Working principle & advantages & disadvantages of Rogowski coil

The working principle of the Rogowski coil is based on Faraday's law, which describes the proportional relationship between the total electromotive force induced in the closed circuit and the time rate of change of the total magnetic flux of the connected circuit.

The rogowski coil is similar to the AC current transformer in that the voltage is directed to the second coil, where it is proportional to the current passing through the insulated conductor. The key difference is that the rogowski coil has a hollow core, which is the opposite of the current transformer, which relies on the high permeability steel core and the second winding to achieve magnetic coupling. The hollow core adopts the design of lower insertion resistance to achieve faster signal response and linear signal voltage.

The hollow core coil is placed in a ring around the conductor with current, and the magnetic field generated by alternating current will induce voltage in the coil. Rogowski coil generates a voltage that is proportional to the rate of change (derivative) of the current in the coil loop. The coil voltage is then integrated so that the probe provides an output voltage proportional to the input current signal.

Advantages of Rogowski coil

– high current measurement without core saturation
– flexible use
– maximum bandwidth > 30 MHz
– non invasive or non-destructive measurement
– low cost

Limitation of Rogowski coil

– AC only - Rogowski coil cannot handle DC current, only AC current is supported.
– sensitivity - compared with current transformer, Rogowski coil has lower sensitivity due to lack of high permeability core.

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