Skip to content

Current Transformer for accurate current metering

There are high requirements, e.g. in smart-meter applications, for current transformer (CT) especially towards accuracy and phase failure. Nanoperm cores can be built up quite small and do have a good linearity, low losses and a very good stability over temperature. Due to that we can realize CTs with low phase and amplitude errors, which gain a high reliability. Products made out of Nanoperm having a good thermal overcurrent and surge strength which makes them ideal for the usage in the power grid.

High permeability up to the high kHz-area makes Nanoperm for the detection of high frequencies in the (power-) electronics indispensable. On top of that more and more appliances are using DC currents so that CT have to handle a certain DC offset. These requirements can be fulfilled with Nanoperm and so we are offering a wide range of standard solutions and are happy to work out customized solution with you as customer.

Active sensors for DC-current measurement

For accurate measurements of DC failures often Royer-Oscillators are used, e.g. in charging cables for e-cars, Wallboxes (household), public charging stations or even in the electric vehicle itself. This concept drives the core into saturation which leads to a change in the conducting phase of the transistor and the core will be saturated in the opposite direction. Due to a F-hysteresis loop (thin hysteresis curve) of Nanoperm, which implies a small remanenz and coercive force, small DC currents in the range of Milliamps can be well detected. Du to good temperature stability, the Nanoperm products can be used very well under changing environmental conditions.

Nanoperm helps to realize sensors which are capable to detect DC and AC current with various frequencies, so that the requirements of IEC 62752, IEC 62955, UL2231 can be kept without using an expensive RCD type B.


If transformers are used in the range of several Kilohertz or higher usual core materials made of iron-silicon-alloys are not applicable due to high eddy current losses. Nanoperm has a very thin hysteresis curve which means low losses and it is very stable over a wide temperature range. The high saturation induction of 1,2 T is about three times higher compared to ferrites. The usage of Nanoperm cores allows a high efficiency with low installation space. Due to permeabilities of about 90.000 at 10 kHz the stray inductance is very low if the windings are applied evenly. This makes them ideal for the usage with frequency converters even if they are built up with SiC and GaN semiconductors.