The cooling system of high-power power frequency online UPS (usually referring to online uninterruptible power supply with rated power ≥ 10kVA, using power frequency transformer as rectifier/inverter isolation or output isolation) is one of the core components to ensure its long-term stable operation. Due to its high power density, large losses in power frequency transformers, and concentrated heating of power devices (IGBT, rectifier bridge, etc.), if the heat dissipation fails, it will directly lead to device overheating damage, decreased output performance, and even machine shutdown. Therefore, its heat dissipation design needs to take into account the three core goals of "efficient heat conduction", "uniform temperature control", and "redundant reliability".
1、 The main heat source of high-power power frequency online UPS (the core object of heat dissipation design)
Before analyzing the heat dissipation system, it is necessary to first clarify its core heating components - the differences in heat generation and thermal characteristics of different components, which determine the targeted design of the heat dissipation scheme
2、 The mainstream cooling solution for high-power power frequency online UPS (multi-dimensional collaborative design)
In response to the characteristics of the above-mentioned heat sources, the industry mainstream adopts a composite solution of "zone heat dissipation+multi-media heat conduction+intelligent temperature control", which can be broken down into the following four core dimensions:
1. Structural layout: Source optimized heat flow path (passive heat dissipation foundation)
The internal layout of high-power power frequency UPS prioritizes the principle of "heat source separation and smooth heat flow" to reduce thermal interference from a physical structure perspective
Heat source zoning arrangement: Independently arrange the most concentrated power frequency transformers and reactors at the bottom or side of the chassis (utilizing the natural convection characteristics of rising hot air to prevent heat from spreading upward to the control board); Power devices (IGBT modules) are centrally installed in independent "power cabinets" or "heat dissipation chambers", completely isolated from control circuits (temperature sensitive low-voltage components such as CPUs and sampling chips).
Pre planning of air ducts: Clear "air inlet cooling outlet" channels are reserved inside the chassis, such as: bottom/side air inlet → passing through transformers/reactors → blowing towards power device heat sinks → top/rear air outlet, to avoid "dead corners" causing hot air to be trapped.
Metal shell thermal conductivity enhancement: The chassis is made of cold-rolled steel plate or aluminum alloy material (the thermal conductivity of aluminum alloy is about 200W/(m · K), much higher than that of steel). Some models install thermal pads between the transformer and reactor shells and the chassis to accelerate heat conduction to the outside world.
2. Thermal and heat dissipation components: the key to "heat export" of the core heat source
Differentiated heat conduction/dissipation components are used to ensure rapid heat transfer from the heating element to the cooling medium (air/liquid) based on the thermal characteristics of different heat sources
3. Intelligent temperature control system: dynamically matching heat dissipation requirements (energy-saving+reliable)
The heat dissipation of high-power power frequency UPS is not achieved through "full load operation", but through temperature sampling and logic control to achieve "on-demand heat dissipation", balancing heat dissipation efficiency and energy consumption:
Multi point temperature sampling: Install NTC thermistors or PT100 platinum resistors at key locations (IGBT heat sinks, transformer windings, chassis air vents) to monitor temperature in real-time (sampling accuracy ± 1 ℃).
Hierarchical control strategy:
Low temperature range (such as ambient temperature<25 ℃, IGBT temperature<50 ℃): The fan runs at low speed, only meeting basic heat dissipation needs, reducing noise and energy consumption;
Medium temperature range (ambient temperature 25-35 ℃, IGBT temperature 50-70 ℃): The fan speed increases linearly with temperature to ensure timely removal of heat;
High temperature range (ambient temperature>35 ℃, IGBT temperature 70-85 ℃): The fan runs at full speed and triggers a "capacity reduction warning" (indicating that the user's load is too high);
Overtemperature protection (IGBT temperature>90 ℃ or transformer temperature>120 ℃): Immediately cut off some non critical loads. If the temperature continues to rise, trigger the whole machine to shut down to avoid device burnout.
4. Environmental Adaptation Design: Coping with Complex Application Scenarios
High power frequency UPS is commonly used in industrial workshops, data centers, outdoor base stations, and other scenarios, and the cooling system needs to adapt to different environmental challenges:
Dustproof design: Install a detachable dust-proof net at the air inlet (some models come with dust-proof cotton) to prevent dust from blocking the fins of the heat sink; Industrial models adopt a "positive pressure air duct" (maintaining a slight positive pressure inside the chassis) to prevent external dust from entering.
Moisture proof/anti-corrosion design: For coastal or high humidity scenarios, the surface of the heat sink is treated with "electrophoretic rust prevention", and the fan motor adopts a sealed structure; The chemical scene model adopts a fully enclosed heat dissipation chamber filled with inert gas inside.
High temperature environment adaptation: For outdoor or high-temperature workshop models, "dual cycle heat dissipation" (internal air cooling+external water cooling) can be used, or "phase change heat dissipation materials" can be installed on the heat sink (using material phase change heat absorption to buffer temperature surges).
3、 Maintenance points for cooling system (extending UPS life)
The heat dissipation efficiency of high-power power frequency UPS will decrease over time and requires regular maintenance:
Clean the dust screen/heat sink: Remove the dust screen and clean it every 3-6 months (1-2 months in industrial scenarios). Use compressed air (pressure ≤ 0.3MPa) to blow away the dust between the fins of the heat sink to avoid increasing thermal resistance;
Check the status of the fan: listen to the running noise of the fan (whether there is any abnormal noise), measure the speed (whether it conforms to the temperature control logic), replace the aging fan every 2-3 years (to avoid bearing wear causing it to stop running);
Temperature sensor detection: Regularly check the temperature of each point through the UPS monitoring interface, compare the actual measured values (such as using an infrared thermometer to measure the temperature of IGBT heat sink), and ensure that the sensor has no drift;
Maintenance of liquid cooling system: If it is a liquid cooling model, check the coolant level and purity every year, replace the coolant every 3 years to avoid pipeline blockage or corrosion.
4、 Summary
The heat dissipation design of high-power power frequency online UPS is a multidimensional system engineering of "structure, materials, control, and environment", with the core logic of "accurate identification of heat sources - efficient export of heat - dynamic matching requirements - adaptation to complex scenarios". The reliability of its cooling system directly determines the MTBF (mean time between failures) of the UPS. Therefore, when selecting, in addition to focusing on parameters such as power and redundancy, it is also necessary to evaluate whether the cooling scheme is suitable for its own application scenario (such as ambient temperature, dust level, installation space), and ensure long-term stability of the cooling efficiency through standardized maintenance.
