Led Lighting Spd Design Installation Guide Page 16 LED Lighting SPD Design & Installation Guide

LED Lighting Surge Protection Modules Design and Installation Guide 2015 Littelfuse LED Lighting SPD Module Design and Installation Guide www.littelfuse.com Matching the Resistor to the Indicating LED Green/red indicating LEDs are available in the market with different form factors, sizes and ratings. Since the LED connected to SPD is fed by AC line voltage, it is important to choose an LED rated to withstand the full AC voltage in the reverse-bias mode. Adding another adequately rated diode to the LED circuit (parallel or series) could also prevent the LED from being damaged by the AC voltage. The value of the current-limiting resistor is chosen to match the optimal LED driving condition. Its resistance and wattage are determined by the AC line voltage and the desired current for driving the LED. For example, in a 240V AC circuit, a resistor rated 150k and 0.5W will limit the current to 1.6mA to drive the LED. The LED can be driven by a lower current than its full current rating and still illuminate with a minimum brightness level. As long as the brightness is visually acceptable under sunlight, keep the driving current low to save energy by minimizing the power dissipated by the current limiting resistor. Indication wires from SPDs are electrically energized by AC power line. Unused wires must be capped off by wire nuts to prevent the risk of short circuit or shock hazard. Coordination between the SPD and the Power Supply Unit to Reduce "Surge Let-through" Surge Protection Modules and MOV Coordination Generally, most LED power supplies are a constant current type, and are often referred to as LED drivers. These can be purchased as off-the-shelf assemblies containing MOVs to meet lower level surge requirements. Typically, drivers are rated to handle surges in the range of 1-4kV. The varistor (MOV2 in Figure 18 ) is usually located downstream of the fuse on the AC mains, and can range from 7 to 14mm in diameter. However, to provide higher level surge immunity, outdoor lighting original equipment manufacturers (OEMs) may want to add surge protection devices (SPDs) on the AC input lines of their luminaires ahead of the LED driver. Coordination between the SPD and the Power Supply Unit 16

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