Ratio metric current measurement
OwnerJames J. Kinsellainventor
Life of this patent
Estimating the term…
Abstract
The total current flow in a given electric circuit path is estimated by measuring the current in a second parallel current path and applying a ratio of the conductivity of the main and secondary path. Earth leakage current is measured by passing three wires through a toroid so as to detect differential current flow. Each wire is a conduction path wire parallel to each phase cable. The relative harmonic content between the fundamental and higher frequency components of a load current are calculated using a conduction path parallel to the main power cables.
Claims20
A method of monitoring the magnitude of an electric current flowing in a main conducting path of a circuit during the circuit's operation, by continuously sensing only a fraction of the current to be monitored, said method comprising:
- dividing at least a portion of the main conducting path of the circuit into a primary conducting path and a secondary conducting path, the primary and secondary conducting paths being in parallel with one another;
- predetermining a ratio that substantially defines what portion of a current flowing in the main conducting path will flow into the primary conducting path and what portion of the current flowing in the main conducting path will flow into the secondary conducting path;
- coupling a current sensor to the secondary conducting path to continuously sense the magnitude of current presently flowing in the secondary path;
- and
- inferring a total magnitude of current presently flowing in the main conducting path of the circuit based on said sensed magnitude of current, said inferring further comprising:
- determining the magnitude of the current presently flowing in the primary conducting path from the magnitude of the sensed current and the predetermined current ratio;
- and
- adding the determined magnitude of the current presently flowing in the primary conducting path to the sensed magnitude of the current presently flowing in the secondary path.
A method of monitoring the magnitude of a ratio between high-frequency components and a fundamental component of an electric current flowing in a main conducting path of a circuit during the circuit's operation, by continuously sensing only a fraction of the current for which the magnitude is to be monitored, said method comprising:
- dividing at least a portion of the main conducting path of the circuit into a primary conducting path and a secondary conducting path, the primary and secondary conducting paths being in parallel with one another;
- predetermining a nominal magnitude ratio between a plurality of high frequency components and a fundamental component of, the current flowing in the main conducting path;
- coupling a current sensor to the secondary conducting path to continuously sense and output the magnitudes of the high frequency and fundamental components of the current presently flowing in the secondary path;
- processing the output from the current sensor to continuously derive a magnitude ratio for the current presently flowing in the conducting path;
- and
- when the derived magnitude ratio exceeds the nominal magnitude ratio by a predetermined threshold indicating the presence of a fault condition, opening the circuit conducting path to halt operation of the circuit.
A current monitoring apparatus for monitoring the magnitude of an electric current flowing in a main conducting path of a circuit during the circuit's operation, said monitoring circuit sensing only a fraction of the current to be monitored, said circuit comprising:
- a secondary conducting path conductively coupled at two points along the conducting path of the circuit, the portion of the main conducting path of the circuit falling between the two points forming a primary conducting path that is in parallel with the secondary conducting path;
- a current sensor coupled to the secondary conducting path to continuously sense the magnitude of current presently flowing in the secondary path;
- and
- a processing device coupled to an output of the current sensor, wherein the processing device is configured to infer a total magnitude of current presently flowing in the main conducting path of the circuit based on the sensed amount of current and a predetermined ratio that substantially defines what portion of a current flowing in the main conducting path will flow into the primary conducting path and what portion of the current flowing in the main conducting path will flow into the secondary conducting path.
Dependencies are inferred from the claim text.