CRS Electronics was requested to conduct cold-temperature evaluations of the product family. Testing was carried out in our environmental chamber to assess fixture operational behaviour in cold temperature conditions.
For cold temperature installations, most power supplies have trouble with cold-start below a certain threshold. This is exacerbated by the LED forward voltage dependence on temperature, causing a significant rise in the required voltage to drive the LED board. When tested, the Meanwell supplies started to show reduced output for cold starts at -32°C, but self-heating should allow the units to operate at full or near to full power. Below -32°C cold-start operation of this supply cannot be guaranteed, and continuous operation is recommended.
The Autec supplies are more tolerant of cold temperatures than the Meanwell drivers. The Autec configuration (123.5’ cable test for maximum voltage drop) successfully cold started to 98% of full power from a power supply temperature of -45°C, working at full power above this level. The best performing minimum operational temperature, with full power output during continuous operation, was achieved with the Autec supplies at -60°C ambient. The minimum operating temperature will be lower during field use when the effects of maximum allowable voltage drop are not being experienced, as they were in this testing.
The 3-conductor head with Meanwell power supply and 5-conductor head with dual Autec supplies were connected and powered up in the CRS Electronics environmental test chamber which was at room temperature and humidity (un-powered). The cable distance between power supply and head was 3.5 feet for the 5-conductor head, and 3-feet for the 3-conductor head. After approximately 1 minute when power draw had stabilized, the current draw and voltage were measured for each head. A second Meanwell power supply was also tested, to ensure that more than one supply of each type was evaluated.
When tested with a 3-foot cable distance, both power supplies tested out normally. Each supply was tuned to 6.0A output. Cold-start testing was done at a range of temperatures, with the onset of current limited behaviour at around -30°C. At -32°C the supplies cold start to around 70% of nominal current, and self-heating of the power supply should allow full power operation at steady state. Cold start at -45°C was unsuccessful. Minimum operational temperature is -60°C ambient at reduced power.
When tested with a 3.5-foot cable distance, both power supplies tested out normally at 3.5A output. When 120 feet of #18AWG 3-conductor SOOW cable was installed in addition to the 3.5-foot lead from the head, the additional voltage drop due to the line losses was compensated by an increased output voltage and the supplies continued to output 3.5A each, as expected. With good operation with a 123.5 foot cable distance at room temperature, this setup was used for further cold-temperature testing. Cold temperatures will act to further raise the output voltage, providing more operational stress on the power supplies.
Cold-start testing was done at a range of temperatures, with the supplies successfully starting up to 98% of full power from -45°C. Cold start at -50°C was unsuccessful. The minimum operational temperature, with full power output during continuous operation, was -60°C ambient. The minimum operating temperature will be lower during field use when the effects of maximum allowable voltage drop are not being experienced, as they were in this testing.