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Registered Member #1596
Joined: Fri Jul 18 2008, 08:43PM
Location: USA
Posts: 65
Alright, I am kinda lost here!!! Any input is appreciated!!! I am running that transformer with 3C90 core, and according to my calculations it should dissipate around 7W of power if you multiply the core volume by core lose. The core under the wiring heats up substantially, at least 60 deg after 20 mins. I tried everything, even got some litz wire off ebay for the primary to exlude it as a possible heat source.
1. when I compute a core lose, should I use the whole volume or only count the beam which is under the windings ~25% of the total core? Only that portion actually heats up.
2. Is there are any methods of cooling the core? How do I extract the heat from under the windings? Because now it just stays there and spreads to the primary, bobbin and secondary...
The core can take u pto a 100deg according to specs, but still this is really annoying, I dont want the whole trans to reach 60-80 degrees.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
60'C is I think just about right for a core pushed to the max. If you still want to reduce the losses, you need to decrease your primary volts/turn. I think material 77 actually has lowest loss somewhere around that temperature.
For high current primaries it is often most practical to use copper foil tape, which gives a lot of skin surface and is usually cheaper than same performance litz wire.
Cooling the core is going to be a rather difficult thing if you really need it. I can't think of anything apart from immersing the whole transformer into oil.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
The core heats up from the windings as well. Are you sure you've calculated the core loss right?
Anyway, 60C is perfectly normal, most cores in consumer appliances seem to run around 100C (the flyback core in my old TV got so hot that even touching it was painful).
The lowest temperature I've seen at which a core starts losing any of its magnetic properties was ~125C, so you're absolutely fine with 60C.
Of course if you want you can point a small fan to it (should reduce the temp by a fair bit) or put it under oil...
Registered Member #1596
Joined: Fri Jul 18 2008, 08:43PM
Location: USA
Posts: 65
yeah, the secondary was encapsulated with a high viscosity epoxy inside of a home made vacuum chamber. Also the initial 10kV voltage drops across the arc to around 1-2 kV right after the breakdown and stays like that, so corona shouldnt be an issue.
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Ferrite Core: Cooling
