SEMI F47
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SEMI F47 is an industry standard for voltage sag immunity. It says that industrial equipment must tolerate
voltage sags, or dips, on the AC mains supply to specific depths and durations. It is such a good and useful
standard that many other industries use it, either formally or informally.
Equipment that complies with SEMI F47 is more reliable, and more productive. |
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| The voltage sags required by SEMI F47 typically occur about once per month in semiconductor fabs (fabrication facilities) around the world. So industrial equipment that cannot tolerate these sags typically fails, without explanation, about once per month. | |
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| In most cases, it is not necessary to add expensive power conditioning devices to the industrial equipment. Instead, F47 testing by companies like Power Standards Lab identifies the weak points, and suggests low-cost or zero-cost solutions. These solutions range from minor changes in power supply configuration, to software delays, to different relay and contactor selection. | |
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 A typical SEMI F47 voltage sag (top) and how it affects a power supply (bottom). This problem was fixed by increasing the size of a capacitor, at a cost of a few dollars.
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