Design and Implementation of a Self-Inductance Measuring Circuit for an Air-Cored Induction Coils

In induction heating applications like brazing or welding of small sections, the need arises for an air-cored induction coils to be used in such applications. The determination of the self-inductances of these coils is required because they must be connected in parallel with a capacitor to form a tank circuit to achieve high current. The determination of the actual resonance frequency of the tank circuit is very essential to the heated parts of the specimen and the time of the process. Since, the shape and geometry of these coils is too complicated to be treated analytically using traditional methods to determine its self-inductance, and the actual connection of the tank circuit inserts connection resistance effects too. Then the practical determination of the real resonance frequency is a complicated task. This paper deals with implementation of a measuring circuit has the ability to measure the self-inductance of the induction coil experimentally as it connected in parallel to the tank capacitor. Faraday's formula is used to calculate the self-inductance. Real experiments are conducted to prove the reality of the measurement for different shapes of induction coils. The achieved results agree with those obtained numerically using the Finite Element Method (FEM) and with that obtained from an accurate measuring device.