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What are Rogowski Coils
Rogowski Coils are electrical devices used for measuring alternating AC current. The Rogowski Coil is named after the German physicist Walter Rogowski. Output signals from a Rogowski CT is fed to transducers used for measuring which then give standardised AC current of max. 1 A at the output. Rogowski Current Transformers are flexible and measures current for power metering and analysis of power quality. They are ideal solutions when space is limited and when needing a rope-style CT to physically wrap around a irregular shaped conductor or wire.
They are used for current measurement of AC currents. Mostly for retrospective installation in existing systems but often on power rails or power cables. Rogowski coils separate making installation around the primary conductor is possible. The output signal coil and fed to a measurement transducer. The Rope CT has flexible sensor coils that wrap easily around the conductor carrying the current. A Rogowski can measure up to a couple thousand amperes of large currents without increasing transducer size.
Rogowski Coil Linearity
An important property of Rogowski coils is that it is inherently linear. As the coil does not contain saturable components. Also the output increases linearly in proportion to the current up to the operating limit determined by voltage breakdown. Rogowski coils are easy to calibrate due to linearity as transducers can be calibrated at any convenient current level. The calibration will be accurate for all currents including very large ones. Also, because of the Rogowski Coils linearity, the transducers have a broad dynamic range and great transient responses.
Flexibility –They have a flexible lightweight clip-around sensor coil that is easy to wrap around a current-carrying conductor. Making them easily inserted into components that are hard to reach in a circuit.
Lower cost – The Rogowski coil is usually cheaper than a hall effect sensor or transformer.
Non-intrusive or lossless measurement — The Rogowski coil has a fast signal response and very linear signal voltage due to drawing very little current from the DUT by low insertion impedance.
AC Current Only – Rogowski Coils will not handle DC current. Only AC.
Sensitivity -Compared to a current transformer the Rogowski coil has a lower sensitivity from not having a high permeability magnetic core.
Alike an AC current transformer the Rogowski coil has a voltage induced into a secondary coil which is proportional to the current flow through an isolated conductor. Although, Rogowski coils can measure large currents without saturation due to its “air” core that is non-magnetic. The air core is designed to enable a faster signal response and a very linear signal voltage by having a lower insertion impedance. Compared to the hall effect sensor/current transformer the Rogowski coil is very cost effective. Making Rogowski coils the most ideal measuring tool for up to thousands of amperes of AC current.
The RCS-5A is an excellent alternative to standard 5A current transformers. The RCS-5A from Magnelab offers the ability to choose from several different amperage input ratings. This allows for flexibility when installing it in the field. Users can assess the needs on site, and depending on the current level that needs to be monitored, they can select the setting that works best for them.
The RCS-5A can be ordered with a variety of different sized Rogowski coils. You can choose from Rogowski coils with 12″, 18″, 24″, or 36″ lengths (or round openings of roughly 4″, 6″, 8″, or 12″). The flexible Rogowski coil opens at the connector junction and may be installed on a bus bar or existing cable in a matter of seconds.
Most Common Uses
The linearity accuracy of the RCT-5A is 0.5%. The RCS-5A Three Phase Rogowski Coil set requires external power and the power supply is included with the kit. This device is most commonly used in power meters, energy sub meters, condition monitoring, power quality monitoring and distributed measurement systems. The RCS-5A is UL Listed, and RoHS compliant, as well as meeting CE and ISO standards. This product is made in the USA.
- Rated input from 500, 1000, 2500, and 5000 amps
- Output of 5A (Three Phase Set)
- Linearity 0.5%
- Overall Accuracy 1.0%
- Custom diameters, and other parameters are available
- UL Listed
The RCS-1800 three-phase flexible rogowski coil converts AC input current of up to 5000 amperes to an AC output of 0.333 volt. In order for it to operate properly, it will need a DC power supply that has to operate between 9 and 36 Vdc. The RCS-1800 comes in two models, one with screw terminals and one coming with an integrator that has flexible strain relief cables attached to it. With the RCS-1800, you will get an 18 inch rogowski coil that has multiple options for the amp rating. When you purchase it, therefore, you do have to indicate which amp rating you will require. Do also note that you will need a power supply for the integrator, which must be between 9 and 36 volts.