What is Operating Temperature?
The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.
The operating temperature is dependent on various natural and artificial environmental conditions. These include the weather, humidity, wind, sunshine, altitude and location where the equipment is used. The artificial conditions include the enclosure, the load, nearby equipment, whether the equipment is used indoors or outdoors, additional cooling options and much more.
Additionally, the operating temperature is affected by how fast the heat dissipated by the equipment is taken away, otherwise, this adds to the operating temperature which is the sum of the heat dissipated and the ambient temperature.
Most power supplies operate in the ambient temperature of about 25°C, and are therefore tested and rated at this temperature by manufacturers. However, due to heat dissipation by components such as the video cards and CPUs, the operating temperature of the power supply will definitely increase and its actual wattage lowered. High quality power supplies are usually tested and rated a higher temperature such as 50°C or higher.
Manufacturers specify the ambient temperature range over which the power supply or electronic equipment will operate efficiently and safely. Some equipment such as the military and outdoor telecommunication equipment operate in harsh environments, and sometimes hard to access areas such as the top of the masts.
Equipment designed for harsh environments must therefore have more reliable components and be able to withstand the wide variations in operating temperature and other environmental conditions. They use more expensive components and enclosures in addition to being rated at higher temperatures compared to the domestic and commercial electronic equipment which operates in a fairly stable and almost predictable environment.
Power supplies are rated based on the following normal operating temperature ranges:
- Commercial / domestic: 0°C to 85°C
- Industrial: -40°C to 100°C
- Automotive: −40°C to 125°C
- Extended: −40°C to 125°C
- Military: −55°C to 125°C
Due to the wide variation of operating temperatures, most manufacturers tend to rate their equipment at higher temperatures than the maximum temperature possible. They will specify the maximum operating temperature that the equipment will work safely without the need to derate or have additional cooling.
Derating is then used if the operating temperature deviates from the standard recommended by the manufacturer.