Resistor vs transformer

[[email protected]]

"Peter Bennett"
"Phil Allison"


** From the bareness of unit pictured and the makers application notes -
those transformers are NOT intended to be sold direct to the public.
Rather, they are intended to be incorporated into an installation or
particular item of equipment.

One would think that if they were being sold for professional use, they
wouldn't be fitted with plugs, sockets or leads.

General purpose ( ie with US 2 or 3 pin outlet) auto-transformers that
convert 230v to 115v are " PROHIBITED ITEMS " under the *legally binding*
Australian wiring regulations ( AS3000 ).

Aussie regulations very closely follow European regulations - particularly
the UK ones.

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.

Step-downs, similar to the ones from Hammond but with carry handles, were
recently withdrawn from all *retail* sale here due to the safety hazard
they can create and because liability insurers excluded them from coverage.

I suppose we do have to protect the Phil Allisons of this world.

 

[Phil Allison]

<[email protected]>


** Just keep right on publicly demonstrating what a lying, know nothing
fuckwit you are - Slow Man.

There just might be some newcomers here you don't know already.





........ Phil

 

[Winfield Hill]

[email protected] wrote...

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'm glad to say we don't have those rules here in Massachusetts.

 

[Winfield Hill]

Phil Allison wrote...

Peter Bennett wrote...

** From the bareness of unit pictured and the makers application notes
- those transformers are NOT intended to be sold direct to the public.
Rather, they are intended to be incorporated into an installation or
particular item of equipment.

I see "for use where equipment is already isolated" which is not quite
the same thing as "incorporated into an installation".

General purpose (ie with US 2 or 3 pin outlet) auto-transformers that
convert 230v to 115v are "PROHIBITED ITEMS" under the *legally binding*
Australian wiring regulations (AS3000).

Aussie regulations very closely follow European regulations - particularly
the UK ones.

Step-downs, similar to the ones from Hammond but with carry handles, were
recently withdrawn from all *retail* sale here due to the safety hazard
they can create and because liability insurers excluded them from coverage.

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.

 

[Phil Allison]

"Winfield Hill"

I see "for use where equipment is already isolated" which is not quite
the same thing as "incorporated into an installation".

** 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.

Yes, auto-transformers don't provide isolation.

** Not the issue.

At all.

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.

** 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.

If I were Weinberger, going out to buy a transformer, I'd probably get
an isolated transformer.

** Like the one in the URL I supplied:

Sizes start from about 20 VA in wall wart form - eg:

http://www.dse.com.au/cgi-bin/dse.storefront/43eb0fc307c2afea2740c0a87f9c075e/Product/View/M1155

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.

But if I was in a pinch I'd use Bill Sloman's
suggestion in a second without worry

** 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.

I certainly have used it many times inside instrument designs.

** 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.

In fact, it's safe to say it's a
standard approach for dealing with 115/230V capability.

** 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

 

[Fred Bloggs]

It's a question of price and availability. Split primary transformers
are a commodity product available off the shelf in a vast range of
sizes. Auto-transformers are a niche product, and you are likely to
have to buy a bigger transformer than you need at a consumer price.

Phil Allison's example cost some $A59 (including tax) equivalne to
$43.60 or 36.5 euro which is a couple of times more than you'd have to
spend on a regular transformer and a box to put it in.

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:
http://www.alldual.com/trans/VolTRANS/StepDown.htm

 

[lemonjuice]

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

 

[lemonjuice]

"Spehro Pefhany"


** HUH ????

Its "not a very good idea " in the same league as jumping from an aeroplane
in flight with no parachute !!!


When a 120 volt primary mains transformer is subjected to 240 volts, the
result is sudden and dramatic.The iron core becomes completely saturated
eliminating nearly all primary inductance and leaving only the winding
resistance to limit current flow.

Eg:

falling in the next few seconds as the copper wire heats.

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

 

[lemonjuice]

You *can*, but it's generally not a very good idea.


Best regards,
Spehro Pefhany

I've been able to use "SOMETIMES" step downs as step ups!

lemonjuice

 

[The Phantom]

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?

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?

 

[lemonjuice]

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

 

[Chris Jones]

"Fred Bloggs"


** Of course.

Sizes start from about 20 VA in wall wart form - eg :

http://www.dse.com.au/cgi-bin/dse.storefront/43eb0fc307c2afea2740c0a87f9c075e/Product/View/M1155


Just beware if the device draws power on one half cycle only - OR its
internal transformer fries running on 50 Hz instead of 60Hz.




........ Phil

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

 

[John Fields]

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?

---
And, at 33,400 feet per pound, his primary would weigh

176,930,410 ft
---------------- = 5297 lb
33,400 ft/lb

Just more of his bullshit, I suspect.[/QUOTE]

 

[[email protected]]

"Winfield Hill"

** 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.

Try explaining that in a way that makes sense or - better, granting you
dire expository skills - find a URL that
explains the point comprehensibly.

** 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.

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 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 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 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.

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

<snip>

 

[Phil Allison]

If the part had an internal iron transformer, it would have a 110V/230V
change-over plug ...

** LOL !!

What a fucking moron Da Slow Man is.

What planet does the cretin live on ??

- not that anybody would bother isolating the power
supply for a wireless repeater.

** 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.

Not to mention the chances of exceeding the safe max ground leakage
current level prescribed in Europe and Australia.

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

** WHAT BULLSHIT !!!

The max allowed ground leakage for an appliance is circa 1 mA.

SLOW MAN = PUBLIC MENACE



......... Phil

 

[Phil Allison]

"Fred Bloggs"

We don't really know what's going on here.

** But some of us have a better idea than others.

Here is a low end utilitarian cheapie:
http://www.alldual.com/trans/VolTRANS/StepDown.htm

** Look exactly like the Chinese auto-transformer step-downs that were
withdrawn by importers and electronics retailers across Australia on safety
grounds.




......... Phil

 

[[email protected]]

** LOL !!

What a fucking 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.

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.

** WHAT BULLSHIT !!!

The max allowed ground leakage for an appliance is circa 1 mA.

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.

 

[[email protected]]

"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.

"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.

 

[Phil Allison]

** LOL !!

What a fucking moron Da Slow Man is.

What planet does the cretin live on ??

Which it can get with ferrite cored transformer...

** 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.

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.

** 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 FUCKING public menace.

The device won't - of itself - be unsafe,

** 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

 

[Phil Allison]

"Safety grounds" often translates as "cheaper that the regular
supplier".

** 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 fucking public menace.





......... Phil