Current sense TA 150511

These current transformers can be built with any possible turns ratio, depending on what the application requires, but the typical ratios are the following ones: 1:50, 1:100, 1:200, 1:500, 1:1000. As the number of turns increases, the optimum working frequency range moves towards low frequencies, while the minimum working frequency is related to the capability of the core to transfer the current pulse, that is the transfer area of the transformer. The burden resistance sets the output voltage range, and after the designer has chosen the signal level, the minimum working frequency is fixed and for higher frequencies the detection circuit will not show any signal distortion. The maximum working frequency is influenced mainly by two factors: the core material behaviour versus frequency and the number of turns, in fact each pair of turns composes a parasitic capacitor and the total amount of this effect is a big capacity that limits the current transformer’s bandwidth.