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Littelfuse Xtreme Varistor Radial Leaded Varistors | Tech Explainer

February 13, 2023 by Mouser Electronics

This Tech Explainer is part of a video series that details specific products and technologies and their applications.



Littelfuse Xtreme Varistor Radial Leaded Varistors

Varistors are often the front-line solution for protection against voltage surges from lightning strikes, ESD surges, and inductive load switching from generators, motors, and transformers.

Composed of a matrix of conductive zinc oxide grains separated by grain boundaries, varistors exhibit a non-linear voltage-current characteristic. The boundaries themselves are responsible for blocking conduction at low voltages and are the source of the nonlinear electrical conduction at higher voltages.

When large voltages form across the varistor, the impedance changes many orders of magnitude going from a near-open circuit to a highly conductive level.

This clamps the transient voltage to a safe level by providing the current from a transient a low-impedance path to ground.

The electrical properties of varistors are controlled by the physical dimensions of the varistor body. The powder is pressed into a form of predetermined thickness in order to obtain a desired value of nominal voltage. To obtain the desired ratings of peak current and energy capability, the electrode area and mass of the device are varied.

Selecting a varistor depends upon the operating voltage of the protected equipment as well as the tolerance of its operating voltage. The maximum clamping voltage relates to the maximum allowable voltage of the protected equipment while the peak current value is the maximum expected surge current and number of hits.

The Xtreme varistor series are radial leaded varistors that are specially designed for applications requiring a high energy and current absorption with multiple surge pulse withstanding capability.

The proprietary formulation and sintering achieves robust surge performance that helps prevent damage and catastrophic failures in extreme conditions. The UL-94 flammability rating  ensures burning stops within ten seconds.

The small footprint ensures the Xtreme radial lead varistors can be used in small applications such as home appliances, outdoor LEDs, GFCIs, smart e-meters, and home automation systems.

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