High-performance investigation of a snubber circuit-based split source inverter for nonlinear loads using PWM techniques

Author(s):  
P. U. Poornima ◽  
R. Sridhar
Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1690
Author(s):  
Marco di Benedetto ◽  
Luca Bigarelli ◽  
Alessandro Lidozzi ◽  
Luca Solero

This paper focuses on the investigation and implementation of a high-performance power conversion system to reduce the overvoltage phenomenon in variable speed electric drive applications. Particularly, the pros and cons of using Silicon Carbide power MOSFETs in the power converter when a long power cable is employed in electric motor drive systems has been addressed. The three-phase two level inverter with the addition of snubber circuits that consist of capacitors and diodes has been investigated, designed and tested in order to mitigate the overvoltage problems without sacrificing the conversion efficiency. Given that the snubber circuit added to the switches can increase losses, an additional circuit is used to recover the energy from the snubber circuit. The proposed analysis has been then validated through an experimental campaign performed on the converter prototype. The experimental results show that the proposed converter can reduce the overvoltage at the electric motor terminals with excellent conversion efficiency compared to the classical solution like the three-phase two level inverter.


Author(s):  
A. V. Crewe ◽  
M. Isaacson ◽  
D. Johnson

A double focusing magnetic spectrometer has been constructed for use with a field emission electron gun scanning microscope in order to study the electron energy loss mechanism in thin specimens. It is of the uniform field sector type with curved pole pieces. The shape of the pole pieces is determined by requiring that all particles be focused to a point at the image slit (point 1). The resultant shape gives perfect focusing in the median plane (Fig. 1) and first order focusing in the vertical plane (Fig. 2).


Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.


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