[Source: Gaogong LED 's " LED Good Products" magazine May issue / Chen Yufeng Translation / Zhao Yong] GARY CHAN said, how to deal with the pressure difference is still a hidden design difficulty, moisture and ventilation design can enhance the reliability of LED lamps, Extend its service life.
Many commercial and residential lighting has been upgraded to LED light sources because solid-state lighting (SSL) luminaires continue to deliver more than 100,000 hours of light, and it is also the most environmentally friendly and reliable lighting solution available today—especially in outdoor lighting. However, in outdoor applications and harsh environments, potential water leaks can cause lamp failure and failure. Although product developers can seal the luminaire and isolate the luminaire from the environment, the negligible pressure differential between the inside and outside of the luminaire can cause many problems. Let's explore this pressure issue and consider mechanical design to eliminate this problem to ensure the life of the luminaire.
The benefits of LED luminaires are endless.
In addition to the long life mentioned above, solid-state lighting products fully comply with the Restriction of Hazardous Substances (RoHS) regulations, saving up to 85% in energy consumption over traditional lighting technologies.
Although LEDs can last for more than 20 years, this life cycle adds value to the entire lighting system only when the accompanying electronics, power and drive power supplies, and the entire fixture are as reliable and durable as LEDs. All parts of the luminaire must be able to withstand the harsh conditions of the environment, whether it is the tropical climate of the Caribbean or the coolness of Alaska.
The challenge of harsh environments According to a study by RTI International, the main cause of LED lamp failures is drive power problems such as capacitor and interconnect failures, voltage, moisture or other chemical intrusions.
Traditional drive power supplies have a five-year warranty, but experiments have shown that these drive power supplies have a high failure rate. Reliability issues are typically caused by seals, joints, and joints that are damaged by environmental conditions.
Most engineers typically use the following three methods to enhance the durability of the luminaire housing, protecting the drive power and electronics: using a more durable seal or gasket to improve the seal; increasing the thickness of the housing to reduce the movement of the enclosure around the seal; / Or install more screws around the seal or gasket to maintain a more durable seal.
However, even with these measures, the seal leaks, causing water intrusion and eventually condensation on the lens and mirror.
This often happens because sealing the entire luminaire can prevent the luminaire from handling pressure fluctuations, whether positive or negative (or vacuum). When such pressure fluctuations occur, large stresses are formed on the seal ring and other joints, thereby affecting the sealing effect. Over time, frequent expansion and contraction of the seal will void the weak points of the seal, thereby losing the seal, allowing water, dust and contaminants to enter the fixture, causing potential corrosion, short circuits or electronic component failure.
Temperature changes, whether external, internal or internal and external, are one of the most common causes of differential pressure. External temperature changes can be very intense (for example, sudden rainstorms in hot summers), or they may change more smoothly as the seasons alternate. The temperature can be reduced by 10 to 20 °C every day to night, and the seasonal temperature difference between winter and summer can reach 40 °C or more.
As the temperature rises, the air inside the luminaire expands, creating a positive pressure on the seals, joints, and joints. When the temperature drops, the internal air contracts and creates a vacuum, again causing pressure on the seal.
A temperature change of 30 °C causes about 10% of the air to flow into or out of the luminaire.
For different sized luminaires, a rapid drop in external temperature can cause a vacuum of 0.5 psi (35 mbar) or higher inside the luminaire. When a vacuum occurs, water, dust, and contaminants can enter the housing. In the better case, it only accelerates the corrosion; but in severe cases, a catastrophic failure will occur. Corrosion can damage the LEDs, wires and cables, and other electronic components contained in the fixture, and ultimately shorten the life of the fixture.
Figure 1 shows the temperature fluctuations inside and outside the luminaire, which is shown in relation to the switching period of the power supply. When the light is turned on, the temperature inside the lamp rises. With the switch of the luminaire, the temperature change will cause a sudden pressure difference (Fig. 2). When there is a pressure difference, the luminaire releases the pressure by sucking in or excluding air. If the air cannot enter and exit the luminaire at this time, the pressure difference will be applied to Sealing ring.
Unfinished , please refer to the May issue of Gaogong LED 's " LED Good Products" magazine.
Many commercial and residential lighting has been upgraded to LED light sources because solid-state lighting (SSL) luminaires continue to deliver more than 100,000 hours of light, and it is also the most environmentally friendly and reliable lighting solution available today—especially in outdoor lighting. However, in outdoor applications and harsh environments, potential water leaks can cause lamp failure and failure. Although product developers can seal the luminaire and isolate the luminaire from the environment, the negligible pressure differential between the inside and outside of the luminaire can cause many problems. Let's explore this pressure issue and consider mechanical design to eliminate this problem to ensure the life of the luminaire.
The benefits of LED luminaires are endless.
In addition to the long life mentioned above, solid-state lighting products fully comply with the Restriction of Hazardous Substances (RoHS) regulations, saving up to 85% in energy consumption over traditional lighting technologies.
Although LEDs can last for more than 20 years, this life cycle adds value to the entire lighting system only when the accompanying electronics, power and drive power supplies, and the entire fixture are as reliable and durable as LEDs. All parts of the luminaire must be able to withstand the harsh conditions of the environment, whether it is the tropical climate of the Caribbean or the coolness of Alaska.
The challenge of harsh environments According to a study by RTI International, the main cause of LED lamp failures is drive power problems such as capacitor and interconnect failures, voltage, moisture or other chemical intrusions.
Traditional drive power supplies have a five-year warranty, but experiments have shown that these drive power supplies have a high failure rate. Reliability issues are typically caused by seals, joints, and joints that are damaged by environmental conditions.
Most engineers typically use the following three methods to enhance the durability of the luminaire housing, protecting the drive power and electronics: using a more durable seal or gasket to improve the seal; increasing the thickness of the housing to reduce the movement of the enclosure around the seal; / Or install more screws around the seal or gasket to maintain a more durable seal.
However, even with these measures, the seal leaks, causing water intrusion and eventually condensation on the lens and mirror.
This often happens because sealing the entire luminaire can prevent the luminaire from handling pressure fluctuations, whether positive or negative (or vacuum). When such pressure fluctuations occur, large stresses are formed on the seal ring and other joints, thereby affecting the sealing effect. Over time, frequent expansion and contraction of the seal will void the weak points of the seal, thereby losing the seal, allowing water, dust and contaminants to enter the fixture, causing potential corrosion, short circuits or electronic component failure.
Temperature changes, whether external, internal or internal and external, are one of the most common causes of differential pressure. External temperature changes can be very intense (for example, sudden rainstorms in hot summers), or they may change more smoothly as the seasons alternate. The temperature can be reduced by 10 to 20 °C every day to night, and the seasonal temperature difference between winter and summer can reach 40 °C or more.
As the temperature rises, the air inside the luminaire expands, creating a positive pressure on the seals, joints, and joints. When the temperature drops, the internal air contracts and creates a vacuum, again causing pressure on the seal.
A temperature change of 30 °C causes about 10% of the air to flow into or out of the luminaire.
For different sized luminaires, a rapid drop in external temperature can cause a vacuum of 0.5 psi (35 mbar) or higher inside the luminaire. When a vacuum occurs, water, dust, and contaminants can enter the housing. In the better case, it only accelerates the corrosion; but in severe cases, a catastrophic failure will occur. Corrosion can damage the LEDs, wires and cables, and other electronic components contained in the fixture, and ultimately shorten the life of the fixture.
Figure 1 shows the temperature fluctuations inside and outside the luminaire, which is shown in relation to the switching period of the power supply. When the light is turned on, the temperature inside the lamp rises. With the switch of the luminaire, the temperature change will cause a sudden pressure difference (Fig. 2). When there is a pressure difference, the luminaire releases the pressure by sucking in or excluding air. If the air cannot enter and exit the luminaire at this time, the pressure difference will be applied to Sealing ring.
Unfinished , please refer to the May issue of Gaogong LED 's " LED Good Products" magazine.
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