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Rogowski Coils

Magnelab offers a large array of products for power monitoring. They offer several styles of AC current sensor or DC current sensor including models that feature a Rogowski coil, split-core and solid core design. Magnelab has a current sensor to suit almost any need.

At Magnelab, you are able to find a huge selection of current transformers, current sensors, split core current transformers and flexible core coils (Rogowski coils). In fact, the Magnelab flexible current transformer is one of the highest rated by customers on the market, which is a true testament to how good our products are. We want to make sure you can get the job done properly.

Our flexible/rope CT uses a Rogowski coil. This system was named after Walter Rogowski, who developed the electrical device that allowed AC (alternating current) to be measured, as well as high speed current pulses. It is made up of a helical coil of wire and the lead on one end of the wire returns through the center of the coil to the other end. This means that both terminals are always at the same side of the coil. This entire coil of wire is then wrapped around the conductor carrying the current that needs to be measured – this is usually a straight electrical conductor. No iron or other metal core is involved in this construction. What is critical, however, is the diameter of the coil, the winding density and the rigidity of the winding. Put together, they help to preserve immunity to the various external fields, while also ensuring that it is not too sensitive to the way the measured conductor is positioned.

The voltage that the coil induces is in exact proportion to the derivative (rate of change) of the current found in the straight conductor. Hence, the Rogowski coil’s output is generally connected to a type of integrated circuit, so that the output signal is in proportion to the current itself. This is precisely what our flexible/rope CT can offer, particularly when used together with a current sensor.

There are a number of clear advantages to using this type of system. Because it isn’t a closed loop, as the two terminals are connected, the coil is flexible and open ended, which means it will not disturb a live conductor while it is wrapped around it. Of course, it is very important to position it properly. Like with the ACT-0036 current transformer, the accuracy can change dramatically if not positioned properly. This is why it is best to use a precise locking system.

The flexible/rope CT also has low inductance. As a result, if currents change very rapidly, it can still respond to it correctly. In fact, the speed can often be as low as just a few nanoseconds. There is no iron within the flexible rope, which means that, even under large currents, it is highly linear. This can be used in welding, electric power transmission, pulsed power and more. Additionally, only very small reference currents are needed for calibration.

There are a number of other benefits. The construction cost is generally reduced, for instance, and there is no risk of the secondary winding opening. It is also easy to compensate for the temperature. Finally, there is no need for an increase in secondary turns to keep a constant current output. Hence, a smaller coil is needed than would be used in a current transformer.

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