Ferrite Toroid for 100KHz 1000W ???

[gary350]

How do I know if a toroid will work for 100 KHz and 1500 watts. I need to wind it with #12 solid copper wire.

Toroid Core FT140-43 Ferrite | eBay

One FT140-43 Toroid Core. Ht = 0.500 in / 12.7 mm +/- 0.50 mm. ID = 0.900 in / 23.0 mm +/- 0.55 mm. OD= 1.400 in / 35.55 mm +/- 0.75 mm.

www.ebay.com

 

[Papabravo]

It all depends on what the toroid is used for and if the power level at which you intend to use it will saturate the core. Do you know what to look for in the datasheet for the core to make that determination?

 

[Dick Cappels]

For starters, at 100 kHz solid copper around ferrite is likely to get you huge losses because of eddy losses within the wire itself from fields from the core cutting across the diameter of the wire.

I would start with multiple strands of a small gauge wire in parallel as in Litz wire.

You would do well to find a ready-made inductor that fits your need, or if you have a budget get one designed by somebody with experience at this kind of frequency and power level. In the long run it would save you money.

Otherwise, get yourself a good book on the topic, starting with this article by Lloyd Dixon Jr.:
https://www.ti.com/seclit/ml/slup132/slup132.pdf and prepare to make several iterations of the inductor as you learn about it.

 

[Papabravo]

I'm still curious about the application. What will the toroidal inductor be used for? Do you have a 100kHz transmitter? Is this for an SMPS application?

 

[gary350]

Here is the circuit. The toroid's I have now saturate. Current slowly goes up to about 30a then suddenly jumps to over 100a and circuit goes up in smoke.

 

[Papabravo]

There is no choke in the datasheet diagram for this circuit. Why is there one in your version? What are you trying to accomplish by shorting the Rectified AC line to the +15V DC supply. Are you on drugs?

 

[gary350]

Choke is on the + terminal. Not sure where drawing for that went..

 

[Papabravo]

Choke is on the + terminal. Not sure where drawing for that went..

I know that !! The drawing you previously had had here showed the choke connecting the +AC Rectified Line to the +15V DC supply. That looked like a very strange thing to do and it is not on the reference circuit from the datasheet.
WHY IS IT THERE??

 

[ronsimpson]

One FT140-43 Toroid Core Brand: Fair-Rite
AL=885 +/- 20 % uH=(AL*Turns2)/1000
Wideband Transformers 5 - 400 MHz
Power Transformers 0.5 - 30 MHz
RFI Suppression 5 - 500 MHz
OD= 1.400 in / 35.55 mm +/- 0.75 mm
ID = 0.900 in / 23.0 mm +/- 0.55 mm
Ht = 0.500 in / 12.7 mm +/- 0.50 mm

uH=(885 * Turns^2)/1000 (^2 = squared)
The unknown manufacture said to us the part above 500khz. I see examples in the 10 to 200mhz range.

 

[rjenkinsgb]

I'd guess this is another self-oscillating induction heater design, and the inductor its supposed to be a commutation choke, to limit current under shoot-through conditions.

The IC is designed to suit high voltage and low gate capacitance FETs (1nF, from the data sheet).

I'm betting the FETs in use have very gate capacitance so do not switch cleanly within the dead time allowed within the IC - so the current is crazy.

The choke will be some internet designers attempt at a work-around.

 

[Papabravo]

I'd guess this is another self-oscillating induction heater design, and the inductor its supposed to be a commutation choke, to limit current under shoot-through conditions.

The IC is designed to suit high voltage and low gate capacitance FETs (1nF, from the data sheet).

I'm betting the FETs in use have very gate capacitance so do not switch cleanly within the dead time allowed within the IC - so the current is crazy.

The choke will be some internet designers attempt at a work-around.

I'm not sure we knew which FETs were being used since the "darwing" from post #5 was a copy of the reference circuit from the datasheet with some hand scratchings on it. The "choke" was definitely one of the scratchings. I also suspect that the TS deleted the schematic from that post accidentally on purpose.

 

[gary350]

Resonant Circuit I had before had choke coil & capacitors. This H circuit is NOT a resonant circuit it shows no caps & no choke. Maybe this circuit does not require a choke?

 

[rjenkinsgb]

What power FETs are you using?

 

[Papabravo]

Resonant Circuit I had before had choke coil & capacitors. This H circuit is NOT a resonant circuit it shows no caps & no choke. Maybe this circuit does not require a choke?

View attachment 138037

Yeah. It is not the case that every circuit requires the same components. Why would you think that it should be so? I'm pretty sure that concept was not part of any formal training.

 

[gary350]

What power FETs are you using?

Mosfet 55NF06

The H circuit makes the induction coil be a short circuit across the power supply.. The power supply is 15 VDC 1500 watts 100a it needs current limiting. Mosfets are 55 amps.

 

[rjenkinsgb]

Mosfet 55NF06

OK, they are quite reasonable, only 1.2nF gate.

The bridge does not need an inductor in the supply, but is does need some seriously large and low ESR caps across the supply, capable of handling the ripple current and storing the recovered energy fed back from the FET diodes.

 

[Tony Stewart]

This company has cores that can be used at 100kHz up to 25 kW https://www.mag-inc.com/getattachme...agneticsTypicalPowerHandlingChart2012-(1).pdf