Views:0 Author:Site Editor Publish Time: 2019-09-10 Origin:Site
A varistor is an abbreviation for a voltage sensitive resistor and is a non-linear resistance element. The resistance of the varistor is related to the magnitude of the voltage applied across the two ends. When the voltage applied to the varistor is within its nominal value, the resistance of the resistor is infinite and almost no current flows. When the voltage across the varistor is slightly greater than the nominal voltage, the varistor quickly breaks through and the resistance quickly drops, causing the resistor to be in a conducting state. When the voltage drops below the nominal voltage, its resistance begins to increase again, and the varistor returns to a high-impedance state. When the voltage across the varistor exceeds its large control voltage, it will break down completely and will not recover on its own.
Taking the 10D471 we tested as an example, the test data of different temperatures under the 2000A inrush current shows that the control voltage of the rising region is not affected by the temperature below 200 °C, indicating that the current still plays a decisive role. From the influence of the thermal excitation current and the barrier reduction on the varistor voltage, the nonlinearity, and the breakdown region control voltage, the control voltage in the rising region below 400 °C is not affected by the temperature.
Because the control voltage of the rising region is affected by the barrier and the grain resistance at the same time, the semiconductor characteristic of the crystal grain should be the temperature increase resistivity decrease, and its function is to control the voltage drop. The control voltage of the rising region is not higher than 200C °C. The fact that it is affected by temperature indicates that the temperature has no effect on the grain resistance when the temperature is not very high, which should be compared with the carrier excited by the impurity and the problem when the intrinsic excitation reaches a very high temperature. While the impurities and problems are fully excited at room temperature, the grain resistivity remains stable at very high temperatures.
That is to say, from the current peak current impact level of the product, the grain temperature rise will not exceed 200 °C during the entire impact process, so the impact itself will not cause the influence of the grain resistance change on the control voltage. The impact itself does not cause the influence of the grain resistance change on the control voltage. The temperature rise of the 10D471 after two consecutive shocks exceeds 70 °C. The results of multiple impacts in high and low temperature indicate that the control voltage has no change, which can be inferred at 300C. The grain resistance below °C does not change, and the control voltage of the rising region is not caused by the grain resistance. When not exceeding 300 ° C to 400 ° C, the control voltage of the rising region is not affected by temperature, and the potential drop at 500 ° C may cause a significant decrease in the control voltage of the rising region.