Ultra High Voltage Switch for Bidirectional DC-DC Converter Driving Dielectric Elastomer Actuator

Specific applications, such as dielectric elastomer actuators (DEAs) or electroactive polymers, require to switch voltage levels exceeding the ratings of existing semiconductor devices. In low power application, reversible flyback are widely used to supply DEAs. Lowering the parallel parasitic capacitance of the high voltage switch is important to improve the energy transfer, while it becomes mandatory to increase the output voltage of flyback above 2.5 kV. In this paper, a Pulsed Transformer Gate Driver (PTGD) is used to drive series-connected MOSFET and therefore push the limits from 4.5 kV up to 16 kV. At these high voltage levels, the structure reveals a drastic voltage unbalance related to the transformer interwinding parasitic capacitance. The compensation method proposed to achieve voltage balance only adds few passive components and reduces significantly the additional parallel capacitance of the switch compared to common load side voltage balancing methods. Finally and as proof of concept, a half-bridge bidirectional converter was designed from this switch technology and drove an actual dielectric elastomer actuator at 16 kV

Możliwość ograniczenia uszkodzeń owoców przez owocnicę jabłkową (Hoplocampa testudinea Klug) w ekologicznym sadzie jabłoniowym

In 2010-2012, in the Experimental Ecological Orchard of the Research Institute of Horticulture in Skierniewice, a study was conducted on the possibility of reducing populations of the apple sawfly (Hoplocampa testudinea Klug) using biological formulations. The tests involved treatments with an extract from the wood of Quassia amara (4 kg/ha) and an extract from the seeds of Azadirachta indica in the form of a ready-made formulation NeemAzal-T/S at a rate of 2.5 l/ha with the addition of a 0.3% sugar solution. A single treatment was performed in the first two years, and two treatments in the last year. The effectiveness of the protection of fruitlets against damage varied and for the Q. amara extract was from 8.3% (one treatment) to 86.1% (two treatments), and for the NeemAzal-T/S formulation from 4.8% (one treatment) to 44.3% (two treatments). In relation to the damage to fruits, the efficacy of the treatments also varied, ranging from 10.3% to 60% for the Q. amara extract, and from 0% to 46.7% for NeemAzal-T/S.W latach 2010-2012 w Ekologicznym Sadzie Doświadczalnym Instytutu Ogrodnictwa wykonano badania nad możliwością ograniczenia populacji owocnicy jabłkowej (Hoplocampa testudinea Klug) przy pomocy preparatów biologicznych. Badano wywar z drewna gorzkli właściwej (Quassia amara) (4 kg/ha) oraz ekstrakt z nasion miodli indyjskiej (Azadirachta indica) w postaci gotowego preparatu NeemAzal-T/S w dawce 2,5 l/ha z dodatkiem 0,3% roztworu cukru. W pierwszych dwu latach wykonano 1 zabieg, a w ostatnim roku 2 zabiegi. Efektywność zabezpieczenia zawiązków owocowych przed uszkodzeniami była zróżnicowana i wyniosła dla wywaru z Quassia amara od 8,3% (1 zabieg) do 86,1% (dwa zabiegi), a preparatu Nee-mAzal-T/S od 4,8% (1 zabieg) do 44,3% (2 zabiegi). W stosunku do uszkodzeń owoców efektywność zabiegów również była zróżnicowana i wyniosła od 10,3% do 60% dla wywaru z Quassia amara oraz od 0% do 46,7% dla preparatu NeemAzal-T/S

Reakcja roslinnosci drzewiastej pasow przydroznych Krakowa na zasolenie i pH gleby

W wyniku szczegółowych obserwacji stanu zachowania roślin drzewiastych (klonu pospolitego (Acer platanoides), klonu jaworu (Acer pseudoplatanus), jesionu wyniosłego (Fraxinus excelsior) oraz lip (Tilia cordata, T. x europaea) w pasach drogowych Krakowa stwierdzono masowe występowanie u większości badanych drzew podobnych objawów uszkodzeń, w postaci nekrotycznego zbrunatnienia blaszek liściowych, obejmującego 10-80% powierzchni blaszki oraz przedwczesnego opadania liści, niezależnie od rodzaju i gatunku. Ponadto obserwowano zamieranie pędów, zwłaszcza w środkowej części koron. Susz obejmował niejednokrotnie 80-90% konarów i gałęzi. Często w miejsce przedwcześnie opadłych liści rozwijały się nowe, jasnozielone, o zredukowanej powierzchni blaszki. Analiza fitopatologiczna i entomologiczna badanych próbek drzew wykluczyła działanie organizmów żywych. Wyniki pomiarów próbek gleb, pobranych spod chorych drzew, wykazały nadmierne jej zasolenie - od 0,5 do 0,8 mS·cm⁻¹. Stwierdzono również występowanie podwyższonego alkalicznego odczynu podłoża, przyjmującego wartość w zakresie pH 8-10. Biorąc pod uwagę całokształt wyników obserwacji sugeruje się, że masowe uszkodzenia drzew w pasach przydrożnych centrum Krakowa są spowodowane zniszczeniem gleby jako środowiska wzrostu korzeni drzew, w szczególności nadmiernym jej zasoleniem i alkalizacją.As a result of the thorough observation of the performance of tree plants (Acer platanoides, Acer pseudoplatanus, Fraxinus excelsior and Tilia cordata, T. x europaea) along the communication routes of Kraków a significant demonstration of similar damage was detected. In particular, it took the forms of necrotic browning of leaves, this effect concerned from 10 to 80 % of the leaves or the premature falling of leaves regardless of the genus or species. In addition dying of branches was observed, in particular in the middle part of the tree crones. The dryness frequently concerned as much as 80-90% of twigs and branches. Often in the place of fallen leaves new ones were formed, however with a smaller surface of the blade leaf (20-30% decrease of leaf area). The phytopathological and entomological analysis of the examined tree samples excluded an influence of any living organisms. The results of the analysis of the soil samples collected from under the damaged trees showed that it was high salinated, from 0.5 to 0.8 mS·cm⁻¹. It was also determined that there is a higher alkaic pH factor of the ground (about 8-10). Taking into consideration the entire results of the observation it is suggested that the massive damages to the trees along the communication routes of the centre of Kraków are caused by the destruction of soil as a environment of root growth, in particular its excessive salinity and alkalisation

Multi-level high-voltage power supply for dea application

In order to reap the benefits of Dielectric Elastomer Actuator (DEA) high energy density, the electronics powering the actuator should be as small as possible. Knowing that only a small fraction of the energy delivered to DEAs is effectively converted into mechanical energy, the power supply has to be highly efficient and bidirectional in order to recover the unused energy, which requires more volume. Furthermore, DEA applications call for high voltage (up to 18kV for a 200um film), but as the voltage increases, so does the volume. In addition, there are no MOS transistors rated above 4.5kV, which limits our options. Since these goals are contradictory, we need to demonstrate the feasibility of DEA integration and find its limits. Therefore we present a prototype of Multi-Level Converter designed for DEA, which is a bidirectional structure that has proven to be especially effective in the power electronics field. A Multi-Level Converter overcomes the voltage limitation by equally distributing the desired voltage among levels; because the voltage of each level is sufficiently low, smaller available parts can now be used. Our prototype includes 20 levels of 1kV each. A numerical study of this topology has demonstrated that the efficiency is above 90%. Upcoming experimental works will discuss the advantages and the drawbacks of such Multi-Level Converters. Finally, the volume of the DEA will be compared with the volume of electronics

High voltage switch for compact bidirectional dc-dc converter driving dielectric electroactive polymer actuators

Driving DEAs requires time-varying high voltage power supplies, up to 18kV for 200um polymer layers. HV amplifiers are commonly used but bulky and expensive. Designing embedded actuators requires compact and efficient powersupplies. Furthermore, only a little part of the electrical energy delivered to the DEA is converted to mechanical energy. The major part is stored in the capacitance of the actuator and needs to be recollected to maximise the system's efficiency. Low cost integrated bidirectional DC-DC converters (ex. Flyback) have been proven reliable to drive DEAs at voltages up to 2,5kV. To design a reversible converter with an output voltage up to 18kV, a high voltage switch is needed. Yet, the maximum breakdown voltage for a MOSFET with current ratings inferior to 200mA is 4,5kV. Our simulation and experimental work demonstrate a reliable driving circuit for triggering two series connected MOSFETs. A wide voltage switching range is achieved (0 to 8kV) with a 200mA current rating. Using the Transformer Gate Driver topology, galvanic insulation and synchronisation of each gate driver is ensured. To gain an equal distribution of the bus voltage over the MOSFETs, mastering the parasitic capacitances is mandatory. A design method has been developed to compensate these parasites and ensure the reliability of the device. The architecture of the high voltage switch is N-scalable and a switching range from 0 to 18kV could be achieved when stacking five MOSFETs in series

Mineral composition of fruits and leaves of San Andreas® everbearing strawberry in soilless cultivation

Technological progress in the cultivation of horticultural and fruit plants makes the use of soil becoming less and less important. Growing plants in soilless substrates is becoming more and more common. The aim of the study was to determine the variability of the mineral composition of fruits and leaves of everbearing strawberry of the San Andreas® variety in soilless cultivation. Research was carried out at the experimental plantation of Polski Instytut Truskawki Sp. z o.o. (geographical coordinates: 50°02′11″N and 19°81′19″E). The cultivation of everbearing strawberry of the San Andreas® variety was carried out in a gutter system under covers in coconut substrate. The stability of the chemical composition of strawberry leaves and fruits depends on fertilisation, weather factors, and the quality of water used for fertigation. Despite maintaining the content of nutrient in the rhizosphere at the level recommended for organic substrates, low potassium and calcium content and high magnesium content in strawberry leaves were determined. Among the macroelements analysed in strawberry leaves, the lowest variation coefficient values were found for nitrogen, magnesium and calcium, and in fruits – for nitrogen, phosphorus, and magnesium. The highest variation coefficients were obtained for phosphorus and sodium in strawberry leaves, and for sulphur and sodium in strawberry fruits. Variation coefficient values of copper, zinc, and manganese content in leaves were similar. The content of iron in leaves and zinc in fruits was characterised by the lowest variation coefficients during the growing period