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dude_500

Wed Jun 29 2011, 07:15AM

Registered Member #2288 Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179

Here is my latest project, since TSC finally got my ferrite shipped (took a few weeks). The name is derived from the fact that it will have roughly the same voltage and power handling of a pole pig, except it is dramatically smaller due to being ferrite based.

Started putting the transformer together today, just need to put all the primaries in parallel and put a winding on the secondary.

As for the bridge, I'll be using a CM400 full-bridge I used on an old project, although I'll probably put together a new driver for it.

The cores are 50ALL-102-57-25. I'm hoping to get 15-20kW through it at low duty cycles.

I'll post updates as I finish it up and start testing it.

Patrick

Wed Jun 29 2011, 09:08AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Thats some nice poly carb youve got there.

How much did those cost for each full set?

I have some U cores and planars made out of 50ALL too, how did you calculate your primary current and H value?

TY, looks good.
-Patrick

Dr. Dark Current

Wed Jun 29 2011, 09:39AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Looks big. Maybe the transformer would like putting the primary on the center leg, this way you use less wire and have much less leakage inductance. Depends on what you want to achieve though, with your current configuration the leakage could be enough to limit output short-circuit current to a non-destructive value.

dude_500

Thu Jun 30 2011, 05:29AM

Registered Member #2288 Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179

Patrick wrote ...

How much did those cost for each full set?

They are sold by the single U for $7.30 each, so this transformer pictured cost $60 (for ferrite only, not sure what the rest cost as it was all laying around)

Patrick wrote ...

I have some U cores and planars made out of 50ALL too, how did you calculate your primary current and H value?

I did not calculate H value, I wound the primary for 35V per turn, to be run off of 208 3-phase rectified. As for current, it will be around 50 amps in the primary at 300VDC if I run at 15kW.

Patrick

Thu Jun 30 2011, 06:54AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

dude_500 wrote ...

I did not calculate H value, I wound the primary for 35V per turn, to be run off of 208 3-phase rectified. As for current, it will be around 50 amps in the primary at 300VDC if I run at 15kW.

How do you know 50 amps will go through if you didnt calculate the H value?

Dr. Dark Current

Thu Jun 30 2011, 08:29AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

It is kVA, not kW... If you'll run at 15 kVA with the secondary shorted, you will get much less kW real output power.

Patrick

Thu Jun 30 2011, 05:30PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

The problem i found with the 50ALL is that they traded the H value for the flattness in all other respects, so you may not get as much primary current as the other ferrite types.

klugesmith

Thu Jun 30 2011, 05:46PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Patrick wrote ...

dude_500 wrote ...
I did not calculate H value, I wound the primary for 35V per turn, to be run off of 208 3-phase rectified. As for current, it will be around 50 amps in the primary at 300VDC if I run at 15kW.

How do you know 50 amps will go through if you didnt calculate the H value?

I bet he is talking about the primary current with the design load on transformer secondary.
Not the no-load magnetizing current, which should be a small fraction of that.

Patrick

Thu Jun 30 2011, 06:15PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Klugesmith wrote ...

Patrick wrote ...

dude_500 wrote ...
I did not calculate H value, I wound the primary for 35V per turn, to be run off of 208 3-phase rectified. As for current, it will be around 50 amps in the primary at 300VDC if I run at 15kW.

How do you know 50 amps will go through if you didnt calculate the H value?

I bet he is talking about the primary current with the design load on transformer secondary.
Not the no-load magnetizing current, which should be a small fraction of that.

but how much current will establish saturation, the 50ALL saturates more easily then other ferrites, TSC doesnt give us the typical BH loop graph either.

klugesmith

Fri Jul 01 2011, 12:02AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Saturation is a voltage thing, and has little to do with load current.

Suppose that with no load, you measure the primary current and infer
the B-H operating point and/or curve.
Now when you connect a load and current flows in the secondary,
there is a corresponding increase in primary current, such that their
magnetizing effects cancel. So the magnetic flux swing does not change.

More precisely, it actually goes down to the extent that IR losses
use up some of the applied primary voltage. That leaves less to be
bucked by the induced voltage in primary.

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