Core Shape and Size Selection

- Maximum allowable temperature is 110°C, and the maximum ambient temperature rating is 55°C -> ΔT = (110 - 55) = 55°C.
- The total loss budget for the transformer is Ptrafo,max = 3 W.
- Rth,trafo,max = ΔT / Ptrafo,max = 18.3°C/W.
- The PQ35/35 core satisfies this requirement.
- The coil former for PQ35/35 shows an Rth of 16.5°C/W and is able to dissipate up to 3.3 W at an ambient temperature of 55°C.