Forums

Cooling of overloaded transformer

Started by Klaus Kragelund April 1, 2018
On Monday, April 2, 2018 at 1:12:48 AM UTC+2, k...@notreal.com wrote:
> On Sun, 1 Apr 2018 15:15:45 -0700 (PDT), Klaus Kragelund > <klauskvik@hotmail.com> wrote: > > >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 burn&rsquo;t 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. > >> > >By the way, it's only certain brands > > > >Kitchen Aid > > Have a kitchen full of KitchenAid appliances. >
In Denmark, Kitchen Aid is considered top notch I have had to repair an older mixer before, with a worn worm drive gear. The toaster we had died, and I could not repair it. (was an intermittent problem, so difficult to locate).
> >Festool tools > > ...and a basement full of those. ;-) > > Are they even more expensive than they are here? > >
Festool products are the best, good German design Some are the same price, the plunge saws are almost the same price, probably due it's popularity The accessories are a half price, likewise with the cordless drills. The big miter saw is something like 30% off. The local Woodcraft store does not have the best price, so need to order online before going over there, so it has been delivered at the hotel Cheers Klaus
On Monday, April 2, 2018 at 3:48:19 AM UTC+2, Steve Wilson wrote:
> 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.
Could maybe work. Unless is has a capacitive dropper supply that doesn't like the chopped up voltage. Maybe I should take it apart to have a look see Cheers Klaus
Klaus Kragelund <klauskvik@hotmail.com> wrote:

> On Monday, April 2, 2018 at 3:48:19 AM UTC+2, Steve Wilson wrote:
>> 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-40 >> aa- 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.
> Could maybe work. Unless is has a capacitive dropper supply that doesn't > like the chopped up voltage. Maybe I should take it apart to have a look > see Cheers
The capacitive dropper would probably get messed up with the chopped AC. Certainly the capacitor would have to be replaced with a higher voltage rating. But maybe a larger output filter capacitor could help. Worst case, you might add a small 220v transformer to drop the voltage. Your wife would not like the wires running all over. Get a $19 220v toaster from ebay and paint KitchenAid on the side:)
> Klaus
On Monday, April 2, 2018 at 10:43:46 AM UTC+2, Steve Wilson wrote:
> Klaus Kragelund <klauskvik@hotmail.com> wrote: > > > On Monday, April 2, 2018 at 3:48:19 AM UTC+2, Steve Wilson wrote: > > >> 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-40 > >> aa- 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. > > > Could maybe work. Unless is has a capacitive dropper supply that doesn't > > like the chopped up voltage. Maybe I should take it apart to have a look > > see Cheers > > The capacitive dropper would probably get messed up with the chopped AC. > Certainly the capacitor would have to be replaced with a higher voltage > rating. But maybe a larger output filter capacitor could help. Worst case, > you might add a small 220v transformer to drop the voltage. > > Your wife would not like the wires running all over. > > Get a $19 220v toaster from ebay and paint KitchenAid on the side:) >
She won't have anything but Kitchen Aid Just bought this one: https://www.ebay.com/itm/282901899954?var=582540063532 2kW, so it is plenty overrated. I just need to add a switch in front, so it is not on all the time, magnetizing current will be burning some unnecessary watts Cheers Klaus
Klaus Kragelund <klauskvik@hotmail.com> wrote:

> Just bought this one:
> https://www.ebay.com/itm/282901899954?var=582540063532
> 2kW, so it is plenty overrated. I just need to add a switch in front, so > it is not on all the time, magnetizing current will be burning some > unnecessary watts
Doesn't it already have a power switch? It's from the UK, so shipping shouldn't be too bad. Nice solution for a difficult problem. You can probably run all the appliances from the same transformer and keep the clutter down.
> Cheers
> Klaus
On Monday, April 2, 2018 at 11:43:03 AM UTC+2, Steve Wilson wrote:
> Klaus Kragelund <klauskvik@hotmail.com> wrote: > > > Just bought this one: > > > https://www.ebay.com/itm/282901899954?var=582540063532 > > > 2kW, so it is plenty overrated. I just need to add a switch in front, so > > it is not on all the time, magnetizing current will be burning some > > unnecessary watts > > Doesn't it already have a power switch?
Yes, but I will have it hidden in a cabinet behind another device, so no easy access. Will place an outlet close by to turn it on/off
> > It's from the UK, so shipping shouldn't be too bad. > > Nice solution for a difficult problem. You can probably run all the > appliances from the same transformer and keep the clutter down. >
Yes, should be enough to power all the device at the same time :-) Cheers Klaus
On Apr 2, 2018, Klaus Kragelund wrote
(in article<26538930-dff6-4417-81c6-985544aa4c75@googlegroups.com>):

> 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-22 > > 0- 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-Voltag > e-Converter-500W-1KW-2KW/282901899954?hash=item41de446ab2:m:mopAAzqmEbGVAKpB9l > psPjw>
At that price, must be Chinese. Should work OK, but I&rsquo;d verify that the transformer does not overheat - the Chinese can be wildly optimistic about such things as power ratings. That&rsquo;s why I was looking at 3 Kw claimed. Joe
> > modify the toaster to run on 230 with a diode in series with the > heating element ?
bzzzt wrong I'll let someone else explain why. mark
On Monday, April 2, 2018 at 10:56:46 AM UTC-4, mako...@yahoo.com wrote:
> > > > modify the toaster to run on 230 with a diode in series with the > > heating element ? > > bzzzt wrong > > I'll let someone else explain why. > > mark
Huh, well except for screwing up the power factor on the AC line, what's wrong with it? George H.
Den mandag den 2. april 2018 kl. 18.03.59 UTC+2 skrev George Herold:
> On Monday, April 2, 2018 at 10:56:46 AM UTC-4, mako...@yahoo.com wrote: > > > > > > modify the toaster to run on 230 with a diode in series with the > > > heating element ? > > > > bzzzt wrong > > > > I'll let someone else explain why. > > > > mark > > Huh, well except for screwing up the power factor on the AC line, > what's wrong with it?
P = V^2/R I must have been low on coffee