development are made.

Review Article: Thermoelectric Technology Assessment: Application to Air Conditioning and Refrigeration

Abstract: A combination of factors—notably environmental concerns about global warming and ozone depletion due to refrigerants and the increasing demand for electronics and optoelectronic cooling—led to renewed activity in alternative cooling technologies. Currently, thermoelectric cooling is considered a popular cooling technology. This paper provides a critical review of thermoelectric technology and assesses its potential applications in air conditioning and refrigeration. The first part of this paper is devoted to the basic concept of thermoelectrics, with an overview of current thermoelectric materials and devices. The second part is a general overview of the applications of thermoelectric technology, with an emphasis on those related to air conditioning and refrigeration.

A Wavelet Filtering Scheme for Noise and Vibration Reduction in High-frequency Signal Injection-Based Sensorless Control of PMSM at Low Speed

Abstract: This paper presents a technique for noise and vibration reduction in low-speed sensorless control algorithm of surface mounted permanent magnet synchronous machines (SM-PMSM). The signal processing involved in high-frequency-based sensorless control algorithms has a significant effect on the vibration and noise accompanying such algorithms. Therefore, a wavelet filtering approach is proposed. This wavelet filter is capable of extracting the position information even at low values of injection voltage amplitude where conventional filters fail to extract the information. This leads to a reduction in the machine's noise and vibration. Furthermore, an optimization using hardware-in-the-loop method based on genetic algorithms was implemented in real time to obtain the optimum value of the injected voltages amplitude and frequency causing the least possible vibration with acceptable position estimation accuracy. Consequently, a significant reduction in vibration and noise was achieved. The proposed techniques were implemented on a 2-hp SM-PMSM motor both experimentally and through simulations. Comparisons between numerical and test results confirm the validity of the proposed techniques.

One-step fixed-lag smoothers for Markovian switching systems

Abstract: Suboptimal approaches to the one-step fixed-lag smoothing problem for Markovian switching systems are examined in this paper. Two algorithms are developed for obtaining one-step fixed-lag smoothed estimates. The first algorithm is an approximation that considers the models over the two most recent sampling periods, while the second one considers only the models over the most recent sampling period. Simulation results are presented to compare the performances of these smoothing algorithms.