Molypermalloy MPP Powder Cores
MPP cores are very stable relative to flux density, temperature and DC current. They are normally used for inductors and other energy storage applications.
MPP cores are normally sold pre-graded to a specific permeability tolerance. This makes them ideally suited to pure inductors, because the precise inductance will be known before winding, allowing suitable adjustments to be made to the number of turns, if required. MPP cores are also widely used for energy storage inductors due to their low inductance swing when DC bias is applied.
The lower permeability MPP cores can be used at frequencies above 500KHz. As the permeability of the core increases, stability tends to decrease. The most popular MPP permeabilities are in the 60 to 173 range, where all the advantages of the MPP product are most apparent.
MPP has the advantage of having constant permeability as the flux density varies up to about 3500 gauss. Above this level, permeability does tend to drop off. Other powdered core materials, such as Iron Powder, have permeability that varies with flux, adding to the potential instability of the device.
Disadvantages of Molypermalloy (MPP) cores are:
High manufacturing costs mean MPP cores are amongst the most expensive of the powder cores
The available shape is limited to toroidal only, due to very high pressing pressures required.
Advantages of Molypermalloy (MPP) cores are:
Permeability is ultra temperature stable
Permeability is stable with variations in AC flux density
High energy per unit storage of volume
Available in small permeability increments
Lowest loss of all powder materials
Lowest magnetostriction coefficient of the powder core materials, meaning very quiet in operation.
Line output (flyback) transformers
Power Factor Correction (PFC) inductors
In-line noise filters
High Q filters
Part Numbering System:
MP-xxxyyy-2 Where xxx represents core dia. in inches and yyy represents the permeability and 2 represents the finish.
For reference, the previous part numbering system (now superseded) was… A-xxxyyy-2 Where xxx was a random number indicating the dimension/permeability specification for that core and yyy was the AL value in millihenries per 1000 turns.
If required, the two numbering systems can be cross referenced here.