One would think that if they were being sold for professional use, they wouldn't be fitted with plugs, sockets or leads.
The same sort of rules that make it difficult for me to buy a free mains socket to replace the failing moulded-on mains socket on my garden extension cord.
I suppose we do have to protect the Phil Allisons of this world.
There just might be some newcomers here you don't know already.
....... Phil
I'm glad to say we don't have those rules here in Massachusetts.
I see "for use where equipment is already isolated" which is not quite the same thing as "incorporated into an installation".
Yes, auto-transformers don't provide isolation. But anything we connect directly to the ac line is, by definition, not isolated. So, anything we would normally connect directly to the ac line is not isolated either, and surely can therefore be wired to an autotransformer without changing its ac-power-line connection safety status.
"The load connected to an autotransformer shall be considered as energized directly." That's a clear statement we can live with.
Don't tell us about hot vs neutral polarity, or 230 vs 120V, because all systems, such as Weinberger's wireless receiver unit, need to have sufficient insulation to protect the user against miswired ac outlets.
If I were Weinberger, going out to buy a transformer, I'd probably get an isolated transformer. But if I was in a pinch I'd use Bill Sloman's suggestion in a second without worry. I certainly have used it many times inside instrument designs. In fact, it's safe to say it's a standard approach for dealing with 115/230V capability.
"Winfield Hill"
** Win is a man who "just sees what he wants to see and disregards the rest .... "He even treats drivel written by a marketing puke as reliable tech info.
** Not the issue.At all.
** Active - Neutral reversal is not a hazard in itself. Only in combination with an auto- transformer step-down or other wiring error does it sometimes becomes one.BTW
Win,
Best not tell folk what * NOT* to tell you.
For that is the mark of a colossal fool.
** Like the one in the URL I supplied:Sizes start from about 20 VA in wall wart form - eg:
Much better, much safer & ready to use with no effort.
Just beware if the device draws power on one half cycle only - OR its internal transformer fries running on 50Hz instead of 60Hz.
** Then you would be a dangerous fool indeed !Using *identical* 115 volt windings in series makes no allowance for output voltage drop under load.
The OP's auto dialler device was not specified beyond a nominal "6 watt" consumption rating which may well equate to a 12 VA rating = 100mA rms draw = up to 250mA peak current pulses. The winding resistance for a 12 VA, 230 volt transformer primary is typically 250 ohms (or 2 x 125 ohms if split). PLUS the unit may well have an internal iron transformer that runs heavily into saturation when fed from a 50 Hz supply.
The end result IS the auto dialler device may very well see effectively a
90 to 100 volt supply - not the expected 115/120 - and may not function properly when it is most needed to SAVE LIVES !!!!The auto dialler unit may also contain low value film caps from line to ground - common practice in US appliances - such caps may not may not tolerate the application 240 volts AC on a *long term* basis without failure. Not to mention the chances of exceeding the safe max ground leakage current level prescribed in Europe and Australia.
** An **entirely** different matter to using the same idea linked externally to some arbitrary, untried 120 volt *only* device.You really need to learn to think things through better - Win.
** Shame the unit in question HAS NOT been designed for such capability.The only safe conversion method is to use an isolation step-down of comfortably greater VA rating than the load 120 volt, 60Hz appliance normally requires.
Then you only have the 50 / 60 Hz issue still left to worry about.
........ Phil
We don't really know what's going on here. If all the alarms are on a dedicated circuit then you can consolidate all the transformer cost into a single transformer. The prime power converter market for 220-110 runs the full range from pricey designer models to low end utilitarian cheapies. Here is a low end utilitarian cheapie:
Hans your common sense, will tell you Ancient just feels dumb, he didn't mention/know about the possibility of having a series connection at the secondaries. A look at a Transformer catalogue of a major supplier will show you how many are sold that have either series / parallel connections at the primary and secondary . Just ignore his advice.
lemonjuice
65 ohms. If connected >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
initially - rapidly
How come my 120 to 12 V step down transformer with New England Heavyformar wires, 40AWG Wire size with 1162575 turns on the primary and 116258 turns on the secondary on a Kascke core shows a DC resistance of 185.6MEG? Simple your typical figure is flawed.
And while I'm at it wise guy cut out the resistance stuff. You have to talk about impedance. So all your Ohm law calculations are flawed . The impedance which actually determines the current in the above case is MORE the 10 times the resistance!
lemonjuice
I've been able to use "SOMETIMES" step downs as step ups!
lemonjuice
65 ohms. If connected >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
initially - rapidly
Is this the resistance of the primary? 40 gauge wire has a DC resistance at room temp of about 1.049 ohms/foot. If your primary has a resistance of
185.6 megohms, then you have about 185,600,000/1.049 = 176,930,410 feet of wire on the primary. Is the transformer really that big?Yeah its huge ... whether as big as your figure portrays is another thread. My point was just to illustrate how varied the resistance of the transformer primaries can be.
lemonjuice
And beware that the open circuit output voltage can be quite a bit higher than the loaded voltage, which in combination with 50Hz line frequency can and does sometimes fry things. E.g. one wall-wart type I bought in Australia put out 135V when running from 239VRMS mains. I had to replace it with a home made one after it destroyed my appliance. Possibly not legal but caused less fires.
Chris
Try explaining that in a way that makes sense or - better, granting you dire expository skills - find a URL that explains the point comprehensibly.
If the part had an internal iron transformer, it would have a 110V/230V change-over plug - not that anybody would bother isolating the power supply for a wireless repeater. Try to think about what "wireless" implies in this context.
The OP could always measure the voltage coming out at the centre-tap, which should give a pretty fair idea of the magnitude of the regulation problem - if any. Any losses would be pulling the centre tap down from a nominal 115V, which puts him 4,5% ahead of the game to start with.
The OP lives in Germany, where earth leakage trips are mandatory - if the set-up did exceed the safe ground leakage currents, the ELCB would detect it immediately
** LOL !!
What a f****ng moron Da Slow Man is.
What planet does the cretin live on ??
** ROTFL !!Even worse insanity.
The unit is a mains powered radio receiver that LINKS to a telephone line.
It need to have ALL KINDS of safety and telecoms approvals for that job.
** WHAT BULLSHIT !!!The max allowed ground leakage for an appliance is circa 1 mA.
SLOW MAN = PUBLIC MENACE
........ Phil
"Fred Bloggs"
** But some of us have a better idea than others. ** Look exactly like the Chinese auto-transformer step-downs that were withdrawn by importers and electronics retailers across Australia on safety grounds......... Phil
Which it can get with ferrite cored transformer on the modem output with a bandwidth covering 300Hz to 3kHz at negligible power - the transformer won't do on-hook/off-hook but that can be managed by a small relay or the right kind of opto-isolator.
Phil may not be insane, but he certainly hasn't worked in telecoms.
Phil is right about the current levels, but his argument is total nonsense - if the device had internal capacitors that caused it to exceed the legally permissible ground leakage limits, this is a problem with the device, not the means used to power it. The device won't - of itself - be unsafe, and you'd have to stack up a lot of them to get to the 15mA sensitivity of typical ELCBs - many more to get up to the 60mA needed to kill somebody by transdermal shock.
"Safety grounds" often translates as "cheaper that the regular supplier".
Read up on "non-tariff barriers to trade". The U.S.A. has been using asimilar trick to exclude Australian beef from the U.S. market for as long as I can remember.
** LOL !!
What a f****ng moron Da Slow Man is.
What planet does the cretin live on ??
** Blah blah blah....All wild guesswork.
BTW has no-body twigged that such a auto dialler unit made *expressly* for the 120 volt market is NOT going to have the relevant telecoms approvals for use in Germany etc.
** Shame how such capacitors will pass DOUBLE current when fed from 240 volts as opposed to 120 volts AC.Shame how same US items have film cap of up to 47nF fitted from AC line to ground.
Shame how the type of film caps US makers use reliably with 120 volts fail SHORT due to internal corona when fed by a 240 volt supply.
This alone crates a fatal shock hazard !!!!
Shame how Bill Sloman is F****NG public menace.
** Yes, it may very well be unsafe when used with an auto-transformer stepdown.One *cannot know* without a full and detailed inspection of the unit.
The only SAFE advice to give when this is NOT possible is to use an isolation stepdown.
....... Phil
** Arguing from " a position of ignorance" is Bill Sloman's one specialty.
Since he has an overwhelming abundance of ignorance available for the purpose.
Da Slow Man is a f****ng public menace.
........ Phil
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