Here at AGW we have experienced an increase in interest and demand for flexible Rogowski coils, used in applications such as sensors in electrical protection systems and monitoring current in electricity sub-stations. Our winding technique used in manufacture means we have developed a successful technique to feed the finished end of the winding back through the centre of the flexible tube to meet the start of the winding.
What makes a Flexible Rogowski coil different to a Current Transformer?
Standard Current Transformers* require a closed loop core to carry the winding. This core must fit around the primary conductor, which is being measured, which can be very difficult to achieve when the primary conductor is physically large or is difficult to access.
A flexible Rogowski coil does not require a closed loop core like a Current Transformer. The two connections of the secondary winding are brought out at the same position and the finish of the winding is brought back to the position of the start. This leaves a free end that can be wrapped around the conductor which is being measured. Obviously, the coil needs to be flexible, in order to be wrapped.
An integrator circuit, which is attached to the Rogowski coil, then provides the information about the current ratio.
How a Rogowski Coil works
AGW’s unique winding technique
AGW have developed a specialised winding technique for the manufacture of flexible Rogowski coils.
We are able to accurately wind the coil wire on to flexible tube. This requires supporting the flexible tube in a manner that creates a stiff rod, which will not be deformed by the wire’s tension during the winding process.
The wire has to be accurately wound on to the tube to ensure evenness and consistency. Our machines have sufficient control to be able to perform the winding process to these demanding specifications.
Our technique allows the finished end of the winding to be fed back through the centre of the flexible tube to meet the start of the winding.
If you would like to enquire about our Rogowski coils or our other manufacturing techniques, please contact AGW on 01246 473086 or fill out a contact form.
Current transformers measure the current in a conductor (the primary) by comparing it to the current in a coil wound on a core (the secondary) which closes around the conductor. The current in the primary induces a current in the secondary. The size of this current is proportional to the turn ratio between the primary and secondary e.g. A 100 turns secondary will carry of 1/100th of the current that the single turn primary conductor carries. The secondary current can be measured and the primary current calculated.
This means that a large current in a physically large conductor can be measured without actually touching that conductor.