# Pulse transformer

#### Coucou80

Joined Apr 7, 2018
78
Hello,
As an engineer I look up for formulas and experiments that I can find arround in order to come up with my own ideas and design.

As we know, this is the formula to calculate the amount of turns for primary winding for a given core and frequency:
N(p) = (Vin x 10^8) / (4 B A f).
For the secondary winding I understand that its a rule of 3 calculation based on finding of the primary set of winding.

Question:
Based on the above formula, does that mean at that given value of Freq and findings of the primary and secondary set of winding for this transformer core, it will operate at resonance regardless of the input voltage ?

#### michael8

Joined Jan 11, 2015
428
There's a lot of context missing from your question (rule of 3?). Anyway, most power transformer
design doesn't have anything to do with resonance (other than, perhaps avoiding it).

#### Coucou80

Joined Apr 7, 2018
78
What i meant by rule of 3 is the calculation of the secondary winding number of turns based on the findings of the primary winding (number of volts per turns) in relation of the desired out voltage output.
I’m not looking at high power transformer with iron core like microwave oven stuff, not at all !! Just ferite core pulse transformer with 70 to 100watts max. If resonance is something you want to avoid, then what happen if you power the designed transformer at the frequency selected in the calculation based on the above formula that I’ve mentionned. My assumption/understanding is that the voltage at the secondary winding would be at its maximum=> at the desired calculated output. Isn’t it?

#### michael8

Joined Jan 11, 2015
428
That equation is calculating the number of turns in the primary to meet a specific magnetic flux in the core.
This is to aid in avoiding to high a flux which would saturate the core causing huge losses.

The ratio of the primary to secondary voltage will be the same as the ratio of the primary to secondary
turns (ignoring losses) as is normal for a transformer.

#### Danko

Joined Nov 22, 2017
1,857
Ratio of pulse transformer is 1:2.
Pulse input voltage is 12V, 50 kHz.
Output voltage changes from 0 to 600 V
at load R1 changing from 0 to 1 MΩ:

Last edited:

#### michael8

Joined Jan 11, 2015
428
In #5 currents in the primary and secondary occur at different times, this is flyback mode, not transformer mode.
pulsetransformer0.asc

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