Aumov LV Ultramov Varistor Design Guide Page 6 Varistor Design Guide For DC & Automotive Applications

2015 Littelfuse DC Application Varistor Design Guide DC Application Varistor Design Guide Enhanced protection level-Higher surge withstanding and longer life An LV UltraMOV Varistor can withstand higher surge current/energy and more surge strikes than the same size varistor from the standard Littelfuse series. For example, a new 10mm LV UltraMOV Varistor is rated at 2000A max. surge current, which is four times higher than a standard one. The higher surge rating also can provide longer life and reliability because there will be less degradation of the MOV over its lifetime. Reduced component size-More compact designs An LV UltraMOV Varistor is smaller than a standard Littelfuse varistor with the same surge capability. This reduces both PCB space requirements and component height. For example, an ordinary 10mm MOV capable of 500A maximum surge current could be replaced by a new 5mm LV UltraMOV Varistor with the same 500A surge rating; MOV size is reduced from 10mm to 5mm and mounting height is reduced from 14mm to 10mm. Higher operating temperature range An LV UltraMOV Varistor with the phenolic coating option can be operated in environments up to 125C, making it suitable for use in more severe conditions such as industrial applications. Varistor Basics Varistors are voltage dependent, nonlinear devices that behave electrically similar to back-to-back Zener diodes. The symmetrical, sharp breakdown characteristics shown here enable the varistor to provide excellent transient suppression performance. When exposed to high voltage transients, the varistor impedance changes many orders of magnitude-from a near open-circuit to a highly conductive level-thereby clamping the transient voltage to a safe level. The potentially destructive energy of the incoming transient pulse is absorbed by the varistor, thereby protecting vulnerable circuit components. About the LV UltraMOV and Varistor Basics (continued) 5

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