TDK RM Type Ferrite Cores


One of the most demanded core types for inductive elements after type E (in Russian terminology, SH-shaped type) is type RM. RM (Rectangular Modular) cores were designed to increase the packing density of printed circuit elements, so their special shape is a key feature of RM core inductors.

Our product range includes the most popular B6580 , B6581 series of RM type ferrite cores. TDK's entire product line of RM ferrite cores is defined by core dimensions ranging from RM 4 to RM 14. The core dimensions correspond to standard PCB grids. For example, RM 6 means that the core with the coil former fills the square base area of 6 × 6 modules (the length of side 1 of the module is 2.54 mm) = 15.24 × 15.24 mm 2 . In each series there are options for cores both with and without a gap. In addition to the overall dimensions, the determining factors for RM-type cores are the effective length of the magnetic path I e , the effective magnetic cross section A e , the relative effective magnetic permeability µ e and the inductance factor A L .

Appearance of RM type ferrite core Appearance of RM type ferrite core

Initially, RM cores were developed for two main applications that are still used today:

  • Highly stable, very low loss inductors (materials N48, M33 and K1).
  • Broadband low distortion inductors (materials T66, T38, T57, N30).

However, RM-type cores are now increasingly being used in inductors for power applications - AC/DC and DC/DC type converters, chargers, inverters, etc. The RM series of cores made of N87, N97, N88, N96, N95, N92, N49 and PC200 (no gap) materials are particularly suitable for this purpose. RM type cores without a central hole (they have a higher value of the inductance A L and higher power) are actively used in transformers.

Separately, TDK's range of RM cores includes low-profile RM cores, the overall height of which is significantly reduced, which makes them suitable for creating interface and matching transformers, as well as chokes, transformers and energy storage for DC / DC converters with high frequency. pulses (materials N87, N49 and PC200). Low profile RM cores are also suitable for applications where the winding is printed directly on the PCB and the core is attached to the board from both sides - for example, a planar type transformer:

Planar transformer on low profile RM core Planar transformer on low profile RM core

For a number of cores of the RM type, additional accessories are available - a coil frame for winding transformer windings and leads for desoldering on a printed circuit board, including SMD (for surface mounting), as well as mounting brackets. For example, for cores RM 8 - RM 12 in our assortment there are coil frames and brackets from the B6581 series . Coils for RM cores with large lead spacing are also produced for ease of use.

Assembly diagram of an RM core inductor Assembly diagram of an RM core inductor

For more detailed technical specifications of TDK type RM ferrite cores, see Specifications on the product page.