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The heat dissipation problem of the inverter

Jan 23, 2021

The heat dissipation problem of the inverter

If you want to use the inverter correctly, you must seriously think about heat dissipation. The failure rate of the inverter increases exponentially with the increase in temperature. The service life decreases exponentially with increasing temperature. When the ambient temperature rises by 10 degrees, the service life of the inverter is halved. Therefore, pay attention to the problem of heat dissipation! When the inverter is working, the current flowing through the inverter is very large, and the heat generated by the inverter is also very large. The influence of the heat cannot be ignored.


Generally, the inverter is installed in the control cabinet. To know the approximate calorific value of an inverter, you can use the following formula to estimate: Approximate calorific value = inverter capacity (KW55[W] Here, suppose the inverter capacity is the over-current capacity based on constant torque load 150%*60 If the inverter has a DC reactor or a communication reactor, and it is also in the cabinet, the heat will be greater at this time. The reactor equipment is better on the front of the inverter or above the test. At this time, budget can be used : Inverter capacity (KW60[W] Since the hardware of each inverter manufacturer is similar, the above formula can be used for products of various brands.


Note: If there is a braking resistor, because the heat dissipation of the braking resistor is very large, it is best to isolate the device from the frequency converter, such as on or next to the cabinet. So, how to reduce the heating value in the control cabinet? When the inverter is installed in the control cabinet, the heating value of the inverter should be considered. According to the increase in heat value occurring in the cabinet, the size of the cabinet should be increased appropriately.


Therefore, in order to reduce the size of the control cabinet as much as possible, it is necessary to reduce the heat value generated in the cabinet as much as possible. If the radiator of the inverter is placed outside the control cabinet when the inverter is installed, 70% of the heat generated by the inverter will be released to the outside of the control cabinet. Because the large-capacity inverter has a great heat generation, it is more effective for the large-capacity inverter.


The main body and the radiator can also be separated by an isolation plate, so that the heat dissipation of the radiator does not affect the main body of the inverter. This effect is also very good. The heat dissipation design of the inverter is based on a vertical device, and the heat dissipation will be worse if it is placed horizontally! Regarding the cooling fan, the inverter with a slightly higher power generally has a cooling fan. At the same time, it is also recommended to install a cooling fan on the air outlet of the control cabinet. A filter should be added to the air inlet to prevent dust from entering the control cabinet. Note that the fans on the control cabinet and the inverter are required.


In addition, the following two issues should be paid attention to for heat dissipation:


1 At altitudes higher than 1000m, because the air density is reduced, the cooling air volume of the cabinet should be increased to improve the cooling effect. In theory, the inverter should also consider derating, 1000m every -5%, but in fact, because the load capacity and heat dissipation capacity of the inverter are generally larger than the actual use, it depends on the specific application. For example, in the area of 1500m, but periodic loads, such as elevators, do not need to derate.


2 Switching frequency: The heating of the inverter mainly comes from the heating of IGBT, which is concentrated at the moment of opening and closing. Therefore, when the switching frequency is high, the heat generation of the inverter will increase. Some manufacturers claim that reducing the switching frequency can expand the capacity. This is the reason.