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Xantrex: STXR Problem - Thermal Derating
http://solar-guppy.com/forum/viewtopic.php?f=19&t=432		 Page 3 of 3
Author:  Matsavol [ Tue Jul 03, 2007 9:46 pm GMT ErdGMT ]
Post subject: 
Hey.. we have a electronics basics debate ongoing here... :lol:

240Vac (sinusoidal, RMS) is about 680V Pk-Pk. The positive half wave peak is at +340V and the negative half way peak at -340V when referenced to Neutral. With full wave (bridge) rectifier the bulk capacitor would be charged to +340Vdc (minus 2x the diodes forward voltage drop). The only case you would be seeing the full peak-to-peak DC is with some voltage doubler rectification circuit where each half of the sine waves are rectified in their own capacitor and the capacitors are connected in series. (This is how the 120/240V voltage selector switch works in PC power supplies, for example. It changes the circuit from voltage doubler to full bridge and vise versa.)

Maybe it is now more clear... or not? :roll:
Author:  Matsavol [ Wed Jul 04, 2007 8:28 pm GMT EthGMT ]
Post subject: 
I guess you guys forgot International aspect: In UK they have one phase 240Vac. In Europe the most common voltage is 230Vac.

In the US the 240Vac is really two phase (or line) 120Vac, where the phases are 180 degrees apart. This makes it behave like 240Vac (between phases, that is).
Author:  mike90045 [ Wed Jul 04, 2007 10:06 pm GMT EthGMT ]
Post subject: 
http://www.sengpielaudio.com/calculator-db-volt.htm

(half way down has a pretty RMS - PP converter)

I don't know if this is in Euro volts or American volts :o
Author:  thevoiceofmoderation [ Mon Jul 09, 2007 4:08 pm GMT EthGMT ]
Post subject:  thermal derate
Mr Guppy sir,

Can you tell me what the formula for derating is on the ST2500? I'm considering using a snap-action thermal switch attached to the heat sink to control the fan and I want it to kick-in before derating begins.

Thanks
Author:  Solar Guppy [ Mon Jul 09, 2007 8:06 pm GMT EthGMT ]
Post subject: 
The derating starts at 60C on the heat sink .. I would suggest a bit lower and you sould be ok .. keep in mind you will be running full on, which is pretty loud!
Author:  thevoiceofmoderation [ Tue Jul 31, 2007 11:00 am GMT EstGMT ]
Post subject:  St2500 fans
Well, turns out I didn't need a switch or Triac. When I opened the thing up, I found the fan was hot (had power) and wasn't spinning. I found a subtitute fan I like - It does use slightly more power but it's cheap, has two ball bearing and fits. I did cut the wires off the dead fan and soldered them onto the new, covering with shrink tubing.

Rotron P/N GAA1238-230BB
about $12 at Digikey or $16 at Newark (better deal - no handling fees)
Author:  Kenji [ Mon Apr 28, 2008 3:10 pm GMT EthGMT ]
Post subject: 
For whatever it's worth, my STXR2500 just started exhibiting these symptoms. Xantrex told me that since it's a UPG unit (whatever that means), I could ship it to them for repair, but I opted to take advantage of their $999 customer loyalty option to upgrade to a new GT2.5. Hopefully the GT line is more reliable than their ST line (I went through two ST2500s and one STXR2500 in 7 years).
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