Advanced Materials Research Vols. 354-355

Abstract: The definition and the sources of the particulate pollutant in the transformer oil were described in the article. The prevention and elimination of the particulate pollutant were introduced as well.

Abstract: Based on the platform of laser-triggered surface flashover in pulsed voltage, experiment of laser-triggered surface flashover is carried out in air and vacuum condition with pulsed voltage. A single/double harmonic, with wavelength of 1064/532 nm, Q-switched Nd:YAG laser is applied to trigger the surface flashover. The test system consists of flat electrodes and columned insulator. The material of electrode is copper and the material of insulator is Al₂O₃. Laser pulse’s wavelengths are 532nm and 1064nm, and laser is focused with rectangle. The results of experiment show that flashover delay time and jitter time decrease with increase of pulsed voltage or laser energy density, the delay time of 1064nm laser trigger is larger than that of 532nm laser trigger, and the delay time and jitter time in vacuum condition are less than the delay time and jitter time in air condition.

Abstract: At present, the contribution of partial discharge (PD) to power equipment insulation diagnosis is highly valued globally. However, most PD measurements are still performed in the laboratory, the main reason being that the effects of on-field noise suppression are still limited and unsatisfactory. To date, among noise suppression methods, wavelet de-noising is the most common. This study focuses on improving the effects of on-field noise suppression. The shape features (pulse equivalent bandwidth and pulse duration time) can be analyzed, and PD signals can consequently be discovered. This study applied the proposed method to on-field and laboratory experiments, and presents a discussion of the outcomes regarding the effects on noise suppression. This method can improve the effects of noise suppression.

Abstract: Discharge may take place in high voltage apparatuses in the form of void discharge, corona discharge and surface discharge. Understanding of the discharge is very important to know the condition of the insulation. Partial discharge (PD) current pulse waveforms contain essentially all the available information concerning the PD generation and thus the available information concerning the physical mechanism of degradation and breakdown of insulation. In this paper, three types of discharge model for polyethelene insulation material are constructed and the PD current pulse waveforms are extracted from experiments. In order to obtain pulse waveform characteristics, the extracted pulse waveforms are pre-selected and normalized, and then a Sampling Counting Ratio (SCR) classification technique is investigated to reveal the multi-peak and oscillation information about the PD current pulse waveforms. Results show that the classification would enable us to estimate the progress and degree of the degradation.

Abstract: In this paper the temperature field of Concrete Filled Steel Tube (CFST) member under solar radiation is simulated. The results show that temperature distribution caused by solar radiation is nonlinear over the cross-section of CFST member, and it is significantly varied with time and sections, the largest nonlinear temperature difference is over 26.3°C.

Abstract: An experimental study of heat transfer characteristics of narrow rectangular channels with rib turbulators for Re in the range of 10000-60000 was performed. To simulate the actual geometry and heat transfer structure of blade/vane internal cooling passage, each of the test channels was welded by four stainless steel plates. Because of the three dimensional heat conduction in the walls and heat conduction between the ribbed and smooth walls, the measured temperature distribution along the axial direction of the test channel is a smooth continuous curve, and when the Re is low, the average Nu of the ribbed and smooth walls are nearly the same. For each aspect ratio channels, the average Nu for the channel of α=45° is about 15 to 25 percent higher than that of α=60°. In addition, we have developed the semi-empirical correlations, covering the range of Re, to predict heat transfer coefficient of the channels. The correlations can be used in the design of turbine blade/vane cooling channels.

Abstract: With the development of AC (alternating current )technique, larger power PMSM ( permanent m- agnet synchronous motor ) has been applied in the marine electric propulsion systems. In this paper the imple- mentation of the DTC (direct torque control) systems for a variable-speed 4088kW PMSM in ship electric propulsion systems has been studied. A novel control method using SVPWM (space vector pulse width mo- dulation) was proposed and a SVPWM module was designed. Then a DTC – SVPWM simulation model of PMSM with the load of propeller was found. The simulation results shows that the variable frequency speed regulation system have good response performance in the process of the motor start or speedup and through comparing the simulation results with the experiment data of the PMSM, the validity of the model is verified.

Abstract: Motor winding temperature rise test is the most important test that examines whether the insulation material and the production process meet the motor design life or not. Therefore, it is the key to accurately process the temperature rise test data. For a motor, several motors with the same model and the special motor, the paper puts forward the different methods to process the test data. In addition, the paper takes a single phase AC series excited motor for example, and proves that these methods are effective.

Abstract: Because of special structure for the Brushless Doubly-Fed Machine (BDFM) and complex magnetic field coupling of different pole pairs, general parameter calculation and experiment methods are not accurate and fit for the BDFM. A parameter calculation method of the equivalent circuit for the BDFM based on the genetic algorithm (GA) is presented in this paper. The parameters of the equivalent circuit are considered as a group of unknown variables to solve the mathematical equation in different operating conditions. The difference between calculated and measured values is taken as a target function to be minimized through optimizing the parameters of the equivalent circuit by using the GA. The calculated results show that the method is valid to solve the related problems and it is suitable to be applied in the parameter calculation for the BDFM.

Abstract: This paper presents the results of my experiments that may open a new path for advanced applications by using continuous closed superconducting YBCO loops. I examined a novel arrangement of a perfectly closed superconducting loop made of HTS wire in DC and AC flux transformer. I designed a self-limiting transformer with this solution. At the same time I also tested the operation of the continuous YBCO loop developed with my own technology. In the first experiment I used YBCO superconducting rings made from a bulk. Later I used superconducting wire. I could carry out these experiments because earlier I had elaborated the machining of the YBCO bulk and wire.