Rogowski Coil Current Sensors are used to measure AC waveforms, they cannot be used for DC measurements. Typically they have an advantage over iron cored current sensors at high current, as they are air cored and hence smaller and lighter than a current transformer. We have designed and made a sensor that works well at 150A full scale and higher.
The scale is set by the gain of the amplifier and we can set it up to read 20A full scale. The target is to read 5A with an error of 2%, but achieved 20%. The question is if we embark on a project to achieve 2% at 5A will there be a market for the product competing with Hall Sensor products. Here is a file that describes the Rogowski Current Sensor and the R&D project.
Choose the lowest range of current for which you would use a Rogowski Coil in preference to an iron cored sensor...
Thanks for your help.
This type of coil has advantages over other types of current transformers.
- It is not a closed loop, because the second terminal is passed back through the centre of the toroid core (commonly a plastic or rubber tube) and connected along the first terminal. This allows the coil to be open-ended and flexible, allowing it to be wrapped around a live conductor without disturbing it. However, positioning of the measured conductor is important in that case: It has been shown that, with flexible sensors, the effect of the position on the accuracy ranges from 1 to 3%. Another technique uses two rigid winding halves with a precise locking mechanism.
- Due to its low inductance, it can respond to fast-changing currents, down to several nanoseconds.
- Because it has no iron core to saturate, it is highly linear even when subjected to large currents, such as those used in electric power transmission, welding, or pulsed power applications. This linearity also enables a high-current Rogowski coil to be calibrated using much smaller reference currents.
- No danger of opening the secondary winding.
- Lower construction costs.
- Temperature compensation is simple.
- Conventional current transformers require an increase of the number of secondary turns, in order to keep the output current constant. Therefore, a Rogowski coil for large current is smaller than an equivalent rating current transformer.