High frequency online UPS, due to its high power density, generates a large amount of heat from power electronic components such as rectifiers and inverters during operation. Its cooling system uses mainstream methods such as air cooling and liquid cooling, combined with intelligent control mechanisms, to selectively dissipate heat from different components and ensure stable operation of the equipment. The working principles of different cooling methods are as follows:
Air cooled cooling system
This is the most commonly used cooling method in high-frequency online UPS, with a simple structure and easy maintenance. It is divided into two forms: basic air cooling and intelligent air cooling, and is widely suitable for small and medium power models.
Basic air cooling: UPS chassis will reserve air inlet and outlet ports, and be equipped with cooling fans. Some models will also install cooling fins on the surface of core heating components such as rectifiers and inverters. When the fan is running, it draws external cold air into the machine, and the airflow flows through the heat sink and the surfaces of various heating elements, taking away heat through thermal convection. Finally, the hot air carrying heat is discharged from the air outlet, forming a complete heat dissipation airflow cycle. Some cabinet style UPS systems also install fans on the back panel to further enhance air circulation inside the unit.
Intelligent speed regulation and air cooling: This advanced form is commonly used in medium and high-power high-frequency online UPS systems. The device is equipped with built-in current sensors and temperature sensors to monitor the load rate and temperature of key components such as rectifiers and IGBT inverters in real time. The controller determines the target control temperature based on the detected load rate through algorithms, and then compares the real-time temperature to adjust the PWM drive signal of the cooling fan, thereby changing the fan speed. For example, when the load rate is high or the device temperature suddenly rises, the fan automatically speeds up to accelerate heat dissipation; When the load is low and the temperature is low, slowing down the fan can not only reduce energy consumption and noise, but also extend the service life of the fan. Some high-end models will also adopt fan redundancy design to enhance the reliability of the cooling system.
Liquid cooled cooling system
This system has higher heat dissipation efficiency and is suitable for high-power, high power density high-frequency online UPS. It can solve the problem of insufficient air cooling heat dissipation and is commonly used in data centers and industrial high-power scenarios. There are two main application solutions:
Targeted cavity liquid cooling: For core heating components such as electronic control components, a heat absorbing cover is used to seal and form a closed cavity. Electronic fluorine liquid is injected into the cavity and negative pressure is maintained. The evaporation tube inside the heat absorbing cover comes into contact with the electronic fluorine liquid. At the same time, the evaporator tube is connected to the external condenser tube through a compression pump and an expansion valve, and the condenser tube is also equipped with heat dissipation fins. After absorbing the heat from the electronic control components, the electronic fluorine liquid is transferred to the condenser tube through the evaporator tube, and the heat is dissipated through the heat sink. The condensed medium then flows back to the evaporator tube, forming a circulating refrigeration system. Some designs will also be equipped with electrode airflow plates to accelerate the airflow around the heat sink and improve condensation efficiency.
Partition circulation liquid cooling: According to the internal structure of UPS, the battery compartment cooling chamber and functional compartment cooling chamber are divided to cool down the battery and functional components respectively. The system is equipped with a storage tank, a temperature control box, and a circulation pipeline. The temperature control box adjusts the coolant temperature through low-temperature and high-temperature pipes, and the control module dynamically adjusts the strategy based on the UPS charging and discharging status. For example, during the fast charging stage, if the temperature rises quickly, the coolant is controlled to circulate rapidly at a lower temperature; The temperature during the float charging stage is stable, and the coolant temperature can be appropriately increased to save energy. The heated coolant flows back to the storage tank for cooling and then circulates again.
Composite cooling system
Some high-end high-frequency online UPS systems will combine the advantages of air cooling and liquid cooling to form a composite cooling system. For example, the liquid cooling system is responsible for taking away the main heat from core high-power components such as rectifiers and inverters, and then accelerating the air flow inside the machine through a small fan to discharge the heat generated by auxiliary components such as batteries. At the same time, it can also dissipate a small amount of waste heat on the surface of the liquid cooling pipeline. In addition, such systems are often equipped with dust removal structures to avoid dust accumulation and affect the efficiency of heat dissipation components, ensuring the long-term stable operation of the heat dissipation system.
