toroid iso

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Coating Toroids

A magnetic toroidal powder core is typically coated with individual epoxy finishes that can provide added benefits, including:

  • Moisture resistanceCustom Coil Winding
  • Wax tight seal
  • Chemical resistance
  • Durability
  • Strength
  • Strong dielectric properties

After the core has been coated, the voltage must be broken down and tested. This is done by inserting cores in between to separate weighted pads (made of wire mesh). Adjusting the force will produce uniform pressure (10 psi), which simulates winding pressure. 60 HZ rms voltage at 1.25 of the allowed limit is the standard conditions needed for testing cores in random sample sets. Keeping it at an average rate will reduce the likelihood of breakdown voltage in production batches.

Larger toroids (diameter of at least 16.5) are commonly coated with arylene, which is done to minimize the constriction of inside diameter. Toroids coated with parylene have their maximum HT and OD reduced by roughly 0.18 mm. The minimum ID increased by as much as 0.18 mm.

Expoy coatings can work at temperatures up to 200 Celcius. Parylene coating is lower, at 130 Celcius (it can be used at 200 for short periods of time). Operating in high temperatures does not phase the magnetic properties of powder toroid cores.

Coil Winding

For more information on core coating, please do not hesitate to reach out to us. We specialize in transformer winding, and we do toroid and custom coil winding.

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