1,720,972 research outputs found
Comparison of DBI and ZSI supply for PM brushless DC drives powered by fuel cell
No full textNominal voltage of the traction motors being used in electric vehicles is typically higher than the voltage generated by the onboard DC sources. Thus, motors of AC type require boost as well as inversion of available DC voltage. This can be done either by a DC-DC boosted inverter (DBI) or by the recently introduced Z-source inverter (ZSI). Since drives with PM brushless DC (BLDC) motor are largely utilized in the traction of light electric vehicles, it is of interest to carry out a comparative analysis of the two supplies when feeding such kind of motor. In this paper, DBI and ZSI supplies are designed for the study case of an electric city scooter propelled by a PM BLDC motor and powered by a fuel cell with the assistance of a battery. Ratings of the transistors and sizes of the passive components for the two supplies are determined as a function of the fraction of the fuel cell power to the nominal power of the traction motor. The design results are discussed
Brushless DC drive operation during phase commutation under various switching patterns
No full textThe paper deals with the operation of a brushless DC drive during the phase commutation. At first, the various switching patterns that can be used to command the inverter are identified. It is demonstrated that the switching patterns are a combination of two basic commutation modes. For each mode, the current transients during the phase commutation are determined as well as two significant commutation-related quantities, namely the decay angle of the current in the outgoing phase and the maximum current excursion in the non-commutating phase. The results obtained for the two modes are then compared, showing that each switching pattern gives a brushless DC drive specific propertie
Power sizing of wireless power systems feeding in-motion electric vehicles at constant power
Full text linkThe paper is concerned with the wireless power (WP) systems feeding in-motion electric vehicles (EVs) and focuses on the power sizing of three key WP system components, namely the track coils, the pickup and the voltage supply. It is assumed that the track is made of lumped type with no overlapped coupling of the pickup, and that the track coils and the pickup are compensated for by series resonating capacitors. Power sizing equations are formulated for a WP system that is controlled in the way of transferring a constant power to EVs during their motion over a large part of the track coils. Due to the variation of the coupling between the pickup and a track coil, the transfer of a constant power requires the adjustment of the currents in the WP system, obtained by commanding the embedded power conversion units. Two solutions are examined: by one solution, the pickup side current is controlled at a proper value whilst the track side current is regulated at a constant level; by the other solution, the opposite occurs. Power sizing equations are expressed in terms of specifications and parameters of the WP system. The equations outline that the power sizing is higher for the components in the side where the current control is executed. At last, the case study of a WP system is examined, showing the convenience of the track-side control
Analytical Study vs. Speed Characteristics of PM Brushless DC Drives
No full textPM brushless DC (BLDC) motors should be fed by
square-wave currents synchronized with the back emfs to
develop a constant torque with the required value. In practice,
phase inductances and limited source voltage produce non ideal
square-wave currents and unbalanced phase currents during
commutations. Such phenomena affect the torque developed by
the PM BLDC drives by deviating its value from the requested
one and by giving rise to torque ripple. In this paper, an
analytical study of the torque characteristics, namely motor
torque and torque ripple, of PM BLDC drives is carried out as a
function of the motor speed and is supported by experimental
data. Torque characteristics are expressed in terms of a quantity
distinctive of the motor, thus giving a generalized formulation to
the results
Efficient Wireless Charging of Batteries with Controlled Temperature and Asymmetrical Coil Coupling
No full textPresent work considers the case of stationary Wireless charging (WC) of an Electric Vehicle (EV) with Li-ion batteries. Coil misalignment is quite common in WC and also charging of a Li-ion battery requires proper care. In this view asymmetrical coil system with suitable charging strategy has been proposed. At first analytical electro-thermal model of Lithium ion battery is developed to get preliminary behaviour and further analysed through 1D model in Finite Element Method based software to comment on heat distribution during charging. Evaluation of electrical parameters of WC with LCLS compensation is carried out and validated through MATLAB simulation. At the end proposed strategy has been extended to the case of temperature regulated charging
Characteristics of Z-source inverter supply for permanent magnet brushless motors
No full textZ-source inverters (ZSIs) supply AC loads from a DC source and boost the voltage of the DC source in a single stage. Such an ability is much needed in electric vehicles where the rated voltage of the traction motors is usually higher than the voltage generated by the onboard DC sources. Being the technological trend in the traction drives directed toward the employment of PM brushless motors, the use of a ZSI for their supply is a cutting-edge issue, which is investigated in this paper. The paper starts by formulating the equations of a ZSI in a suitable form. Then the characteristics of the ZSI supply for the two basic types of PM brushless motor, namely the DC and AC types, are assessed with regards to the switch solicitation and utilization. As a comparison, the characteristics of the traditional DC-DC boosted inverter supply are also given
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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