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Abstract
The high performance of medium-voltage direct current (MVDC) power supply system is a pre-requisite for several industrial applications. To meet the higher voltage direct current (DC) breaking requirements in the fields of aviation, aerospace, and new energy, this article proposes a novel MVDC commutation breaking topology that combines a load-carrying branch and an arcing branch in parallel. In contrast to the conventional structure based on semiconductor devices, each branch in the proposed topology contains a mechanical contact, which provides a lower on-state loss and higher voltage-breaking capacity. Moreover, the theoretical analysis and experimental results verified the asynchronous operation of the current-loading and confirmed that the arcing branch can realize the natural commutation of the current for the breaking of overload current or short-circuit current. A detailed equivalent model that combines the micro-electrical contact theory and phase-change characteristics of the electrode material was then established to investigate the molten metal bridge and pseudo arc phenomenon of the contact area during the commutation process. The results indicated that although the presence of a molten metal bridge and pseudo arc increase the current commutation time and erosion of the electrode material, the commutation process can be conducted. Finally, based on the softening voltage of the electrode material under the rated conditions, in addition to the phase change during dynamic commutation, the roughness σ and elastic modulus E can be adjusted appropriately to achieve arc-less current commutation.
Highlights
The medium-voltage direct current (MVDC) power supply system has received significant research attention in the aerospace, urban rail transit, new energy vehicles, and maritime transport fields
The resonance circuit in a conventional hybrid circuit breakers (HCBs) is composed of a mechanical switch (MS) and an LC resonance circuit connected in parallel, which can redirect the switch current
T=Tm, T (k) > Tm where, cp is the specific heat at the constant pressure of the metal material; t is the calculation step, which is equal to 1e-8 s; τ (k) is the increase in temperature of the metal material at each calculation step; T, as obtained by the summation of τ (k), is the current temperature of the material, which is used to determine whether there is a phasechange of the electrode material during the commutation process
Summary
The medium-voltage direct current (MVDC) power supply system has received significant research attention in the aerospace, urban rail transit, new energy vehicles, and maritime transport fields. B. Jia et al.: Analysis and Experimental Research on a Novel Multi-Contact MVDC Natural Current Commutation achieve circuit breaking, the switching on-state loss, which is dependent on the semiconductor devices’ characteristics, is generally large. The control circuit drives the semiconductor device to conduct at a sustained voltage that generates an arc discharge between metal contacts, which results in the ablation of the electrode material. Compared with conventional hybrid topology and existing switchgear, the proposed topology is advantageous in that the commutation branch does not contain semiconductor devices and transistors It exhibits the following characteristics: 1) The load-carrying branch conducts a large proportion of the rated current, due to the design of the contact overtravel between different branch contacts.
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