10 Amp Variac Variable Transformer with Isolation, 1000va Max, 0~130 Volt Output
|Price:||$159.00 + $34.50 shipping|
- PHC SC-10T Variac with 10 amp Fuse, Partial Isolation
- Input: AC 120V, Output: AC 0 to 130 Volt
- VA: 1000VA. Max, 9.1 Amp. Max (surge), 7 Amp Max Operating (2 hours), 5 Amp (Continuous)
- Note that most device have surge (when first turn on) much higher than operating amp rating.
- 'Limited Isolation' - Grounding pass through and bypasses the isolation, which means the grounding isn't isolated
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Partial (or Limited) Isolation - The grounding pass through and bypasses the isolation, which means the grounding isn't isolated. You may be able to use a 3 prong to 2 prong plug adapter to on either input or output to cut off the grounding.
Variac is a variable transformer and a great device for quality control testing, equipment testing on low and high voltage, control over heat, speed, and more.
In order to purchase the right variac, it is critical that you know the amp usage by your electronic device. It is always best to be conservative otherwise you risk destroying the variac and it can be very dangerous. For example, if your device requires 5 amp, buy the variac with up to 10 amp. A rating of 1000VA means that at 100volt, the unit can sustain at maximum 10amp. If at 120 volt the unit can sustain at 8.3amp
Note - Indoor use only. Do not operate in a condition that may cause electrocution and fire. Do not operate in a wet environment. Do not operate near flammable substance.
Top customer reviews
**IF THE FACTORY SHIPPED IT IN THE CONDITION IT IS AFTER THE MINOR MODS I MADE I, WOULD RATE IT A FULL '5 STARS'**!
I've been "RadioActive" for over 60 years, starting when I was about 10 years old. So I have a LOT of electronics experience, both in my Professional Career and as a hobby.
But this is REALLY about the Variac I bought, the good, the bad and the ugly!
I needed both a Variac and an isolation transformer for my home workbench, but I don't have a large bench area. I really figured that 500va units would be more than large enough as I DON'T work on tube transmitters and such now-a-days. I can't man-handle them, not even a boatanchor like an R-390A receiver etc. But in doing a lot of research this was the ONLY unit I found that was an "Isolated" Variac. Reviews indicated that it is a TRUE ISOLATION transformer (backed up by my own tests).
I read the reviews, both good and bad and decided to buy it anyway, figuring if it DID have problems I could fix it or return it.
ONE of the things that repeatedly came up in reviews was a "wobbly shaft and excessive knob height". I figured I could probably take care of that IF mine had those bad 'features'. It did. . .
When it arrived I was a bit surprised, the unit is larger and HEAVIER than I expected (about 21 lbs). And like others said, it "STUNK" with a capital S. That doesn't bother me, a lot of the Chinese stuff I've bought stinks when first opened but it dissipates fairly quickly.
Examination showed that YES, it DID have a 'WOBBLY SHAFT'. After making sure that the unit was fine electrically, no sparks, or bad/bouncing readings when adjusting the Voltage (in other words, good contact between wiper and transformer windings) I then checked to make sure that it is truly an 'Isolated' Variac. IT IS, there is no continuity between the primary and secondary windings. ONLY the round ground pin from the AC line input is fed through to the outlet. This is a GOOD thing as it's a safety ground, but important.
I used my DVM to compare the actual Voltage output against that which the analog meter showed. I checked it at both 50 & 110 Volts output. As close as I could read the small analog meter the readings were DEAD ON accurate. That was a surprise!
NOTE: Some reviewers have said that the Voltage output doesn't correspond to the KNOB reading. DUH!! First, the arrow on the knob doesn't line up with '0' when it's turned all the way down. SECONDARILY, actual Voltage output will depend on what you put into it. Some people have NO CLUE. Use either the internal meter or external meter to determine the actual Voltage output. In fact I'm going to make a small interface box to go between the Variac and the DUT (Device Under Test) to easily measure both Voltage and Current draw of the DUT. . .
NOW TO SEE ABOUT FIXING THAT WOBBLE!
Having determined the unit is working correctly, no obvious electrical problems, I pulled the knob and examined the "Wiper assembly" to see why it wobbled. The shaft goes all the way through the unit and is visible from the bottom. It appears to have a lower bearing that is OK.
The "wiper" is on a husky piece of plastic (think it's white Nylon). There are two metal inserts on that plastic thingy, and two setscrews that are threaded into the metal inserts. NOT easy to get a screwdriver in to check their tightness.
***NOTE: DO THE FOLLOWING AT YOUR OWN RISK, BOTH FOR SAFETY AND 'RETURN-ABILITY' REASONS. ONCE YOU DO IT, IT'S LIKELY YOU'RE STUCK WITH IT AND WILL BE UNABLE TO RETURN IT!!!***
HERE'S HOW I FIXED THE SHAFT WOBBLE. . .
1. I found that taking two screws out of the front panel that holds the meter, switch and outlet there is a nice large hole that allows access to the setscrews and upper shaft. I checked, one setscrew was loose, the other one not as tight to the shaft as it could have been.
2. I loosened the second screw, pushed DOWN on the wiper assembly and tightened the set screws. This alone took a lot of the wobble out of the shaft. It still had a little bit as it doesn't have a true bearing at the top.
3. Examination showed that I could probably make it better though. I found a round piece of Phenolic about 2.75 inches in diameter and 1/8 inch thick. I drilled a hole in the center and slid it down over the shaft. This was to act as a washer or "rubbing surface" for the knob (there are three screws in the top, under the knob that would otherwise rub).
4. I then drilled the knob shaft hole ALL the way through the knob. This allowed pushing the knob further down the shaft so that it was actually lightly rubbing on the Phenolic washer. In this position the shaft protrudes out the top of the knob maybe 1/16th inch, perfectly tolerable!
NOTE: The slight bit of shaft protruding above the knob IS NOT a safety issue as the shaft is grounded through the lower bearing to the case, which is grounded to the round ground pin on the power plug. BUT if you're concerned about it, glue a small plastic cap over the exposed shaft after installing the knob.
5. Checked ALL my work, VOILA! Almost NO shaft wobble at all, it feels very good. Remounted the front meter panel with it's two screws. While it was off I checked the Chinese soldering, ALL soldering looked VERY good for Chinese workmanship (I'm used to having to rework the solder on some Chinese products I've bought)!
6. I then checked to make SURE that there were no Voltage glitches or dropouts throughout the knob range, there weren't. The unit feels nice and smooth and functions as it should.
AFTER DOING THESE MODS I RATE THE UNIT A 5+ AND AM VERY HAPPY WITH THE RESULTS. It's likely that this unit will last me the rest of my natural life with little or not problems.
Most basic variacs are NOT isolated, so I was surprised that this one claimed to be. Naturally, I was skeptical, so I emailed the manufacturer and asked for a wiring diagram of both the SC-10T and one of their non-isolated models. They responded within a couple hours with a schematic and spec sheet for both the SC-10T (isolated) and SC-20M (non-isolated). I was impressed with their speed and willingness to provide documentation. I'm sure they have to legally, but they made me feel like they were happy to provide it nonetheless. Impressive! The schematics do indicate that at the heart of the SC-10T is a galvanically isolated variable transformer, and the heart of the SC-20M is a non-isolated variable transformer. Upon receiving it, I immediately opened it to verify that the wiring was as shown in the schematic (any warranty is voided now, I know, but my life is worth at least a kajliion warranties). It was all as shown except that the fuse came after the switch and the schematic showed the fuse before the switch. That doesn't matter as much as the fact that they're both correctly on the high side of the primary. meh. With the variac unplugged, I checked continuity with my DMM between the input plug and the secondary outputs. The only things that are connected are the mains earth connections, but that was already shown in the schematic. What's very important to note here is that there was no continuity between either of the secondary connections and mains earth, indicating that the output should float if the mains earth connection isn't used. Also important is that the casing is all connected to mains earth. This is good, but once again keep in mind that, depending on how you reference the output, touching the tested equipment at the same time as the case of the variac could shock you.
For your convenience, I've made a video demonstrating the isolation features of the SC-10T. I've chosen to give this product 5 stars for two reasons: 1. It is an incredibly affordable isolated variac for equipment testing, and 2.) customer service through the company is stellar. The build quality is only OK, but comparing the specs and safety features of this variac to what I expect out of this price range, I'm impressed enough to give it a relative rating of 5 stars. If you have an unlimited budget or are running an official lab, please buy a dedicated lab-grade variac or regulated high-voltage power supply. If, like me, you're using this at home for hobbyist use, I definitely recommend! After I finished filming I also tested the secondary side of the variac with my oscilloscope. I even attached an ammeter with a 25mA range to the ground probe of my scope so that I could see if there was even a tiny amount of current flowing through to mains earth. Nothing! Then I switched the two oscilloscope probes around and measured the other way. Zero! Waveforms looked nice and sinusoidal, with little-to-no shape change as the amplitude increased. This thing really works!
*obligatory paranoid CYA statement: always know what you're doing with high voltages, and take this review as reference only. Always do your own testing. I am not responsible for your actions. Genuinely, though, be safe!*
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