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High-end step-down transformer

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Literata
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High-end step-down transformer

Postby Literata » Sun, 31 Dec 2017 6:04 am

This is not another generic power-converter question :-)

I'm looking for a high-end 220V->110V step-down transformer (for US equipment) that is properly engineered and provides quality power output inside the ~3000W envelope. Most of the transformers found in consumer electronics stores are poorly made and sometimes outright dangerous (I'm an electrical engineer by training).

I am thinking something along the lines of a data-center quality step-down unit, maybe something like this except with 220-240V input:

https://www.amazon.com/APC-Smart-UPS-St ... B0150PY5MS

The only semi-reputable product I've found is made by APC (Schneider):

http://www.apc.com/shop/us/en/products/ ... /P-SURT003

Do folks have any recommendations? I'd prefer to spend under $2000, but if it takes more than that to get decent quality I can stretch.

I've done a search on the forum and haven't found any threads focused on high-end transformers.

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Re: High-end step-down transformer

Postby Strong Eagle » Sun, 31 Dec 2017 6:42 am

I'll agree with you that there is a lot of consumer grade junk out there... especially in Singapore, as imported from China... what could go wrong.

And, I agree with you, there's not much in the way of high end transformer threads because, in the end, the question becomes, "Why?"

Most folks that have moved from the USA have pretty much given up on trying to use 120 volt appliances because of the cost... or, if you're cheap, the safety issue. Is it worth it to spend $$$$ to run a high wattage appliance?

TV's aren't worth the hassle because the OTA signal is not compatible with Asia, although HDMI is OK.

So... I can't really comment, except to say that as BSEE myself, you certainly wouldn't go wrong with either of the pieces of equipment you noted... just be aware that by the time shipping and GST are factored in, the cost will be about double.

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Re: High-end step-down transformer

Postby Literata » Sun, 31 Dec 2017 8:14 am

Strong Eagle wrote:In the end, the question becomes, "Why?"

Most folks that have moved from the USA have pretty much given up on trying to use 120 volt appliances because of the cost... or, if you're cheap, the safety issue. Is it worth it to spend $$$$ to run a high wattage appliance?


I hear ya (and thanks for the quick response!).

In my case I actually need at least 2 transformers to run $50K+ worth of equipment through, including some business critical stuff so the cost-benefit is not really an issue. But fire or failure from a crappy China-made transformer would definitely be an issue!

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Re: High-end step-down transformer

Postby BBCDoc » Wed, 03 Jan 2018 2:09 am

Go to Sim Lim Tower, some of the basement shops will custom make one for your needs.


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Re: High-end step-down transformer

Postby Strong Eagle » Wed, 03 Jan 2018 2:55 am

I see that those transformers can pull as much as 30 amps. I don't know what setting you'll be using them in, and, in my experience, high amperage circuits are a rarity in Singapore residential circuits.

Singapore seems to be a hybrid of the British and American wiring systems. The Brits, as you know, used the 100 amp (or less) "mains" that looped all the way around the house to various outlets, then used fused/breaker outlets and plugs, 13 amps as I recall being typical.

The typical Singapore house will have a 100 amp main circuit breaker, and then a bunch of 15 amp breakers in the box as might be found in a typical American home. Then each outlet/plug again has its own British style 13 amp breaker/fuse.

Even dryers sold in Singapore are designed to run on 13 amps... it is very rare to see a British 30 amp, 240 outlet anywhere. The 30 amp outlets I have seen take the kinds of plugs (the big one) shown below.

Image

So... good luck on finding a power source with sufficient oomph to power those transformers.

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Re: High-end step-down transformer

Postby PNGMK » Wed, 03 Jan 2018 7:00 am

I've posted on this topic myself a few times. You need to avoid 'auto-transformers' as they are none isolating and tend to trip the house ELCB's and induce ground loops. Every single unit in Sim Lim in a box will be an auto type and is worthless. The isolating units look like a transformer if that makes any sense.

I have a www.ACUPWR.com unit (Accurate Power - 150 W unit - USA Made) I ordered from the USA which cost $100 or so delivered. It's a proper isolating step down transformer with a thermal overload switch built in. They do a range of power levels and I recommend them but make sure you are ordering an ISOLATING type, not Auto type.

The max size you can plug into the mains here is 220VAC x 13A (~2500 W) but honestly pulling 2500W out of a plug here without the wiring going can be sometimes fraught with issues. Not all 13A sockets are wired up for 13A service. I'd be happier with 2000W.
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Re: High-end step-down transformer

Postby PNGMK » Wed, 03 Jan 2018 7:06 am

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Re: High-end step-down transformer

Postby Strong Eagle » Wed, 03 Jan 2018 8:10 am

PNGMK wrote:The max size you can plug into the mains here is 220VAC x 13A (~2500 W) but honestly pulling 2500W out of a plug here without the wiring going can be sometimes fraught with issues. Not all 13A sockets are wired up for 13A service. I'd be happier with 2000W.


Spot on advice from PNGMK, especially if you check out max current carrying capacities of various gauges of wire... 13 amp for 16 gauge wire... and because the fuses are all 13 amp in British stuff, you'll find lots of older places (like mine) that use 16 gauge and not 14, for house wiring.

I can't speak to new properties in Singapore as I never lived in one... but if you're in an older semi-D, the wiring leaves lots to be desired, and 2000 watts is about the max... most dryers are max rated at 10 amps and don't draw that much.

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Re: High-end step-down transformer

Postby PNGMK » Wed, 03 Jan 2018 1:01 pm

BBCDoc wrote:Go to Sim Lim Tower, some of the basement shops will custom make one for your needs.


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Don't. Not without a recommendation to a specific shop.
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Re: High-end step-down transformer

Postby Literata » Tue, 09 Jan 2018 1:26 am

Strong Eagle wrote:
PNGMK wrote:The max size you can plug into the mains here is 220VAC x 13A (~2500 W) but honestly pulling 2500W out of a plug here without the wiring going can be sometimes fraught with issues. Not all 13A sockets are wired up for 13A service. I'd be happier with 2000W.


Spot on advice from PNGMK...


Thank you both here.

After doing research on typical housing power envelope in SG, it looks like the data-center grade converters may not work too well in Singapore households.

As it happens my research concluded with exactly the same vendor: Acupwr. They are recommended by the US DoD for military staff abroad, and it looks like they use proper components with proper safety margins and tolerances. Plus thermal protection to safeguard against overheating/fire.

1. PNGMK....more specifically, I ended up ordering a couple of the exact transformer model you recommended, after arriving at that conclusion independently.

2. Acupwr also makes specialized transformers for high-powered motors (blenders, fridges, some fans etc) which depend on the USA 60Hz AC frequency (Singapore is 50Hz). Here.

3. I could not find specs on Acupwr's efficiency/vampire current draw, but whatever...relative to the $50k cost of replacing the electronics in SG I'm willing to absorb the extra electricity cost.

I hope this thread will be useful for future searchers, as it looks like 3 engineers came to the same conclusion here!

additional search keywords: power converter, step-down transformer, power protection, 110V 120V electronics, voltage conversion, voltage converter, appliances

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Re: High-end step-down transformer

Postby PNGMK » Tue, 09 Jan 2018 6:15 am

1. There's no way a transformer can convert power frequency (it looks like they've allowed some over-rating mainly). That's where you need a motor-alternator (old school) or inverter (power electronics) solution. (Brings back memories of some missionaries from the states complaining their records/reel-reel tape recorders were playing 'slow' - back then it was common for the belts and pulleys to have a second pulley set that you could move the belt to for a different frequency so we'd fix it that way).

2. The parasitic draw will be typical of a iron core transformer - nothing crazy - I'm estimating a a few percent. The power factor should also be pretty high (i.e. efficiency). Tesla was a damn smart guy.

These type of isolating power transformers were much more common when I was a kid growing up on a US mission base in PNG (240 VAC to 110 VAC). I am surprised they are getting hard to find now.
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Re: High-end step-down transformer

Postby Literata » Tue, 09 Jan 2018 6:26 am

PNGMK wrote:1. There's no way a transformer can convert power frequency (it looks like they've allowed some over-rating mainly). That's where you need a motor-alternator (old school) or inverter (power electronics) solution.


Actually it's not that hard to do. The solenoid transformer cannot do it but the electronics to do the conversion vary from very simple (if you don't care about sine wave purity) to very difficult. I know this because I built one in EE223 in college :-)

You can buy one here for example:

http://www.gohz.com/frequency-converter

Most AC motors aren't too bothered by sine wave purity so I think this should work fine. In any case I won't need one as the motors in my equipment are DC.

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Re: High-end step-down transformer

Postby Strong Eagle » Tue, 09 Jan 2018 6:46 am

Interesting... pure sine wave converters have really dropped in price. I was looking into backup UPS systems a while back... pure sine wave was much more expensive than a stepped sine, and naturally, the latest server power supplies want a pure sine wave.

I did ultimately find a couple of UPS with pure sine wave output from Cyber Power, which were much cheaper than those offered by APC.


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