Using American Microwave Oven in UK
Bill Davy
I've bought an American microwave (GE PEM31) for its physical size (it's
very shallow). It takes 1.2KVA (110VAC @60Hz).
Q1) Does anyone know if I just need to drop the voltage or does the
frequency matter? I do not really mind if the platter rotates a tad slower,
the timing settings are a bit off. The microwave frequency is determined
by the mechanical structure of the magnetron.
Q2) Suggestions for suitable supplier of converter (or I shall just use RS,
Maplin, or Farnell) and what are they called (transformer, auto-transformer,
inverter, converter, etc)
Q3) Is there a better source of information if it is not available here?
Q4) If I open it up to find answers, what am I looking for?
TIA
Bill
PS I am new to this group so apologise in advance for everything.
Paul D.Smith
who knows! There are plenty of companies importing US fridges so you might
be able to find out the answer from them.
Other's may be able to comment on the 50/60Hz issue. My suspicion is that
it won't matter although the clock might be inaccurate if it takes its
timings from the mains frequency - but don't take my word for any of this!
Paul DS.
Dave Plowman (News)
Bill Davy <Bi...@SynectixLtd.com> wrote:
> Q2) Suggestions for suitable supplier of converter (or I shall just use
> RS, Maplin, or Farnell) and what are they called (transformer,
> auto-transformer, inverter, converter, etc)
Trouble is large ones are likely to cost as much as the microwave.
--
*If you can't see my mirrors, I'm doing my hair*
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
Appin
from "Dave Plowman (News)" <da...@davenoise.co.uk> contains these words:
> In article <j4ydnRYQ0_5IEgna...@bt.com>,
> Bill Davy <Bi...@SynectixLtd.com> wrote:
> > Q2) Suggestions for suitable supplier of converter (or I shall just use
> > RS, Maplin, or Farnell) and what are they called (transformer,
> > auto-transformer, inverter, converter, etc)
> Trouble is large ones are likely to cost as much as the microwave.
Companies importing American fridges often use 90 volt transofrmers to
make allowance for the difference in frequency. But these things are
very often suck it and see.
Andy Dingley
> Q1) Does anyone know if I just need to drop the voltage or does the
> frequency matter?
No idea, and I'm not going to hazard a guess.
60Hz is more efficient for running crude old iron-cored transformers,
and you've got an appliance there that contains a honking great
example of such a thing, designed from the country that still thinks
"big crude old iron" is a good idea. Run such a transformer on 50Hz
and it _will_ run hotter, the only question is how much so and whether
it's enough to mattter.
Frequency very rarely makes an issue here, but if it were going to,
your microwave would be a prime candidate for being the first kitchen
appliance to self-immolate because of it.
I'd ask GE directly. I'd have done this before even buying it.
Ron Lowe
news:9c778164-574e-4d0f...@d21g2000prf.googlegroups.com...
Ohh, me! me! ask me!
We've got tons of US 110/60 kit at work, and the place is wired for US-style
110/60.
This is supplied from a bank of rotary convertors.
Perhaps the OP would like a rotary convertor in the kitchen?
I can probably find an old one that would only need a bit of tarting up, a
new belt and a lick of paint.
Not *too* noisy, if you crank the stereo up.
Would fit neatly under the worktop in a double unit carcass.
Sorted.
--
Ron
SJP
"Bill Davy" <Bi...@SynectixLtd.com> wrote in message
news:j4ydnRYQ0_5IEgna...@bt.com...
>
>
> I've bought an American microwave (GE PEM31) for its physical size (it's
> very shallow). It takes 1.2KVA (110VAC @60Hz).
>
>
>
>
Q1) Why?
Brian Sharrock
"SJP" <som...@somewhere.invalid> wrote in message
news:jNudnSxy8Nm1dAna...@bt.com...
OTOH: I've noticed a lot (OK, perhaps two examples .... ) of 'shallow'
microwave cookers for sale in the UK (England) this year..
B&Q are offering an example advertised as fitting into a wall cupboard ...
getting it off the worktop, it's less than 300mm deep.
Those I've examined seem to fit into the '17 litre' class of device.
IS the OP attempting to solve a problem for which there's already a
solution?
--
Brian
Andrew Gabriel
"Bill Davy" <Bi...@SynectixLtd.com> writes:
>
>
> I've bought an American microwave (GE PEM31) for its physical size (it's
> very shallow). It takes 1.2KVA (110VAC @60Hz).
That's quite funny. I used to get US visitors buying their
microwaves in the UK because they couldn't get combination
ones in the US (they draw more power than you can get from
a standard US socket).
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Dave Plowman (News)
Andrew Gabriel <and...@cucumber.demon.co.uk> wrote:
> In article <j4ydnRYQ0_5IEgna...@bt.com>,
> "Bill Davy" <Bi...@SynectixLtd.com> writes:
> >
> >
> > I've bought an American microwave (GE PEM31) for its physical size
> > (it's very shallow). It takes 1.2KVA (110VAC @60Hz).
> That's quite funny. I used to get US visitors buying their
> microwaves in the UK because they couldn't get combination
> ones in the US (they draw more power than you can get from
> a standard US socket).
Are they any use? To me the beauty of a microwave is not having to wait
for it to heat up - and that it doesn't get stuff burnt on to it. But then
I only use mine for vegetables and reheating stuff which is in a suitable
container anyway. For cooking things that need an oven or grille I use the
oven or grille. ;-)
--
Andy Hall
Gabriel) said:
> In article <j4ydnRYQ0_5IEgna...@bt.com>,
> "Bill Davy" <Bi...@SynectixLtd.com> writes:
>>
>>
>> I've bought an American microwave (GE PEM31) for its physical size (it's
>> very shallow). It takes 1.2KVA (110VAC @60Hz).
>
> That's quite funny. I used to get US visitors buying their
> microwaves in the UK because they couldn't get combination
> ones in the US (they draw more power than you can get from
> a standard US socket).
Would have been amusing to see them heating their pizzas in the laundry
room.:-)
Appin
from and...@cucumber.demon.co.uk (Andrew Gabriel) contains these words:
> In article <j4ydnRYQ0_5IEgna...@bt.com>,
> "Bill Davy" <Bi...@SynectixLtd.com> writes:
> >
> >
> > I've bought an American microwave (GE PEM31) for its physical size (it's
> > very shallow). It takes 1.2KVA (110VAC @60Hz).
> That's quite funny. I used to get US visitors buying their
> microwaves in the UK because they couldn't get combination
> ones in the US (they draw more power than you can get from
> a standard US socket).
Assuming you're referring to a NEMA 5-15 as a standard US socket.
A Nema 6-15 will cheerfully deliver 15 amps at around 235 volts, though
both legs will be at approx 117 volts potential to ground/earth.
Appin
from Andy Hall <an...@hall.nospam> contains these words:
Why? Many houses are wired so that by simply changing any duplex 117
volt NEMA 5-15 receptacle for a single NEMA 6-15 receptacle one can have
235 volts 15 amps avialable. The socket looks not unlike our 13 amp
socket. Often find NEMA 6-20s for using a room-sized air conditioner.
No need to go to the basement.
Andy Hall
Until one looks at the manufacturing quality and realises that they are
an accident waiting to happen.
> Often find NEMA 6-20s for using a room-sized air conditioner.
> No need to go to the basement.
Who said anything about the basement?
Andy Dingley
<da...@davenoise.co.uk> wrote:
>> That's quite funny. I used to get US visitors buying their
>> microwaves in the UK because they couldn't get combination
>> ones in the US (they draw more power than you can get from
>> a standard US socket).
>
>Are they any use?
No! If you ever use the hot oven, it's about an hour before it's cool
enough to use as a microwave. Damn silly things.
Bill Davy
news:8%8lj.84965$wD5....@newsfe3-gui.ntli.net...
I have just checked the B&Q site and the shallowest item they mention is:
Built-in Microwave Oven AMW4401X Stainless Steel 750w: 320mm (Online: out of
stock, In Store: Not ranged, Price £229).
I did look at domestically available appliances, including looking at
marine/caravan applications. I even bought one only to find the figure
given for the depth of the unit was actually the cavity depth so had to send
that back.
The PEM31 is 12 9/32" deep (quaint, I know, but 312 mm). That includes
space for the cable's bend radius.
Another advantage of the PEM31 is that there is a kit to hang it under a
unit. Also, for getting the chill off a red wine, you can stop the
turntable rotating. Also, it is a mark two. Anyway, the thing is here now
and so far, nobody seems to "know" the answer, which is fine.
Including shipping and the support bracket kit it was $390. Obviously the
converter will add to the cost.
I'll open it up and see if there is a lump of iron so I can see if iron loss
is likely to be an issue. And then I'll fire it up at 220VAC 50Hz and see
what happens. I will do that on an outside socket, sitting on a cement slab
but out of the rain.
Bill
www.SynectixLtd.com is not relevant
Appin
from Andy Hall <an...@hall.nospam> contains these words:
> >> Would have been amusing to see them heating their pizzas in the laundry
> >> room.:-)
> >
> > Why? Many houses are wired so that by simply changing any duplex 117
> > volt NEMA 5-15 receptacle for a single NEMA 6-15 receptacle one can have
> > 235 volts 15 amps avialable. The socket looks not unlike our 13 amp
> > socket.
> Until one looks at the manufacturing quality and realises that they are
> an accident waiting to happen.
I agree that most American plugs and sockets are accidents either
waiting to happen or in the process of happening. However
decent-quality receptacles and plugs ARE available, at a price, though
not from the box-shifters. NEMA 6 stuff is usually somewhat better
quality than NEMA 5.
> > No need to go to the basement.
> Who said anything about the basement?
That's where the laundry room usually is in America. At least in the
vast majority of houses across the country.
Dave Plowman (News)
I've never tried one, although I've had a microwave near enough from when
they first came out, but my thoughts were when seeing them advertised was
that they were a solution to a problem that didn't exist - or meant for
those who didn't understand microwaves.
--
* I like you. You remind me of when I was young and stupid
Andy Hall
> The message <47954a76@qaanaaq>
> from Andy Hall <an...@hall.nospam> contains these words:
>
>
>
>>>> Would have been amusing to see them heating their pizzas in the laundry
>>>> room.:-)
>>>
>>> Why? Many houses are wired so that by simply changing any duplex 117
>>> volt NEMA 5-15 receptacle for a single NEMA 6-15 receptacle one can have
>>> 235 volts 15 amps avialable. The socket looks not unlike our 13 amp
>>> socket.
>
>> Until one looks at the manufacturing quality and realises that they are
>> an accident waiting to happen.
>
> I agree that most American plugs and sockets are accidents either
> waiting to happen or in the process of happening. However
> decent-quality receptacles and plugs ARE available, at a price, though
> not from the box-shifters. NEMA 6 stuff is usually somewhat better
> quality than NEMA 5.
Seemingly not from Home Depot, though.
>
>
>>> No need to go to the basement.
>
>> Who said anything about the basement?
>
> That's where the laundry room usually is in America. At least in the
> vast majority of houses across the country.
It does assume having a basement, and that seems regional.
Paul D.Smith
> Including shipping and the support bracket kit it was $390. Obviously the
> converter will add to the cost.
>
> I'll open it up and see if there is a lump of iron so I can see if iron
> loss is likely to be an issue. And then I'll fire it up at 220VAC 50Hz
> and see what happens. I will do that on an outside socket, sitting on a
> cement slab but out of the rain.
So you're prepared to explode $390.00? Next time you feel like that send me
just $300.00 (saving $90.00 - what an offer) and I'll send you a picture of
a balloon popping ;-).
FWIW I was once at a trade show where smoke and burning smells emanated from
my nieghbours' stand. They'd plugged a 110V 4-way block into the French
mains and it didn't like it. They been confused by the "30kV" note on the
side (the level of lightning protection!). 110V and 220V/240V do not mix
and US goods are almost never designed to survive the higher voltage.
Paul DS.
Bill Davy
news:4795effd$0$26255$4d4e...@read.news.uk.uu.net...
Using a transformer but still at 50Hz, of course. Doh.
Opened the box up and three transformers (and a circuit diagram)!
No space to fit a toroid either.
Just have to see if the increased iron losses are tolerable.
Edgar
8><----
>
> I'll open it up and see if there is a lump of iron so I can see if
> iron loss is likely to be an issue. And then I'll fire it up at
> 220VAC 50Hz and see what happens. I will do that on an outside
> socket, sitting on a cement slab but out of the rain.
>
>
> Bill
>
Here's another silly idea. Go to America and buy a petrol generator
supplying the correct voltage and frequency for your appliance (1.2KVA
at 110VAC @60Hz). Take the microwave along with you and get the
supplier to demonstrate the two running together before buying.
Edgar
Bertie Doe
1500watt element at 110v. The suggestion was to use a 110volt Variac, as per
http://tinyurl.com/2sh47p I don't know whether they're too bulky for a
kithen, but would it do the job?
Bertie
--
Links to some online UK coffee bean and machine suppliers:-
http://www.geocities.com/cumberpach/
matthew...@gmail.com
> In article <47952f0d$0$509$5a6ae...@news.aaisp.net.uk>,
> Andrew Gabriel <and...@cucumber.demon.co.uk> wrote:
>
> > In article <j4ydnRYQ0_5IEgnanZ2dnUVZ8surn...@bt.com>,
> > "Bill Davy" <B...@SynectixLtd.com> writes:
>
> > > I've bought an American microwave (GE PEM31) for its physical size
> > > (it's very shallow). It takes 1.2KVA (110VAC @60Hz).
> > That's quite funny. I used to get US visitors buying their
> > microwaves in the UK because they couldn't get combination
> > ones in the US (they draw more power than you can get from
> > a standard US socket).
>
> Are they any use? To me the beauty of a microwave is not having to wait
> for it to heat up - and that it doesn't get stuff burnt on to it. But then
> I only use mine for vegetables and reheating stuff which is in a suitable
> container anyway. For cooking things that need an oven or grille I use the
> oven or grille. ;-)
>
> --
>
> To e-mail, change noise into sound.
My wife once set some sausages to cook (!) in the combined microwave /
grill using the combination setting. Needless to say the hot fat
created by the microwave was set alight within minutes so when she
returned to the kitchen there was something of a mess. And she made
me write a letter of complaint to the manufacturers that there should
have been warnings about doing this sort of thing!!
Matt
Andrew Gabriel
Mine is a Sharp combination microwave/grille/fan/convection
oven and I use all parts of it, and sometimes two of them
together. The fan oven alone is a useful second oven if I
need two different temperatures (most commonly if main oven
is too hot for plate warming, and also when it's my turn to
do Christmas for the extended family and need more oven space).
I don't use it on high settings as it's not self cleaning,
and whilst it heats very quickly to low/medium temperatures,
it takes ages to get right up to max, longer than my main
oven. Convection oven has excellent electronic temperature
control down to 40C (which my main oven can't do), which
is perfect for bread rising. Starting the bread off with a
burst of microwave it an excellent way to get the proving
started off quickly. (I can make a loaf of bread in an hour
this way, although final baking is in main oven.)
I do use microwave and grilling together sometimes (good
for something like a macaroni cheese in 10 minutes which
comes out like it was baked in the oven for much longer).
Andrew Gabriel
You don't find them in kitchens for worktop appliances.
Hence no one sells any worktop appliances > 1400W in the
US. What you find is that companies like Sharp simply
don't ship their top end appliances to the US, so
the non-combi version of my Microwave was available in
the US, but not the Combi one which is 2650W. Even the
non-combi version had a slightly reduced microwave power
in the US. (You find that with things like vacuum cleaners
too, although for slightly different reasons.)
Bertie Doe
"Andrew Gabriel"
> You don't find them in kitchens for worktop appliances.
> Hence no one sells any worktop appliances > 1400W in the
> US. What you find is that companies like Sharp simply
> don't ship their top end appliances to the US, so
> the non-combi version of my Microwave was available in
> the US, but not the Combi one which is 2650W. Even the
> non-combi version had a slightly reduced microwave power
> in the US. (You find that with things like vacuum cleaners
> too, although for slightly different reasons.)
> --
> Andrew Gabriel
In the USA they do suffer with their 112volts supply. 2650w/112v = 23amps.
Whereas 2650w/220v = 12amps.
Bertie
spuorg...@gowanhill.com
> The question came up on another site, regarding a roasting oven using a
> 1500watt element at 110v.
Heating-only appliances can be used with what the Americans call a
"convertor" which is basically a whopping great diode that blocks half
the AC waveform. Doesn't work with anything motor driven or
electronic, of course.
Appin
There are certainly houses without basements, but basements are more
general in the US than the absence of them is general here.
Andrew Gabriel
Ouch -- that won't work for heating appliances either.
240VAC RMS half wave rectified is 170V RMS, not 120V RMS.
That means the appliance will generate twice the heat it
was designed for. This is combined with the insulation
being exposed to twice the voltage it was designed for.
I rather suspect it will have a very short, and possibly
unsafe life.
My parents still have a very nice 120V 1050W electric
frying pan we bought when we lived in the US in 1960's.
It (and several other US appliances which we brought
back but have since been disposed of) used to be run
from a large transformer. About 10 years ago, I decided
to build a small switching regulator as the extra very
heavy transformer was an impediment to using the frying
pan. Following on from your scheme, if you half wave
rectify, and you only let every other +ve cycle through,
you will get the right power dissipation. However, I
dismissed that partly for the reason I mentioned above
about the insulation voltage being over-stressed, and
also partly because I though there was some risk of the
element being stressed by generating 4 times the power
it was designed for on a 25% duty cycle.
So what I did instead was to take each mains cycle, and
cut out the +ve and -ve going peaks. It's quite a
complicated piece of Calculus working out what the phase
angle is for doing the switching (particularly when you
haven't used calculus for some years) to achieve 120V RMS,
but ISTR it comes out around 43 degrees. This means the
element is exposed to a max voltage of
sin(43) x 340V (peak) = 232V instead of the 170V peak
it was designed for. This is only 30% higher than
it was designed for, rather than 100% higher if it
were to be exposed to the 240VAC peak voltage.
This has worked fine for some 10 years now, but aware
of even the 30% insulation stressing, it's always run on
an RCD.
Appin
from "Bertie Doe" <monteb...@ntl.com> contains these words:
> The question came up on another site, regarding a roasting oven using a
> 1500watt element at 110v. The suggestion was to use a 110volt Variac,
> as per
> http://tinyurl.com/2sh47p I don't know whether they're too bulky for a
> kithen, but would it do the job?
Not too big, but expensive.
Most full-size electric stoves in the US run off 230 volts anyway.
Older ones used to use complicated switching of sections of each
element in their radiant hob rings between series and parallel using 230
and 115 volt supplies to give multiple heats, but most use more modern
controls nowadays. Where there are clocks, however, these are almost
always 115 voltt 60 Hz. Where an appliance has two elements in parallel
running off 115 volts, they can be rewired to run in series off 230
volts. It isn't exactly rocket science.
Appin
from "Paul D.Smith" <paul_d...@x-hotmail.com> contains these words:
> 110V and 220V/240V do not mix
> and US goods are almost never designed to survive the higher voltage.
All houses have 230/115 volt (or thereabouts) supplies. Two hot wires
at 115 volts potential to ground and one neutral wire at 0V. 230 volts
between the two hot wires. And almost every house has some appliances
which use 230 volts. Dryer, air-conditioning units, electric stove,
etc. etc.
However what you say is indeed true of most small domestic appliances.
Appin
from "Bertie Doe" <monteb...@ntl.com> contains these words:
> In the USA they do suffer with their 112volts supply. 2650w/112v = 23amps.
> Whereas 2650w/220v = 12amps.
Yes, but in general terms there is little use domestically of 110 volt
receptacles (soeckets) other than NEMA 5-15s. In other words, 15 amps
tops, from 110/120 volt supplies.
You do see occasional NEMA 5-20s (one of the flat pins horizontal to
prevent it going into a NEMA 5-15 receptacle) but generally if you need
more than 15 amps you should go to a NEMA 6 which is a 230 volt supply.
The way their receptacles are wired it's common to find both hot wires
at any wallbox, with one of the duplex sockets wired to one hot wire and
the other to the other. In such an instance simply changing the NEMA
5-15 receptacle to a single NEMA 6-15 one will give you 230 volts
without any rewiring at all. Neat.
Andy Hall
Until it all falls apart, the wirenuts overheat and the place burns to
the ground.
Not so neat.
Bertie Doe
"Appin" <ap...@zetnet.co.uk> wrote in message
news:3130303036363...@zetnet.co.uk...
Thanks for that and apologies to Bill for butting in here. The Americans are
quite good at designing coffee roasters. The appliance in question has good
spec http://tinyurl.com/38ppj3 and has grabbed the attention of uk coffee
geeks (it's half the price of the competition) if you look at roaster
specification, you'll see it does use timers and during the roasting, there
are options to to vary the heat profiles (depending on bean variety)
throughout the 15 min roast period. It's a radiant heat oven plus
circulating fan. Depending which roast profile you use, the element and fan,
will be switching off and on during the roast. So will the above transformer
do the job still?
Bertie
Appin
from Andy Hall <an...@hall.nospam> contains these words:
> On 2008-01-22 21:11:29 +0000, Appin <ap...@zetnet.co.uk> said:
Use a decent receptacle and it won't fall apart. Granted the general
quality of NEMA 5-15 receptacles is dire, but good receptacles and
indeed good plugs can be obtained,. NEMA 6 (230 volt) fittings are
generally better quality, in my experience.
> the wirenuts overheat
There's no particular reason for wirenuts to overheat if they're good
quality wirenuts and the joints are properly made. Good wirenuts are
nothing remotely like as dire as the late and completely unlamented
"Scruits" if you're old enough to remember them in this country.
> and the place burns to the ground.
It'll run cooler on 230 volts :-)
> Not so neat.
Never had a building burn on me in North America. And one of the houses
I lived in is still standing there at 200 years old. Fieldstone
foundation and three floors of timber-frame construction above.
Appin
> Bertie
It might, but we're only guessing at the circuit and the probable answer
is "Not worth trying"
Points worth noting:
That URL isn't for a variac. It's for a 55-0-55 volt site transformer
-- centre tapped and giving 55 volts from each leg to earth with 110
volts between the two live wires. Not the sort of supply expected by a
US appliance, quite apart from the potential relevance of frequency
differences, A good price on it, though.
A variac may refer to a VARIABLE auotransformer or may refer to an
electronic "circuits," usually an SCR (silicon controlled rectifier) or
Triac type circuit, which changes the waveform into a square wave so
that the practical effect when it comes to dimming lights is similar to
a reduction in voltage by a transformer.
Andy Hall
> The message <479664b3@qaanaaq>
> from Andy Hall <an...@hall.nospam> contains these words:
>
>> On 2008-01-22 21:11:29 +0000, Appin <ap...@zetnet.co.uk> said:
>
>>> The message <1hslj.17050$g%2.1...@newsfe4-gui.ntli.net>
>>> from "Bertie Doe" <monteb...@ntl.com> contains these words:
>>>
>>>
>>>
>>>
>>>> In the USA they do suffer with their 112volts supply. 2650w/112v =
>>>> 23amps.
>>>> Whereas 2650w/220v = 12amps.
>>>
>>>
>>> Yes, but in general terms there is little use domestically of 110 volt
>>> receptacles (soeckets) other than NEMA 5-15s. In other words, 15 amps
>>> tops, from 110/120 volt supplies.
>>>
>>> You do see occasional NEMA 5-20s (one of the flat pins horizontal to
>>> prevent it going into a NEMA 5-15 receptacle) but generally if you need
>>> more than 15 amps you should go to a NEMA 6 which is a 230 volt supply.
>>>
>>> The way their receptacles are wired it's common to find both hot wires
>>> at any wallbox, with one of the duplex sockets wired to one hot wire and
>>> the other to the other. In such an instance simply changing the NEMA
>>> 5-15 receptacle to a single NEMA 6-15 one will give you 230 volts
>>> without any rewiring at all. Neat.
>
>> Until it all falls apart,
>
> Use a decent receptacle and it won't fall apart. Granted the general
> quality of NEMA 5-15 receptacles is dire, but good receptacles and
> indeed good plugs can be obtained,.
The question is more one of "are they" than "can they"
> NEMA 6 (230 volt) fittings are
> generally better quality, in my experience.
They couldn't be worse that the 110v ones.
>
>
>> the wirenuts overheat
>
> There's no particular reason for wirenuts to overheat if they're good
> quality wirenuts and the joints are properly made.
Mmm.....
> Good wirenuts are
> nothing remotely like as dire as the late and completely unlamented
> "Scruits" if you're old enough to remember them in this country.
I have seen some. They were deprecated over 50 years ago in the UK.
>
>
>> and the place burns to the ground.
>
> It'll run cooler on 230 volts :-)
>
>
>> Not so neat.
>
> Never had a building burn on me in North America. And one of the houses
> I lived in is still standing there at 200 years old. Fieldstone
> foundation and three floors of timber-frame construction above.
Well.... the adjusted rate of fires caused by fixed wiring in the
U.S. is said to be very high in comparison with Europe. In the UK, it
is virtually non existent.
Paul D.Smith
Are you talking about US 3-phase or do you really mean you get +115V,
0, -115V?
Paul DS
Appin
from "Paul D.Smith" <paul_d...@x-hotmail.com> contains these words:
> "Appin" <ap...@zetnet.co.uk> wrote in message
> news:3130303036363...@zetnet.co.uk...
> > The message <4795effd$0$26255$4d4e...@read.news.uk.uu.net>
> > from "Paul D.Smith" <paul_d...@x-hotmail.com> contains these words:
> >
> >> 110V and 220V/240V do not mix
> >> and US goods are almost never designed to survive the higher voltage.
> >
> > All houses have 230/115 volt (or thereabouts) supplies. Two hot wires
> > at 115 volts potential to ground and one neutral wire at 0V. 230 volts
> > between the two hot wires. And almost every house has some appliances
> > which use 230 volts. Dryer, air-conditioning units, electric stove,
> > etc. etc.
> >
> > However what you say is indeed true of most small domestic appliances.
> Are you talking about US 3-phase or do you really mean you get +115V,
> 0, -115V?
In a domestic situation its 115-0-115
Appin
from Andy Hall <an...@hall.nospam> contains these words:
> >
> > Use a decent receptacle and it won't fall apart. Granted the general
> > quality of NEMA 5-15 receptacles is dire, but good receptacles and
> > indeed good plugs can be obtained,.
> The question is more one of "are they" than "can they"
In anyhting I've ever done, yes. Can't answer for other people.
> > NEMA 6 (230 volt) fittings are
> > generally better quality, in my experience.
> They couldn't be worse that the 110v ones.
I think you mean the box shifters' NEMA 5-15s
> >
> >> the wirenuts overheat
> >
> > There's no particular reason for wirenuts to overheat if they're good
> > quality wirenuts and the joints are properly made.
> Mmm.....
I'm not a wild fan of wirenuts, because they're not idiot-proof and poor
ones do exist. There is, however, no cure for idiocy and once the
technique of making a good wirenut joint is mastered the joints are
perfectly satisfactory and, in the circumstances of the physical
constraints of the standard American box and the size of American
conductors, a realistic way of fitting accessories.
> > Good wirenuts are
> > nothing remotely like as dire as the late and completely unlamented
> > "Scruits" if you're old enough to remember them in this country.
> I have seen some. They were deprecated over 50 years ago in the UK.
They were in general use, even in some quality work. The virtual
disappeaance of multiple junction boxes with the introduction of loop-in
wiring for lighting and of ring circuits for power got rid of them. But
a proper wirenut is a vastly more sophisticated device than a Scruit and
in a properly made joint ensuresmuch better than a poorly-made terminal
connection.
> Well.... the adjusted rate of fires caused by fixed wiring in the
> U.S. is said to be very high in comparison with Europe. In the UK, it
> is virtually non existent.
Agreed. Though a great deal of wiring in the US is up to a century old
-- lots of "knob and tube" still in everyday use. And they did have a
totally-disastrous flirtation with alumin(i)um wiring about 40 years
ago.
Bertie Doe
"Appin" wrote in
> That URL isn't for a variac. It's for a 55-0-55 volt site transformer
> -- centre tapped and giving 55 volts from each leg to earth with 110
> volts between the two live wires. Not the sort of supply expected by a
> US appliance, quite apart from the potential relevance of frequency
> differences, A good price on it, though.
>
> A variac may refer to a VARIABLE auotransformer or may refer to an
> electronic "circuits," usually an SCR (silicon controlled rectifier) or
> Triac type circuit, which changes the waveform into a square wave so
> that the practical effect when it comes to dimming lights is similar to
> a reduction in voltage by a transformer.
Thanks Appin, I'll refer this thread to the coffee group - caveat emptor!!
Bertie
Andy Hall
> The message <47968e28@qaanaaq>
> from Andy Hall <an...@hall.nospam> contains these words:
>
>
>>>
>>> Use a decent receptacle and it won't fall apart. Granted the general
>>> quality of NEMA 5-15 receptacles is dire, but good receptacles and
>>> indeed good plugs can be obtained,.
>
>> The question is more one of "are they" than "can they"
>
> In anyhting I've ever done, yes. Can't answer for other people.
From the problems that I hear that people have with their electrical
installations, it would appear that crappy connectors are widespread.
>
>
>>> NEMA 6 (230 volt) fittings are
>>> generally better quality, in my experience.
>
>> They couldn't be worse that the 110v ones.
>
> I think you mean the box shifters' NEMA 5-15s
If the volume market is crap, the outcome is crap.
>
>
>
>>>
>>>> the wirenuts overheat
>>>
>>> There's no particular reason for wirenuts to overheat if they're good
>>> quality wirenuts and the joints are properly made.
>
>> Mmm.....
>
> I'm not a wild fan of wirenuts, because they're not idiot-proof and poor
> ones do exist. There is, however, no cure for idiocy and once the
> technique of making a good wirenut joint is mastered the joints are
> perfectly satisfactory and, in the circumstances of the physical
> constraints of the standard American box and the size of American
> conductors, a realistic way of fitting accessories.
Dodgy connectors with high current loads? Possibility to make poor
connections? Not a recipe for success and safety.
>
>
>>> Good wirenuts are
>>> nothing remotely like as dire as the late and completely unlamented
>>> "Scruits" if you're old enough to remember them in this country.
>
>> I have seen some. They were deprecated over 50 years ago in the UK.
>
> They were in general use, even in some quality work. The virtual
> disappeaance of multiple junction boxes with the introduction of loop-in
> wiring for lighting and of ring circuits for power got rid of them. But
> a proper wirenut is a vastly more sophisticated device than a Scruit and
> in a properly made joint ensuresmuch better than a poorly-made terminal
> connection.
The question is then one of are the connections well made......
Dave Plowman (News)
Bertie Doe <monteb...@ntl.com> wrote:
> The question came up on another site, regarding a roasting oven using a
> 1500watt element at 110v. The suggestion was to use a 110volt Variac, as
> per http://tinyurl.com/2sh47p I don't know whether they're too bulky
> for a kithen, but would it do the job?
A 'variac' is a transformer with multi-taps so you can get an effectively
near infinite variety of output voltages - very roughly from zero to max.
Used in a workshop to bring a faulty piece of equipment gradually up to
voltage while looking for the fault. Etc. And way more expensive than a
240-110v transformer of the same current.
What you've shown is a site transformer designed to use 110v tools on a
building site for safety reasons. It would be fine for any 110v use - but
rather bigger than needed for most being 3.3kW - about three times that of
any likely US appliance.
--
*A dog's not just for Christmas, it's alright on a Friday night too*
Dave Plowman da...@davenoise.co.uk London SW
Andy Burns
> What you've shown is a site transformer designed to use 110v tools on a
> building site for safety reasons. It would be fine for any 110v use - but
> rather bigger than needed for most being 3.3kW - about three times that of
> any likely US appliance.
And they weigh a bloody ton, not really the sort of thing you want
kicking around in a kitchen.
Bill Davy
news:13pe7n3...@corp.supernews.com...
I've ordered http://tinyurl.com/2uox5m :
AT1500 : 1.5kVA Stepup stepdown transformer
0-120-240V (Hardwired with screw terminals)
Step up from 120V to 240V or step down from 240V to 120V
Price for 1+: £54.00 each.
Price for 5+: £48.60 each.
Price for 25+: £45.90 each.
Weight: 8 kg.
VA: 1500 VA.
a.. Screw terminal 0-120-240v or 0-115-230v
b.. Stepup from 120v to 240v or Stepdown from 240v to 120v
c.. Dimensions: 165x80mm
It is quite compact and I hope I can hide it away nicely, perhaps nailed
(metaphorically) to the wall above a cabinet.
We shall see what happens.
Bill
PS www.SynectixLtd.com is not relevant
Grumps
> I've bought an American microwave (GE PEM31) for its physical size
> (it's very shallow). It takes 1.2KVA (110VAC @60Hz).
>
>
>
> frequency matter? I do not really mind if the platter rotates a tad
> slower, the timing settings are a bit off. The microwave frequency
> is determined by the mechanical structure of the magnetron.
>
>
>
> Q2) Suggestions for suitable supplier of converter (or I shall just
> use RS, Maplin, or Farnell) and what are they called (transformer,
> auto-transformer, inverter, converter, etc)
>
>
>
> Q3) Is there a better source of information if it is not available
> here?
>
>
> Q4) If I open it up to find answers, what am I looking for?
>
>
>
> TIA
>
> Bill
>
> PS I am new to this group so apologise in advance for everything.
You should've bought two and connect them in series.
Dave Plowman (News)
> AT1500 : 1.5kVA Stepup stepdown transformer
> 0-120-240V (Hardwired with screw terminals)
> Step up from 120V to 240V or step down from 240V to 120V
> Price for 1+: £54.00 each.
> Price for 5+: £48.60 each.
> Price for 25+: £45.90 each.
> Weight: 8 kg.
> VA: 1500 VA.
> a.. Screw terminal 0-120-240v or 0-115-230v
> b.. Stepup from 120v to 240v or Stepdown from 240v to 120v
> c.. Dimensions: 165x80mm
> It is quite compact and I hope I can hide it away nicely, perhaps nailed
> (metaphorically) to the wall above a cabinet.
> We shall see what happens.
This type of transformer is designed to be mounted inside an appliance,
etc. For safety I'd fit it inside a flame proof box - to also provide
mechanical protection to it. The actual windings are only insulated by a
thin layer and could easily be damaged if not protected. Also be aware
that the fixing must not be a conducting loop round the windings. It
should really come with a pukka fixing kit like other such toroidal
transformers.
--
*Why is it that doctors call what they do "practice"?
Paul D.Smith
> In a domestic situation its 115-0-115
Thanks - I really must have a closer look at my in-laws supply next time I'm
over there.
Paul DS
Chip
<monteb...@ntl.com> spake thusly in uk.d-i-y:
Another thing to watch out for with the construction site transformers
-incidentally, the 110v output is slightly lower than the 117-120v
expected by the device, which helps with the 'lower frequency
overheating' problem- is that they are built for cheapness and
ruggedness, not efficiency. The off load efficiency is absolutely
dire, they waste 'loads of watts'[1] in magnetising current and
therefore heating up the transformer.
They'd be fine probably for a coffee roaster, as the mains would be
turned off after / between uses, but for a microwave (as per the
thread title) which needs to be powered 24/7 because of the clock, no
good at all.
The custom made 120v transformers usually use toroidal transformers,
and should be much more efficient.
[1] No, I haven't measured the wattage, hence no figures, but an
unloaded 2.2kva transformer certainly gets warm enough to suggest
around 100-150w of no load losses, plus the inrush can cause mcb
tripping on domestic "B" curve MCBs.
--
_
( ) ASCII ribbon campaign against html e-mail
X and usenet posts
/ \
Brian Sharrock
"Paul D.Smith" <paul_d...@x-hotmail.com> wrote in message
news:47976001$0$26252$4d4e...@read.news.uk.uu.net...
the USA distribute power to domestic customers in a 230V 60Hz 3 phase
process {Rather like the UK process],
The three phases are distributed individually in a balanced manner to
houses -so each house only sees one phase of 230V AC. {again, Rather like
the UK process]
There is a crucial difference however _at_ the house connection. USA
practise is to feed 230V AC to the primary of a transformer and take off
_two_ supplies of 115V AC from the centre-tapped secondary. Thus it's
_possible _ to have one 115V wire (they call it the 'Hot wire' - at
instantaneously plus115V while another , perhaps adjacent, 'hot wire' is at
, instantaneous, minus 15V AC [The exercise of calculating peak voltage
from the RMS values is left to the reader].
When USA equipment requires a 'full' 230V then their usage ('Codes') permit
a receptacle which uses the 'Hot' wires from the two opposed lines to be
utilised.
[Some USA-ians I've encountered have referred to such usage as 'Two-phase';
this is deprecated by the 'trade']
There _are_ variations in the 'Codes'; The County of Los Angeles has very
stringent 'Codes' .
The rather bizarre practise of pole-mounted oil-filled transformers has to
be seen at night-time during a hurricane to be appreciated - lots of
explosions and flares can make the sky seem like Guy Fawkes night.
--
Brian
Paul D.Smith
Thanks for the lesson in 230V 3 phase, 230V single, +/- 115V.
> The rather bizarre practise of pole-mounted oil-filled transformers has to
> be seen at night-time during a hurricane to be appreciated - lots of
> explosions and flares can make the sky seem like Guy Fawkes night.
>
Ever heard of the "Parrots of Flatbush"? They're some sort of parakeet that
escaped/was released in New York city around the Flatbush area. Expected to
die out during their first winter, they proved that smart parrot smart and
co-operation are a force to reckon with. They've been building large
communal nests (as they do in the wild) around suitable warm spots - or as
you refer to them, oil filled transformers.
Things are fine until the transformers get too warm, by which point the
parrots have moved out just before the bang.
They have learnt this behaviour after their first NY winter which they spent
nesting around flood lights overlooking a rail yard. Presumably they didn't
like the lights and so found other, darker places of warmth.
Paul DS.
Andy Hall
>
> The rather bizarre practise of pole-mounted oil-filled transformers has to
> be seen at night-time during a hurricane to be appreciated - lots of
> explosions and flares can make the sky seem like Guy Fawkes night.
Yes I've seen this - it's entertaining.
Mind you, anything more than the lightest of breezes is a "storm"
Bertie Doe
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:4f659fe...@davenoise.co.uk...
> In article <x%olj.51259$Hc3....@newsfe1-gui.ntli.net>,
> Bertie Doe <monteb...@ntl.com> wrote:
>> The question came up on another site, regarding a roasting oven using a
>> 1500watt element at 110v. The suggestion was to use a 110volt Variac, as
>> per http://tinyurl.com/2sh47p I don't know whether they're too bulky
>> for a kithen, but would it do the job?
>
> A 'variac' is a transformer with multi-taps so you can get an effectively
> near infinite variety of output voltages - very roughly from zero to max.
> Used in a workshop to bring a faulty piece of equipment gradually up to
> voltage while looking for the fault. Etc. And way more expensive than a
> 240-110v transformer of the same current.
>
> What you've shown is a site transformer designed to use 110v tools on a
> building site for safety reasons. It would be fine for any 110v use - but
> rather bigger than needed for most being 3.3kW - about three times that of
> any likely US appliance.
>
be on a higher amperage than 240?
Bertie
Man at B&Q
> "Dave Plowman (News)" <d...@davenoise.co.uk> wrote in messagenews:4f659fe...@davenoise.co.uk...
>
>
>
> > In article <x%olj.51259$Hc3.18...@newsfe1-gui.ntli.net>,
> > Bertie Doe <montebrasi...@ntl.com> wrote:
> >> The question came up on another site, regarding a roasting oven using a
> >> 1500watt element at 110v. The suggestion was to use a 110volt Variac, as
> >> for a kithen, but would it do the job?
>
> > A 'variac' is a transformer with multi-taps so you can get an effectively
> > near infinite variety of output voltages - very roughly from zero to max.
> > Used in a workshop to bring a faulty piece of equipment gradually up to
> > voltage while looking for the fault. Etc. And way more expensive than a
> > 240-110v transformer of the same current.
>
> > What you've shown is a site transformer designed to use 110v tools on a
> > building site for safety reasons. It would be fine for any 110v use - but
> > rather bigger than needed for most being 3.3kW - about three times that of
> > any likely US appliance.
>
> Isn't there an old saying "It's the amps that hurts" Won't 110v site tools
> be on a higher amperage than 240?
>
>
> - Show quoted text -
It's the volts that jolts
And the amps that cramps
You need to understand a little more about the relationship between
voltage and current.
The current through a load is not determined by what current is
available, but by what the load allows to flow through itself. Thus,
your house wiring (in the UK) has 13A sockets but not every appliance
that you plug in takes a 13A current.
In the simple case of a resistor we use ohms law and a lower voltage
supply will always result in a lower current through a given resistor,
with a linear relationship between voltage and current.
The human body is a little more complex but you should get the idea by
now.
MBQ
Dave Plowman (News)
Bertie Doe <monteb...@ntl.com> wrote:
> > What you've shown is a site transformer designed to use 110v tools on
> > a building site for safety reasons. It would be fine for any 110v use
> > - but rather bigger than needed for most being 3.3kW - about three
> > times that of any likely US appliance.
> >
> Isn't there an old saying "It's the amps that hurts" Won't 110v site
> tools be on a higher amperage than 240?
The 'amperage' a tool is drawing has no effect on electrocution if you get
a 'shock' from that tool. That is down to the resistance of the path
through the body. And the higher the voltage the more current flows
through the body. Hence your expression. Assuming that voltage source is
capable of supplying the current needed to kill you.
--
*Be nice to your kids. They'll choose your nursing home.
Bertie Doe
"Man at B&Q" wrote in message
"Bertie Doe"
> > What you've shown is a site transformer designed to use 110v tools on a
> > building site for safety reasons. It would be fine for any 110v use -
> > but
> > rather bigger than needed for most being 3.3kW - about three times that
> > of
> > any likely US appliance.
>
> Isn't there an old saying "It's the amps that hurts" Won't 110v site tools
> be on a higher amperage than 240?
>
> Bertie- Hide quoted text -
>
> - Show quoted text -
>It's the volts that jolts
>And the amps that cramps
>You need to understand a little more about the relationship between
>voltage and current.
>The current through a load is not determined by what current is
>available, but by what the load allows to flow through itself. Thus,
>your house wiring (in the UK) has 13A sockets but not every appliance
>that you plug in takes a 13A current.
>In the simple case of a resistor we use ohms law and a lower voltage
>supply will always result in a lower current through a given resistor,
>with a linear relationship between voltage and current.
>The human body is a little more complex but you should get the idea by
>now.
Thanks for that, "it's the volts that jolts" or 'Man from B&Q, saves man
from BBQ'
Bertie
devonsteve
> On 22 Jan, 00:49, "Dave Plowman (News)" <d...@davenoise.co.uk> wrote:
>
>
>
>
>
> > In article <47952f0d$0$509$5a6ae...@news.aaisp.net.uk>,
> > Andrew Gabriel <and...@cucumber.demon.co.uk> wrote:
>
> > > In article <j4ydnRYQ0_5IEgnanZ2dnUVZ8surn...@bt.com>,
> > > "Bill Davy" <B...@SynectixLtd.com> writes:
>
> > > > I've bought an American microwave (GE PEM31) for its physical size
> > > > (it's very shallow). It takes 1.2KVA (110VAC @60Hz).
> > > microwaves in the UK because they couldn't get combination
> > > ones in the US (they draw more power than you can get from
> > > a standard US socket).
>
> > Are they any use? To me the beauty of a microwave is not having to wait
> > for it to heat up - and that it doesn't get stuff burnt on to it. But then
> > I only use mine for vegetables and reheating stuff which is in a suitable
> > container anyway. For cooking things that need an oven or grille I use the
> > oven or grille. ;-)
>
> > --
>
> > Dave Plowman d...@davenoise.co.uk London SW
> > To e-mail, change noise into sound.
>
> grill using the combination setting. Needless to say the hot fat
> created by the microwave was set alight within minutes so when she
> returned to the kitchen there was something of a mess. And she made
> me write a letter of complaint to the manufacturers that there should
> have been warnings about doing this sort of thing!!
>
> Matt- Hide quoted text -
>
> - Show quoted text -
I want a microwave bed ,, you know the sort , ten minutes sleep in
it is equal to 8 hours in a standard bed
Andrew Gabriel
"Brian Sharrock" <b.sha...@ntlworld.com> writes:
> In general -although that's a dangerous phrase to use - Supply companies in
> the USA distribute power to domestic customers in a 230V 60Hz 3 phase
> process {Rather like the UK process],
>
> The three phases are distributed individually in a balanced manner to
> houses -so each house only sees one phase of 230V AC. {again, Rather like
> the UK process]
>
> There is a crucial difference however _at_ the house connection. USA
> practise is to feed 230V AC to the primary of a transformer and take off
> _two_ supplies of 115V AC from the centre-tapped secondary. Thus it's
> _possible _ to have one 115V wire (they call it the 'Hot wire' - at
> instantaneously plus115V while another , perhaps adjacent, 'hot wire' is at
> , instantaneous, minus 15V AC [The exercise of calculating peak voltage
> from the RMS values is left to the reader].
Sorry, but much of that was completely wrong.
In general, only a single phase high voltage feed (4kV or higher)
is provided to feed each street. (Other phases may be carried
through for feeding other streets.) The HV feeds the primary of
a single phase transformer, which has a 120-0-120V secondary
winding. Each transformer feeds just a few houses max, as the
120V regulation goes to pieces after 100yds or so of feeder.
(From then on, it is as you described).
> When USA equipment requires a 'full' 230V then their usage ('Codes') permit
> a receptacle which uses the 'Hot' wires from the two opposed lines to be
> utilised.
> [Some USA-ians I've encountered have referred to such usage as 'Two-phase';
> this is deprecated by the 'trade']
This isn't regarded as 'Two-phase' in the US. They have a
completely different supply system for which they use that
term, and get very hot under the collar if you try to say
their 120-0-120V supply is two phase.
> There _are_ variations in the 'Codes'; The County of Los Angeles has very
> stringent 'Codes' .
>
> The rather bizarre practise of pole-mounted oil-filled transformers has to
> be seen at night-time during a hurricane to be appreciated - lots of
> explosions and flares can make the sky seem like Guy Fawkes night.
Yes, they're good when the transformer is overloaded for
a while. You have a dustbin full of boiling oil which
suddenly explodes (sometimes into a fireball) 30' up above
the pavement. It's a sort of modern equivalent of
medievel boiling oil.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Ron Lowe
news:4798d813$0$514$5a6a...@news.aaisp.net.uk...
> In article <n%Ylj.32792$a61....@newsfe3-win.ntli.net>,
> "Brian Sharrock" <b.sha...@ntlworld.com> writes:
>> In general -although that's a dangerous phrase to use - Supply companies
>> in
>> the USA distribute power to domestic customers in a 230V 60Hz 3 phase
>> process {Rather like the UK process],
>
> In general, only a single phase high voltage feed (4kV or higher)
> is provided to feed each street. (Other phases may be carried
> through for feeding other streets.) The HV feeds the primary of
> a single phase transformer, which has a 120-0-120V secondary
> winding. Each transformer feeds just a few houses max, as the
> 120V regulation goes to pieces after 100yds or so of feeder.
> (From then on, it is as you described).
Yes, that's been my experience too.
This means that it can be very expensive and difficult to get a 3-phase
supply, compared to here, since there is not usually 3 phases in the HV
supply on the street. Of course, you can get 3 phases. But you need to
pony up for it.
Incidentally, they've just put in a new 500KVA sub-station at my work ( UK )
as part of an expansion. It was quite interesting to see all that was
involved in running the new section of the 11KV ring, installing the fancy
switch and xfmr, isolating the portion of the 11KV ring, 'spiking' the cable
and cutting it.
I was out in the rain peering at what they were doing and bugging them with
questions. They seemed surprised anyone was interested, but were very happy
to show me what they were doing.
--
Ron
Andy Wade
> It's the volts that jolts
> And the amps that cramps
Or "volts that jolts, but mils* that kills."
* i.e. milliamps
--
Andy
Fergus McMenemie
> >> 110V and 220V/240V do not mix
> >> and US goods are almost never designed to survive the higher voltage.
> >
> > All houses have 230/115 volt (or thereabouts) supplies. Two hot wires
> > at 115 volts potential to ground and one neutral wire at 0V. 230 volts
> > between the two hot wires. And almost every house has some appliances
> > which use 230 volts. Dryer, air-conditioning units, electric stove,
> > etc. etc.
> >
> > However what you say is indeed true of most small domestic appliances.
When I moved back from the USA the wify made me bring the fancy
microwave we had had there. I was not too sure what I was getting
into (I have a Bsc ing Electrical Engineering) so I rented a 240v -
110v transformer as used by UK tradesman used everywhere. From memory
(this was years ago) the transformer was easily rated for the
ovens full power. However when plugged in and sorted to cook some
bacon, the noise from the microwave was very, very loud. It was a
transformer hum but very loud.
The microwave was unpluged, the transformer returned and eventually
gifted to somebody else who was on their way to the US. We had to
buy another transformer!
The only thing I could figure was that the microwaves internal
transformer or some other internal oscilator was tuned to 60Hz
operation and did not get on with 50Hz.
My transformer was most definetly 110V not 240v.
Howver this is going over old ground. (Usenet is circular). Have
a look at
http://groups.google.co.uk/group/sci.electronics.design/browse_thread/th
read/f6edc17d8b604420/3d906598dd3cc881?lnk=st&q=%22microwave+oven%22+mai
n+frequency#3d906598dd3cc881
Freq may matter! Look at the plate.
Regards
Bill Davy
news:1ib8n18.1j3vrae1u9kd60N%fer...@twig.demon.co.uk...
I looked at that thread (http://tinyurl.com/3asjpu - please consider using
TinyURL for long URLs). Some interesting thoughts, and some pure tosh
("microwave trannies even in normal use overheat in 15 minutes" - I
regularly cook beetroot for 30 minutes).
Anyway, I will post the facts, just the facts, ASAP.
Bill
PS www.SynectixLtd.com is irrelevant.
PPS And let's not be distracted by what exactly a "microwave tranny" is,
please.
Edgar
> When I moved back from the USA the wify made me bring the fancy
> microwave we had had there. I was not too sure what I was getting
> into (I have a Bsc ing Electrical Engineering) so I rented a 240v -
> 110v transformer as used by UK tradesman used everywhere. From memory
> (this was years ago) the transformer was easily rated for the
> ovens full power. However when plugged in and sorted to cook some
> bacon, the noise from the microwave was very, very loud. It was a
> transformer hum but very loud.
>
> The microwave was unpluged, the transformer returned and eventually
> gifted to somebody else who was on their way to the US. We had to
> buy another transformer!
>
> The only thing I could figure was that the microwaves internal
> transformer or some other internal oscilator was tuned to 60Hz
> operation and did not get on with 50Hz.
>
> My transformer was most definetly 110V not 240v.
>
> Howver this is going over old ground. (Usenet is circular). Have
> a look at
>
>
>
http://groups.google.co.uk/group/sci.electronics.design/browse_thread/th
>
read/f6edc17d8b604420/3d906598dd3cc881?lnk=st&q=%22microwave+oven%22+mai
> n+frequency#3d906598dd3cc881
>
> Freq may matter! Look at the plate.
>
> Regards
Your studies didn't include transformer theory?
What kind of Electrical Engineering was it then. It doesn't seem to have
included electrical or engineering.
Of course frequency matters.
Edgar
Fergus McMenemie
> Of course frequency matters.
Yep you are right. But I/we are so used to ignoring is as a concern when
messing with transformers and supplies. We look at the rating plate to
see what voltage a device requires. But how often do we consciously look
for and check the frequency range?
The indicated thread reminded me of all kind of things I had got used to
ignoring!
Dave
> The message <4f64a9b...@davenoise.co.uk>
> from "Dave Plowman (News)" <da...@davenoise.co.uk> contains these words:
>
>
>>In article <j4ydnRYQ0_5IEgna...@bt.com>,
>> Bill Davy <Bi...@SynectixLtd.com> wrote:
>>
>>>Q2) Suggestions for suitable supplier of converter (or I shall just use
>>>RS, Maplin, or Farnell) and what are they called (transformer,
>>>auto-transformer, inverter, converter, etc)
>
>
>
>
>>Trouble is large ones are likely to cost as much as the microwave.
>
>
> Companies importing American fridges often use 90 volt transofrmers to
> make allowance for the difference in frequency. But these things are
> very often suck it and see.
How does reducing the voltage change the difference in frequency? I
can't see how this will work. Or does a transofrmer do things different
to a transformer? :-)
Dave
Andrew Gabriel
Dave <dave...@btopenworld.com> writes:
> Appin wrote:
>> Companies importing American fridges often use 90 volt transofrmers to
>> make allowance for the difference in frequency. But these things are
>> very often suck it and see.
>
> How does reducing the voltage change the difference in frequency? I
> can't see how this will work. Or does a transofrmer do things different
> to a transformer? :-)
At 50Hz, the compressor motor is being underrun by about 17%.
When you underrun an induction motor in this way, you must
also reduce the voltage by about the same amount or the current
increases due to reduced reactance at reduced frequency and
causes the motor to overheat, although that should be 100V
rather than 90V.
The danger with doing this is that there may be insufficient
starting torque to get the thing started. Fridge/freezer
compressors do expect this in normal operation though (happens
if they try to start before pressure difference has dissipated),
so they have an overcurrent cutout with timed auto-reset.
I suspect that the heat pump capacity will be reduced whereas
the power consumption won't be, so it may well be less efficient
than a unit fitted with a compressor designed for the correct
mains frequency.
Steve Firth
> I've bought an American microwave (GE PEM31) for its physical size (it's
> very shallow).
Definitely American then.
Dave
Dave
Appin
from and...@cucumber.demon.co.uk (Andrew Gabriel) contains these words:
> In article <poidnbhvEeK...@bt.com>,
> Dave <dave...@btopenworld.com> writes:
> > Appin wrote:
> >> Companies importing American fridges often use 90 volt transofrmers to
> >> make allowance for the difference in frequency. But these things are
> >> very often suck it and see.
> >
> > How does reducing the voltage change the difference in frequency? I
> > can't see how this will work. Or does a transofrmer do things different
> > to a transformer? :-)
> At 50Hz, the compressor motor is being underrun by about 17%.
> When you underrun an induction motor in this way, you must
> also reduce the voltage by about the same amount or the current
> increases due to reduced reactance at reduced frequency and
> causes the motor to overheat, although that should be 100V
> rather than 90V.
I'm not really arguing the point, merely pointing out what's done by one
of the major importers. Part of the the question relates to what the
design voltage of the equipment actually is.
In the US, the nominal supply voltage has crept up since it was
originally standardised at 100 volts.
http://chem.ch.huji.ac.il/history/stanley.html
The supply nowadays is variously described as 110 volts and 120 volts
and usually the latter is now accepted as the normal specification.
Electricity suppliers aim to keep most customers supplied between 114
and 126 V most of the time. However a distinction should be made between
the voltage at the point of supply (nominal system voltage) and the
voltage rating of the equipment (utilization voltage). Typically the
utilization voltage is 3 to 5 % lower than the nominal system voltage.
Equipment will often carry slightly lower nameplate voltages to allow
for voltage drop. At 110 volts supply voltage 17% underrun would give
you 91.3 volts, so maybe the guys in question had reached a reasonable
enough conclusion, though they'd probably reached it empirically rather
than by calculation.
Thanks for the detailed reasoning in your calculation, though. Nice to
have the theory behind the practice.
Bill Davy
news:j4ydnRYQ0_5IEgna...@bt.com...
>
>
> I've bought an American microwave (GE PEM31) for its physical size (it's
>
>
>
> frequency matter? I do not really mind if the platter rotates a tad
> slower,
> the timing settings are a bit off. The microwave frequency is determined
> by the mechanical structure of the magnetron.
>
>
>
> RS,
> Maplin, or Farnell) and what are they called (transformer,
> auto-transformer, inverter, converter, etc)
>
>
>
>
>
>
> Q4) If I open it up to find answers, what am I looking for?
>
>
>
> TIA
>
> Bill
>
> PS I am new to this group so apologise in advance for everything.
>
>
Right. The facts.
I bought a nice little toroidal auto-transformer (http://tinyurl.com/2uox5m)
and ran it on that. The oven makes a nasty smell after boiling water for
about twenty minutes, with or without the cover. The main mains transformer
is very hot. Annoyingly, with the cover on, the air coming out from the
cooling fan (which is pumping a lot of air) is cold which suggests they have
not really sorted out the cooling system, but that is no help for me.
The auto-transformer stays cool.
The clock runs slow.
Hey ho, now I know.
Bill
PS www.SynectixLtd.com is irrelevant
Appin
from "Bill Davy" <Bi...@SynectixLtd.com> contains these words:
> I bought a nice little toroidal auto-transformer
> (http://tinyurl.com/2uox5m)
Not 90v or 100v? :-)
John
Andrew Gabriel
"Bill Davy" <Bi...@SynectixLtd.com> writes:
>
> Right. The facts.
>
> I bought a nice little toroidal auto-transformer (http://tinyurl.com/2uox5m)
> and ran it on that. The oven makes a nasty smell after boiling water for
> about twenty minutes, with or without the cover.
Without the cover, that's probably your flesh burning.
> The main mains transformer
> is very hot. Annoyingly, with the cover on, the air coming out from the
> cooling fan (which is pumping a lot of air) is cold which suggests they have
> not really sorted out the cooling system, but that is no help for me.
It probably wasn't designed for the transformer giving off the
amount of heat it will be doing on 50Hz. It probably wasn't
designed for running at full power for 20 minutes -- I suspect
many other domestic microwaves might have problems with that
too.