Voltage Sag ProtectorA 0.1 s dip shouldn't stop your line for hours

It depends on what kind of "unstable" it is. If tools trip when the lights flicker and run normally after restart, that's a voltage sag — exactly what a sag protector is for. For long outages you need a UPS or generator; for sustained high or low voltage you need an AVR; if equipment is burned out by surges, you need surge protection. Check the trip records to see which it is, then decide. Lightning trips: surge or sag? →

A voltage sag is a brief drop to 10–90% of rated voltage that then recovers — the power isn't cut. An outage is a drop below 10%. Per IEEE 1159, a sag lasts half a cycle to 1 minute; those in Taiwan's science parks usually last about 0.1 s, and people only see the lights flicker.

Because the tool's control system can't ride through a 0.1-second power dip. Pumps, heaters and motors survive on inertia, but PLCs, control power supplies and contactors reset within milliseconds; the tool alarms and stops, and it takes hours to reboot, check and requalify.

Most sags originate outside the plant — lightning, line faults, neighboring customer faults, excavation damage — so a factory can't stop them, only help its equipment ride through. There are three layers: choose SEMI F47-compliant equipment; add sag protectors or UPS to the control circuits that reset; and use power quality monitoring to log every sag and protect the tools that trip most first. See all 5 prevention methods →

A UPS provides backup during outages; a sag protector handles sags within 3 seconds. An online UPS also handles sags, but double conversion running 24 hours loses about 3–6% of power continuously, and lead-acid batteries need replacing every 3–5 years. A sag protector runs on bypass with almost no loss and uses supercapacitors that need no battery replacement. If every control circuit that resets is already on an adequately sized online UPS, you don't need one.

Because SEMI F47 only requires the main equipment to keep running at 50% voltage for 0.2 s, 70% for 0.5 s and 80% for 1 s. Real sags in Taiwan often go below 50%, are unbalanced across phases or repeat, and peripherals like robots, communications and control power supplies aren't necessarily validated — so F47-compliant tools can still stop.

Size it for the control circuits you're protecting, not the whole tool. A 100 kVA tool usually needs only a few kVA if you protect just the PLC, IPC, robot, control power and EMO circuits; an air compressor with only its control unit connected needs just 850 VA. Standard models are single-phase 850 VA–10 kVA and three-phase 5–200 kVA; actual capacity depends on an on-site review of the tool's wiring. See 5 calculation steps with worked examples →

Up to 3 seconds at rated load (2 seconds for the 850 VA and 1 kVA models), with an average switchover time of 0.7–1 ms. It's designed for sags, not outage backup; outages longer than 3 seconds still need a UPS or generator, and the two can coexist.

Yes, as long as the cumulative ride-through stays within its capacity. Three-phase models can compensate continuously within their 3-second capacity; single-phase 850 VA and 1 kVA models can compensate repeatedly within 2 seconds. They recharge automatically after discharge.

No. The sag protector is built on a bypass architecture; if it detects over-temperature, a capacitor fault, overcurrent or overvoltage, it switches back to bypass automatically and the tool stays on utility power.

No batteries to replace. It stores energy in supercapacitors with a design life of about 10 years; inspection is recommended in year 8, and built-in capacitor performance measurement lets you track their condition in advance. By comparison, UPS lead-acid batteries usually need replacing every 3–5 years.

Price depends mainly on four things: the load capacity to protect (from single-phase 850 VA to three-phase 200 kVA, a wide range), phase and voltage, installation location and wiring work, and whether customization is needed. Because only the control circuits that reset are protected, the capacity needed is usually far smaller than the whole tool — so measuring first gives the most accurate quote. Send us the tool models and trip records and we'll provide a formal quote after an on-site assessment. Book an assessment and quote →

It depends on where it's wired. If internal tool wiring is involved, the warranty may be affected, so confirm the wiring method with the equipment maker before deployment; DEYly can evaluate it together with the equipment maker.