What is the function of varistor?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. A capacitor may be installed across the signal lines. However, this capacitor cannot suppress voltage surges.
What leads to variable resistance in varistors?
The resistance of a varistor is variable and depends on the voltage applied. The word is composed of parts of the words “variable resistor. Their resistance decreases when the voltage increases. In case of excessive voltage increases, their resistance drops dramatically.
What is the function of a varistor?
The main application of the Varistor is in protecting the circuits against voltage transient. The semiconductor body of the Varistors aids in the same. Like a zener diode, Varistor’s VI characteristic curve shows a surge in current after a particular threshold voltage. This threshold voltage is called the rated voltage or the clamping voltage.
What happens when the voltage is too high on a varistor?
When the voltage at both ends of the varistor exceeds its maximum limit voltage, it will break through the damage completely and will not be able to recover on its own. The text symbol of varistor is “RV” or “R” in the circuit, and figure 1 is its circuit graphic symbol.
What is the clamping voltage of a varistor?
The clamping voltage or the Varistor voltage shown in the figure is defined as the voltage up to which the current through the Varistor is very low, mostly of the order of few milli-amperes. This current is commonly called the leakage current.
What is the voltage ratio and maximum energy of a varistor?
The voltage ratio is the ratio of the voltage generated when the varistor current is 1 mA to the voltage generated when the varistor current is 0.1 mA. The maximum energy, Em, is the maximum energy of a surge current or a pulse current that can be dissipated by the varistor.