What is the SEMI F47 line sag spec all about?

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We have now all seen lights dim at dwelling or at work and this is a sign that the AC line voltage has been decreased or sagged. Though an occasional dimming of lights may be tolerated, with regards to manufacturing facility automation tools, line sag may be the source of a manufacturing shutdown, leading to vital income losses. Since the manufacturing of semiconductors, together with microprocessors, is a really exact and costly course of, again in 1999 the Semiconductor Gear and Supplies Institute (SEMI), established requirements relative to AC line sag immunity. This specification is known as the SEMI F47 Voltage Sag Immunity Commonplace and has been revised periodically. As a result of many different manufacturing facility automation processes are equally essential, a few of these manufacturing merchandise must adjust to the SEMI F47 commonplace as properly.


Mainly, this commonplace requires that the AC-DC power provide that is utilized in semiconductor manufacturing, or in different manufacturing facility automation tools, proceed to offer the required output voltage and present, even when the enter voltage dips under its specified limits. As may be seen in the chart under, in the blue space, the fundamental specs require that the power provide carry out usually even when the enter voltage sags right down to 50% of its nominal voltage for as much as 200 ms, or sags to 70% for as much as 500 ms, and sags to 80% for as much as one second. Since this sag proportion refers to the nominal line voltage, this implies for instance that with a nominal 220VAC enter, the AC voltage can sag right down to 50% or 110VAC for as much as 200 ms, right down to 70% or 154VAC for 500 ms, and right down to 80% or 176VAC for as much as one second.


There are further sag ride-through “suggestions” inside the newest version of the commonplace, which is the SEMI F47-0706 (these suggestions usually are not necessities) that features operation of the power provide with 0% enter power (no power) for as much as 20 ms. This suggestion may be accommodated by insuring the chosen power provide has a “hold-up time” specification of 20 ms or longer. Different newly advisable thresholds inside the SEMI F47-0706 embody sags of 80% for 10 seconds, and steady sags of 90%. Most power provides that meet the earlier variations of this commonplace, the SEMI F47-0200, and have a hold-up spec of 20 ms or higher, ought to have the ability to meet the new suggestions (not necessities) as properly.

The best and lowest price methodology of complying with the SEMI F47 commonplace is to make use of a power provide with a common enter, similar to 90 to 264VAC, and function it from a 220VAC or increased line enter. On this approach you robotically meet and exceed the commonplace since this sort of power provide can function right down to 90VAC (even decrease than the 50% line sag spec of 110VAC). Notice that this methodology does apply to auto-strap power provides.

One other approach of assembly the SEMI F47 is to attract much less power than the provide can usually present (de-rate the provide). For those who do that, at all times verify with the producer to substantiate that your decreased load will enable the provide to completely meet the SEMI F47 commonplace. This will likely require further testing to substantiate compliance, both by the power provide producer or the end-product OEM. Alternatively, the power provide producer might be able to modify the provide to fulfill the SEMI F47 commonplace.

Some manufacturing facility automation tools require the use of SEMI F47 “licensed” power provides, which implies the provides had been examined by an out of doors company or laboratory and located to completely adjust to the commonplace (much like UL certification). If this is a requirement, at all times search for provides which have present certifications from a dependable manufacture, as a result of the price of getting this sort of certification can quantity to $2,000 or extra. There is a grandfather clause in the up to date requirements that gives for tools that was examined or licensed below the earlier variations of the commonplace to not require re-testing or re-certification.

Many industrial-type power provides are designed and/or licensed to fulfill the SEMI F47. These provides could also be a bit dearer, however it will likely be the lowest price answer, particularly in the event you examine it to the price of including an external fixed voltage transformer or UPS to the enter of the power provide.

Energy provide producers similar to TDK-Lambda provide provides which can be SEMI F47 licensed and provides that function with a large common enter of 90 to 264VAC. As well as, modified provides may be offered that meet this and different prevailing power provide specifications.