MEMM

[PaulLowrance]

Hi Rob,

Can you believe NTE actually makes BUZ11's. It's NTE2389. Go to -->
http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm
and enter BUZ11

Better yet is that there version is faster yet. TdON = 25ns typ., TdOff = 125ns typ.  That's great because there's at least 3 stories nearby that have a large stock of NTE parts.

Also Jameco has part #870209 which is a BUZ11. There are two nearby stores that sell Jameco parts. According to Jameco they sell for 40 cents each at quantity of one.

http://mouser.com sells BUZ11's from a lot of different manufacturers.

http://www.digikey.com just has one version from Fairchild Semiconductor.

Can you post your femm files.

Did you put in the material for the Metglas core (B/H curve), I had to do this the other day for a ferrite and it was not easy?

Attached is the FEMM file, but as previously mentioned all magnetic materials do not have the same permeability at 30 KHz versus DC.  The permeability used by FEMM is DC permeability. Now what you could do if you wanted to be really accurate is create a FEMM properties of Metglas 2605SA1 using the metglas DC permeability graphs, but you would then have to K-factor the coil current. The DC permeability of your metgals is 600000, but at 30 KHz is more like 10000. At 25 volts on the coil generates 280mA. So instead of setting the current to 280mA you would have to lower it to 0.280A * 10000 / 600000 = 0.0047A  So in your FEMM you would be using the DC permeability of 2605SA1, but the current would be 0.0047 amps (not 0.280 amps).

I still need to order the bits for the pulse circuit.  Are you getting a TL494 chip?
I noticed that the TL494IN is the one to go for as it works at -40c to +85c, (brrrrrr to damm thats hot!).

I'll have to see if NTE has that or something close. Probably not, so I'll end up using a good old 555, lol. I kind of like those old buggers.

Rob,
You could possibly pick up a few 100 Kohm Thermistors? If you see the core temperature slowly decrease then you have it! I just bought some 100 Kohm thermistors for $2 each and some heat sync grease at radio shack for $2. I have two thermistors, one on the core and the other for canceling out room temperature changes. That way you can sense minute core temperature changes.

See the attached FEMM file.

Regards,
Paul Lowrance

[MeggerMan]

Hi Paul,
Thanks for the FEMM files.


I have a temperature probe I can attach to the core, and using the supplied chart I can work out the exact temperature from the resistance change.

Well the core has arrived, very professional bit of kit.

The ultimate core  "the AMCC-320":






Regards

Rob

[PaulLowrance]

Great snapshots.  Looking forward to seeing the data. Be careful inserting the PM's as Metglas is very brittle. That's probably another reason for using ceramics, initially.

What's the sensitivity of your temperature probe?

Paul Lowrance

[MeggerMan]

Hi Paul,
Do you have any photos of your core?
You can upload to photobucket like I do for free.

Quote from: PaulLowrance

Be careful inserting the PM's as Metglas is very brittle.

Yes, some edge bits are flaking off when you handle it, like chrome slivers.
I am very careful as to how I handle it as I appreciate it is a very fragile device.

Quote from: PaulLowrance

What's the sensitivity of your temperature probe?

Tolerance I think is 0.2 C at 20C changing to 0.05 C at 40C.






Regards

Rob

[MeggerMan]

Hi Paul,
I just ran your silmulation and noticed the input coils as being round in shape, surely these will be rectangular and tighter to the core than shown.
I do not think you will get the 100 turns in the small circle.
Also you have set the depth to 0.75 inches, this should be 50mm (2 inches).
I do not understand why the second input coil is set as air?
I would have thought it best to create a second current circuit and assign it to this but as a coil.

Sorry for picking holes in your sim.
Next step is to create a material like the Metglass, that means entering an BH curve.

Regards

Rob