Rogowski Coil Literature  Rocoil Logo
This page collects together literature about the working of Rogowski Coils and associated equipment together with specifications for Rocoil products.

HISTORICAL INTEREST

On a Magnetic Potentiometer, A. P. Chattock: 1887
This paper describes the use of a winding on a long, flexible former for making magnetic measurements. Download PDF

Die Messung der magnetischen Spannung. (Messung des Linienintegrals der magnetischen Fieldstärke.)
W. Rogowski und W. Steinhaus: 1912
The paper that gave Rogowski Coils their name. Download PDF

DESIGN AND APPLICATIONS

Using Rogowski coils for transient current measurements, D.A. Ward and J. La T. Exon, June 1993:
ABSTRACT: In recent years the Rogowski-coil method of measuring electric currentt has developed from a 'laboratory curiosity' to a versatile measuring system with many applications throughout industry and in research. The technique posesses many features which offer an advantage over iron-cored current measuring devices and these are well illustrated by considering how it can be used for measuring transient currents. The paper describes the principle ofoperation of Rogowski coils and the practical aspects of using them and gives several examples of their use in making transient measurements. The Rogowski coil is a conceptually simple device. Its theory of operation illustrates some basic principles of electromagnetism applied in a practical device. The coil itself provides an elegant demonstration of Ampères Law and, because of its inherent linearity, the response of a coil under extreme measuring situations is much easier to treat theoretically than iron-cored measuring instruments. The educational aspects of studying Rogowski coils should not be overlooked. Download PDF


The effect of temperature on the output of a Rogowski coil measuring system, D. A. Ward, November 2014
ABSTRACT: This paper describes the effect of temperature on measurements made using both rigid and flexible Rogowski coils. Temperature changes affect both types of coil by causing the former material to expand and by changing the resistance of the winding. With rigid coils it is possible to design a measuring system so that these two effects cancel each other out. With flexible coils, which are wound on a rubber-like former, the softness of the former makes the self-cancelling system more difficult to implement.

We describe a theoretical model which attempts to explain the consequences of increasing the temperature of a flexible coil. The effect of temperature on the output of the coil is shown to depend on the relationship between the cross-section of the wire used for the winding and the cross-section of the 'return conductor' along the centre of the coil. The theory has been compared with actual measuremkents on a range of different coil designs and shows broad agreement. Whilst the theoretical model suggests how a coil could be designed to minimise temperature effects there are other practical constraints which have to be taken into consideration and the paper also considers these. Download PDF



The effect of some winding defects on the output of a Rogowski coil Part 1 - Basic theory and concepts,
D. A. Ward, March 2017
ABSTRACT: An ideal, perfectly wound, Rogowski coil should respond only to currents which thread the coil. It should not matter if the current-carrying conductor is off-axis or threads the coil obliquely. Furthermore the coil should have zero response to electric currents and other sources of magnetic fields which are external to the loop of the coil. These properties follow as a consequence of Ampères Law.
In a 'real' coil there are inevitably winding defects and the ideal properties described above cannot be achieved in practice. This paper describes a simple method of determining how winding defects can affect the performance of a coil. The method can be used for accurate calculations as well as providing a method of making qualitative estimates without the need for mathematical analysis.
For de-mountable coils, such as flexible coils and split-rigid coils, the most significant potential defect is the inevitable gap in the winding where the coil is opened so that it can be placed round the conductor. The method described for calculating the effect of winding defects, such as a gap, is illustrated by a number of examples and is compared with actual measurements on coils. Download PDF

The effect of some winding defects on the output of a Rogowski coil Part 2 - Real Coils,
D. A. Ward, September 2018
ABSTRACT: In a previous Note the basic concepts relating to a gap in the winding of an otherwise perfect coil were discussed for the special case where the plane of the coil is perpendicular to the conductor. This Note looks at some more practical aspects. Methods are described for minimising the effect of the gap in the winding of a flexible coil where the ends are joined. It is also shown how other winding defects such as bumps or hollows in the coil former can be evaluated. The concepts involved when a coil is not oriented perpendicular to the conductor are also discussed. Download PDF

Dealing with droop,
D. A. Ward, June 2017
SUMMARY This Note discusses the low-frequency behaviour of Rogowski coil current-measuring systems when they are used for transient measurements. In the case of continuous currents the low-frequency limitations cause phase and amplitude errors. For transient measurements they cause a droop effect where, at the end of the transient, the output of the measuring system does not return to zero even though the current being measured is zero. The droop effect is mainly determined by the design of the integrator. A theoretical analysis is given for droop in both passive and active integrators. The constraints which apply in designing integrators to reduce the magnitude of the effect are described.
Finally it is shown how a measured wave-form can be 'corrected' to compensate for the droop. Download PDF

 
 FURTHER INFORMATION  
 More about flexible coils  Download PDF file
 Specification 1000 Series Coils  Download PDF file
 Specification 4000 Series Coils  Download PDF file
  Specification Rigid Coils  Download PDF file
  Comparison with other current measurement methods  Download PDF file

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