Calculation methods for core size
Which method is better to select the core needed? I know that there are several methods, I have studied them in books, such as the one by Erickson and Maksimov, and in another on the design of transformers and inductors. I don't know which method is better and how to apply it in a real case, I would like to learn what size is correct with suitable parameters.
I've tried two methods:
- the first one: Kg(electrical)= Energy^/(Ke*Alpha) where Ke=0.145*(output power)*(Bm)^2*10^-4 and "Alpha" is regulation in %.
- the second one: Kg=(Rho*Lm^2*Im,max^2*Irms_tot^2*10^8)/(Bm^2*Pcu*Ku) where Pcu is copper loss, Bm is max flux density, Ku is winding utilization factor, Im is peak magnetising current and Lm is the primary inductance.
I know both these valuations are giving different values of core geometry, and I have used two formulas to calculate Kg
Kg=(Core Cross Section)^2*(Winding Area)/(MLT) (Based on Erickson Formula) and
Kg=(Core Cross Section)^2*(Winding Area)*Ku/(MLT)
the first one gives me results more similar to what is required and with the other one i depend on the tables given in the book.
But i don't know if these methods are ok or do i have to use some other.
"Trial" process can be done with paper, pencil & calculator, iterating on paper gets you a lot closer to a real transformer that won't overheat... You need to iterate, as judgement is needed as to frequency and Bpk, and cooling available.
If you have chosen the core using these methods certainly both will work. If you can test both of them do it and do this a few times, you'll develop your own skills and preferences, because that's the real difference between the methods.
Okay i'll try this