On a Method of Measuring the Natural Oscillation Frequency of Testing Transformers

Abstract

This paper describes a method employed by the authors, to find quite easily and quickly the natural oscillation frequency of high tension testing transforaners, and also some results obtained by this method. The free oscillation produced in the secondary winding is directly observed by Braun tube, applying repeated voltage impulses into the primary winding.
A testing transformer 100k. V. A., 250, 000 volts was tested and it was found that the series resonance frequency is about 700 cycles while the parallel resonance frequency about 140 cycles.
A variable condenser of known capacity was connected across the secondary winding, under various conditions of primary and secondary windings and it was confirmed that the square of the natural oscillation period increases linearly by the increase of the capacity (Fig. 6). The self capacity of the secondary winding was thus found as shown in table 1.
The effect of resistance in the primary circuit upon the natural frequency was invcstigated experimentally and was explained by theoretical considera tion.
The natural frequency of a telephone receiver was also measured by our method.
This paper contains the following items. [1] Jntroduction [2] Method of measurement [3] Construction of transformer under test [4] Experimental results [5] Theoretical consideration [6] Measurement of natural frequency of telephone receiver [7] Accuracy and limit of applicability of this method.