The Frequency Tripler

The most common form of static frequency tripler consists of a 3-phase transformer operated at a fairly high flux density, with an open-delta secondary connected to the triple-frequency load. The nonlinear property of the B/H characteristic of the core material is used to obtain the frequency conversion, and the unwanted fundamental component is removed by the method of connection. There is no theoretical reason why such a frequency tripler should not be designed starting only with the magnetization curve of the core material, but to do this is exceedingly tedious. A more practical approach is to abstract the required information experimentally and present it in a manner convenient to the designer. A series of tests were performed to obtain the information necessary; the cases investigated included pure resistive loads, pure inductive loads and capacitive ballast added to a resistive load to improve the performance of the tripler. The main information obtained is: (a) the relation between the triple-frequency output voltage and current with the input voltage and current at all values and for each type of load; (b) the phase of the output; (c) the iron losses. In addition, an important ferro-resonance phenomenon which occurs when the tripler is connected to a capacitive load is described. A method of deducing the relevant characteristics of the tripler starting from the magnetization curve is included mainly to throw light on the mechanism of tripling under differing load conditions. Reasonable agreement was obtained between experimental and predicted values.