What is SEMI F47?

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.
SEMI F47 is an industry standard that sets out, in 6 pages, the requirements for voltage sag immunity in semiconductor fab equipment.

Why use SEMI F47?

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.
SEMI F47 voltage sag
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.

SEMI F47 Contactor Testing Video

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How Expensive is SEMI F47?

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.

SEMI F47 voltage sag
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