Examples of MgO core and winding

Category: Products > Extrusions For Heater Industry


Cartridge Wind cores, Cartridge heater cores, Swageable Cores, Swageable Insulators

INTRO: MgO wind cores are used for production of high watt density cartridge heaters.  This heater is characterized by the ability to run at very high power compared to conventional designs.  The heating element is wound on the periphery of the MgO core which permits very effective heat transfer to the surface which is typically a precision diameter for good thermal contact with the heated object.

Description: MgO wind cores require a proper combination of dimensional, material, physical, electrical, and microstructural properties.  They are extruded into the final shape with no machining of dimensions except for length.  The MgO grade is a high performance heater grade with optimum dielectric and insulation resistance properties.  The grain structure must provide proper firing results for strength and dimensions, and proper compression reaction upon swaging.

MgO is the material of choice due to it’s performance as an electrical insulator and it’s relatively good thermal conductivity compared to other ceramics.  This permits high operating voltages, low leakage and ground fault currents, and good heat transfer.

As an un-machined finished product, dimensional tolerances must allow for normal fabrication tolerances, or accept the consequences of additional cost for inspection and reject rates.  Fortunately, these tolerances are very well defined and can be accommodated with reasonable engineering allowances.

Heater Grades

It is not necessary to stipulate an TATEHO OZARK grade.  TATEHO OZARK uses high quality electrical grade fused MgO.  The minimum MgO content is 96.4% MgO with appropriate limits for impurities and magnetic iron.

For the purpose of finished part identification, TATEHO OZARK part naming will use the prefix “T”.

Your certification paperwork may indicate specific designations, which are used internally to specify and engineer the perfect MgO grind and blend for your part.

The following are typical analyses or limits for powders used to produce MgO wind cores. All raw materials are high quality fused grain powders which are processed in-house to obtain optimum particle size distributions for end use.

CONTENTTypical CKM MgOStandard MgO Spec
MgO (%)98.38>97.0
CaO (%)0.42<1.5
SiO2 (%).60<3.0
Fe2O3 (%)0.07<0.15
Al2O3 (%)0.38<1.0
C (PPM)<50 ppm<200 ppm
S (PPM)<10 ppm<50 ppm
B (PPM)<10 ppm<50 ppm
Cd (PPM)<10 ppm<10 ppm

Insulators are fired to uniform mechanical strengths which have been established for optimum handling and swaging characteristics for different applications. A true mechanical test does not exist to characterize “crushability”. A Modulus of Rupture measurement is normally provided for historical tracking purposes.  This test is a modified three point bending test performed according to ASTM standard E1652 Appendix 4 and has many limitations.