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Anonymous Poster #1

High-Impedance Transformers

02/28/2015 9:10 PM

Can you explain the structure and working principle of a transformer with high impedance. Thanks in advance
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Tom_Consulting
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#1

Re: high-impedance transformers

02/28/2015 9:22 PM
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dvmdsc
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#2

Re: high-impedance transformers

02/28/2015 10:08 PM

Impedance transformers match the impedance between source and the load.

Initially they were used in class A tube amplifiers to match the the higher impedance of the end stage to that one of the speaker.

Values between 400 to 10.000 Ohms primary to 2-50 ohms secondary were usually applied. This transformer found a lot of applications in all kind of sizes from miniature in Microphone and line audio signals transfer. (typical 200 to 1- 500 kOms)

In fact when matched well, the secondary had the primary value only with the right load connected. Not matching/or open secondary side destroyed many amplifiers.

Googlin' Impedance transformers shows also the quadrat (or square) ratio between the windings.

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#3

Re: high-impedance transformers

02/28/2015 10:11 PM

It all starts with Maxwell's Equations. What do you understand of these deceptively simple looking equations?

Seriously, if you tell me how much of these equations you understand I can then try to tailor my answer so you can understand transformers more clearly.

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#4

Re: high-impedance transformers

02/28/2015 11:02 PM

High Impedance Transformers

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#5
In reply to #4

Re: high-impedance transformers

03/01/2015 9:59 AM

Remind me again, what kind of "Transformers" it is, High Impotence or High Impedance?

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#6

Re: High-Impedance Transformers

03/01/2015 12:43 PM

Z is rated in Ω ohms, go on, think. How would it be affected in a conductor or wire? --Length of winding----, go on, ...cross section of wire --go on, ...purity of wire/material property(resistivity)

Growing peppers is more complicated than this but have fun.

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#7

Re: High-Impedance Transformers

03/01/2015 6:09 PM

What type, voltage , etc? Can you provide more information.

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#8

Re: High-Impedance Transformers

03/01/2015 6:37 PM

A transformer with high impedance is a lousy poorly designed transformer. Or did you mean a transformer for matching a low impedance (source or load) to a high impedance (source or load)?
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#10
In reply to #8

Re: High-Impedance Transformers

03/01/2015 9:46 PM

sorry, it was a transformer for matching a low impedance to a high impedance.
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#12
In reply to #10

Re: High-Impedance Transformers

03/01/2015 10:43 PM

Oh, easy then. To match impedances, you will want a transformer whose core material is appropriate for the frequency ranges of interest, and a turns ratio that is the square root of the ratio of primary impedance to secondary impedance.

http://en.wikipedia.org/wiki/Transformer

This can be shown thusly:

Vp = voltage primary

Vs = voltage secondary

Ip = current primary

Is = current secondary

A = transformer turns ratio = Vp /Vs

or

Vp = Vs * A

and since current ratio is inversely proportional to the voltage ratio (constant power on both sides of the transformer)

Ip = Is / A

And since twinkle-twinkle little star, V = I times R (or Z)

Zp = Vp / Ip dividing the two equations above

Vp / Ip = (Vs * A) / (Is / A)

Vp / Ip = (Vs / Is) * A^2

Zp = Zs * A^2

or

Zp / Zs = A^2

A = (Zp / Zs)^0.5 or A = √(Zp/Zs)

Good luck with your quest.
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#11
In reply to #8

Re: High-Impedance Transformers

03/01/2015 10:22 PM

The coil of your ignition is lousy too?

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#13
In reply to #11

Re: High-Impedance Transformers

03/01/2015 11:09 PM

Your ignition coil is a coupled inductor, not a transformer.

Ignition coils would make very lousy transformers.
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#9

Re: High-Impedance Transformers

03/01/2015 8:42 PM

No need to get fancy, all other things being equal, the impedance of a transformer is a function of the coupling between the coils, the reluctance of the material of the core and its construction.

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#14

Re: High-Impedance Transformers

03/02/2015 11:26 AM

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