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Reliability
PV panels normally provide a 25 year life time and manufacturer's warranty, while PV inverters have only recently extended their warranty from 5 to 10 years. Total system costs need to consider both original and replacement costs for the inverter system over the 25 life time of the PV system. As result the inverter cost and reliability are a major factor in cost effectiveness of the PV system. The importance of this factor will grow as the cost of PV modules decrease sharply over the next few years. - Sandia Inverter Reliability 35KB pdf
Several key issues reduce the lifetime of inverters. The most important are 1) operating temperature of the electronics and 2) electrical transient stresses. The operating temperature issue is common to all electronics, but the electrical transient stresses primarily effect high power systems.
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1)
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The operating temperature of the electronics is determined by ambient temperature, the amount of waste heat generated (heat dissipation), and the ability of the system to transfer the waste heat out the system. The most important design issue is to provide high efficiency of operation to reduce heat dissipation. If the heat dissipation is low enough, cooling fans can also be eliminated. This reduces maintenance and potentially improves reliability, as forced air systems have screens that need to be periodically cleaned.
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2)
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Power electronics have an additional critical issue with electrical transient stresses. The large electrolytic capacitors used in these products are generally considered the most likely component to fail. Reducing the electrical stress on the electrolytic capacitor components will increase operating life time of the inverter and the entire PV system
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The EMPS converter/inverter system's high efficiency reduces heat dissipation. It is the first fully soft-switching inverter system where the switching occurs only at zero voltage and zero current times. This improves switching efficiency, but also minimizes electrical transients that stress sensitive electrolytic capacitors and extend operating life.
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