Transformer primary power loss

[bowman1710]

Hi guys,

Quick question on transformers and losses:

If i have a transformer primary with a 350V pulse @ 333KHz and the primary inductance is say 3mH, is the magnetising power lost in the primary:

XL=2*pi*333khz*3mH=6270ohm

Plossmagnetising=(350/6270)^2*6270=19.5W??

Does the duty cycle come into play because I feel like i am missing something here.

 

[FvM]

You are calculating reactive power. It has nothing to do with transformer losses.

 

[schmitt trigger]

Magnetizing current has two components: The imaginary component from the primary inductance, and the real component from the core loss.

Unfortunately, the only way to actually measure core loss is to apply enough volts-time to the primary, to operate at its rated flux density. This is not something you can achieve with an inductance meter.

 

[Orson Cart]

Transformer loss = R(ac) x Irms primary plus same for secondary, plus core losses best estimated from data sheet for cores being used, e.g. 100mT peak at 300kHz, most good materials will have losses of around 200-400mW per cubic cm of material.
Add all 3 together, hope that you are using 3F35 or better core material (or < 50mT pk for 333kHz) and away you go...
p.s. note that R(ac) is the resistance of the wire at 333kHz, often several times higher than Rdc, unless you are using 44-48 awg stranded litz wire, and there are no big gaps in the ferrite near your first layer of winding....
good luck...