Analysis of the heat generation of the photovoltaic inverter shell and the heat dissipation principle of the inverter

Inverters running in summer may feel hot to the touch due to their high shell temperature. And why does the casing feel hot? The following will do some analysis and answers for these two problems combined with inverter heat dissipation.

The components in the inverter have their rated operating temperature. If the heat dissipation performance of the inverter is poor, as the inverter continues to work, the heat of the components will not be transferred to the outside world, and its temperature will become higher and higher. Excessive temperature will reduce the performance and life of the components. In order to keep the operating temperature of the internal components of the inverter within the rated temperature range and ensure its performance and service life, heat-conducting materials are required to transfer the heat inside the inverter.

From the perspective of heat conduction, the more balanced the temperature inside and outside the inverter, that is, the closer the temperature of the internal heating components to the heat sink and the outer shell, the better the heat conduction. If the inverter is cold outside and hot inside, it means that the heat dissipation performance of the inverter is not good.

Inverter Heat Dissipation and Heat Dissipation Design

1. In the circuit, as long as the current is applied to the active components, heat will be generated. The main heating components in the inverter are: switching tubes (IGBT, MOSfet), magnetic core components (inductors, transformers), etc. Therefore, in order to ensure that the components can work at the rated temperature, the heat dissipation capability of the system is very important.

2. To make the heat dissipation performance excellent, it can be achieved by the following points:

①The larger the heat dissipation area, the better the effect

For example, the heating power of a 5kW inverter is 125W. According to the maximum heat flux density that can be borne by natural cooling at 60°C, the heat dissipation area is at least about 0.25m2. In order to ensure that the volume remains unchanged, the surface area of the radiator is increased. The design of multi-radiating teeth and folds increases the contact area between the radiator and the air, which is conducive to rapid heat dissipation.

②Closer-radiator tight docking structure

The inverter casing is made of aluminum alloy, which has good thermal conductivity. As shown in the figure above, the integral shell structure is adopted, the radiator and the shell are directly connected closely through a large area, and the heat of the components can be directly transferred to the aluminum alloy shell through the radiator, forming a heat dissipation path from the device → radiator → shell → air .

3. Reasons for heating and hands scalding of the inverter shell

1. 1. In order to reduce the temperature of the components better and faster and ensure the longer service life of the components, the design of the integral shell and the radiator is closely contacted, so that the shell becomes an important part of the heat dissipation of the system, the heat dissipation performance is enhanced, so the temperature of shell is high, which is a normal phenomenon of the inverter.

2. Somatosensory temperature: The human body’s somatosensory temperature is around 36°C, and there will be a warm feeling; at around 45°C, there will be a hot feeling; at around 50°C, there will be a burning pain; Formation of burns will happen at 60°C.

Due to the need for heat dissipation of the inverter and the particularity of the working environment (outdoor direct sunlight), the safety standard stipulates that the temperature of the inverter shell cannot exceed 70°C. When the external ambient temperature is 40°C in summer, the shell temperature is generally 55°C to 60 ℃, so when people touch the inverter shell, they will feel scalded.