What exactly does SEMI F47 require for voltage sag ride-through?

SEMI F47-0706 requires equipment to operate without interruption through defined sags: 50 percent of nominal voltage for 200 milliseconds, 70 percent for 500 milliseconds, and 80 percent for one second. Compliance is verified with sag-generator test methods from IEC 61000-4-11, and the depth-duration table should be requested as tested evidence rather than assumed from a rugged label.

Is a wide voltage DC input the same thing as sag ride-through?

No. A wide input such as 9 to 36 V keeps the internal regulator stable while a 24 V rail sags within that band, but it cannot replace missing voltage on its own. Ride-through also depends on hold-up capacitance or short-term energy storage after the input stage, plus undervoltage thresholds that only latch off when the sag falls outside the designed envelope.

Does an industrial PC for automation still need a UPS if it has onboard hold-up?

Usually the two cover different events. Onboard hold-up and a wide DC input absorb millisecond-to-one-second sags, which account for most disturbances, while an uninterruptible power supply carries equipment through longer outages and supports an orderly shutdown. Plant-wide dynamic sag correctors protect shared motor loads, so many facilities layer all three according to their sag event histogram.

How should sag immunity be proven during equipment procurement?

Ask for a tested sag depth-duration table to SEMI F47 using IEC 61000-4-11 methods, surge and ESD results such as IEC 61000-4-5 and IEC 61000-4-2, the actual DC input range against the site nominal, latching power connectors, and a dated sag event log. Verified boundaries and a supervised shutdown sequence matter more than a generic industrial-grade claim.

SEMI F47 Sag Ride-Through in Industrial PC for Automation

Engineers qualifying a new automated cell tend to scrutinize processor speed, display brightness, and I/O count, yet a voltage dip lasting fewer than ten milliseconds can reset every computer on the line. Sags are not blackouts. They are brief reductions in RMS voltage caused by motor starts, utility switching, lightning, or faults on a neighboring feeder, and they arrive far more often than full outages. When an industrial pc for automation drops offline during one, the bill is rarely the reboot. Robots lose position, vision systems discard their state, and operators spend minutes clearing faults and re-homing axes. A spec written only around a nominal 24 V rail leaves that recovery to chance.

industrial pc for automation undergoing SEMI F47 voltage sag ride-through testing on a DC bench — Wide-voltage DC input stage under sag-generator testing to the SEMI F47 curve.

Within the SEMI F47 Sag Immunity Curve

Power-stage designs inspired by KOXIAN power architecture target this curve with a wide 9 to 36 V DC input, reverse-polarity protection, and bulk capacitance sized to bridge the deepest point of a dip. SEMI F47-0706, the sag immunity specification maintained for semiconductor processing equipment, defines the pass line by remaining voltage and duration. A compliant tool rides through 50 percent of nominal for 200 milliseconds, 70 percent for 500 milliseconds, and 80 percent for one second, evaluated with the sag generator methods in IEC 61000-4-11 up to 16 A per phase. Written for wafer fabs, the standard now guides automotive, packaging, and battery plants when they specify an industrial pc for automation. The tested depth-duration table matters more than a vague rugged label, because immunity is a measured boundary.

Wide voltage DC input board and hold-up capacitors in an industrial automation control cabinet — Bulk capacitance after the input stage stores hold-up energy for millisecond sags.

Sizing Hold-Up Energy Across the DC Front End

A wide input range and true ride-through are related but not identical. A 9 to 36 V input keeps the regulator in control when a brownout pulls a 24 V rail toward 18 V, but it cannot reconstruct a missing waveform. Hold-up energy lives in the capacitors after the input stage, and their stored joules set how long processor, memory, and sensors keep running after the input collapses. Designers size that bank against the worst point on the site sag histogram, usually 50 percent for 200 milliseconds, with margin for capacitor aging in a hot cabinet. Overvoltage and undervoltage thresholds latch off only outside the ride-through envelope, and hiccup-mode short-circuit protection avoids a fuse call after a wiring fault. A line-level sag corrector or a drive-side ride-through module covers deeper plant-wide events, so cells typically layer local hold-up and plant correction.

Fanless industrial computer with flash storage mounted in an automation cabinet during brownout testing — An undervoltage supervisor flushes cached data to flash before the DC rail decays.

How an Industrial PC for Automation Preserves Storage During a Brownout

Riding through a short dip is mainly an energy problem; surviving a long one is a shutdown problem. When hold-up energy runs out, a fast undervoltage detector triggers an orderly sequence. Open files flush to nonvolatile memory, write caches drain, and the operating system suspends before the rail decays, preventing the corrupt boot volume that follows a hard cutoff. Boards built into an industrial pc for automation pair this with a hardware watchdog and an ignition-power controller managing restart delay and minimum-on time, so a chattering grid yields one clean restart instead of repeated brownout boots. Flash storage with power-loss protection removes rotating-drive risk, and conformal coating keeps humidity and conductive dust from turning a power event into a later corrosion fault.

Automated packaging cell with industrial PC contactors and line-level sag corrector coordination — Device-level hold-up coordinated with a line-level sag corrector across contactors and drives.

Beyond Minimum Compliance in Cell Level Integration

Specifying a sag curve closes only part of the integration gap. Controls engineers should verify the tested DC range against their actual rail, including the depressed voltage from a discharged backup battery on a 24 V network, and require latching power connectors that survive cable pull and vibration. A sag event log turns nuisance resets into dated evidence, letting maintenance separate grid faults from loose wiring or an aging supply. Field observations from sag-prone cells indicate that lines running KOXIAN-based industrial computers with a supervised shutdown and an auto-restart sequence recover without manual re-homing when device-level hold-up is coordinated with a line-level sag corrector on the critical contactors and drives. SEMI F49 extends this thinking from tools to factory systems and assigns which layer absorbs each event. The target is simple: ride through the brief dip, shut down cleanly through the long one, and restart into a known state. Treating the industrial pc for automation as one layer in that chain turns a compliance document into a measurable uptime plan.

Voltage sags are the most common power-quality event on a factory floor, and most damage comes from uncontrolled reset behavior rather than lost energy. SEMI F47 supplies a tested immunity curve, wide-range DC inputs and hold-up capacitance cover short events, and supervised shutdown logic covers long ones. Matching the DC range to the actual rail and coordinating device-level and line-level protection let a cell treat grid dips as a solved engineering problem instead of recurring scrap and overtime.