Transformer Poser:

[rattus]

Just for fun consider an ideal xfrmr with a primary of N turns and two secondaries of N turns each.

Now load one secondary with Z1 and the other with Z2. What is the reflected load?

Now connect the secondaries in series and leave Z1 and Z2 connected. What is the reflected load?

Now disconnect Z1 and Z2 from the center tap but leave them connected in series. What is the reflected load?

 

[templdl]

Re: Transformer Poser:

Looks like you have discovered something there, perpetual current flow which may work well when applied to power cars. This would eliminate the need for gas and our dependency on oil.

 

[charlie b]

Re: Transformer Poser:

It is the time period between the second cup of coffee and the first glass of bourbon, and I am generally useless in that interval. But I'll give it a stab:

(A) Z1 + Z2
(B) Z1 + Z2
(C) 0.25 (Z1 + Z2)

If I were a gambling man (which I am not, but if I were), I would put my lowest bet of my answer for (B).

 

[rattus]

Re: Transformer Poser:

OK, Charlie has taken the bait, so let's hear from the rest.

 

[steve66]

Re: Transformer Poser:

My guesses:

1. The reflected load is the parallel combination of Z1 and Z2.

2. It is still the parallel combination of Z1 and Z2.

3. 0.25(Z1 + Z2) or infinity, depending on if you connect leads so the windings are wound the same direction, or not.

(I know its bad news not to agree with Charlie, but I think I might be right on this one )

Steve

 

[charlie b]

Re: Transformer Poser:

I think you are too, Steve. And feel free to disagree with me anytime, or at least any time that I am wrong.

 

[jim dungar]

Re: Transformer Poser:

I have been told I'm a different type of person, so:
1) Z1+Z2
2) Z1+Z2
3) Z1+Z2

 

[rattus]

Re: Transformer Poser:

I see we are getting some disagreement here. May start a record setting thread.

 

[al hildenbrand]

Re: Transformer Poser:

Rattus,

You do like 1:1 transformers. . .I've probably missed a couple other of your examples, but the one I recall also used 1:1 turns ratio.

1) Z1 + Z2

2) Z1 + Z2, regardless of polarity of secondary windings.

3) Two possible answers: ?(Z1 + Z2) or "apparent" open secondary. This last configuration results in a turns ratio of 1:2, that is, the primary has half the number of windings that the secondary has, and is essentially a different transformer than in the first two questions.

 

[jim dungar]

Re: Transformer Poser:

1) 1 per unit V across each load -> Z1+Z2

2) 1 per unit V across each load -> Z1+Z2

3) 2 per unit V across total load -> Z1+Z2

 

[rattus]

Re: Transformer Poser:

OK Gents, time is up!

Steve got it right.

For Case 1 and Case 2, Z1 and Z2 are reflected in parallel.

Zp = Z1Z2/(Z1 + Z2)

For Case 3, we have a simple transformer with Ns/Np = 2.

Hope this has been educational.

Zp = (Z1 + Z2)/4

[ September 21, 2005, 10:11 PM: Message edited by: rattus ]