A good faith effort has been made to make the information contained in this site
accurate and complete. However, there is the possibility of misstatements and misinterpretations.
If errors are found, they will be corrected immediately. The information contained
in this site is only the first step toward a formal agreement. Please see our terms
and conditions for more information.
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
Current Measurement Technologies
Several instruments that measure electrical currents are available but most or all
of them have deficiencies. Current transformers are the most widely used AC (only)
instruments but they major limitations and significant power losses that have prompted
several other current sensors designs to be developed. The Rogowski coil was one
of the first alternatives to gain a spot in power system measurements but it also
only measures AC current and none of the countless design variations despite claims
to the contrary have overcome that flaw. After decades of development, fiber optic
systems based on the magneto-optic effect are being sold but seem best suited to
measure high DC currents used in aluminum smelting and arc furnaces.
This website introduces another method of measuring current based on the Bio- Savart
law of magnetic's. The magnetic flux surrounding a conductor is concentrated by
very high permeability Nickel-Iron alloy to a density that can be accurately measured
by Hall Effect Devices. The flux density is proportional to the conductor current
and the relationship is linear for AC, DC , and transients including the important
asymmetrical currents cause by power system faults. This arrangement is called a
magnetic field current sensor or MFCS.
Measuring Transformer Losses
Transformer Loss Measuring System
Power transformers load and no load loss tests require high precision instrumentation
and frequent calibration checks to insure accurate measurements. Current transformers
with electronic flux compensation can be used to measure current accurately but the
cost is very high. A cost effective alternative is used in the above installation.
Magnetic field currents sensors (MFCS) are installed around the inside end of the
bushings (see arrow). The accuracy depends on the calibration which can be done
in situ and portable calibrators are available that can inject know currents with
no disassembly. Accuracy can be demonstrated and testing resumed in a few hours.