What do they mean by Output Power Derating?

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All power provides have a specified “Working Temperature Vary”. For instance, TDK-Lambda’s AC-DC switch-mode SWS600L collection of 600 watt, single output power provides have an working temperature vary from “-20°C to +74°C”. Nonetheless, the spec additionally states: “…derating linearly to 50% load above 50°C”. What does this mean?

Please seek advice from Determine 1 under. Most power provide producers present any such curve to make it simpler for the tip person to find out the utmost output power that may offered by a power provide at varied working or ambient temperatures. Ta = Temperature of the Ambient Air, or, the temperature of the air surrounding the power provide, particularly the air on the consumption of a fan-cooled provide. By evaluating the “Working Temperature Vary” specification listed above to the derating curve, the next data might be seen:

  • The provision can ship 100% of its rated output power load (600 watts) from -20°C to +50°C ambient temperatures
  • Above 50°C ambient, the provision can ship a lowered quantity of power
  • At 60°C ambient, the provision can present about 80% of its max. rated power (0.80 x 600 = 480 watts)
  • At 74°C ambient, the provision can present 50% of its max. rated power load (0.50 x 600 = 300 watts)

Determine 1: SWS600L Output Power Derating Curve

Along with the provision’s regular “working temperature vary” and output derating-curve, some provides like this one, have a specified low-temperature “start-up” functionality (i.e., -40°C). Because of this the provision can “start-up” or be “turned-on” with an ambient temperature as little as -40°C (under the -20°C spec) and ship 100% of its rated power, nevertheless, the provision’s output regulation, hold-up time, ripple & noise, and different specifications can't be totally assured till the provision warms as much as at the very least -20°C. This chilly temperature start-up is a pleasant feature to have, particularly for outdoor-mounted functions. As soon as the provision is turned-on it's going to often self-heat because of the warmth generated by its internal digital power elements.