The effect of coating on the power loss of amorphous ribbon toroids

In this investigation, the power loss and permeabilities of amorphous ribbon toroids have been measured under sinusoidal induction conditions up to 1.0 T over a frequency range from 20 Hz to 20 kHz. The toroids were made from Metglas 2605SC type material (Fe81B13.5Si3.5C2) and separate toroids were treated with four different coatings and a Physical insulating media. The coatings, some of which are commonly used in the steel industry, are: (a) magnesium oxide, (b) water based emulsion paint, (c) "Varnite" - a water soluble resin, (d)"VHT 1200"- a high temperature aerosol spray paint and (e) a high temperature insulating tape. The toroids were tested under four conditions, viz: (i) as-cast, (ii) coated and unannealed, (iii) uncoated and annealed and (iv) coated and annealed. These measurements enable the effect of the coatings before and after annealing to be assessed. The results obtained for power loss and permeability for toroids treated with the coatings show no appreciable beneficial effect on the properties of the toroids. The results of this investigation have shown that the optimum properties of amorphous ribbon toroids are obtained by the annealing process and that the performance of toroids can not be appreciably improved by the use of coatings or an insulating medium. Therefore, there is no commercial advantage to be obtained by coating or insulating amorphous ribbon toroids.