Design and Analysis of High-Speed Induction Machines for Submerged Cryogenic Pumps

This paper discusses the electromagnetic design and loss analysis of a 15 kW, 13500 rpm induction machine for a single-stage submerged cryogenic pump. The study starts from an existing machine driving a three-stage cryogenic pump, rated 7.5 kW at 7300 rpm. The new motor design is approached by increasing the rotating speed of the reference machine at fixed outer diameter, aiming at an optimum between efficiency and power factor. Experimental investigations are carried out on the reference machine to analyze its thermal behavior. The results allow to obtain initial values for the electrical loadability of cryogenic induction machines. The electromagnetic design of the high-speed motor is successfully carried out with the help of detailed numerical simulations, particularly devoted to a precise analysis of the losses active in the machine. Special care is given to the iron losses, estimated with two different approaches

Losses Analysis of Induction Motors under Ambient and Cryogenic Conditions

Cryogenic induction machines have been re-emerging as a potential solution to increase the current power density for challenging specific power applications. Compared with an ambient temperature operation, cryogenic conditions allow higher power density and increased efficiency due to the decrease of electric resistivity of conducting materials and increased cooling capability. This work focuses on the losses analysis of induction machines immersed in liquid nitrogen. Under ambient and cryogenic conditions, experimental tests are performed and presented for two induction machines, a 90 W 40 V induction machine, and a 550 W 400 V induction machine, to evaluate the mechanical, iron and residual losses, and the change of their equivalent circuit parameters

Analysis of JPEG2000 quality in photogrammetric applications

The recording of a large amount of data required for high resolution digital images is a common problem in digital photogrammetric applications, where several digital images occur for each block. One solution could be, that of using compression algorithms (JPEG, ECW and now JPEG 2000) that allow an extremely large amount of image data to be compressed into a relatively small amount of data. Even the most recent compressor algorithms declare a lossless compression ratio, the most efficient are lossy (the compression of the image data decreases the geometric and radiometric quality information). The effects of the JPEG2000 compression algorithm on the geometric quality of compressed images is studied in this analisis. This evaluation has been made for the case of automatic and manual stereo plotting. In the first, an automatic Least Square Matching (LSM) collimation procedure was applied to the image of a calibrated grid (acquired with a DTP scanner at 700 dpi) at different compression ratios, and to the uncompressed grid image. The difference between the compressed and uncompressed image coordinates was evaluated. In the second case, a stereoscopic model made up of two aerial photos of the town of Pavia was oriented and used (coupled to several ratio compressed images), to extract the 3D coordinate values of a point set, and to evaluate the differences between the compressed and uncompressed images. The results were compared with those previously obtained by the authors with the JPEG and ECW algorithm

A new procedure for the automatic production of true orthophotos

The digital orthophoto is a cheap and efficient product that is used to represent the correct shape of any 3D object, in photographic form, by means of its orthogonal projection onto a predefined plane. In mapping applications, if the zone to be represented contains urban areas, the problem becomes more complex because there are many discontinuity lines (breaklines) and hidden areas: this requires a more sophisticated orthoprojection procedure. The lack of information corresponding to the hidden areas is avoided if use is made of all the images (“multi-image ” procedure) available in the photogrammetric block. More rigorous interpolation methods should be used to take into account the problem of discontinuities. Stereoplotting of the many break-lines (a difficult and expensive procedure) or, even, a DTM formed by a large amount of points (the so-called “dense DTM”, or DDTM) gives the necessary data. For this purpose, the authors have recently conceived and implemented an original software composed of the following modules: AccOrtho (=ACCurate ORTHOphoto), to produce rigorous digital orthophotos starting from multiple images and a DDTM; GeneDDTM (GENEration of a DDTM), which is able to build a dense DTM (suitable for AccOrtho) from a 3D digital map, using sophisticated interpolation techniques. This paper describes the two software structures in detail and a practical application of both the programmes for a relevant mapping project, which is still in progress: a true orthophoto of the whole town of Turin, in 1:2.000 scale. 1