We know that the operating environment of the inverter is between - 10 ° C and + 50 ° C. The failure rate of frequency converter increases exponentially with the temperature. The service life decreases exponentially with the increase of temperature. It is reported that the service life of frequency converter will be halved when the ambient temperature is increased by 10 ℃. Therefore, we should pay attention to the problem of heat dissipation! When the frequency converter works, the current flowing through the frequency converter is very large, and the heat generated by the frequency converter is also very large, so the effect of its heat generation cannot be ignored. If the problem of converter heat dissipation is not handled well, it will affect the use state and service life of the converter, and even cause the damage of the converter.

1、 Heat dissipation method of frequency converter:

The heating of frequency converter is caused by internal loss. The main circuit accounts for 98% and the control circuit accounts for 2% in the loss of each part of the frequency converter. The data shows that the power consumption of the converter is generally 4~ 5% of its capacity. Among them, the inverter accounts for about 50%, the rectifier and DC circuit for about 40%, and the control and protection circuit for 5 ~ 15%. The 10C rule shows that when the temperature of the device decreases by 10 ° C, the reliability of the device will double. In order to ensure the normal and reliable operation of the frequency converter, it is necessary to deal with the heat dissipation of the frequency converter. The problem of converter heat dissipation is mainly the temperature and heat dissipation of converter working environment.

For the heat dissipation method of frequency converter, it is generally divided into the following three types:

1. Internal fan cooling

The built-in fan is generally used for the general inverter with small capacity. Through the correct installation of the frequency converter, the heat dissipation capacity of the internal fan of the frequency converter can be maximized. The built-in fan can take away the heat inside the frequency converter. Heat is dissipated through the iron plate of the box where the frequency converter is located. The method of cooling only through the fan inside the frequency converter is applicable to the control box with a separate frequency converter and the control box with fewer control elements. If there are several inverters in the inverter control box, or other electrical components with large heat dissipation, the effect of heat dissipation is not very obvious.

2. Fan cooling

By adding several fans with air exchange and convection function in the control box where the frequency converter is installed, the heat dissipation effect of the frequency converter can be greatly improved and the temperature of the working environment of the frequency converter can be reduced. The capacity of the fan can be calculated by the heat dissipation of the frequency converter. Let's talk about general selection methods:

According to our experience, the heat generated by the power consumption of every 1kW is calculated. The exhaust air volume of the fan is required to be 360m3 / h, while the power consumption of the frequency converter is 4-5% of its capacity. Here, we can calculate the relationship between the fan and its capacity as per 5%

Exhaust air volume of fan (m3 / h): converter capacity x 5% * 360m3 / h / kw

According to the above empirical formula, we can select fans for 90kw general inverter

Exhaust air volume of fan (m3 / h): 90kw * 5% * 360m3 / h / kw

Exhaust air volume of fan = 1620m3 / h

Then select the models of fans from different manufacturers through the exhaust air volume of fans. Get fans that meet our conditions.

Generally speaking, fan cooling is the main means of converter cooling at this stage. It is especially suitable for the large control cabinet, as well as the electrical components in the control cabinet working at the same time and heating at the same time. It is suitable for highly integrated centralized control cabinet and control box. And in recent years, due to the continuous progress of science and technology, the cooling fan is not as large as the previous years, small and powerful fans are everywhere. Cost performance is also much better than other ways of heat dissipation.

3. Air conditioning cooling

With the progress of science and technology, air conditioning is gradually applied to the production of control cabinet. And become one of the important means of heat dissipation. However, the frequency converter is rarely used for heat dissipation because of its high cost and relatively large volume. As the capacity of the general frequency converter ranges from several KVA to several + KVA, the capacity is not particularly large, so it is difficult to make the cost performance acceptable to the user. Only in special occasions (such as the special strict requirements on the working environment) and the frequency converter with a large capacity can be used This way. In addition, some of the air conditioners also involve the removal of waste water, so it is also necessary to consider more comprehensive in the process of panel cabinet complete set, increasing the design cost.

In addition, there are other reasons to consider the heat dissipation effect of the frequency converter, such as high altitude (> 1000m), because of the decrease of air density, the heat dissipation capacity should be increased appropriately; there are also switching frequencies, the heat of the frequency converter mainly comes from IGBT (insulated gate bipolar crystal tube), and the heat of IGBT is concentrated in the moment of opening and closing. Therefore, when the switching frequency is high, the heating capacity of the frequency converter becomes larger.

The fact shows that to deal with the heat dissipation of the frequency converter well requires not only the designer to do it from the frequency converter itself, but also the user to use it correctly and install it in strict accordance with the use instructions, with enough ventilation space and suitable use environment, and to maintain it regularly as much as possible, especially in the multi dust industries such as coal and carbon, to dust the use environment and the air duct of the frequency converter regularly, so as to Make the heat dissipation system of frequency converter play the normal function, make the temperature rise of frequency converter within the allowable value, the frequency converter can operate reliably, and bring greater economic and social benefits to the enterprise.

2、 Daily inspection items of frequency converter:

① Whether the sound changes abnormally during the operation of the motor, including whether the vibration occurs during the operation of the motor.

② Whether the installation environment of frequency converter changes. If the ambient temperature is normal, the working temperature of the frequency converter is generally required to be within the range of - 10 ° C to + 40 ° C, preferably around 25 "C.

③ Whether the frequency converter cooling fan works normally, including whether the frequency converter cooling channel is unblocked. Whether the output current, voltage, frequency and other data of the inverter on the display panel are normal. Whether the characters on the display panel are clear and lack of strokes.

④ Whether the frequency converter is overheated. The infrared thermometer can be used to detect whether the radiator of the frequency converter is overheated or has peculiar smell. Check whether there is fault alarm display in the operation of frequency converter.

⑤ Regularly clean the filter screen of the air inlet in the electrical control cabinet. Keep the control cabinet and frequency converter in a good clean state at all times. Effectively remove the dust on the surface of the frequency converter to prevent the dust from entering the inverter. Especially metal dust. Effectively remove the oil contamination of the converter cooling fan.

⑥ Use the annual overhaul time to open the frequency converter, place the inspection in the interior that cannot be seen in normal daily operation, and carry out cleaning work. Use brush or vacuum cleaner to clean the circuit board of frequency converter, internal rectifier module, IGBT module, DC filter electrolytic capacitor, input and output reactor and other parts. The unqualified electronic components shall be replaced (Note: the internal filter electrolytic capacitor of frequency converter generally needs to be replaced in 4-5 years).

⑦ Check the cooling electric fan, which is easy to damage components. Its life is limited by bearings (it is an axial fan. According to the operation of frequency converter, the fan or fan bearing shall be replaced once every 2-3 years.