USA mains voltage.

"Phil Allison"

The transformer I have is a single multitapped one and is made to order by SES in Melbourne. I can change it as I like but need to make a few more batches of 10 or so to use up stock. I will consider doing this in conjunction with choosing an inlet selector/IEC module which does not require a rear panel metalwork or artwork change (no small deal).

The 120V sounds like an appropriate choice. There is a fair overhead on the secondary voltages, I might do a variac check on the next one as a check.

"John Fields"

** The Chinese and others are still making huge numbers of iron core transformers - for small AC adaptors mostly plus toroidal and R-core types in all sizes.

SMPSs only shine when you need regulation of the DC voltage.

My Westinghouse ( 5 yo) gas oven has 300VA auto-transformer for the SiC igniter that only comes in 120VAC rating.

Very few audio power amps and no tube guitar amps use SMPSs.

.... Phil

Michael Karas wrote in news: snipped-for-privacy@news.eternal-september.org:

A valid point but this is a low volume specialised product with not much complexity and a reputation for reliability. The voltage is preset to the end customers country. Plus, my customer is paranoid about design changes and previous bad experience with switch-mode designs.

I've not seen _low_ voltage. Here in the land of intense air conditioning I've seen 130VAC off season, which is why I buy 130V bulbs... still available from 1000bulbs.com ;-) ...Jim Thompson

[On the Road, in New York]

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Is there some reason (large load, etc. ) that you can't use a switch mode, power factor corrected power supply capable of accepting a wide range of input voltages?

Better yet, design your product with a wall wart of lump in the line type supply that you can source, already designed and tested from a repotable source.

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On a clear desk, you can sleep forever.

"Paul Hovnanian P.E." wrote in news:YsOdnby7vfi3TtTTnZ2dnUVZ snipped-for-privacy@posted.isomediainc:

No single off the shelf switchmode will give 600V 30mA, 9V 7A, and +/- 15V low noise.

You can start with a PFC, universal switchmode supply to make one or two voltages, +-15 maybe, and convert from there. We buy a MeanWell

150 watt, UL/CE switchmode PFC supply for about $30. We can't buy a transformer for that, much less the line voltage tap-switch module and rectifiers and caps that a transformer would need.

John

John Larkin wrote in news: snipped-for-privacy@4ax.com:

I agree with that philosophy where products are available. Except in this particular case the 600V and 9V supply wil probably add up to more than the cost of transformer+selector switch+labour.

On a sunny day (Mon, 15 Aug 2011 20:46:49 -0700) it happened John Larkin wrote in :

Hey, I have a couple on MeanWell 7.5V 20 A in operation here. Those have a 115V/230V switch on the side. Dirt cheap, and so far no problems, I push them to the max. Just a bit of a surge when you plug them in ...

As far as reliability goes compared to the big iron transformers, in my view the most fragile parts are the capacitors, electrolytics. Those are present in both designs, but many will have a lower value in the switcher.... than in a 50- Hz or 60 Hz secondary filter.

I just replaced a low ESR type in my PC mobo, it was swelling up... These MeanWell are very reliable, used a lot in industry here.

--
It's supposed to be, but in real life it'll vary more than that.

I usually design assuming +/- 10% (108 -> 132V), but depending on
where your widgets are going to be used, erring on the side of caution
may be wise.

As Speff posted earlier:

"+/-5% _at the mains plug_ is very optimistic. Better to design for
+10/-15% or wider (especially momentarily on the low side)."

Yes, but realize that each 'drop' can vary somewhat. But the goal of the utility company is that the customer get 120/240 volts.

That is *very* unusual, and I suspect that the 'customer' should contact the local utility and see about having the pole transformer upgraded. It is NOT acceptable to drop to under 100 volts.

Many years ago 115, 117, 110 and some other voltages were 'local' standards. As the years progressed, it was realized that a national standard was needed, and 120 was chosen.

Yep, Japan's standard is 100 volts--the only country that I know of with that voltage! How'd that happen? Got me!

I find it difficult to imagine any electronic device that won't handle a spread from 110 to 130 without any problems at all. If it doesn't handle that spread then I'd call that a design flaw. Ideally you should be able to handle 100 to 140 volts without serious impairment to functionality, though that may be a bit idealistic.

--
I'm never going to grow up.

That confuses voltage and frequency in the question and reply. For frequency, a transformer designed for 50 hz will usually work just fine at 60, but one designed for 60 may not work well at all on 50 hz power.

Ignoring issues such as ferro-resonate transformers and other frequency optimized transformers.

--
I'm never going to grow up.

"Peter Dope"

** The end result of very long cable runs from overloaded US supplied 110 volt diesel generators back in 1945. The average voltage at outlets was around 90 to 100 volts - so lamps and other locally made appliances were sized for this.

Most of Japan's pre WW2 electricity system was destroyed by USAAF bombing.

... Phil

I always thought that the 120 VAC spec was for the service entrance, and 115 VAC at the receptacle. I frankly don't know where the 117 or 100 numbers comes from.

Anyway got the real scoop on this? I may have learned it at one time, but have since forgotten it.

-mpm

I meant, 117 or 110 numbers in the above, not 100.

You have it backwards. It is crappy US only transformers in cheapo wallwarts that saturate on Japanese 50Hz mains and they don't exactly blow up so much as run mad hot, then melt the casing, blow fuses and/or catch fire. Decent cheap generic global PSUs are widely available to US ex-pats in Akihabara and similar electronics markets in Japan.

Many unregulated supplies have enough headroom that the 20% lower voltage isn't an issue unless under heavy load, but the lower frequency in the 50Hz part of Japan can be bad for US 60Hz only transformers. It is much less of a problem these days with modern switchers.

Domestic Japanese kit is always good for 50 or 60Hz - it has to be. Most will tolerate a 20% overvoltage on the mains input without too much complaint, but obviously will run hotter as a result.

Regards, Martin Brown

"Martin Brown = Fool "

** No - you have.

** Impossible - since the AC voltage is only 100 volts

** All total, ABSOLUTE BULLSHIT !!!

... Phil

Yes, you're correct..

120 at the pole, 115 at the plug with a load on it. 5% drop on the average is what's allowed in voltage drop from the service to your outlets with a load. Lowest Voltages(loaded heavy) : 110, 220 and 440 Loaded voltages(average) : 115v, 230, and 460. highest(unloaded): 120, 240 and 480..

It's not uncommon to see the high voltages exceed their limits, for example, we may see 125, 245 and 496 volts here..

Of course you also have 208 which there really isn't a window spec that I know of, unless you count the 5%. Most of the time that I know of, this is used for lighting and a tap is used (Delta) to get your 120 service. I have seen 220 equipment operating off of 208 voltages and seem to be ok as long as you don't push them to the limits, motors for example.

Jamie

A decent modern circuit design would take 50 to 300 VAC input without any switching.

The use of the switch indicates incompetent design.

--
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