Breve-Tufvassons PFS 250 heat development


The Breve-Tufvassons PFS 250 is an isolation transformer I bought on ebay. It is a small unit that can be easily carried. Whenever I repair things on the go, I take that little unit with me. Just the extra bit of security so that I feel comfortable when working on mains powered devices.

During one of the last RepairCafes I recognized that the transformer gets quite hot although nothing was plugged in. So I decided to do some further investigation.

At home I plugged the unit into my Gossen Metrawatt Secutest SII+ and left it on for tree hours. In the picture below you can see a measurement of the power consumption. The power consumption was constant at 10W.


I also took infrared pictures every half hour to see how the temperature rises and what the maximum temperature is.

AufbauIR_0404 - 0h30mIR_0406 - 1h00mIR_0408 - 1h30mIR_0408 - 1h30mIR_0410 - 2h00mIR_0412 - 2h30mIR_0414 - 3h00m

After tree hours the temperature was steady and didn’t increase any more. The room temperature was at about 24°C.

The Breve-Tufvassons PFS 250 doesn’t come with a power switch so you ether have to leave it on all the time or always pull the plug. Because I didn’t like neither I just installed a little switch in front of the unit. Now I can turn the transformer on when I have a device plugged in and the other time the transformer is switched off and doesn’t get that hot.