Transformer temperature

[jantheman]

Having just connected up a bucking transformer and eventually found a half decent box to put it in, see Here (http://theartofsound.net/forum/showthread.php?t=11411) (Bottom of page)
http://i1120.photobucket.com/albums/l499/jantheman87/HiFi/DSCN0185.jpg?t=1307879621
I am wondering about just how hot a transformer can get without overheating or causing damage/fire risk.
Trying the thing out with the usual connected gear, it does get fairly warm. Nowhere near to hot to touch but warm all the same. I'm probably going to add some holes for ventilation both top and bottom just to help.
I was looking round for an old digi thermometer to check temps but as usual, I can't find it so I dont have an accurate ref point at the moment.
Any and all help appreciated.

[Mark Grant]

This would do for checking the temperature:

http://cgi.ebay.co.uk/STYLISH-DIGITAL-THERMOMETER-UK-SELLER-FAST-DISPATCH-/330570828444?pt=UK_HomeGarden_Garden_PlantsSeedsBu lbs_JN&hash=item4cf78e8a9c

Put the sensor in the box near the transformer or maybe fix it to the transformer and the display where you can see it.

[spendorman]

Many years ago I had a lot to do with testing electric motors. In particular, temperature rise of the windings. There are different classes. This may give some idea:

http://www.google.co.uk/url?sa=t&source=web&cd=1&ved=0CBgQFjAA&url=http%3A%2F%2Fen.noratel.ezpublish.no%2Fcontent %2Fdownload%2F5251%2F420449%2Ffile%2F16-3eng.pdf&rct=j&q=transformer%20temperature%20class&ei=WHv0TYnZLYfQhAfC8PTqBg&usg=AFQjCNHMOCKiak1vG-I-Xc-3V6UZpfxHtQ&cad=rja

If you can keep your finger on the metal of the transformer, it is not running very hot and will probably be OK.

[jantheman]

Thanks Mark and Alex.
After much kicking and screaming I have managed to find my digi thermometer. I have fixed it to the tranny core with blutack and its reading 40C. That is with no real load on it, just stuff in standby. I'll try it later with a 'normal' load and report back.
Alex, thanks for the link. My tranny is rated as 'B' 130 so a rise of 80 (i assume deg C) above ambient is top limit....TBH...I dont think it gets anywhere near that but now I have the thermomener I can check.
Will report back later.
Thanks

[jantheman]

As promised here are the results from the Eurovision jury here in the UK.
Oh...sorry...wrong subject.:lolsign:

Temperature monitoring of transformer.
Ambient temp 18C. Case closed. Temp probe stuck to core laminations with Blutack.
Temps are Deg C.
Output voltage is 232 +/- 1V
Power consumption: all connected equipment in standby, about 10W
Amps, Dac and Mac on, everything else in standby, about 300W

Start........41.1....all connected equipment in standby.
30 mins....42.3....Amps, Dac and Mac on, everything else in standby. (15 mins for warm up, music playing for 15 mins)
60 mins....42.7....Amps, Dac and Mac on, everything else in standby.
90 mins....43.1....Amps, Dac and Mac on, everything else in standby.
120 mins..43.4....Amps, Dac and Mac on, everything else in standby.
150 mins..43.6....Amps, Dac and Mac on, everything else in standby.

I think 150 mins is long enough to get a good idea of temperature rises. The increase seems fairly linear to start and then 'just' starting to level off after 90mins, just how high it will go before being flat has yet to be determined. I'll get round to it (sometime).
It would seem that the temps are well within the tranny spec so in the end, theres really seems to be nothing to worry about. I still may make provision for ventilation, maybe just drill some holes or get a fancy computer fan grille type of thing.
Your thoughts please.......

[Reid Malenfant]

Unless you are going to load the thing seriously there hardly seems any point in messing about :eyebrows:

Even in the middle of summer with ambient temps of 35C or so, the actual temperature rise in use will still keep the thing quite cool by the looks of things :)

If i was you Ray i'd enjoy the music & find something more interesting to do :cool:

[spendorman]

A wooden box would not be my first choice. Far better to have metal. In fact, I would be a bit concerned with wood.

[Reid Malenfant]

Something is telling me the wood would need to get to 451F before it'll self ignite, i seem to remember that paper is made of wood pulp ;)

Handy knowing a few old films :eyebrows:

[spendorman]

if a loose connection develops, say wire in terminal block, arcing may occur.

[Reid Malenfant]

True, but as long as the connections are tight now i can't imagine how they'd possibly loosen themselves off.

I actually agree with you Alex, i'd prefer a metal case over wood :) However i honestly can't see why a wooden case can't be used & used safely, after all we have manufacturers building power amps into acrylic boxes & they are made out of oil :eyebrows:

[jantheman]

Mark..listen to some music?...a novel concept.......however that was how i did the test...
35C even in the summer...Mark, you're an optimist.....:lol:
Alex...I dont think the terminals will come loose, they are spring loaded (Wago cage clamp terminals) and very tight. Info here. (http://www.wago.com/infomaterial/pdf/51184677.pdf)
This (http://www.youtube.com/watch?v=uMG66uUp5cM) is impressive.
As for the box, I had a job and a half finding this one....:lol:
Is wood a suitable material?....Wooden TT plinths immediately spring to mind with their hardboard bases also some older TV's used to use chipboard for their cabinets etc etc. Maybe if something else comes along I will swap it over but for now............
Job's a good un I think......