transformer, 4 Times rule for multiple of reactance to resistance being transformed...

[amdx]

I have this graph showing the \'Z_Normalized sub i\' vs the multiple of
reactance to resistance needing transforming.
I don\'t know what the \'Z_Normalized sub i\' means. Or, how I could use it
to calculate input resistance, current, voltage or what I can do with it.
Can someone explain it to me?
> https://www.dropbox.com/s/fwfzwrjxg9e7ayo/4%20Times%20Rule%20Graph.png?dl=0

                        Thanks, Mikek

 

[piglet]

On 16/09/2022 22:48, amdx wrote:

I have this graph showing the \'Z_Normalized sub i\' vs the multiple of
reactance to resistance needing transforming.
I don\'t know what the \'Z_Normalized sub i\' means. Or, how I could use it
to calculate input resistance, current, voltage or what I can do with it.
Can someone explain it to me?
https://www.dropbox.com/s/fwfzwrjxg9e7ayo/4%20Times%20Rule%20Graph.png?dl=0


                        Thanks, Mikek

My take is that Zi represents the input impedance of the transformer. So
for example if you are working in a 100ohm system and the primary
inductance is such that its reactance is 400ohm (the 4x thick black
line) then the impedance presented is 97ohms reading from the graph with
phase shift of 15deg.

The rule of thumb I always remembered was that the primary XL should be
at least ten times the wanted impedance. That graph is interesting
showing the effects of using a much lower winding inductance.

piglet

 

[amdx]

On 9/17/2022 1:17 AM, piglet wrote:

On 16/09/2022 22:48, amdx wrote:
I have this graph showing the \'Z_Normalized sub i\' vs the multiple of
reactance to resistance needing transforming.
I don\'t know what the \'Z_Normalized sub i\' means. Or, how I could use
it to calculate input resistance, current, voltage or what I can do
with it.
Can someone explain it to me?
https://www.dropbox.com/s/fwfzwrjxg9e7ayo/4%20Times%20Rule%20Graph.png?dl=0


                         Thanks, Mikek


My take is that Zi represents the input impedance of the transformer.
So for example if you are working in a 100ohm system and the primary
inductance is such that its reactance is 400ohm (the 4x thick black
line) then the impedance presented is 97ohms reading from the graph
with phase shift of 15deg.

The rule of thumb I always remembered was that the primary XL should
be at least ten times the wanted impedance. That graph is interesting
showing the effects of using a much lower winding inductance.

piglet

 That\'s the way I tried to use it. A 50 ohm transformation resistance
with a 50 ohm transformer reactance, would look like
50Ω x .7 (as on the graph) or 35Ω at the 1 multiple point. It just
didn\'t agree with a low end roll off of a transformer
someone graphed. All the ham radio books I have seen used a 4 times
multiple, I always wondered how that worked and finally found that graph.
I worked with a physicist a that designed power amps for ultrasonic
transducers, his designs used 3.5 times.
They worked, not sure what 4 times would have changed.

                  Thanks, Mikek