hello,

I've just finished a module of Transformer theory in trade school and was

hoping to try some of it out.

I plan on experimenting with winding my own toroidal power transformer.

I require a 1:2 step up at 20V 150hz supply aiming at 150-300VA or so.

I have found a general ballpark equation to calculate primary turns for an

EI type transformer which goes like this:

is N = (E · 10^8)/ (4.44·f·A·B),

N= number of pri turns

E= supply voltage

f= frequency

A= Cross sectional area of core (I think in square inches)

B=max flux lines = rough figure of 60,000

Using a toroidal core with a CSA of 1sq" it gives me 50 turns for the

primary.

Is this equaiton correct?

Is the value of B ok for say a Mains 300VA toroidal core off the shelf?

If anyone can help me answer these two questions, or point me somewhere that

can I would be very greatfull.

Thankyou

gavin.

- posted
19 years ago