Calculating Pulse Transformer Frequency at Voltage

[Honk]

Hi.
I need some help in explaining in a simple way how to calculate the minimum allowable
frequency at a certain voltage when selecting a pulse transformer.
The one I'm looking at has an ET value of 45Vusec.

I'm feeding it 22.5KHz at +/-6VAC square wave. It seems to work fine but I fear it is operating out of spec.
Can someone nice her please help me (in s simple way) how to calculate the data from the ET value?

Regards / Honk

 

[Baluncore]

Maybe start here; http://www.butlerwinding.com/pulse-trans-voltage-time-product/

 

[jim hardy]

Can someone nice her please help me (in s simple way) how to calculate the data from the ET value?

I really like that Butler link.

I'm no pulse transformer expert, but hre's the basic physics you start from.

Volts in a coil is proportional to Δflux /Δtime. dΦ/dt

so Φ = ∫volts dt
for one half cycle of your square wave volts is constant so it can move to other side of integral sign
Φ = volts X time
and they're telling you your transformer can hold enough flux to withstand 45 volt- microseconds, that is 45 volts for 1 microsecond or 1 volt for 45 microseconds
or 6 volts for 7.5 microseconds.

So what is frequency of a square wave with half cycle duration of 7.5 microseconds ?
Any lower frequency saturates it.

Note that is for unidirectional applied voltage.
Since your bipolar square wave drives the core between negative and positive Φ_max not zero and max, you probably would get away with running it at half that frequency provided wave is square ie 50% duty cycle ..

See? You knew that already.

old jim