The performance of the brushless doubly-fed machine (BDFM) is analysed using a perphase equivalent circuit. An expression for the rating of the machine as a function of magnetic and electric loadings is developed, and the rating is compared to those of the doubly-fed induction machine and cascaded induction machines. As the magnetic field in a BDFM is complex, the magnetic loading is considered in detail and a new generalised loading is derived. The BDFM suffers a reduction rating of about one-quarter in comparison to comparable conventional machines, arising from penalties in magnetic and electric loadings consequent on the presence of two stator to rotor couplings. The handling of reactive power has an important effect on the machine performance and this point is illustrated with experimental results from a frame size 180 BDFM. The tests were carried out at modest flux densities to avoid the effects of saturation, but the implications of saturation are considered.

This paper discusses the design of the Brushless , Doubly-Fed (Induction) Machine (BDFM). It is focused on the evaluation of the electric and magnetic loadings of the machine and their allocation to two stator windings. A

This paper discusses the inverter ratings of BrushIt can be shown (Appendix A) that for an ideal BDFM less Doubly-Fed Machine (BDFM) adjustable speed drive (ASD) operating at constant torque the control winding rating, S2, is or generator (ASG) systems. Based on the per phase equivalent related to the machine rating, Smn, by circuit model, the ratings of the two inverters in a bidirectional converter are evaluated individually. An approach to minimise the total inverter rating is presented, taking into account power = 2 factor constraints of the power grid. The effects of speed S m-f2 7-3 deviation and control winding excitation on the inverter ratings I i 3 are discussed. Predictions of inverter ratings are presented with Equation (3) has been conventionally used to determnine the experimental verification. A design example is also provided in covreraig3] 4.Hwe,asaeulofteeiwhich the total inverter rating is minimised for a practical BDFM tacnerte ragntiing [3],u[].aHoevras an resulkoate rnutnesis-a based ASG system. tne,mgeiigidcacsadlaaeidcacsi Index Terms-BDFM, inverter rating, ASD, ASG practical BDFM, calculations based on an ideal BDFM need to be modified for a full evaluation of the converter rating.

This paper presents an iterative method for the stator design optimisation of the Brushless Doubly-Fed Machine (BDFM) based on a per phase equivalent circuit model and a tabu search method. Maximum power output from a frame size 180 BDFM is obtained by optimally dividing the overall electric and magnetic loadings between the stator windings. Parameters of the per phase equivalent circuit are calculated according to geometric dimensions for different designs. The relationship between BDFM power output and the control winding excitation is discussed. Comparisons between the original and optimised stator designs are given with experimental verifications.

the tip surface of the VA-CNF [3,4]. The double-gated We report micro-fabricated double-gated vertically aligned carbon nano fiber array acts as a field ionizer when the CNF carbon nanofiber (CNF) arrays for ionization of gasses in low tip is biased to have the highest potential relative to the gates power portable mass spectrometers. The devices can be and the collector as shown in Figure 2. The potential barrier operated in one of two modes -electron impact ionization experienced by tunneling electron is shown in Figure 3 and it (ElI) or field ionization (FI). When operated as electron can be approximated as a trapezoidal barrier. Using the WKB impact ionizer, power dissipation was reduced from >1 W approximation, the ion current is expressed as typical of thermionic emission based electron impact ionizers

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The low-temperature synthesis (450–560 °C) of single-walled carbon nanotubes (SWCNTs) on a triple-layered catalyst, Al/Fe/Mo, was performed using aromatic hydrocarbon radicals which were produced from the pyrolysis of C2H2. Two approaches were used; in the first, these hydrocarbon radicals were produced using a high-temperature heater (830 °C), but the substrate where the SWCNTs were grown was placed on a thermal insulator above it such that the substrate was at a much lower temperature. In the second approach, a heated nozzle system operating at 830 °C was used to introduce the hydrocarbon radicals onto the substrate which was located a few centimetres below it. Both these approaches rely on the thermal dissociation and recombination of C2H2 for the formation of complex high-order radicals, i.e. C6H9, C5H9, C6H13, whose presence was confirmed by in situ mass spectroscopy. The density of SWCNTs deposited could be correlated directly with the concentration of these precursors.