Inductors are devices that store and convert energy. A BH loop characterizes the useful region of operation of a magnetic component. When a gap is introduced into the core either discretely, as in a ferrite or distributed, as in a powder core, the ability of the device to store energy is greatly enhanced, from the region of 0.2 – 2.0 Oersteds for an ungapped core set to 100 – 1000 Oersteds for a gapped core by shearing over the BH loop. Gaps in inductors are introduced for the purposes of: controlling inductance, reducing inductance, maintaining inductance under load and reducing the change in inductance due to shifting currents or temperatures. Ferrite inductors have the advantages of low cost, low losses, flexible geometries, good shielding properties and excellent tolerance capabilities, often in the range of +/- 3%. Pot cores that have tuning capabilities can be adjusted to an exact AL when this is required to balance a capacitor or for other precise applications.
In a power transformer design there are two main goals to keep in mind--keeping the core out of saturation and minimizing core losses. Materials for transformers typically have high permeability, usually ferrites or tape wound cores. The characteristics to consider when choosing between tape wound cores and ferrites are: Frequency and temperature of operation, and unit cost, size and shape. Ferrite cores offer the benefits of low losses, low cost and a wide variety of available shapes and sizes. Pot cores offer the advantage of protective shielding which can be important in EMI/RFI sensitive designs. Planar E cores offer ease of assembly, consistent results and a low profile. Ferrites are typically considered for use at frequencies of 10 kHz and above. Above 20 kHz the ferrite design is typically loss-limited while below 20 kHz the design is typically limited by the flux capacity of the unit. Tape wound cores have higher B max, saturation flux density, so the overall design can be smaller.
Magnetics Curve Fit Equation Tool
The Magnetics Curve Fit Equation Tool is an Excel file for design engineers working on calculations from the formulas in 2015 Magnetics Powder Core Catalog. Magnetic component engineers can compare the core performance including permeability vs. DC Bias, core loss density, normal magnetization, permeability vs. AC Flux, permeability vs. frequency, and permeability vs. temperature. This fully functional tool provides six comparison tables in this file based on five different powder core materials, MPP, High Flux, Kool Mu®, XFlux®, and Kool Mµ® MAX.
Designing with Magnetics Powder Cores
- Powder Core Calculations includes Winding Factor, Mean Length of Turn (MLT), DC Resistance (DCR), Wound Coil Dimensions, and Temperature Rise Calculations.
- Powder Core Loss Calculation provides a step-by-step method to calculate losses generated by powder cores under certain conditions.
Magnetics Ferrite Core Loss Calculator
The Magnetics Ferrite Core Loss Calculator is an easy way to find core loss data on Magnetics' Ferrites at various frequencies and temperatures. See results for P, F, R, T, and L materials by entering frequency, temperature, and peak flux density. It gives designers a way to calculate core loss that can be used in any Excel sheet.
Block Structures and Products for High Current Applications
Rapid expansion in the solar power conversion, wind power conversion, hybrid vehicle, Uninterruptible Power Supplies, and electric drive transportation markets has increased the demand for high current (100-300 amps) inductors. For many high-current applications the limiting factor is not necessarily the ability of the material to provide enough inductance at DC Bias, it is the ability to fit enough turns of the heavy wire or foil to provide the necessary inductance. To address that need, Magnetics tooled up a family of larger E cores and U cores that are able to accommodate both larger wire sizes and greater amounts of wire. In some cases even these large cores were not robust enough to support the inductance required at currents greater than 100 amps. Magnetics Kool Mu® and XFlux® block structures can be made large enough to achieve specified inductance in these types of applications.
Kool Mu and XFlux blocks come in a variety of sizes and shapes for flexibility and customization of a design. New sizes can be tooled.