Constant-frequency multi-resonant converter-fed DC motor drives

Low-inductance dc motors with high power density and low rotor inertia are becoming more attractive, particularly for servo applications. In order to maintain their current ripples within acceptable levels, power converters need to operate at high switching frequencies. However, the increase in switching frequencies realizable by hard-switching techniques accompanies the increase in switching losses and switching stresses. In this paper, recent soft-switching dc-dc converters are discussed for application to dc motor drives. The most feasible one, namely the zero-voltage-switching (ZVS) constant-frequency multi-resonant converter (CF-MRC), has been identified to be appropriate for dc motor drives. This soft-switching converter not only possesses the advantages of achieving high switching frequencies with practically zero switching losses and eliminating variable-frequency operation, but also provides full ranges of voltage conversion and load variation. A ZVS-CF-MRC-fed dc motor drive has been prototyped and tested. Experimental results verify the successful application of the ZVS-CF-MRC to dc motors drives, which takes definite advantages of high efficiency, small current ripples and minimum switching stresses.published_or_final_versio

A new zero-voltage-transition converter for switched reluctance motor drives

Firstly, a new zero-voltage-transition (ZVT) power converter for switched reluctance motor drives is presented. The proposed ZVT converter possesses the definite advantages that both main transistors and diodes can operate with zero-voltage switching (ZVS), unity device voltage and current stresses. Secondly, its zero-current counterpart is also presented, which offers both the main and auxiliary switches operating with zero-current switching (ZCS) and minimum current/voltage stress. They both have simple circuit topology, minimum component count and low cost. This family of power converters is especially advantageous for switched reluctance motor drives demanding efficient regenerative braking, such as in electric vehicle applications.published_or_final_versio

Bidirectional soft-switching converter-fed DC motor drives

Two new soft-switching DC-DC power converters, with the capabilities of bidirectional power flow and soft-switching (either zero-voltage transition or zero-current transition) are developed for DC motor drives. The proposed bidirectional zero-voltage-transition power converter possesses the definite advantages that both main transistors and rectifiers can switch with zero-voltage switching (ZVS) and unity device stresses during both motoring and regenerating modes of operation, while both the main and auxiliary switches of the bidirectional zero-current-transition power converter can operate with zero-current switching (ZCS) and minimum voltage/current stress. These converters are particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiency.published_or_final_versio

A novel two-quadrant zero-current transition converter for dc motor drives

A novel two-quadrant (2Q) zero-current-transition (ZCT) converter with the capabilities of 2Q power flow, and ZCT switching profile for DC motor drives is presented. It possesses the advantages that both the main and auxiliary switches can operate with zero-current switching (ZCS), reduced switching losses and stresses, minimum voltage and current stresses as well as minimum circulating energy during both the motoring and regenerating modes. This converter is particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiencypublished_or_final_versio

A novel zero-current soft-switching converter for switched reluctance motor drives

A new zero-current-transition (ZCT) power converter for switched reluctance motor drive applications is presented. The proposed ZCT power converter possesses the definite advantages that both the main and auxiliary switches are operating with zero-current switching (ZCS), as well as minimum current and voltage stresses. It has a simple circuit topology, minimum component count and low cost. The ZCT technique can significantly reduce the switch-on or -off losses by forcing the current to zero prior to its turn-on or turn-off. The proposed power converter is especially advantageous for switched reluctance motor (SRM) drives demanding efficient regenerative braking, such as electric vehicle application.published_or_final_versio

A novel two-quadrant zero-voltage transition converter for DC motor drives

A novel zero-voltage-transition (ZVT) two-quadrant (2Q) power converter for DC motor drives is presented. It possesses the definite advantage that both main transistors and rectifiers can operate with zero-voltage switching in both motoring and regenerating modes, while both of these switches are only subjected to unity voltage and current stresses, namely the same as its PWM counterparts. This power converter is particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiency. The corresponding theoretical analysis and its high-efficiency performance are supported by both simulation and experimental results.published_or_final_versio

Comparison of hybrid-excitation fault-tolerant in-wheel motor drives for electric vehicles

Paper no. DS2-23Hybrid-excitation in-wheel motor drive receives the attractive merit for its fault-tolerant operation. This paper gives the performance comparison of three types of hybrid-excitation in-wheel motor drives in electric vehicles (EVs) for their fault-tolerant operations. By using finite-time element analysis, the torque output is utilized as the fault indicator to investigate the performances of each motor drive under normal, faulty, and remedial operations.published_or_final_versio

An integrated PM magnetic-geared machine for hybrid electric vehicles

Paper no. DS1-58The free-piston generators have the advantages of simple structure, high power density and high efficiency, so they are proposed for applying in the series hybrid electric vehicles (HEV). In this paper, a novel PM linear magnetic-geared machine serving as the free-piston generator is proposed. The machine consists of a linear permanent magnet synchronous machine (PMSM) and a linear magnetic gear (LMG), which are integrated together. The proposed machine adopts a structure that the high-speed mover of the LMG and the translator of the linear PMSM share the same moving part. There are four main parts in the machine topology, including the low-speed mover with PMs, the ferromagnetic pole pieces, the high-speed mover with PMs and the stator with three-phase windings. In order to improve the speed of the PMSM translator, the magnetic-geared topology is adopted, such that the designed machine can generate the high-voltage electricity and have the high power density. In the magnetic-geared machine, the tubular stator is designed as a 12-slot structure with concentrated windings. In order to integrate the machine and the magnetic gear magnetically and mechanically together, the high-speed mover of the magnetic gear is designed as the translator of the machine. The tubular machine translator consists of one row of PMs. And the low-speed mover of the magnetic gear consists of a tubular iron core and PMs mounted on the inner face of the core. The PMs of both low-speed mover and machine translator are radial magnetized. Between the low-speed mover and the high-speed mover of the magnetic gear, the ferromagnetic pole pieces are fixed there to modulate the magnetic fields. Since the LMG has the advantage of high force density inherently, the proposed novel PM linear magnetic-geared machine can obtain the high power density, high efficiency and weight reduction by comparing with the conventional linear machines. This work is performed and verified by using the finite element analysis (FEA) method.published_or_final_versio

Relationship between intact HIV-1 proviruses in circulating CD4+ T cells and rebound viruses emerging during treatment interruption.

Combination antiretroviral therapy controls but does not cure HIV-1 infection because a small fraction of cells harbor latent viruses that can produce rebound viremia when therapy is interrupted. The circulating latent virus reservoir has been documented by a variety of methods, most prominently by viral outgrowth assays (VOAs) in which CD4+ T cells are activated to produce virus in vitro, or more recently by amplifying proviral near full-length (NFL) sequences from DNA. Analysis of samples obtained in clinical studies in which individuals underwent analytical treatment interruption (ATI), showed little if any overlap between circulating latent viruses obtained from outgrowth cultures and rebound viruses from plasma. To determine whether intact proviruses amplified from DNA are more closely related to rebound viruses than those obtained from VOAs, we assayed 12 individuals who underwent ATI after infusion of a combination of two monoclonal anti-HIV-1 antibodies. A total of 435 intact proviruses obtained by NFL sequencing were compared with 650 latent viruses from VOAs and 246 plasma rebound viruses. Although, intact NFL and outgrowth culture sequences showed similar levels of stability and diversity with 39% overlap, the size of the reservoir estimated from NFL sequencing was larger than and did not correlate with VOAs. Finally, intact proviruses documented by NFL sequencing showed no sequence overlap with rebound viruses; however, they appear to contribute to recombinant viruses found in plasma during rebound

Implementing guidelines for the prescribing of vancomycin and teicoplanin

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