© FRS Consulting-Messerstrom 2014
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Request For Proposal
Please Contact Us to buy, lease or invest in the technology to measure current as described in this site. Additional development is required and the amount of time and cost involved depends on the expertise and resources devoted to accomplishing that goal. Please see our request for proposal for more information.
Beta Ver 4/19/2014
Applications - Field Plots - Accuracy - Testing
The magnetic field current sensor (MFCS) is a precision instrument that requires careful design, construction and operation to provide high quality current measurements in critical applications. It is very rugged and no level of over current alone will cause physical damage or affect performance after the fault is cleared. The ability to measure nearly any transient event including high speed polarity switching of DC currents with clean noise free signals sets it apart from all other current measuring systems.
Two instruments for measuring high voltage conductor current have been constructed and tested. A transformer loss measuring system supplied with MFCS elements has been installed and commissioned with no significant problems. A 115-kV high voltage current transformer has also been constructed with the MFCT system. It has been given high pot tests and is available for further evaluation.
The operation of the MFCS is described in detail using magnetic field plots generated by FEM software. Processing of the signals is performed by circuits on a small PCB. Analysis and presentation of the results can be done with custom software. Calibrations to very high levels of accuracy readily performed.
115-kV MFCT HVCT
Rated 15 A to 1800 A
Reliable measurement of current in high voltage conductors is an on- going challenge. Inaccurate inform- ation from HVCTs cause relay mal- function that damages expensive equipment or causes lost revenue from unnecessary power outages. MFCSs are smaller, lighter and less expensive than iron core transformers and they can capture assymetrical transients.
How to Build An AC/DC/Transient Ammeter
How A Magnetic Field Current Sensor Works
Flux density measurements of the magnetic field around a current carrying conductor can be used to quantify the waveform of the current when a few conditions are met. As long as the conductor is straight for a sufficient distance, well centered in the measuring structure, and free of materials that can be magnetized, there is a linear relationship between the magnetic field strength (H) and the flux density (B). Non-Magnetic Conductive materials concentric with the measuring structure enhance the measurements if they are at a greater distance than where the B field is measured and have the opposite effect if they are inside the circle where the sensor are located.
Strictly speaking the electro-magnetic laws (Biot-Savart) are only for steady current but they actually work very well for a broad range of time varying currents. The justification for this is the “quasistatic approximation” that is applicable for currents in conductors as long as the speeds of the mobile electrons are small compared to the velocity of light.