i am using the excel calculator for designing a flyback transformer - Calculation tool for fixed frequency flyback converter using Gen5 CoolSET™ (Version 1.1)
And i am wondering, what about the air gap for the flyback transformer. i see no remarks about this in the excel calculator.
How should i consider the design parameters? Without a Gap in the transformer core?
Hi @Bogdan ,
Flyback transformers require an air gap to maintain energy handling capability.
In general, if we use a center-gapped transformer, the total gap in the center must be equal to the above-calculated value, whether each center limb has been ground or not. But if spacers are being inserted on both side limbs (say on an EE or EI type of core), the thickness of the spacer on each outer limb must be half of the above-calculated
value because the total air gap is then as desired.
Typically, air gap calculations performed by your transformer manufacturer, you only need to provide some basic parameters such as inductance, core and coil turns.
This is also why “Calculation tool for fixed frequency flyback converter using Gen5 CoolSET™ (Version 1.1)” does not offer this service.
Thank you for sharing some light about this.
Lets take an practical example.
I have used for the initial primary inductance & number of primary turns the "Infineon-CalculationTool_fixed-frequency_5th_generation_CoolSET_ICE5xRxxxxxZx-DevelopmentTools-v01_10-EN" tool.
For my case, for 15V output, 0.2Amp using a E20/10/6 N87 core, it gives me the followings:
Lp = 644uH
Np=~80.2 turns at B = 0.201 Tesla
Considering that i need a gapped core, i took my atention to the core datasheet.
In the situation i chose a E20 core with center leg gapped at 0.5 mm, i see this gap is modifing the AL value.
For a 0.5mm gap, the AL is 102.7nH ( N87 material).
Please corect me if i say something wrong, now that i have my initial Lp from the excel tool, i need to recalculate how many turns i need the required Lp with the "new gapp AL" value (102.7nh)?
For AL = 102.7nh & Np = 80 turns, the new LP is 657uH.
Considering the new primary inductance value of 657uH, i said to re-check the B saturation, for the new inductance value it yelds aprox 0.234 Tesla.
So if i used a 0.5mm gapped core, i can expect a slightly increase in inductance, and a slighty higher losses due to high B
Is this asumption correct?
Hi @Bogdan ,
Sorry about my late reply due to the Chinese New Year holiday.
In the core table of "Infineon-CalculationTool_fixed-frequency_5th_generation_CoolSET_ICE5xRxxxxxZx-DevelopmentTools-v01_10-EN" tool:
Core type: EE20/10/6
Core Material: TP4A is a TDG product, corresponding to the PC44 of TDK.
Core Material N87 is a EPCOS prodct, corresponding to the PC47 of TDK.
So, maybe the AL = 102.7nh is not accurate.