sabu31
Advanced Member level 1
Hi All,
I am having a confusion regarding the method used for selection of core size for high frequency converters. I know there is Area Product Method and Core Geometry Method.
I studied core Geometry method presented in both mentioned in Transformer and Inductor Design Handbook by Col. McLyman and Another Presented in Fundamentals of Power Electronics by Erickon and Maksimovic.
In First method its using formula for Kg(electrical)= Energy^/(Ke*Alpha)
where
Ke=0.145*(output power )*(Bm)^2*10^-4
Alpha is regulation in %
In second method
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
Irms
Im is peak magnetising current
Lm is primary inductance
But both these valuations are giving different values of core geometry. Based on Geometrical size we are getting
Kg=(Core Cross Section)^2*(Winding Area)/(MLT) (Based on Erickson Formula)
Kg=(Core Cross Section)^2*(Winding Area)*Ku/(MLT)
However, despite the only difference in them being Ku. The calculated values of Kg requirement (based on electrical condition) is different from Kg (based on core specifications). From my calculation Erickson Kg method is giving values close to whats required and can be applied using manufacturer core specification datasheet. From Col. McLyman method I have to depend upon tables givnen in the book.
a ) Is there any thing missing in my understanding, why this difference is arising and whats correlation between them.
b) Secondly, in TI app note they are using Area Product Method .Using a definition given as
AP= (LmIscspk*Ifl/(Bm*Ku*J*10^-4))^4/3
There is another formula
Ap=2*Energy10^4/(Bm*J*Ku)
Which is more accurate or commonly used.
c) Which is the method commonly used by magnetics designers (Area Product or Core Geometry. And whats relating all different formulae
I am having a confusion regarding the method used for selection of core size for high frequency converters. I know there is Area Product Method and Core Geometry Method.
I studied core Geometry method presented in both mentioned in Transformer and Inductor Design Handbook by Col. McLyman and Another Presented in Fundamentals of Power Electronics by Erickon and Maksimovic.
In First method its using formula for Kg(electrical)= Energy^/(Ke*Alpha)
where
Ke=0.145*(output power )*(Bm)^2*10^-4
Alpha is regulation in %
In second method
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
Irms
Im is peak magnetising current
Lm is primary inductance
But both these valuations are giving different values of core geometry. Based on Geometrical size we are getting
Kg=(Core Cross Section)^2*(Winding Area)/(MLT) (Based on Erickson Formula)
Kg=(Core Cross Section)^2*(Winding Area)*Ku/(MLT)
However, despite the only difference in them being Ku. The calculated values of Kg requirement (based on electrical condition) is different from Kg (based on core specifications). From my calculation Erickson Kg method is giving values close to whats required and can be applied using manufacturer core specification datasheet. From Col. McLyman method I have to depend upon tables givnen in the book.
a ) Is there any thing missing in my understanding, why this difference is arising and whats correlation between them.
b) Secondly, in TI app note they are using Area Product Method .Using a definition given as
AP= (LmIscspk*Ifl/(Bm*Ku*J*10^-4))^4/3
There is another formula
Ap=2*Energy10^4/(Bm*J*Ku)
Which is more accurate or commonly used.
c) Which is the method commonly used by magnetics designers (Area Product or Core Geometry. And whats relating all different formulae