Current Transformers

Plitron current transformers are custom designed. Contact Plitron Engineers to discuss your applications.

Plitron can design and build current transformers for in product control, as well as large sizes for industrial applications, as well as to hydro utility requirements.

POWER RATINGS, SIZES, APPROVALS

Overview – A current transformer is used as a measuring device to monitor the current flowing in a conductor. A current transformers consists of a single wound secondary, whose primary consists of the single-turn conductor under test.  The single turn conductor is passed through the centre of the toroid, which then induces a current flow in the secondary winding circuit.

By simple calculation, current is determined as 1 / N, where N = secondary turns.

Design Considerations

High accuracy, or as needed – Single or multiple core versions – Various terminations – Saddle bracket or encapsulated – High isolation as needed.

Specifying Current Transformers

CurrentTransThe primary circuit is not affected by the insertion of the CT, so there is potential
for great accuracy. The secondary winding is commonly rated at either 1 Amp or 5 Amps, for reasons of standardization. As a working example, a 6000:1 CT would be calibrated to deliver 5A when the primary current is 6000 Amps. Often the secondary winding is tapped, bringing out multiple leads at predefined ratios, which increases flexibility allowing the same device to be specified into multiple applications.

Accuracy is application dependent and a function of design (as well as load). The load is referred to as ‘burden’, whose value will greatly impact the accuracy. Usually the burden is resistive in nature, consisting of measuring devices and intermediate conductors. A low impedance burden will improve accuracy, thus conductors should be short and of sufficient AWG so as not to add to the burden. IEC maintains accuracy standards covering CT’s.

Plitron can supply current transformers as discrete coils with flying secondary leads, or encapsulated into cases supplied with screw-down connectors.