Guoqiang Zhang

The application of evaporative cooling technology for an electromagnetic separator

An immersed type evaporative cooling electromagnetic separator is presented, including the prototypes configuration, procedures and outcomes of the temperature distribution simulation, as well as the results by experimental research. The comparison between the stimulation and experimental study show that the simulation methods are accurate; meanwhile, the evaporative cooling technique is an effective way for larger capacity electromagnetic separator

Experimental study of partial discharge inception voltage of special fluorocarbon gases and their mixtures in rod-plane gaps under power frequency

Because of the high global warming potential (GWP), SF6 gas was listed as one of the six restricted gases in 1997. Some fluorocarbon gases with low environmental effect and high dielectric performance are studied as the substitution candidates for SF6. This paper presents the partial discharge (PD) capability of some gas mixtures with fluorocarbon at different pressures and ratio of fluorocarbon in rod-plane electrodes under power frequency. The PD inception voltage (PDIV) is measured and analyzed. The experimental results show that the PD capability of some gas mixtures with fluorocarbon is better than that of SF6 and the gas mixtures has a possibility to substitute for SF6.

AC breakdown voltage measurement of a fluorocarbon in gaseous state two-phase-flow state and liquid state

The AC breakdown voltages of a fluorocarbon were measured under three states, including in gaseous state, in boiling two phase flow state and in liquid state. Because the insulating medium in two phase flow could be used in some electrical apparatus, the author measured the breakdown voltage of two phase flow under various pressures in the vessel, various water contents in the coolant. The results would be used for designing and manufacturing of electrical apparatus.

Partial discharge performances under non- uniform electric field in gas mixtures with small fluorocarbons

This paper describes the partial discharge (PD) performances of gas mixtures with small fluorocarbons because their global warming potential (GWP) is smaller than that of SF6 gas, which was regulated as one of six restricted gases. It is difficult to apply pure fluorocarbon gases as insulating medium directly in gas insulated switchgear (GIS) and gas circuit breakers (GCB), because their liquefying temperature is high. Thus, the mixtures have various contents and ratios. The PD inception voltages of gas mixtures containing fluorocarbon and N2 are measured and analyzed as a function of gas pressure, electrode distance and the ratio of the fluorocarbon. The PD performances of fluorocarbon gas and its mixtures are compared with those of SF6 gas, which is now widely used as the insulating medium in GIS and GCB. The results show that gas mixtures containing special fluorocarbon have a possibility to substitute for SF6 gas.

Shape Optimization of Field Windings in a High Temperature Superconducting Synchronous Generator with Finite Element Method

Publisher Summary This chapter presents the optimal design of high temperature superconducting (HTS) field windings in a demonstrative HTS generator model based on magnetic field analysis by finite element method. The optimal shapes of HTS magnet with iron core and without iron core are studied, and the value of the minimum vertical component of magnetic flux density passing through the surface of HTS tapes in each kind of HTS magnet is achieved. Two types of HTS rotors are analyzed. It is proved that the value of the minimum vertical component can be decreased effectively by adopting flux diverters for the configuration with iron core and by adjusting cross-sectional shape of HTS magnet for the configuration without iron core respectively. It is concluded that the iron core type HTS magnet with diverters and the nonmagnetic core type HTS magnet with step-shaped HTS magnet and iron plates are two effective ways to reduce the value of the minimum vertical component.

Design of Cooling System and Temperature Characteristics Analysis of High Temperature Superconducting Demonstrative Synchronous Generator

Publisher Summary This chapter presents the cooling system of a demonstrative high temperature superconducting (HTS) generator, in which solid nitrogen (SN2) is used as cryogen to keep the operating temperature of HTS synchronous machine. Its tasks are to pursue the minimal volume of HTS magnets and utilize the configuration characteristic of conventional generator. Its hybrid rotor has three novel aspects: the HTS magnets are installed on a warm iron core; four Dewar flasks having racetrack outline are distributed symmetrically, and SN2 is used as cryogen. Furthermore, evaporative cooling technology is applied to solve the cooling problem of the stator, which is more effective than air-cooling technology and more safer than water inner cooling technology. The pressure losses of GHe through rotor are analyzed. It can be inferred that centrifugal force has significant impact on GHe flow, and the effects of pressure and Coriolis force can be ignored. The steady temperature field is also simulated by ANSOFT, and the results indicate that the maximal temperature of HTS coils is lower than 30 K and distributed uniformly, while the GHe (15 K) velocity is 0.2 m/s.