Thursday, September 28, 2017

How much inductance does a DBM transformer need?

In a day gone by I was taught the source Z should be 1/10th the load Z. It seems common knowledge today is Zs=Zl for max power transfer. When I was a teen the books said you get max power when Zs=Zl and your generator/battery consumed 1/2 the power, for this reason we set Zl at least 10 times Zs. With the 10 to 1 ratio we still use 9% heating the source. With that in mind and looking the manufacturer datasheets I decided to do a none scientific test using spice to see if I can find the 'perfect' transformer. Andy sent me a circuit which I used for the test. Then I built a circuit and tried it. Here are the circuits used in the test:
 my circuit.
Andy's circuit.

The results:
100 uh 10 uv in 15 uv out

1uh 10uv in 15 uv out

It was looking like it could not go to low so 1ph no output.

I looked through several spec sheets and found coils wound wit 3 turns, 6 turns, etc. The only spec they gave was the Z at a certain frequency. The recommendation was for the transformer Z to be 4 times Zs at the lowest frequency. The test seem to support the fact that more inductance doesn't give more output. It did show that some of the circuits drew a larger current and loaded the source more.

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