CNWe know that the working environment of the inverter is between -10°C and +50°C. The failure rate of the frequency converter increases exponentially with the increase of temperature. The service life decreases exponentially with increasing temperature. It is reported that if the ambient temperature rises by 10 degrees, the service life of the inverter will be halved. Therefore, we must pay attention to the heat dissipation problem! When the frequency converter is working, the current flowing through the frequency converter is very large, and the heat generated by the frequency converter is also very large, so the influence of the heat generation cannot be ignored. If the heat dissipation problem of the inverter is not handled properly, it will affect the use status and service life of the inverter, and even cause damage to the inverter.
1. Cooling method of inverter:
The heat generated by the inverter is generated by internal losses. In the loss of each part of the inverter, the main circuit is the main one, accounting for about 98%, and the control circuit accounts for 2%. Data show that the power consumption of the frequency converter is generally 4-5% of its capacity. Among them, the inverter part accounts for about 50%, the rectifier and DC circuit account for about 40%, and the control and protection circuit account for 5-15%. The 10°C rule states that when the device temperature is lowered by 10°C, the reliability of the device doubles. In order to ensure the normal and reliable operation of the frequency converter, it is necessary to deal with the heat dissipation problem of the frequency converter. The problem of heat dissipation of the inverter is mainly the temperature and heat dissipation of the working environment of the inverter.
For the heat dissipation method of the inverter, it is usually divided into the following three types:
1. Built-in fan cooling
Built-in fan cooling is generally used for small-capacity general-purpose inverters. By installing the frequency converter correctly, the cooling capacity of the built-in fan of the frequency converter can be maximized. The built-in fan can take away the heat inside the inverter. The heat is dissipated through the iron plate of the box where the frequency converter is located. The heat dissipation method only through the fan installed in the frequency converter is suitable for the control box with a separate frequency converter and the control box with fewer control components. If there are several inverters or other electrical components with relatively large heat dissipation in the inverter control box, the heat dissipation effect is not very obvious.
2. Cooling fan
By adding several fans with ventilation 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 inverter. Here's how to choose in general:
Based on experience, we have calculated that the heat generated by 1kW of power consumption requires a fan exhaust volume of 360m3/h, and the power consumption of the inverter is 4 to 5% of its capacity. Here we calculate by 5%, and there can be an inverter The relationship between the suitable fan and its capacity:
Fan exhaust air volume (m3/h) = frequency converter capacity × 5% × 360m3/h/kW
We can select a fan for a 90kW general-purpose inverter according to the above empirical formula
Exhaust air volume of fan (m3/h)=90kW×5%×360m3/h/kW
Fan exhaust air volume = 1620m3/h
Then select the models of fans from different manufacturers according to the exhaust air volume of the fans. Get fans that meet our criteria.
Generally speaking, fan heat dissipation is the main means of inverter heat dissipation at this stage. It is especially suitable for relatively large control cabinets, and when the electrical components in the control cabinet work at the same time and generate heat at the same time. It is suitable for highly integrated centralized control cabinets and control boxes. Moreover, due to the continuous advancement of technology in recent years, cooling fans are not as huge as they were in previous years, and small and powerful fans abound. The cost performance is also much better than other cooling methods.
3. Air conditioning heat dissipation
With the advancement of science and technology, air conditioners are gradually being used more and more in the production of control cabinets and control boxes. And become one of the important means of heat dissipation. However, this way of heat dissipation is rarely used for inverters, because of its high cost and relatively large volume, and because the capacity of general-purpose inverters is from a few kVA to tens of kVA, the capacity is not particularly large, so it is difficult to install The cost performance is acceptable to users, and this method is only used in special occasions (such as particularly strict requirements on the working environment) and inverters with particularly large capacity. Moreover, some of the air conditioners also involve the removal of waste water, so more consideration must be taken in the process of complete sets of panels, which increases the design cost.
In addition, there are other reasons to consider the heat dissipation effect of the inverter, such as high altitude (>1000m), because of the decrease of air density, the heat dissipation capacity should be appropriately increased; and the switching frequency, the heat of the inverter mainly comes from IGBT (Insulated Gate Bipolar Transistor), the heat of IGBT is concentrated at the moment of on and off. Therefore, when the switching frequency is high, the heat generated by the inverter will also increase.
Facts show that dealing with the heat dissipation of the inverter not only requires the designer to do it from the inverter itself, but also requires the user to use it correctly and install it strictly in accordance with the instructions, have enough ventilation space, suitable for the use environment, and do regular maintenance as much as possible. , especially in dusty industries such as coal, regularly remove dust from the operating environment and the air duct of the frequency converter, so that the heat dissipation system of the frequency converter can function normally and the temperature rise of the frequency converter is within the allowable value, so that the frequency converter can be reliable operation, and bring greater economic and social benefits to the enterprise.
Second, the daily inspection items of the inverter:
① Whether the sound changes abnormally during the operation of the motor, including whether there is vibration during the operation of the motor.
②Whether the installation environment of the inverter has changed. Whether the ambient temperature is normal, the working temperature of the inverter is generally required to be within the range of -10°C~+40°C, preferably around 25°C.
③ Whether the cooling fan of the inverter is working normally, including whether the cooling channel of the inverter is unblocked. Check whether the output current, voltage, frequency and other data of the frequency converter on the display panel are normal. Whether the characters on the display panel are clear and whether strokes are missing.
④Whether the inverter is overheated. An infrared thermometer can be used to detect whether the heat sink of the inverter is overheated or whether there is a peculiar smell. Check whether there is a fault alarm display during the operation of the inverter.
⑤ Regularly clean the filter screen of the air inlet duct inside the electrical control cabinet. Always keep the control cabinet and frequency converter in good clean condition. Effectively remove the dust accumulated on the surface of the inverter and prevent the accumulated dust from entering the interior of the inverter. Especially metal dust. Effectively remove the oil from the cooling fan of the inverter.
⑥Use the once-a-year overhaul time to open the inverter, place the inspection on the inside that cannot be seen during daily operation, and perform cleaning work. Use a brush or a vacuum cleaner to clean the circuit board of the inverter and the internal rectifier module, IGBT module, DC filter electrolytic capacitor, input and output reactors and other parts. Replace unqualified electronic components (note: the filter electrolytic capacitor inside the inverter generally needs to be replaced every 4 to 5 years).
⑦ Check the cooling electric fan, the cooling electric fan is an easily damaged component. Its life is limited by the bearings (it's an axial fan). According to the operation of the inverter, the fan or fan bearing is generally replaced every 2 to 3 years.
