Relation of D-C magnetic properties of oriented 48-percent nickel-iron to magnetic-amplifier performance

TO IMPROVE the characteristics of cores for magnetic amplifiers, it is necessary for the metallurgist to isolate and measure those properties under his control as a material producer. The performance of a completed core depends on many factors, not all of which reflect actual magnetic properties of the core material itself. Many methods1¿5 have been used successfully to measure core performance under production conditions for matching and grading; similarly, several excellent papers3,4,6,7 have been presented relating core performance to magnetic-amplifier design. While these dynamic methods are most valuable to the core producer and designer, their very advantage in including all the factors contributing to core performance has proved to be a handicap to one seeking to control factors which can be attributed only to the core material. A wealth of experience has been accumulated in recent years relating metallurgical factors such as chemical composition and processing to d-c magnetic properties. D-c magnetic tests have been widely used to investigate material variations because of their accuracy, reproducibility and the fact that they are unaffected by eddy currents. For example, to study the influence of an objectionable impurity it is important to control or, better, to eliminate other effects such as thickness and volume resistivity. The d-c test accomplishes this because it will reflect the changes caused by the chemical impurity without being influenced by other factors.