Magni Ducatus Finlandiae Russiae partim, partim Sueciae subjecti Sinus item Bothnici ac Finnici nova et accurata delinaetio - [Yleisnäkymä - Overview]

S.l. : Georg. Aug. Vind ca 1750

Developing of AC magnetometer and investigation of magnetic properties of LSMO

In this work AC magnetometer was developed and primary test measurements were performed for temperature range from 77 K up to 350 K in frequency range from 1 kHz up to 20 kHz. In the course of the present work dependencies of magnetization on temperature for Lao7Sr03Mni _yFeyO3 with y = 0.15, 0.20, 0.25 were obtained in DC magnetic field using SQUID magnetometer and in AC magnetic field using the developed AC magnetometer. Lai.XSrXMnO3 (LSMO) compounds belong to the class of Mn perovskites, which demonstrate very high degree of spin polarization. These materials are of great importance for nowadays applications in spintronics, where spin polarized electron transport is used. Spin glass like behavior was found as a characteristic feature of these solid solutions with the freezing temperature in the range 65 — 210 K.

Active du/dt Filtering for Variable-Speed AC Drives

An oscillating overvoltage has become a common phenomenon at the motor terminal in inverter-fed variable-speed drives. The problem has emerged since modern insulated gate bipolar transistors have become the standard choice as the power switch component in lowvoltage frequency converter drives. Theovervoltage phenomenon is a consequence of the pulse shape of inverter output voltage and impedance mismatches between the inverter, motor cable, and motor. The overvoltages are harmful to the electric motor, and may cause, for instance, insulation failure in the motor. Several methods have been developed to mitigate the problem. However, most of them are based on filtering with lossy passive components, the drawbacks of which are typically their cost and size. In this doctoral dissertation, application of a new active du/dt filtering method based on a low-loss LC circuit and active control to eliminate the motor overvoltages is discussed. The main benefits of the method are the controllability of the output voltage du/dt within certain limits, considerably smaller inductances in the filter circuit resulting in a smaller physical component size, and excellent filtering performance when compared with typical traditional du/dt filtering solutions. Moreover, no additional components are required, since the active control of the filter circuit takes place in the process of the upper-level PWM modulation using the same power switches as the inverter output stage. Further, the active du/dt method will benefit from the development of semiconductor power switch modules, as new technologies and materials emerge, because the method requires additional switching in the output stage of the inverter and generation of narrow voltage pulses. Since additional switching is required in the output stage, additional losses are generated in the inverter as a result of the application of the method. Considerations on the application of the active du/dt filtering method in electric drives are presented together with experimental data in order to verify the potential of the method.

De usu symbolorum circa geometrica theoremata ac problemata demonstranda

Invocatio: D.D.

De caussis puritatis ac floris perennis lingvae Arabicae

Invocatio: [hepreaa].

De differentiis ac principiis actionum moralium

Painovuosi nimekkeestä.

An principia moralia ex consensu ac moribus gentium sint repetenda?

Invocatio: I.N.D.O.M.

Magni ducatus Finlandiae Russiae partim, partim Sueciae subjecti; Sinus item Bothnici ac Finnici nova et accurata delineatio. Calamo et sumtibus Tobiae Conradi Lotter, Geogr. Aug. Vind. Cum Priv. S. Vic. in part. Rheni Suev. et Franc. juris.

Mittakaava [N. 1:1800000]. - Ulkoasu: 1 kartta : vär. ; 48,5 x 56,7 cm, lehti 50,2 x 58,5 cm.

Magni ducatus Finlandiae Russiae partim, partim Sueciae subjecti; Sinus item Bothnici ac Finnici nova et accurata delineatio. Calamo et sumtibus Matthaei Seutteri, S.C.M. Geogr. Aug. Vind. Cum Priv. S. Vic. in part. Rheni Suev. et Franc. juris

Mittakaava: [N. 1:1800000]. - Ulkoasu: 1 kartta : vär. ; 49 x 57,8 cm, lehti 53,5 x 64,3 cm.