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Whether it’s wind turbines, tidal energy, solar energy, geothermal, electric motors or generators: a lot of renewable energy technology depends on a single crucial component: the magnetic core.
Magnetic cores convert mechanical energy and store and release it into another system. That’s why they’re used in applications for converting mechanical energy into power including inside high-speed trains. There are two main types of magnetic core: ferrite pot cores and powder cores.
Ferrite Pot cores are used in differential inductors, power inductors, converter and inverter transformers, and power transformers. They are made of 90% ferrite powder along with about 10% epoxy coating powder which is used as an organic binder to increase green strength and adhesion.
Powder cores are also used in inductors and are made of Molypermalloy (MPP), Iron, Sendust, and other alloy powders. Both Ferrite Pot cores and Powder cores can be produced either in a pressing process or a slurry process.
In the pressing production process, 100 to 800 MT presses are used to press the iron powder along with the epoxy binding resin into the form of an E-core. For the process compatible particle size between the epoxy binding resin and the metal powder is important. Too wide of a differential will result in weak green strength.
High green strength after pressing and before cure is important because parts have to be physically moved to the oven. Another important consideration is higher TG for a higher Thermal Class rating. This process creates a core with excellent green strength and high-temperature resistance without affecting inductance value as a function of field strength.
Other than pressing pot cores and powders can be made by mixing the micro metal powders and bind resin into a slurry which is then cured in a mold. This process makes green strength and so particle size less relevant.
So, depending on the production process being used, a different epoxy binding resin maybe more appropriate. However, whichever the method, in both cases the epoxy binding resin must minimize core stress by having low shrinkage and low moisture absorption. Low moisture absorption is important because water’s natural expansion and contraction acts as an additional mechanical force on E-core
All epoxy powders are automatically considered Thermal Class B (130 °C) because of their high silica content, but the higher thermal classes: Class F 155 °C and Class H 180 °C are more desirable because there is an industry trend towards higher power and therefore higher temperatures.
DK15-02 is the current industry standard epoxy binding resin. This is because it is a comfortable thermal class B, but also because it can also be externally applied as an epoxy coating powder.
But the world is a changing place and the golden days of DK18-05 are over. It’s no longer acceptable to use Halogens, which Dk18-05 is full of. Recently the EU added TMA to its list of Substances of Very High Concern (SVHC): making DK18-05 and its many copies no longer suitable for the European Market.
DK15-02’s characteristics meet the requirement as a binding resin and a coating powder. Its low shrinkage and moisture absorption make it great for reducing mechanical stress which is perfect if you are both producing pot-cores and coating powder cores. DK14-2100, on the other hand, has a higher Tg: rating as a thermal class F powder at 155 °C.
At CAPLINQ we work with some of the largest international clients in Europe, Israel, China, and beyond supplying them the epoxy binding resin that they need for their cores. We work with them on selecting the right product, adjusting the formulations for their production process. We also with them to develop completely new and unique customized epoxy binding resin formulations for their unique and specific pot core design requirements.