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How to improve the service life of the inverter?

View: 602021/08/23  
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Photovoltaic inverters are electronic products, limited by internal electronic components, they must have a certain life span. The life of the inverter is determined by the quality of the product, the installation and use environment, and subsequent operation and maintenance. So how to improve the service life of the inverter through correct installation and use and later operation and maintenance?

The main factors affecting the service life of the inverter are: 1. The internal temperature of the inverter 2. The input voltage and current parameters of the inverter; 3. The external environment in which the inverter runs.

The internal temperature of the inverter

The temperature inside the inverter is the most important factor affecting the life of the inverter. Excessive temperature will reduce the performance and life of the components. The internal capacitor of the inverter is a key factor affecting the life of the inverter. There is one of the simplest basic principles: the rule of ten degrees, that is, for every 10 degree decrease in the ambient temperature, the life of the capacitor doubles; every 10 degree increase in the ambient temperature, the life of the capacitor is shortened by half.

The inverter itself is a heat source. The power modules, inductors, switches, cables and other circuits inside will generate heat, and all the heat must be dissipated in time, otherwise the internal temperature will rise higher and higher. Therefore, the heat dissipation design of the inverter is a key link in product R&D and design. At present, the inverter industry basically uses natural cooling and air cooling. All of them are air-cooled. In order to ensure the stability of the internal temperature of the inverter, in addition to product design considerations, special attention should be paid to the following items in installation and use:

(1) The inverter must be installed in a ventilated space and maintain good ventilation with the outside world. If it must be installed in a closed space, an air duct and exhaust fan, or an air conditioner must be installed. It is strictly prohibited to install the inverter in a closed box. It is strictly forbidden to install the inverter in a closed box

(2) The installation location of the inverter should be avoided as far as possible from direct sunlight. If the inverter is installed outdoors, it is best to install it under the eaves on the sun-backed surface or under the solar modules. There are eaves or components blocking the inverter. If it can only be installed in an open place, it is recommended to install a sunshade canopy above the inverter.

(3) Whether it is a single installation or multiple installations of the inverter, it must be installed in accordance with the installation space size given by the inverter manufacturer to ensure that the inverter has sufficient ventilation and heat dissipation space and operation space for later operation and maintenance.

(4) The inverter should be installed as far away as possible from high-temperature areas such as boilers, oil-fired hot air blowers, heating pipes, and air outlets of external units of air conditioners.

Input voltage and current parameters of the inverter

Improper matching of the inverter's input voltage and current parameters will also affect the life of the inverter. The higher the voltage or current the internal components of the inverter bear, the shorter the life of the components. Let’s take the MAX 100-125KTL3-X series inverter as an example. The input working voltage range of this series inverter is 200-1000V. In the case of the same input power of photovoltaic modules, if the input voltage is too low, the current will be too high and approach the critical state, and the input voltage will be too high and the current will decrease, but the voltage will be close to the critical state. In this case, it will not only affect the power generation efficiency of the inverter, but also affect the service life of the inverter. Therefore, we generally recommend that the string input working voltage be configured to the rated voltage of about 600V, and the electrical parameters under the NOCT condition of the component are considered. Characteristic, the string input working voltage is configured to about 650V, which can take into account the high efficiency and service life of the inverter.

If the string input working voltage is configured to be around 800V, not only will the power generation efficiency be reduced, but the power devices and the current bus capacitor will be subjected to high voltage, and the life of the insulation layer will be reduced, which will affect the life of the inverter. If the string input working voltage is configured to 500V, the current will increase by 20% compared to the rated voltage. The heat of the inverter mainly comes from the current. If this is done, the heat will increase by 20%, and the temperature of the inverter will rise,causing the service life to decrease.

In addition, although the current capacity ratio restrictions have been released in the project approval, excessive over-provisioning will cause the inverter to operate at full load for a long time, which will naturally affect the life of the inverter. For this reason, when we are designing the capacity ratio, in addition to In addition to economic factors, the life of the inverter must also be fully considered.

The external environment of inverter operation

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The external environment in which the inverter operates is also an important factor affecting the life of the inverter. At present, the protection level of string inverters on the market can reach IP65 or even IP66. It is dust-proof, rain-proof, and salt-spray-proof. It can adapt to harsh external environments, but in places with more pollution or dust, because dirt will fall on the radiator, it will affect the function of the radiator . Dust, leaves, silt and other fine objects may also enter the air duct of the inverter, which will also affect heat dissipation and thus affect the service life. In this case, it is particularly important to clean up the dirt on the inverter or the cooling fan on a regular basis, so that the inverter has good heat dissipation conditions.

One end of the inverter is connected to the photovoltaic array, and the other end is connected to the power grid. The power quality of the power grid will also affect the life of the inverter, especially the voltage of the rural power grid is unstable, fluctuating high and low, and the grid harmonics are high, which is easy to trigger the inverter. When the voltage exceeds the range, the inverter will stop running, and resume operation when the voltage is normal, but if it restarts frequently, the service life of the inverter will be reduced.

Summary

After the inverters are shipped in batches, they undergo quality inspections one after another, and their design life is almost the same. Therefore, system design, installation, and subsequent operation and maintenance are key factors. In order to improve the actual service life of the inverter, on the one hand, it is necessary to create a good operating environment for the inverter to protect it from wind, sun, and rain; on the other hand, it is necessary to conduct regular inspections to make sure that the cooling air duct of the inverter  is unobstructed to avoid over-temperature derating and other failures.


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