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Cooling of overloaded transformer

Started by Klaus Kragelund April 1, 2018
On Sunday, 1 April 2018 20:15:56 UTC+1, Lasse Langwadt Christensen  wrote:
> Den søndag den 1. april 2018 kl. 16.16.27 UTC+2 skrev Klaus Kragelund: > > Hi > > > > When I go to the states, I usually buy white goods, half price than in Europe > > > > So I have a 600W 230V to 115V transformer installed in a cabinet > > > > Now I have bought a 1300W toaster > > > > Instead of buying a new transformer, I am seriously considering just overloading it, but then keeping the heat down by forced convection, namely a fan > > > > Anyone tried overloading transformers before? > > > > Regards > > > > Klaus > > modify the toaster to run on 230 with a diode in series with the > heating element ?
Double voltage quadruples power, diode only halves it And the electronics wouldn't work, usually powered by a capacitor dropper. NT
On Sunday, 1 April 2018 20:34:07 UTC+1, Steve Wilson  wrote:
> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > > > Den s&oslash;ndag den 1. april 2018 kl. 16.16.27 UTC+2 skrev Klaus Kragelund: > >> Hi > > >> When I go to the states, I usually buy white goods, half price than in > Eu > >> rope > > >> So I have a 600W 230V to 115V transformer installed in a cabinet > > >> Now I have bought a 1300W toaster > > >> Instead of buying a new transformer, I am seriously considering just > over > > loading it, but then keeping the heat down by forced convection, namely a > f > > an > > >> Anyone tried overloading transformers before? > > >> Regards > > >> Klaus > > > modify the toaster to run on 230 with a diode in series with the > > heating element ? > > That would cause a huge unbalanced current in the source transformer. > > There are optical triacs that activate on zero crossings. Set one to give a > 50% duty cycle. The toaster element won't care, but the RC timing circuit > might. That doesn't matter. The potentiometer is not very accurate anyway, > and it drits badly. > > I simply set the toaster pot to maximum and use a separate digital timer to > adjust the browning. I have three settings: 2:15, 2:30 and 2:45 min:sec, > depending on the type of bread, thickness, and length of the slice. The > nice thing is if I somehow forget to set the timer, the toaster timer will > expire before it sets fire to the toast. (BTDT) > > I don't know if that would still work with a 50% duty cycle AC, but it's > worth a try. Maybe the AC rectifier in the toaster would have to be > modified. The circuit is very simple and easily traced. Do the needful. > (Indian phrase. Useful at times.)
Chopping the waveform = immediate death to RC dropper supplies NT
On Sunday, 1 April 2018 23:08:04 UTC+1, Klaus Kragelund  wrote:
> On Sunday, April 1, 2018 at 10:38:11 PM UTC+2, Steve Wilson wrote: > > Klaus Kragelund <klauskvik@hotmail.com> wrote: > > > > > Hi > > > > > When I go to the states, I usually buy white goods, half price than in > > > Europe > > > > > So I have a 600W 230V to 115V transformer installed in a cabinet > > > > > Now I have bought a 1300W toaster > > > > > Instead of buying a new transformer, I am seriously considering just > > > overloading it, but then keeping the heat down by forced convection, > > > namely a fan > > > > > Anyone tried overloading transformers before? > > > > > Regards > > > > > Klaus > > > > Check Amazon US. You can get 220V appliances real cheap. Have them ship to > > your hotel. Here's some toasters: > > > > https://tinyurl.com/ya79ml7n > > Hah, Kitchen Aid folks aren't stupid > > The 220V versions are the same prices as in Denmark > > https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=220v+toaster+kitchen+aid&rh=i%3Aaps%2Ck%3A220v+toaster+kitchen+aid > > 110V is less than half price > > Cheers > > Klaus
well, you only get half as many volts. NT
On 2018-04-01, jrwalliker@gmail.com <jrwalliker@gmail.com> wrote:
> There may be a much simpler solution. Toasters have multiple > heating elements, so why not check whether they are all in series > or in a series/parallel arrangement. If they are in > series/parallel, then converting to series connection might > allow correct operation at 230V. > Manufacturers might make the elements operate at 115V each and > adjust the internal wiring to suit different markets. > > It may not work out, but it would be worth a look inside. > > The solenoid in the "pop-up" mechanism might be a bit harder > to deal with.
the mechanism's powered from a tap on one of the elements, get the element voltage right and it's solved
> John
-- This email has not been checked by half-arsed antivirus software
On 2018-04-01, Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:
> Den s&oslash;ndag den 1. april 2018 kl. 16.16.27 UTC+2 skrev Klaus Kragelund: >> Hi >> >> When I go to the states, I usually buy white goods, half price than in Europe >> >> So I have a 600W 230V to 115V transformer installed in a cabinet >> >> Now I have bought a 1300W toaster >> >> Instead of buying a new transformer, I am seriously considering just overloading it, but then keeping the heat down by forced convection, namely a fan >> >> Anyone tried overloading transformers before? >> >> Regards >> >> Klaus > > modify the toaster to run on 230 with a diode in series with the > heating element ?
That would be a mod for 160V operation, not 230 and could leave the electromagnet under-powered. V^2/R and all that. -- This email has not been checked by half-arsed antivirus software
On 2018-04-01, Steve Wilson <no@spam.com> wrote:
> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: > >> Den s&oslash;ndag den 1. april 2018 kl. 21.34.07 UTC+2 skrev Steve Wilson: >>> > modify the toaster to run on 230 with a diode in series with the >>> > heating element ? > >>> That would cause a huge unbalanced current in the source transformer. > >> skip the transformer, modify the control to run on 230 and stick a diode >> in series with the heating element > > Brutal.
but if it works, and doesn't self-combust your toast's done in half the time. -- This email has not been checked by half-arsed antivirus software
whit3rd <whit3rd@gmail.com> wrote:

> On Sunday, April 1, 2018 at 12:15:56 PM UTC-7, Lasse Langwadt > Christensen wrote:
>> modify the toaster to run on 230 with a diode in series with the >> heating element ?
> A 1kW toaster on 120V has circa 14 ohms resustabce when hot. > On 230V, with 50% duty cycle, that will dissipate circa 1900 watts.
> The solution lies elsewhere...
Very good point. E^2/R = 230^2 / 14 = 3,778.5 Watts. At 50% duty cycle, 3,778.5 / 2 = 1,889.2 Watts. A 40A 220V optoisolated zero cross SSR is $3.83 on ebay : 172531429031 Here's the datasheet: http://www.kvc.com.my/StorageAttachment/Kvcsb/datasheet/510/fotek-ssr-40aa- h.pdf Set it for 25% duty cycle and fix the toaster DC supply to handle 230V. This will make a nice 12.5Hz pulsation in the source transformer, but it should be far enough away to not bother anyone.
On Monday, April 2, 2018 at 12:29:30 AM UTC+2, Steve Wilson wrote:
> Klaus Kragelund <klauskvik@hotmail.com> wrote: > > > Kitchen Aid products are half price. Over the last 2 years I have saved > > more than 1000 USD, compare that to the cost of a transformer of 70 USD? > > > Cheers > > > Klaus > > So then buy a transformer. What's your problem? > > After saving that much, there shouldn't be that many Kitchen Aid products > left. A toaster is a pretty small investment. Why spend $70 for a transformer > to power a $19 toaster?
Well, not a big problem, just wanted to see if I could use an existing one The Kithen Aid toaster is a 55 USD part, and I am not powering one device, but 5 different devices, all though not at the same time Cheers Klaus
On Sunday, April 1, 2018 at 7:14:44 PM UTC+2, Klaus Kragelund wrote:
> On Sunday, April 1, 2018 at 7:00:36 PM UTC+2, amdx wrote: > > On 4/1/2018 9:16 AM, Klaus Kragelund wrote: > > > Hi > > > > > > When I go to the states, I usually buy white goods, half price than in Europe > > > > > > So I have a 600W 230V to 115V transformer installed in a cabinet > > > > > > Now I have bought a 1300W toaster > > > > > > Instead of buying a new transformer, I am seriously considering just overloading it, but then keeping the heat down by forced convection, namely a fan > > > > > > Anyone tried overloading transformers before? > > > > > > Regards > > > > > > Klaus > > > > > > > OK, I'm not suggesting this, but since it is a resistive load, Could > > you put a non-polarized 260uv cap in series with the toaster. The > > capacitive reactance would be equal to the resistance of the toaster, > > or 11.3 ohms. (think speaker crossover caps,it may not be cost effective) > > I would break this up into 13- 20uf capacitors to reduce the current in > > each down to about 1 amp. > > Also the voltage rating, I think it has to be at least 400V, but I'm > > not sure how to calculate that. (hope it's 200V, they are available) > > I once used this to drop about 40V down before a bridge for a 5V > > regulator, where I didn't want anymore heat. I just substituted until I > > had a reasonable input voltage. Harder to calculate because of gulps of > > current at the peaks. > > I would like some comments about calculating this for the resistive > > toaster. > > If you think it is a stupid idea, explain why. > > Explain the pitfalls. > > Mikek > > Capacitive droppers are good, but in this case the load is all over the place (low resistance when cold, higher when warm, different power levels etc) >
I was wrong about the resistance Apparently, a the toaster design underwent some design effort to find a material that could hand the many cycles of heating and cooling: https://en.wikipedia.org/wiki/Nichrome Only 6% increase in resistance from cold to hot Cheers Klaus
On Monday, April 2, 2018 at 1:07:54 AM UTC+2, Joseph Gwinn wrote:
> On Apr 1, 2018, Klaus Kragelund wrote > (in article<1dd94705-9628-42c6-a6b5-bb7b3f36be1b@googlegroups.com>): > > > On Sunday, April 1, 2018 at 9:07:26 PM UTC+2, Joseph Gwinn wrote: > > > On Apr 1, 2018, Klaus Kragelund wrote > > > (in article<6c166a81-64a7-4ed6-af8b-f79545106401@googlegroups.com>): > > > > > > > Hi > > > > > > > > When I go to the states, I usually buy white goods, half price than in > > > > Europe > > > > > > > > So I have a 600W 230V to 115V transformer installed in a cabinet > > > > > > > > Now I have bought a 1300W toaster > > > > > > > > Instead of buying a new transformer, I am seriously considering just > > > > overloading it, but then keeping the heat down by forced convection, > > > > namely a fan > > > > > > > > Anyone tried overloading transformers before? > > > > > > Won&rsquo;t really work, as others have said. My wife burnt her favorite hair > > > dryer out by forgetting to turn the swith from 115 to 230 on a trip some > > > years ago. Solution was to buy a local (European) hair dryer. > > > > > > I wouldn&rsquo;t think that toasters are so expensive (even in Europe) as to be > > > worth buying a big transformer. > > > > Kitchen Aid products are half price. Over the last 2 years I have saved more > > than 1000 USD, compare that to the cost of a transformer of 70 USD? > > A 1500 watt 240:120 transformer for 70 USD? I&rsquo;ve seen lots of > &ldquo;Converters&rdquo; for small dollars, but they are unlikely to be real > transformers (that is, made of iron and copper). One way to tell is to look > at the shipping weight. > > I&rsquo;d believe $140, though: > > .<http://www.rockler.com/step-up-step-down-voltage-transformer-110-120-to-220- > 240v?sid=V9146> > Rockler is a well-respected seller of woodworking equipment and supplies in > the US, and I&rsquo;ve bough many things from them. >
56 USD: https://www.ebay.com/itm/Step-Down-Up-Transformer-230V-110V-AC-UK-to-US-Voltage-Converter-500W-1KW-2KW/282901899954?hash=item41de446ab2:m:mopAAzqmEbGVAKpB9lpsPjw Cheers Klaus