What is the Rogowski coil?
The Rogowski coil is a flexible clip-on hybrid inductor coil that can be easily coiled around a current conductor for measuring. It is capable of measuring large currents of several thousand amperes without expanding the size of the voltage transformer. Rogowski coils are electronic voltage transformers used to measure alternating currents such as fast transients, single-pulse currents of power electronic devices, or sine function currents of power plugs at 50 or 60 Hz. If you are dealing with AC currents in the tens of amps and hoping to measure current flexibly, consider using the current probe of Rogowski coil .
The principle of Rogowski coil
The Rokowski coil is similar to the AC voltage transformer. Its operating voltage is directed to the second coil and is positively correlated with the current through the insulated conductor on shuch point. The obvious difference is that the Rogowski coil has a hollow core, which is opposite to the current-voltage transformer, using a high-permeability steel core to achieve magnetic coupling with a second winding. The hollow core adopts the design scheme of lower insertion impedance to complete fast data signal response and linear data signal working voltage.
An air core coil is placed in a loop around a current-carrying electrical conductor, and the electromagnetic field caused by the alternating current senses a voltage in the coil. The Rogowski coil is converted into a working voltage that is positively correlated with the current elastic coefficient (derivative function) in the coil loop. After that, the working voltage of the coil is fused, so that the Rogowski coil probe can give an output voltage proportional to the input current data signal. The Rogowski coil is converted into the working voltage that is positively correlated with the current elastic coefficient (derivative function) in the coil loop.
Advantages of Rogowski coil probes
Current probes of Rogowski coil have many advantages overdifferent types of current sensor or magnetic induction technology.
–High current measurement without core saturation.Rogowski coils can measure large currents (in the range from several mA to several kA) without core saturation, because the Rogowski coil probe uses a non-magnetic “hollow” core. The limit of the measurable current is limited by the maximum input voltage of the measuring instrument or by the operating voltage collapse limit of the coil/integrator circuit element. Other current sensors will become heavier with the increase in the range of the measured current. The Rogowski coil can maintain the same small volume because it is independent of the current to be measured, which makes the Rogowski coil become the most effective and apecific tool for measuring hundreds or even thousands of amps of AC current.
–Flexible application, the light-shaped and ball–broken sensor coil is flexible in application, and can easily encapsulate the current-carrying electrical conductor. It can be inserted into inaccessible components within the power circuit. Most Rogowski coils are slim enough to fit between the legs of a T0-220 or TO-247 output power semiconductor package without the need for additional coils to connect current probes. This also guarantees the advantage of the coil for integrity measurements of high signal.
–Maximum network bandwidth >30MHz. This enables Rogowski coils to measure current data signals with very fast transition rates – such as data signals in the thousands of A/µsec. The bandwidth test feature allows data analysis of advanced harmonic currents in systems operating at high power switching frequencies, or precise monitoring of power switching waveforms with faster rises or rises.
–Non-invasive or high quality measurements. Because of their low insertion characteristic impedance, the Rogowski coil draws very little current from the machine under test. The characteristic impedance introduced into the equipment under test due to Rogowski coil probes is only a few ohms, so this type of coil is suitable for faster data signal response and very linear data signal operating voltage.
–Low cost. Comparing with Hall effect sensor/voltage transformer coil current probes, Rogowski coils are less expensive. Its lightweight, sandwich-type sensor coils are flexible and can easily encapsulate current-carrying electrical conductors.
Rokowski coil current limiting
–Only for AC current. Rogowski coil cannot deal with DC current, its coil is only suitable for communicating AC current.
–Sensitivity. Comparing to current transformer, Rogowski coils are less sensitive than current transformers due to lack of high magnetization cores.
Digital oscilloscope current probes allow digital oscilloscopes to measure current, extending their primary use beyond measuring operating voltage. For the most part, Rogowski coil current probes magnetically induce current flow in electrical conductors and convert the current into an operating voltage that the probe can query and measure on a digital oscilloscope. The most common method of current measurement is the magnetic induction of an electromagnetic field into an energized electrical conductor.
