High power frequency online UPS (uninterruptible power supply) is a key power guarantee equipment widely used in data centers, industrial control, medical facilities and other scenarios. Its heat dissipation design and environmental adaptability directly affect operational reliability, lifespan, and performance. The following provides a detailed analysis from these two aspects:
1、 Heat dissipation design of high-power power frequency online UPS
High power frequency UPS (usually referring to power ≥ 50kVA) uses power frequency transformers (large volume, high loss), high-power rectifier/inverter modules and other components, which generate a large amount of heat (single power consumption can reach several kW to tens of kW), and heat dissipation design is one of the core technologies.
1. Analysis of main heat sources
The core heating components that require targeted heat dissipation include:
Power frequency transformer: As an iconic component of power frequency UPS, its core losses (hysteresis, eddy current losses) and winding losses (resistance heating) account for 30% -50% of the total losses and are one of the main heat sources.
Rectifiers and inverters: composed of power semiconductor devices such as IGBT and rectifier bridge, with switching losses and conduction losses accounting for 20% -40% of the total losses. The junction temperature of the devices needs to be strictly controlled (usually ≤ 125 ℃).
Battery pack (if built-in): Lead acid batteries generate heat during charging and discharging, and their capacity decay accelerates at high temperatures (with a lifespan halved for every 10 ℃ increase in temperature).
Auxiliary circuit: including control board, capacitors, inductors, etc. Although the loss is small, long-term high temperature can cause capacitor aging and solder joint oxidation.
2. Heat dissipation method and design points
High power frequency UPS mainly uses forced air cooling (natural heat dissipation is only applicable to low-power models), and the design needs to balance "heat dissipation efficiency" and "system reliability":
Fan selection:
Adopt high air volume, high air pressure axial fans or centrifugal fans (the air volume needs to be calculated based on the total heat dissipation, usually requiring 50-100m ³/h of air volume per kW loss), and prioritize models with long lifespan (≥ 50000 hours) and redundant design (N+1 backup, single fan failure does not affect overall heat dissipation).
Example: The total loss of a 100kVA UPS is about 5kW, and the total air volume of the fan needs to be ≥ 300m ³/h.
Air duct design:
The core is "directional diversion and avoiding hotspots", and common design principles include:
Cold air enters from the bottom/front and flows through heating components such as transformers, power modules, and heat sinks, while hot air is discharged from the top/rear (such as "bottom in, top out" or "front out") to avoid hot air backflow.
Adopting isolated air ducts: Separate the air ducts between the strong current area (transformer, power module) and the weak current area (control board) to prevent high temperatures in the strong current area from affecting the weak current components.
Optimize the airflow path: guide the airflow to flow through the heating components through deflectors and baffles, reducing "airflow short circuits" (direct discharge without passing through the heat source).
Heat sink and heat conduction:
Power devices (IGBT, rectifier bridge) need to be connected to large-area aluminum heat sinks through thermal pads/silicone grease. The heat sinks are designed in a comb tooth shape to increase the heat dissipation area (≥ 100cm ² heat dissipation area is required for every 100W loss), and are matched with a fan for forced convection.
Intelligent temperature control system:
Install temperature sensors (NTC, thermocouple) in key areas such as transformers, inverters, and heat sinks to monitor temperature in real time and dynamically adjust fan speed: operate at low speeds at low temperatures to reduce noise and energy consumption, and operate at high speeds at high temperatures to enhance heat dissipation, balancing heat dissipation effectiveness and fan lifespan.
2、 Environmental adaptability of high-power power frequency online UPS
The operating environment of UPS directly affects its stability and lifespan, and it needs to adapt to various environmental factors. The core requirements are as follows:
1. Temperature adaptability
Working temperature range: Manufacturers usually label it as 0-40 ℃ (some industrial models can reach -10-50 ℃), and strict control is required:
High temperature hazards: shortened lifespan of electrolytic capacitors (halving lifespan at 10 ℃ per liter), accelerated insulation aging of transformers, and decreased battery capacity (optimal at 25 ℃, significantly reduced capacity above 30 ℃).
Low temperature hazards: sudden drop in battery capacity (70% of capacity at -10 ℃ is only at 25 ℃), increased switching losses in semiconductor devices.
Response measures: The computer room should be equipped with air conditioning (temperature controlled at 20-25 ℃) to avoid direct sunlight or proximity to heat sources (such as generators and boilers).
2. Humidity adaptability
Suitable humidity: Relative humidity of 20% -80% (no condensation), there is a risk of high or low humidity:
High humidity (>80%): The circuit board becomes damp and moldy, reducing insulation resistance and easily causing short circuits; Corrosion of metal components (such as connectors and heat sinks).
Low humidity (<20%): generates static electricity (voltage can reach thousands of volts), damaging sensitive components such as control chips and sensors.
Response measures: Install dehumidifiers (when high humidity) or humidifiers (when low humidity) to avoid condensation (temperature and humidity sensors can be installed for linkage control).
3. Altitude and air pressure
Rising altitude (>1000 meters) can lead to:
The air is thin, and the heat dissipation capacity decreases (the convective heat dissipation efficiency decreases with altitude, and the heat dissipation capacity decreases by about 10% for every 1000 meters of elevation).
The decrease in air dielectric strength makes high-voltage components (such as transformers and busbars) prone to corona discharge, accelerating insulation aging.
Response measures: Manufacturers usually stipulate that "when operating at full power below an altitude of 1000 meters, the rating must be reduced (by 5% -10% for every 1000 meters increase)"; High altitude areas need to strengthen heat dissipation (increase fan airflow) and increase insulation distance.
4. Dust and pollutants
Hazards of dust (dust, fibers, metal powder):
Covering heat sinks/fans to reduce heat dissipation efficiency; Deposition on the circuit board can lead to poor insulation and even short circuits (metal dust conducts electricity).
Corrosive gases in industrial environments, such as sulfides and chlorine oxides, can corrode copper foils and connector contacts, leading to poor contact.
Response measures:
Install dust-proof nets at the air inlet and outlet (regularly cleaned, with a cycle adjusted according to dust concentration, usually 1-3 months).
Industrial scenes adopt high protection level models (such as IP54, dustproof+splash proof), and the computer room maintains positive pressure (to prevent external dust from entering).
5. Vibration and impact
Vibration (such as near machine tools and pump equipment) may cause loose screws, connector detachment, and loose transformer cores (increased noise and losses).
Response measures: Use shock-absorbing foot pads (made of rubber material), reinforce components (with screws and anti loosening washers), and select locking connectors (such as aviation plugs).
3、 Summary and Extension
The heat dissipation design of high-power power frequency online UPS needs to achieve rapid heat export through "precise heat source positioning+efficient forced air cooling+intelligent temperature control" to avoid hotspots; Environmental adaptability requires the use of "environmental parameter control (temperature and humidity, cleanliness)+targeted design of the model (protection level, shock resistance)" to cope with complex scenarios.
In practical applications, it is necessary to select the appropriate model based on the characteristics of the scenario (such as choosing a wide temperature and high protection model for industrial environments, and a high-efficiency cooling and low-noise model for data centers), and to cooperate with regular maintenance (cleaning dust nets, checking fans, and replacing aging capacitors) in order to maximize the reliability and lifespan of UPS.
