Voltage Response of ZnO Varistors to 8/20 µs Surge Current

2007 ◽  
Vol 280-283 ◽  
pp. 285-288 ◽  
Author(s):  
Zhen Ya Lu ◽  
Zhi Wu Chen ◽  
Feng Jin Yang
Keyword(s):  
Skin Effect ◽  
Voltage Response ◽  
Voltage Waveform ◽  
Residual Voltage ◽  
Zno Varistor ◽  
Rlc Circuit ◽  
Rear Part ◽  
Zno Varistors ◽  
Voltage Peak ◽  
Surge Current

The voltage response of ZnO varistors to 8/20 µs surge current was investigated. The observed frontal spikes on the residual voltage waveforms are caused by the ignition gap, and no frontal spike was observed when a thyristor was used as the discharge trigger. The rear part of the waveform is determined by the damping coefficient of the RLC-circuit. Near the critical point, the residual voltage waveform changes from non-oscillating attenuation modes to distinct across zero oscillating modes along with the increase of the peak current, but there will be no oscillation happen when a thyristor is used as the discharge trigger. The residual voltage peak is not synchronized with the current peak, and the voltage peak is leading, implying that the ZnO varistor appears to be inductive. According to the experiment results, it can be reasonably explained that the voltage peak leading phenomenon is attributed to the transient skin effect of the varistor materials.

Microchemistry of ZnO Varistors

1992 ◽  
Vol 50 (2) ◽  
pp. 1694-1695
Author(s):  
K. K. Soni ◽  
J. Hwang ◽  
V. P. Dravid ◽  
T. O. Mason ◽  
R. Levi-Setti
Keyword(s):  
Grain Boundaries ◽  
Multiple Roles ◽  
Grain Boundary Engineering ◽  
Ion Microprobe ◽  
Dopant Distribution ◽  
Important Ingredient ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Zno Powder ◽  
The University

ZnO varistors are made by mixing semiconducting ZnO powder with powders of other metal oxides e.g. Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, SiO2 etc., followed by conventional pressing and sintering. The non-linear I-V characteristics of ZnO varistors result from the unique properties that the grain boundaries acquire as a result of dopant distribution. Each dopant plays important and sometimes multiple roles in improving the properties. However, the chemical nature of interfaces in this material is formidable mainly because often trace amounts of dopants are involved. A knowledge of the interface microchemistry is an essential component in the ‘grain boundary engineering’ of materials. The most important ingredient in this varistor is Bi2O3 which envelopes the ZnO grains and imparts high resistance to the grain boundaries. The solubility of Bi in ZnO is very small but has not been experimentally determined as a function of temperature.In this study, the dopant distribution in a commercial ZnO varistor was characterized by a scanning ion microprobe (SIM) developed at The University of Chicago (UC) which offers adequate sensitivity and spatial resolution.

Effect of Simultaneous Addition of Zr and Y on Electrical Characteristics of ZnO Varistors

2011 ◽  
Vol 485 ◽  
pp. 257-260 ◽  
Author(s):  
Takayuki Watanabe ◽  
Ai Fukumori ◽  
Yuji Akiyamna ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Leakage Current ◽  
Nonlinear Coefficient ◽  
The Other ◽  
Electrical Characteristics ◽  
Simultaneous Addition ◽  
Zno Varistor ◽  
Low Leakage ◽  
Electrical Degradation ◽  
Low Leakage Current ◽  
Zno Varistors

The effect of simultaneously adding Zr and Y to Bi–Mn–Co–Sb–Si–Cr–Ni-added ZnO varistors (having the same composition as a commercial varistor) on the varistor voltage, leakage current, and resistance to electrical degradation were investigated. Varistor voltage increased with increasing amount of Y for addition of 0–2 mol % Zr. On the other hand, the nonlinear coefficient α prior to electrical degradation changed very little on the addition of both Y and Zr. With the addition of approximately 1 mol% Zr, the leakage current decreased with increasing amount of Y added. A ZnO varistor with a varistor voltage of approximately 600 V/m, a low leakage current, and excellent resistance to electrical degradation was fabricated by adding approximately 2 mol% Y and approximately 1 mol% Zr.

scholarly journals Simulation of the Conductive Process of Nano ZnO Varistors Based on Animation Plane Form

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xin Liu
Keyword(s):  
High Efficiency ◽  
Low Cost ◽  
Pressure Ratio ◽  
Chemical Vapor ◽  
Chemical Vapor Deposition Method ◽  
Nano Zno ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Variable Morphology ◽  
Plane Form

Among many nano materials and chemical materials, zinc oxide nanomaterials have attracted researchers’ interest because of their high efficiency, low cost, easy preparation, and variable morphology. The purpose of this study is to explore the fabrication and conductive process of nano ZnO varistors under the simulation of an animation plane form. In this study, the chemical vapor deposition method was used to prepare nano ZnO. Then, ZnO nanomaterials were mixed with deionized water to form a suspension. Under the action of a micromechanical stirrer, impurities were removed by heat treatment, and then different amount of water was added to obtain a nano ZnO electrode. The conductive process and electrochemical properties of the nano ZnO electrode were investigated and analyzed. The results show that the pressure ratio of the varistor increases obviously after adding nano ZnO. In the range of 0–30%, the pressure ratio of the ZnO varistor increases with the increase in nano ZnO content. When w (nano ZnO) is 30%, the voltage ratio reaches 1.149 and the oxidation peak current ratio of LD decreases by 6%. Therefore, it is concluded that the electrode of nano ZnO varistor valve sheets maintains good stability for a LD conductivity detection process. It also plays an important role in electrochemical research.

scholarly journals Computer Simulation of ZnO Varistors Failures

1997 ◽  
Vol 500 ◽  
Author(s):  
M. Bartkowiak ◽  
G. D. Mahan ◽  
M. G. Comber ◽  
M. A. Alim
Keyword(s):  
Mechanical Model ◽  
Thermal Stresses ◽  
Failure Modes ◽  
High Current ◽  
Zno Varistor ◽  
Failure Data ◽  
Surge Arresters ◽  
Transfer Equations ◽  
Current Densities ◽  
Zno Varistors

ABSTRACTA simple thermo-mechanical model is applied to evaluate the influence of the nonuni-formity of ZnO varistor disks used in surge arresters on their energy handling capability. By solving heat transfer equations for a varistor disk with nonuniform electrical properties, we compute the time dependence of the temperature profile and the distribution of thermal stresses. The model can identify the energy handling limitations of ZnO varistors imposed by three different failure modes: puncture, thermal runaway, and cracking. It conforms to the available failure data, and explains the observation that energy handling improves at high current densities.

High nonlinearity and low residual-voltage ZnO varistor ceramics by synchronously doping Ga 2 O 3 and Al 2 O 3

2016 ◽  
Vol 164 ◽  
pp. 80-83 ◽  
Author(s):  
Hongfeng Zhao ◽  
Jinliang He ◽  
Jun Hu ◽  
Shuiming Chen ◽  
Qingyun Xie
Keyword(s):  
Residual Voltage ◽  
Zno Varistor ◽  
High Nonlinearity

Study on Microstructure and Electrical Properties of ZnO Varistor Ceramics

2011 ◽  
Vol 415-417 ◽  
pp. 2008-2011 ◽  
Author(s):  
Chang Qi Xia ◽  
Qi Bin Liu ◽  
Mo He
Keyword(s):  
Electrical Properties ◽  
Sintering Temperature ◽  
Spinel Phase ◽  
Voltage Gradient ◽  
X Rays ◽  
Sintering Process ◽  
Varistor Ceramic ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Ceramic Sintering

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, which were sintered from 1135 to 1155 °C, the microstructure and properties of varistors were characterized by SEM, X-rays diffraction and DC parameter instrument for varistors. The experimental results show that the spinel phase Zn7Sb2O12 generated during sintering process, very thin amorphous Bi rich films are formed between the ZnO/ZnO grain boundaries, with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. The optimized parameters are that when the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%, the comprehensive electrical properties of ZnO varistors reach maximum.

Gas Sensing Behavior of Porous ZnO Varistors Densified via Rate Controlled Sintering

1996 ◽  
Vol 431 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer
Keyword(s):  
Grain Size ◽  
Gas Sensor ◽  
Breakdown Voltage ◽  
Gas Sensing ◽  
Hydrogen Gas ◽  
Adsorbed Oxygen ◽  
Intergranular Porosity ◽  
Zno Varistor ◽  
Rate Controlled ◽  
Zno Varistors

AbstractA hydrogen gas sensor based on shift in breakdown voltage of a ZnO varistor was developed. Changes in rate controlled sintering schedules resulted in significant variations in microstructure. Microstructures showing more intergranular porosity and finer grain size demonstrated a comparatively more linear and broad response to H2 concentration. A mechanism for the shift in breakdown voltage based on adsorbed oxygen is suggested for this unique and potentially very useful sensor.

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