No abstract

The objective of this paper is to determine the vacuum arc characteristics of a novel axial magnetic field (AMF)–transverse magnetic field (TMF) composite contact under different opening velocities. The AMF–TMF composite contact consists of a pair of outer fixed AMF contacts and a pair of inner movable TMF contacts. Drawn arc experiments were carried out in an L– C discharging circuit with this composite contact system to observe the differences in the arc development process under different opening velocities. The opening velocity of the inner movable contact was set to 1.3, 1.8, and 2.3 m/s. The arc current was up to 20 kA rms. In the experiments, the arc behavior was recorded using a high-speed camera. The arc current of each contact and the arc voltage were measured. Then the arc characteristics, including the arc current transfer characteristics, diffused arc duration, and mental droplet distribution before zero current, were quantitatively analyzed. Furthermore, magnetic field calculation was carried out to explain why the arc characteristics are different under different opening velocities. Experimental results show that with an increase in the opening velocity from 1.3 to 2.3 m/s, the diffused arc duration before zero current increases from 1.05 to 1.75 ms when the cathode is on the fixed side and increases from 1.30 to 1.90 ms when the anode is on the fixed side. In addition, the quantity of mental droplets between contacts before zero current is less with high opening velocity. It indicates stronger short-current breaking capacity under higher opening velocity. From the simulation results, it can be seen that during the arcing period, more current transfers to the fixed AMF contact under higher opening velocity and generates a stronger AMF. It could explain the earlier diffusion of the vacuum arc column under higher opening velocity.

Dry-type transformer is the key hub equipment connecting power generation platform and power consumption platform in marine power system. Partial insulation aging caused by transformer thermal effect is one of the important factors that adversely affect the operation stability. The new ceramic insulation winding prepared by micro-arc oxidation technology has the characteristics of high thermal conductivity and high temperature resistance, and is an ideal product to replace traditional organic insulation materials. Therefore, in this paper, the thermal characteristics and overload capacity of a ceramic insulated aluminum winding dry-type transformer are studied by combining heat flow coupling simulation and experiment. By comparing the temperature field and velocity field characteristics of traditional organic insulated dry-type transformer and ceramic insulated dry-type transformer, the influence of different winding materials on transformer heat dissipation under the same load condition is studied. The hottest spot temperature of ceramic insulated winding dry-type transformer is about 86% of that of traditional organic insulated transformer. The ceramic insulated dry-type transformer has a good overload capacity. Under the premise of meeting the H-class insulation, it can carry 1.4 times the rated load. Finally, the simulation results are compared with the experimental data of the ceramic insulated dry-type transformer. The accuracy of the results was verified.