Some of you asked for a professional-grade surge protector tear-down when I started taking these apart nearly a year ago. Well, that time has come.

I poked a handful of manufacturers back in February to see if any might be interested in sending samples, got a bite from Electronic Systems Protection, received its SA-1810 in April and now we get to go in for a tour. The SA-1810 is ESP/SurgeX's entry-level offering with the most built-in outlets.

If the brand name sounds unfamiliar to you, you may be shocked by its $400 street price and be curious to find out why it is so expensive compared to typical surge suppressors.

For people who have no idea who ESP is, the company originally started doing power conditioning for office equipment in 1985 when power quality issues were causing abnormally high service call frequency on the first generations of electronic copiers and other equipment. As for SurgeX, the company started in 1995 by introducing the concept of series-mode protection using non-sacrificial surge clamping components, which are still the two main features it's known for today. ESP bought SurgeX in 2010, so I'll be using SurgeX, ESP and ESP/SurgeX interchangeably.

The full SurgeX solution is divided into five stages; its SA-1810 implements only the first three, which also happen to be the most important under normal circumstances. Those are:

From this, we can expect the insides to be partitioned in three functional sections in one way or another. On the infographic, stages one and two together form SurgeX's Advanced Series Mode (ASM) protection.

The two functions not included are the Catastrophic Over/Under-Voltage Shutdown (COUVS) protection, which disconnects everything in case of an abnormal voltage condition, and Inrush Current Elimination (ICE), which sequentially turns outlets on via inrush-limiting elements to mitigate inrush current.

The first two have already been hinted at earlier, while the third simply means that the protection scheme does not involve the ground wire. We will get to what these translate to in terms of hardware later when the lid pops. For now, onward to the exterior tour.

To paraphrase: good things come in inconspicuous packages. There's no fancy marketing here, not even a model number. Just the SurgeX brand name and company motto. People who order SurgeX units simply do not need to be reminded why they are doing so by colorful or wordy packaging. They already know, buy it based on recommendations without caring about cost or are obeying a procurement requirement.

ESP does not chance its unit getting mangled during shipping. About three centimeters of stiff foam pad the unit away from its light corrugated cardboard box on every side at both ends. This makes me wonder what the “Fragile” sticker was about.

How difficult can setting up a SurgeX unit be? About as difficult as plugging in any other surge protector: plug it into a power outlet, then plug in your devices. The LED chart on the back of this 8.5x5.5” sheet may seem intimidating until you realize it covers 11 different product lines, one product per row. In the case of this “Standalone” product, the only LED is green, and a light means there is power and the protection is working. When it's off, there is either no power or the protection failed.

Traceability is always nice to have, especially on premium and potentially mission-critical products. The assembly and test slip included with the unit I received indicates that at least three people directly handled the unit. Based on the slip date, it appears this unit was assembled and presumably tested a few days before my first attempt to contact SurgeX.

Foam blocks, the unit itself, the instructions half-sheet and the checklist. That is it for package contents. To be fair, I doubt many people really care for more than that anyway.

Ten yellowish-orange outlets adorn the SA-1810's top, leaving no space for anything else. These should hopefully be enough to accommodate most peoples' accessories.

There are no attempts at fancy or flashy design on the panels either. The sides are bare apart from the branding, Advanced Series Mode surge suppression and power conditioning key features, self-test light-emitting diode and the “A-1-1 Certified” mark in the bottom-left corner of the front panel.

The bottom cover features a product identification and specifications label, along with a “Test ID” that refers to the assembly and test checklist. Along the perimeter, we can see that the enclosure is made from folded sheet metal, with the bottom tray screwed into from the sides.

ESP does not try doing anything fancy with its plug, favoring an off-the-shelf 3x2.08mm2 (or 14/3) PVC jacket cable with straight plug-style rated for 15A and 300V. Personally, I prefer flush-type plugs.

It looks like the molded plug got gouged, though I could not find any protruding or sharp edge on the enclosure to explain how. The shipping box also lacks any holes or impact marks. I am inclined to believe it got damaged prior to shipping and slipped through QA.

On the power cord entry side, we also have a plunger-style 15A circuit breaker. This concludes the preliminary exterior tour. If you are wondering where the switch is, there isn't any on this model.

No “Made in China” here. As you would or should hope to see on more premium products, ESP/SurgeX spared no expense on assembly by manufacturing these in the USA. Some of you might be wondering why a $400 product features the same 330V Voltage Protection Rating as $30 units. The reason for it is simply that 330V is the lowest or best protection rating defined in ANSI/UL 1449-rev3. As for what C22.2 no.8 is, it is just a Canadian complement to UL 1283 for EMI filtering.

Note the warnings. We get the usual indoor use only, accompanied by the timeless classic “no user-serviceable parts inside”, which I do not remember seeing much lately and will gleefully ignore as usual in a moment.

Here is that optional 1449 adjunct Commercial Item Description mentioned earlier. It is the main reason why people and companies fork over $300 for these and equivalents. While basic 1449 certification means a surge protector should not be a safety hazard and can suppress surges, it makes no guarantees about product endurance. Adjunct testing and certification addresses that.

Here, 'A' means the product suppressed 1000 worst-case surges (6kV at up to 3kA) without performance degradation, the first '1' corresponds to the 330V protection rating class, and the second '1' means no ground contamination – no surge current dumped to ground.

Put together, A-1-1 represents the best power line surge protection certifiable under ANSI/UL 1449-rev3. If your surge protection has no CID, it is not rated for endurance.

Four self-tapping and six metal screws later, the bottom cover falls off from the top and the reason why the SA-1810 is the same or similar size to its two-outlet SA-15 variant becomes obvious: the box is actually full, which I suspected from its weight.

In the back, we see the rear of those outlets. To the right, we find the breaker, and at the bottom-right, the load-side EMI filter board. Hiding under a sheet of insulation, the larger board hosts the surge clamping circuitry. Below it, you find SurgeX's reactor, the linchpin behind its Advanced Series Mode surge elimination.

After disconnecting a handful of wires, the top cover can be separated from the base for a less cluttered view. These outlets look every bit as bog-standard from behind as they did from the front, making them very serviceable if need be. The top part's three ground wires (one from the power cord, one from the outlets and the other jumper from the bottom cover) join together on the stud near the bottom-right corner.

You may remember me commenting how some manufacturers choose odd ways to route power to their strips' outlets. None of that nonsense here: power, neutral and ground are all attached to the middle outlet, then fanned out both ways from there.

These outlets look like decent quality and are the rear-entry type with screw-driven wire clamps for live and neutral, which makes them very reusable and replaceable. When I replace outlets for friends and family, this is my preferred wire attachment style to work with.

Instead of looping the solid ground wire around the ground screws and tightening them, ESP/SurgeX went through the extra trouble of folding fork connectors with metal tabs over the tin-plated wire and soldering them. There was somewhat of a solder spill here, but the electrons won't mind.

Unsurprisingly, we find a breaker rated for 15A. Less common is the mentioned ISO 8846 compliance, which pertains to safety in explosive marine craft environments, meaning the breaker is sufficiently gas-tight and thermally isolated to prevent arc heat from detonating an explosive propane-air mix.

While the power cord is the expected 14-gauge copper and 300V insulation rating for a 120V/15A product, all other visible leads and jumpers within the unit are 12-gauge, 600V “boat” cable. With the margins SurgeX earns on these, I would not be surprised if it decided that shaving quarters on manufacturing separate parts for the company's 15A and 20A products was not worth the trouble and potential risk of putting 15A wires in 20A models. As for the higher insulation voltage rating jumpers, the thicker and more tightly controlled insulation reduces the risk of having an insulation breakdown event within the unit during endurance testing or after years of field exposure.

With the outlets and breaker gone, the top looks so much roomier. Even with all of the screws removed, the folded sheet metal enclosure remains reasonably stiff, as you would expect from what appears to be 1.3mm (0.05”)-thick steel.

The lone grounding stud in the top cover, as well as all other studs on the bottom, appear to be press-fitted into the sheet metal.

Here we have a top-down look at that bottom tray once all of its other wires are unplugged. Between the filter board, main board and the reactor under it, it looks quite well-packed from this angle too.

What is the difference between a generic EMI filter and an “impedance-tolerant” one? Simply the addition of small ferrite bead chokes to form a balanced pi (Π) filter with the other X-class capacitor on the main PCB and a 3.3Ω resistor in series with the load-facing 1µF X capacitor to prevent LC resonance. There are also two 2.2nF Y-class capacitors connected from live and neutral to ground through the top-right mounting hole.

With a dual footprint common-mode choke and doubled-up spade terminals everywhere, I believe it is safe to assume this PCB gets reused through much of SurgeX's product lineup.

Check out the simple and straightforward PCB routing; not much imagination is required to see how power makes it way from the inputs to the outputs. The fiberglass board is clear enough that you can even see some of the components' outlines through the PCB. that you can back-light them to see most of what is happening on both sides at the same time. This isn't particularly useful for such a simple PCB, but it's still a handy trick to keep in mind for more complex circuits.

The soldering looks great except for one little detail: achieving mirror-like solder joints requires either a tightly controlled cooling profile for lead-free solder or the cheaper, simpler low-tech option: lead-based solder. I asked Nicholas and was told SurgeX went lead-free for its international products a while ago, but still use 63Pb/37Sn solder for North American models. There's a plan to go lead-free in the works.

The heart and soul of SurgeX's ASM protection is a huge inductor with complementary electronics to take care whatever remaining power surge energy manages to pass through it. High-performance and -endurance surge protection adds a fair amount of complexity compared to basic MOV protection.

How much bigger than conventional MOV protection do you need to go if you want a high-endurance surge protection solution? Well, here is the reactor with its PCB next to a pair of Bourns 20D201K MOVs for comparison. The size and weight differences are not subtle.

How much electronics do you need to do a MOV's job when you do not wish to use a sacrificial element? About this much. And the circuitry is only intended to deal with the remainder of surge energy that manages to pass through SurgeX's reactor.

From left to right, we have an AceWin 1µF X2 cap, a discrete bridge made of Vishay P600G diodes, three 390µF 250V Panasonic ED capacitors, a Vishay 1N5404 diode for the peak detection circuitry, a pair of power resistors to discharge the surge suppression caps, air-core inductors to limit current rise rate through the SCRs and the LittleFuse S4025 SCRs with their trigger components.

The soldering quality looks similar to the filter board. Most modern PCB designers would use copper pours with thermal relief pad connections and 45/90° trace routing. Here, though, SurgeX's PCB engineer decided to forgo copper pours and also use free-hand routing.

If you follow the self-test LED header traces near the bottom-right corner, you find out that it is simply a LED connected directly across the main input capacitor through a pair of series 15kΩ resistors – a glorified “Power On” indicator that doubles as the bleeder circuit for the main surge filtering capacitor.

Following traces around non-populated components reveals that they are alternate footprints, component orientations or alternate signal path implementations, no mysterious missing feature there.

Do you see those two studs just below the reactor's steel casing? These help keep the bulky device from shifting around. I am a little surprised to see no nuts on them, which would properly secure such a large component. But the way they butt right up against the putty tells me they were intentionally left nut-less.

This is my only major bit of criticism about the SA-1810's mechanical design: since there are no nuts on the locator studs, all of the reactor and main PCB's weight is held in check by two metal screws through the side panel, meaning a hard upside-down landing could warp the side panel (although improbable with the combined thickness of the overlapping walls),snap the screws or strip threads in the reactor's housing. The main PCB riding on the reactor might not appreciate getting whipped around in such way, either.

We know this device is physically large (10x10x4 centimeters or 4x4x1.6 inches for those of you who want to know how chunky it is). But how much inductance does it actually provide? By measuring impedance against a 1Ω resistor, I calculated a primary inductance varying from 132µH at 60Hz down to 3.7µH at 20kHz. When you want a high value non magnetically saturatable inductor capable of passing 20ARMS and ~1000A peak primary current, you pay the price in volume, weight and copper.

On an unrelated note, how often do you see “do not expose to rain” on internal components? I believe this is a first for me.

Since the transformer is potted in epoxy or some other tough material to prevent vibrations, help with heat transfer, increase the working voltage and various other reasons, I tried asking for pre-potting pictures. Unfortunately, they were deemed too sensitive for release.

Basically, what you have in there is a pair of loosely coupled copper coils and some low value shunt resistor attached to the secondary winding. Based on US patent 7068487, reactor parameters for a 120V/15A reactor should be 80µH primary inductance, 4µH secondary inductance, a 0.35-0.65 coupling factor between the two windings and a shunt between 0.01 to 0.2 ohm.

The idea here is that when a surge gets presented on the primary, a proportional and opposite voltage appears on the secondary winding, canceling out the residual surge seen by the load relative to the intermediate tap.

With everything removed, we are left with the bottom tray that features four threaded spacers for the filter PCB, one threaded stud for grounding, two more studs to locate the reactor and a glob of RTV presumably intended to keep the reactor from rattling around during shipping.

If the adhesive was intended to secure the reactor on the tray, then it failed in transit since there was no resistance when I lifted it out. The sticker does not show any sign of ever have been in contact with anything, hinting that the RTV may have cured before the reactor ever got dropped in. When I sent a draft copy of this story to Robert for review, he told me the RTV blob should have been bigger and definitely not have come loose on its own.

Under normal operating conditions, AC voltage goes through the rectifier bridge, through D5, top off C2 to AC peak voltage and that is it. The low shunt value (R200) reflected through the L200/L201 transformer effectively shorts it out.

When a surge occurs, L200's inductance opposes any sudden change in current. Part of the surge voltage across L200 appears across L201 to cancel most of the initial spike. Some surge energy gets dumped in C2 causing it to rise a few volts and the sharp rise triggers the SCRs. With C4 and C6 initially discharged, the center leg gets shunted to neutral, diverting the remaining surge energy let-through to C4/C6 and the L201-R200 loop.

When the surge is over, R6 and R9 discharge their respective caps and R200 dissipates the remainder of the energy stored in L201's field.

How does all that translate into actual operation? Time to rig things for poking around. Some of you may have noticed that ground clips are missing from my probes. With this much exposed 117VAC on my bench, they are not worth the risk of accidental shorts.

What is the device at the end of that coax cable you might ask? It is a simple differential probe based on the AD629 amplifier that I use for shunt current measurements. It used to reside on a breadboard until a month ago, when I received the PCB I designed for it.

With nothing plugged in, I measured an integral power of 837mW, which is basically the power being dissipated by the self-test” LED and its 30kΩ bleeder/limiter resistor. Apparent power, the product of RMS voltage and current, is 10.6VA.

The bulk of this 10VA is simply the fundamental current going back and forth through the reactor and X capacitors. Smaller bumps near AC peaks are the peak detection capacitor getting topped off to restore the charge bled off by the LED. As for the narrow glitches on the current waveform, they might be caused by the diodes' reverse recovery.

I do not currently have the necessary equipment to answer the first question. But for the second one, I can use the vacuum cleaner test from my isobar Tear-Down – SCR/triac variable speed drives are fairly good AC noise sources.

My probes were connected to the three reactor legs (input, main board and output) to see if there would be any dips or ringing around turn-on time. The three voltage traces overlap almost perfectly with no apparent oddities, so no problem here even with this unusual load.

Of course, for that first question, simulation may offer a worthy alternative to hands-on measurements. Here, I reproduced the SA-1810's circuitry in LTSpice with some help from Harford's patents to fill in blanks. Robert from ESP kindly providedparameters for the EMI filter magnetics and actual waveforms so I could sanity check my simulation model against them.

Vin is the input voltage with a standard B-class (1.2x50/8x20) surge applied to it, I(V300) is the current passing through the simulated source and finally, Vout(P-N) is the voltage across output live and neutral. After the EMI filter, there is effectively nothing left of the surge and the output voltage peaks at a completely benign 184V, merely 14V above nominal for 120VAC.

What is the lazy hump after the initial surge? Simply the shunt capacitors (C4/C6) finishing to charge since normal SCRs cannot turn off until their anode current drops near zero.

Since I went through the trouble of modeling a combination wave surge generator, I thought I may as well pick up a MOV spice model (Epcos S20K130 here), whack it in and see what happens. After much fiddling with circuit and spice parameters to get around “time step too small” errors, I managed to get these waveforms.

As before, Vin is the input, Ix is the current through the MOV and Vmov is the voltage across the MOV, which also counts as the output voltage. The MOV peaks at 420V and 1700A, 250V above peak AC voltage.

Why don't the voltage input and current waveforms peak at 6kV and 3kA? The first reason is because the specifications are 6kV 1.2x50µs open-circuit and 3kA 8/20µs short-circuit, so the two conditions are intrinsically mutually exclusive since you cannot have 6kV across a short-circuit. The second is that as-modeled, my combination wave pulse shaper only went up to 4.5kV/2.5kA, so not quite up to full spec.

If you were starting to grow tired of power strips that all seemed to look mostly the same inside, the SA-1810 is definitely something different. Through clever use of magnetics, semiconductors and large capacitors, it achieves power line surge suppression that MOVs cannot match. Even after tweaking my surge generator model some more to get closer to 6kV/3kA, the peak output remained under 200V, well within even the most sensitive electronics' comfort zone.

I really liked the overall construction except for the use of RTV to secure the reactor instead of nuts, in equal parts because the RTV failed in my unit and if it had stuck, I would have had to pry it off for the tear-down. This would have likely involved mangling the reactor's sticker, scratching the reactor housing and bottom tray.

Despite its great surge elimination performance and build quality, I cannot help feeling like the $400 street price is still too steep for what it is and does. If you have a large collection of sensitive electronics to protect, though, it should be worth considering.

Thanks go to Nicholas from Caster Communications for having the unit shipped to me, Robert from ESP for sharing his engineering insight, and readers like you whose on-going interest in these stories drive the manufacturers' interest in participating.

3.5 - Male Plug Female Connector

Daniel Sauvageau is a Contributing Writer for Tom's Hardware US. He’s known for his feature tear-downs of components and peripherals.

Insulated Terminal, Cable Tie, Cable Clip, Terminal Block, Wire Connector - Xuanran,