BS EN IEC 63093-9:2020 pdf download

BS EN IEC 63093-9:2020 pdf download.Ferrite cores- Guidelines on dimensions and the limits of surface irregularities Part 9: Planar cores.
5.4 Cracks
Different cracks are shown in Figure 10, Figure 11 and Figure 12. In principle three different types of cracks can be distinguished.
a) Cracks which are parallel to the magnetic flux path (Si, S2, S5, S5, S5). These cracks are magnetically not critical. The maximum length of a single crack is 33 % (113) of the dimension of the relevant surface which is parallel to the crack. In the case of multiple cracks the maximum cumulative length doubles.
b) Cracks which are perpendicular to the magnetic flux path (S3, S3’, S3”, S4. S4’). These cracks are magnetically critical. They can reduce the relative cross-section of the magnetic flux or add an additional air gap into the magnetic circuit, The maximum total length of cracks is 20 % (115) of the dimension of the relevant surface which is parallel to the crack
C) Cracks which go from one edge to another edge (S6), These cracks can cause chipping during the operation In the circuit. The loose particles can cause malfunctions in the circuit. Therefore this type of crack Is not acceptable in any case.
The reference dimensions are given in Figure 13, Figure 14 and Figure 15.
The limits for cracks are given in Table 8. Table 9 and Table 10.
5.5 Flash
There shall be no flash extending from the core into the wire slot.
5.6 Pull-outs
The pull-outs are applicable only for the inner surface where the PCB is seated (as shown in Figure 10. Figure 11 and Figure 12).
For planar EL-cores, low-profile E-cores and low-profile ER-cores, the cumulative area of pull- outs of the core shall be less than 20 % of the total respective surface area.
A.1 General design
The design of low-profile cores standardized by the IEC is based on the form factors that are defined by the following core proportions:
a) .4 > 28
b) C>B
C) A > C
where
A is the overall length of the core back;
B Is the outside height of the core;
C is the core width or floor width at wire aperture.
Those cores which exhibit the planar form factor as defined above, and which were initially designed to meet the requirements of designers for low-profile, board-mounted power transformers and chokes are the ones that have been standardized here. Other cores. originally designed for other uses, are frequently modified to achieve the planar form factor in order to have application In board-mounted power. Most frequently, this is achieved by reducing the leg lengths of standard P0-. RM- and pot-cores. Standardization, If any, for those low-profile sizes is reflected En the relevant IEC standard for the size. (See IEC 63093-4 for RM-cores.)
A.2 EL-core design
The design of the EL standard cores Is based on the following considerations:
a) since the motherboard or multi-layer board shall typically have slots cut out to accept the cores, the core shapes are designed to result in cut outs that are simple and economical;
b) with consideration of the output power of on-board type DC-to-DC converter for telecommunication, seven base sizes from 11 mm to 25 mm are standardised;
C) the outer leg dimensions are selected to allow economical production of cores
(A — EVA 116:
d) with consideration of minimizing leakage inductance, the aspect ratio C is chosen as
C = O,8A
e) the flux path (or cross sectional) area of the centre leg and that of the sum of two outer legs are designed to be equal;
an oval shaped centre leg is selected so that the ratio of the average wire length to the cross section of the winding Is minimized. Copper loss Is a function of this ratio and this ratio is minimized when F,JF1 2,3:
g) the dimension of the back wall thickness is designed to be equal to 1.1(4 — E)12, so that its minimum cross section is close to the cross section of any of the outer legs;
h) the height of H is designed with consideration of slot spacing for telecommunication equipment.