Led Lighting Spd Design Installation Guide Page 9 LED Lighting SPD Design & Installation Guide

2015 Littelfuse LED Lighting SPD Module Design and Installation Guide www.littelfuse.com LED Lighting Surge Protection Modules Design and Installation Guide Modular Solution vs. a Solution Embedded into the Power Supply Unit Outdoor luminaires are easily affected by transient surges inductively coupled into power lines from lightning strikes. IEEE C62.41.2 -2002 categorizes two different exposure levels for outdoor locations (Category C Low and C High) with different suggested surge levels. Similarly, some regions or countries may have different surge level requirements due to different lightning strike density in the area. Although some LED luminaires feature surge protection devices embedded in the power supply unit, Littelfuse recommends that the surge protection circuit be provided as an independent module that's separate from the luminaire power supply; in this way, the same luminaire can be easily marketed globally by attaching different surge protection modules to meet differing surge level requirements. MOVs are widely used in surge protection circuits for their fast response times, high surge energy handling, compact size, and cost-effectiveness. However, after MOVs absorb a certain number of surge strikes, they will begin to degrade and can no longer provide the same protection as new ones. Having a separate surge protection module allows for easy replacement when the original module reaches its end of life. Thermally Protected MOV for SPD Safety MOV technology is not only inexpensive but also highly effective for suppressing transients in power supplies and many other applications, such as the SPD modules that are often placed upstream from an LED driver. MOVs tend to degrade gradually after a large surge or multiple small surges. This degradation leads to increasing MOV leakage current; in turn, this raises the MOV's temperature, even under normal conditions like 120Vac/240Vac operating voltage. A thermal disconnect adjacent to the MOV ( Figure 8 ) can be used to sense the increase in MOV temperature while it continues to degrade to its end-of-life condition; at this point, the thermal disconnect will open the circuit, removing the degraded MOV from the circuit and preventing it from failing catastrophically. Figure 8. A thermal disconnect can open the circuit, preventing a catastrophic failure of a degraded MOV. Modular Solution vs. a Solution Embedded and Thermally Protected MOV for SPD Safety 9

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