Solution and precautions for inverter thermal problems

For the frequency converter, as the temperature rises, the failure rate increases exponentially and the service life decreases exponentially. Therefore, how to properly handle the thermal problem of the inverter? This paper brings the solution to the thermal problem of the inverter and explains the precautions for the heat dissipation problem of the inverter.

How to correctly handle the thermal problem of the inverter? First, we must correctly understand the working principle of the inverter and seriously consider the heat dissipation problem of the inverter.

We know that the failure rate of the inverter increases exponentially with increasing temperature. The service life decreases exponentially with increasing temperature. The ambient temperature rises by 10 degrees and the life of the inverter is halved. Therefore, we must pay attention to the heat dissipation problem! When the inverter works, the current flowing through the inverter is very large, and the heat generated by the inverter is also very large, and the influence of the heat generation cannot be ignored.

Solutions and steps to properly handle the thermal problems of the inverter

Usually, the frequency converter is installed in the control cabinet. We need to know what the heat output of a frequency converter is, which can be estimated by the following formula:

Approximate calorific value = inverter capacity (KW) × 55 [W]

Here, if the inverter capacity is based on the constant torque load (overcurrent capability 150%*60s), if the inverter has a DC reactor or an AC reactor and is also inside the cabinet, the heat will be even more. Larger, so it is better to install the reactor on the side of the inverter or above.

At this time, you can use the estimation: the inverter capacity (KW) × 60 [W] because the hardware of each inverter manufacturer is similar, so the above formula can be used for each brand of products. Note: If there is a braking resistor, because the braking resistor has a large amount of heat dissipation, it is best to install the position separately from the inverter, such as on or near the cabinet.

Then, how can we reduce the heat generated in the control cabinet? When the inverter is installed in the control cabinet, the problem of the heating value of the inverter should be considered. According to the increase in the amount of heat generated in the cabinet, the size of the cabinet should be appropriately increased. Therefore, in order to minimize the size of the control cabinet, it is necessary to reduce the amount of heat generated in the cabinet as much as possible. If the radiator part 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. Since large-capacity inverters have a large amount of heat, they are more effective for large-capacity inverters. It is also possible to use a spacer to separate the body from the heat sink so that the heat dissipation of the heat sink does not affect the body of the inverter, and the effect is also good. The thermal design of the inverter is based on vertical installation, and the heat dissipation will be worse when placed horizontally.

Regarding the cooling fan, the inverter is generally slightly larger in power, and 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 screen is 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 all required, and no one can replace who.

The matters needing attention in the heat dissipation of the inverter:

(1) Where the altitude is 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 frequency converter should also consider derating, 1000m per 5%. However, in fact, because the load capacity and heat dissipation capacity of the designed inverter are generally larger than the actual use, it is also necessary to look at the specific application. For example, at 1500m, but periodic loads, such as elevators, do not need to be derated.

(2) Switching frequency: The heat of the inverter mainly comes from the IGBT, and the heating of the IGBT is concentrated at the moment of opening and closing. Therefore, the natural heat of the inverter becomes larger when the switching frequency is high. Some manufacturers claim that reducing the switching frequency can be expanded, which is the reason.