High primary current saturates the ferrite core materials.
Hysteresis occurs due to magnetization.
Large current handling capacity, more than the other methods shown in this article.
The N depends on the specifications of the transformer. It is a ideal CT transformer with a primary and secondary ratio as 1:N. In the above image, the construction is shown. The measurement is taken across the secondary output. It is Industrial transformer that converts the large value of voltage or current into a much smaller value in its secondary coil. In power distribution or in smart grid, Rogowski coil provides excellent flexibility for current measurements.Ĭurrent Transformer Current Sensing MethodĬurrent transformer or CT is used to sense the current by secondary voltage which is proportional with the current in secondary coil. As Rogowski coil response is very fast over transients or high-frequency sinusoidal waves, it is a good choice to measure high-frequency current transients in the power lines. Rogowski coil provides flexible measuring option. For example, measurement of current in large power modules, especially across the MOSFETs or High power transistors or across the IGBT. Rogowski coil has a wide range of application.
Has low sensitivity than the current transformer.
Temperature compensation is not complex.
Flexibility in handling due to open loop construction.
Safe operation in terms of handling the secondary winding.
It is a good method to detect fast high-frequency current change.
An additional integrator circuit is required for making an output voltage which is proportional to the current. Rogowski coil provides output voltage depending on the rate of current change in the conductor. The Additional circuitry is an integrator circuit. In the above image, the Rogowski coil is shown with additional circuitry. The Rogowski coil is made using a helical shape air core coil and wrapped around the targeted conductor for current measurement. Rogowski coil is named after German physicist Walter Rogowski. Flux Gate current sensing method can also be used in Leakage current measurement, overcurrent detection etc.
Other than this, closed-loop AC and DC current measurement can be easily done by using Flux Gate sensors.
Only suitable for DC or low-frequency AC.įluxgate sensors are used in Solar Inverters to sense the current.
A risk factor increases for voltage or current noise in the primary conductor.
Can measure in a wide range of frequency.
The changes in the current flow can alter the core permeability resulting in the change of inductance across the other coil. There are two coils primary and secondary wrapped around a saturable inductor core. In the above image, the basic construction of a flux gate sensor is shown. Flux Gate sensor uses a saturable inductor but the Hall Effect sensor uses air core. The Hall Effect sensor works similarly to the fluxgate sensor, but there is one difference between them. If the current is high, the inductance become lower, if the current is low, the inductance become high. This change in inductor value is analyzed by the flux gate sensor to sense the current. The permeability of the core is directly proportional to the saturation level, hence the inductance also changes. The saturation level of this inductor is highly sensitive and any internal or external flux density changes the saturation level of the inductor. The inductor core which is used for the fluxgate sensor works in the saturation region. Due to this, Fluxgate sensor is called as Saturable Inductor Current Sensor. Due to this, Smart Grid Monitoring Application also uses a different type of Hall effect sensor to monitor the conductor current.Ī saturable Inductor is the main component for the Fluxgate sensing technique. Many types of linear Hall effect sensor can sense current from several mili-amps to thousands of amperes. Hall Effect sensors are used in clamp meters as well as in many Industrial and Automotive current sensing applications.
Additional circuit requires for useful output.
The sensor drifts and requires compensation.
Can be used in both AC and DC accurately.
Apart from amplifier circuit Hall Effect sensor requires additional circuitry as it is a linear transducer. The output voltage is very low and needs to be amplified to a useful value by using a high gain amplifier with very low noise. During the current sensing process, the current is measured by measuring the magnetic field. The ratio of the output voltage is proportional to the magnetic field. Hall Effect sensor produces an output voltage depending on the magnetic field.