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Ferrite Tranformer for variable frequency

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upervaiz

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Hello,

How can i calculate a ferrite core transformer primary number of turns, if i have a variable frequency pulse at the input of the transformer.

My frequency range is 0.1 HZ to 250 HZ.

How can one design a variable frequency transformer. ??

Your help will be appreciated.

Thank you
 

You specify a wide frequency range, wider than transformers usually are designed for.

Just for fun here's a simulation. Identical transformers have different frequency square waves.



The slower frequency admits high Amperes to the primary. Efficiency is reduced.

The faster frequency produces less power at the secondary. Efficiency is reduced.

----------------------------------------

Edited to add: My caption is incorrect in calling the source a sinewave.
 
Last edited:

Thank you very much for your time. This is very helpful information.


Could you please guide me that how can i design the primary number of turns. if i want to step up the voltage from 30V to 300V ?
 

upervaiz said:
Could you please guide me that how can i design the primary number of turns. if i want to step up the voltage from 30V to 300V ?
Click to expand...

The method I saw goes like this:
(1) Wrap one turn around your core
(2) measure inductance
(3) calculate number of turns to reach target inductance.
 

Flux density is related to the applied turns-volts-seconds, across a cross section area.

Therefore, if your input voltage is fixed and cannot be lowered directly with frequency (this is the usual method), you could get away with a 0.1 Hz frequency if the pulse's duty cycle is very narrow (and I mean VERY NARROW).

Otherwise, you will end up with a gigantic transformer.

You have to use the transformer equations:

https://www.electronics-tutorials.ws/transformer/transformer-basics.html
 

For such low frequencies, you should use an iron core instead of ferrite. You also should specify the voltage amplitude and source/load impedance. Basically you're making an audio transformer but for even lower frequency.
 

BradtheRad said:
Just for fun here's a simulation. Identical transformers have different frequency square waves..
Click to expand...

Highly educative. But I did not understand how a 1:1 transformer produces higher output voltage (first example 0.1Hz) in the secondary (10V supply but 10.18V at the secondary). All other examples are clear.

- - - Updated - - -

upervaiz said:
My frequency range is 0.1 HZ to 250 HZ.

How can one design a variable frequency transformer. ??
Click to expand...

Your desired range of frequency covers more than three decades. If you are using the transformer for power conversion, this is a very bad idea.

You convert the frequencies to periods for convenience. 10s to 4 ms. The pulse at the input should ramp up the current (50% of the max value) in the time of a single period.

With a fixed number of turns, you have a fixed inductance and a fixed time constant. This time constant should be within the range of 10% to 90% of the period (which is difficult to accommodate in the present case).

As others have pointed out, this is difficult as such. If you can have a logarithmic dependence (on frequency), then perhaps...
 

mtwieg said:
For such low frequencies, you should use an iron core instead of ferrite. You also should specify the voltage amplitude and source/load impedance. Basically you're making an audio transformer but for even lower frequency.
Click to expand...

The voltage amplitude is 300V for 180us and rest is of 9V. The load is of R=75ohm and L=142mH.
 

Presume your question is related to the problem already addressed in this previous threads
https://www.edaboard.com/threads/351735/
https://www.edaboard.com/threads/351940/

It's not obvious at first sight how a transformer should be utilized for driving the coil and what's the specific purpose of a transformer in this regard. I fear you are further diverging from a solution.

The voltage amplitude is 300V for 180us and rest is of 9V.
Click to expand...
Output voltage of a transformer is AC, means average voltage over a signal period is zero. If you have e.g. 300V*180us positive voltage*secs area, there must be a corresponding negative voltage*secs area.
 

The threads you mentioned above is already solved. thank you for your guidance:)

The idea is, we don't want to use a separate power supply of 300V for this purpose. I want to step up the voltages from 30 to 300.

First, i thought i can make a pulse transformer for this but then i realized that my input signal has a range of frequency from 0.1hz to 250hz (user dependent).

I searched that only audio transformer can manage this range of frequency. But I don't know how to design this thing.
 

O.K., saving a HV supply.

Feasible transformer parameters (lower cut-off frequency, max ∫Vdt) may be a problem, but as a first step you should give as an idea how the circuit will basically work.

I guess that it's more effective to generate a high DC voltage (not necessarily by a dedicated power supply unit), storeit in a capacitor and use it to boost the coil voltage.
 

My circuit is more less like this;

Pic.png

The timer will set the 180us pulse, then we have a driver for the mosfets switches and that give path to the transformer when they are in "ON" states.
 

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Series connection of a diode and a capacitor doesn't pass any current (capacitor charges up and current stops).
Where's the load?
 
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    CataM

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In the above circuit, the arbitrary load is 4k resistor. Attached with the drain of the last mosfet.
 

I asked about the load because you said "R=75ohm and L=142mH".

HV circuit could be made working like this

Pic.png
 

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