Introduction of Main Components of Photovoltaic Grid-connected Inverter

Photovoltaic inverters are composed of circuit boards, fuses, power switch tubes, inductors, relays, capacitors, displays, fans, radiators, structural parts and other components. The service life of each component is different. The service life of the inverter can be explained by the "barrel theory". The maximum capacity of the barrel is determined by the shortest board, and the service life of the inverter is determined by the component with the shortest life , the most prone to failure of the inverter is the four components: power switch tube, capacitor, display screen, and fan. More solar power inverter from www.stinenergypv.com for your needs.

Power switch tube

The power switch tube is the main device for converting DC to AC, and is the heart of the solar inverter.

At present, the power switch tubes used in the inverter include IGBT, MOSET, etc., which are the most vulnerable parts of the inverter. It has three fears: one is afraid of overvoltage, and a tube with a withstand voltage of 600V. It will blow up in 0.1 seconds; the second is afraid of overcurrent, a tube with a rated current of 50A, if the current passing through it is greater than 50A, it will blow up in less than 0.2 seconds; the third is afraid of overheating, the IGBT junction temperature is generally 150 Degree or 175 degrees, it is generally controlled below 120 degrees, heat dissipation design is one of the most critical technologies of the inverter.

If the power device is damaged, it means that the inverter needs to be replaced as a whole. But there is no need to worry too much, because these factors have been considered in the design of the inverter. Under normal circumstances, there is no problem with the service life of 20 years. When installing the inverter, it is necessary to consider leaving a cooling channel for the inverter. In addition, if the power grid has too high harmonics and too frequent voltage mutations, it will also cause overvoltage damage to the power devices.

Capacitor

Capacitors are energy storage components and one of the essential components of inverters.

Capacitors include electrolytic capacitors, film capacitors, etc., each with its own characteristics, all of which are required by the inverter. There are many reasons that affect the life of electrolytic capacitors, such as overvoltage, harmonic current, high temperature, rapid charging and discharging, etc. Under normal use, the biggest impact is temperature, because the higher the temperature, the faster the evaporation loss of the electrolyte. It should be noted that the temperature here does not refer to the ambient or surface temperature, but to the working temperature of the aluminum foil.

Manufacturers usually mark the capacitor life and test temperature on the capacitor body. The volatilization of the electrolyte limits the life of electrolytic capacitors. Japanese NCC capacitors are one of the best capacitors in the world. Its longest life is 15 years in the specification.

Display screen

The LCD screen of the inverter can display various indicators such as the instantaneous power of the photovoltaic power system , power generation, and input voltage. It would be a very useful part if it could show the cause of the failure.

Most inverters have a display, but some don't. In addition to the above-mentioned advantages, liquid crystal displays have a fatal flaw-short service life. If a liquid crystal display with average quality works for 30,000 to 40,000 hours, it will be severely attenuated and cannot be used. We calculate according to the working hours of the inverter from 6:00 to 20:00, and the LCD monitor works 14 hours a day, which is 5000 hours a year. Assuming that the life of the LCD is 40,000 hours, then its life is 8 years.

At present, household inverters generally retain displays, and medium and high-power string inverters used in power stations do not have LCD displays.

Fan

There are two main heat dissipation methods for string inverters: forced air cooling and natural cooling.

Forced air cooling requires a fan. Through comparison experiments on the heat dissipation capabilities of string inverters, it is found that the heat dissipation effect of forced air cooling is better than that of natural cooling for medium and high-power string inverters. The use of forced air cooling can reduce the temperature rise of key components such as the internal capacitors and IGBTs of the inverter by about 20°C, which can ensure the long life of the inverter and work efficiently, while the temperature rise of the inverter using natural cooling will reduce the life of components. . The lifespan of a high-quality fan is about 40,000 hours. The inverter with intelligent heat dissipation generally starts to work when the power of the inverter is above 30%. The average working time is about 4-5 hours a day, about 1,800 hours a year. question.

The most common failure of the fan is that the power supply of the fan is broken, or foreign matter enters the inside of the fan, which hinders the rotation of the fan.