Patent ID: 9678113
Date: 2017-06-13
CPC Classifications: G01R,H01F,H02M,Y02B,Y04S

Claim:
1. An apparatus comprising: at least one analog section comprising a current transformer comprising a transformer core configured to mount around an alternating current (AC) power line making it a primary winding of the current transformer, the analog section for harvesting energy from a secondary winding wound around the transformer core, and storing it for use by components of the apparatus, a switch for connecting the secondary windings terminals between sampling of a current by a sense resistor and harvesting energy, and a resonance capacitor coupled in parallel to the secondary winding of the current transformer to resonate with the secondary winding inductance at a primary frequency, the resonance capacitor's value being selected so that maximum resonance is achieved at low primary currents; a microcontroller coupled to the at least one analog section to receive harvested energy, to at least an analog signal responsive to the alternating current in the AC power line by the sense resistor, and to at least the switch, wherein the microcontroller is configured to control the switch to connect the secondary windings terminals between sampling of a current by a sense resistor and harvesting energy; a memory coupled to the microcontroller; and a transmitter enabled to periodically transmit, under the control of the microcontroller, information responsive to the power consumption of a load connected to the power line; wherein the current through the AC power line, when present, being of a fixed frequency; wherein the current flowing through a circuit breaker connected to the AC power line ranges from a maximum current to low currents and is the fixed frequency of the current flowing though the AC power line; and wherein the resonance capacitor's value being selected to achieve resonance at the fixed frequency of the current flowing through the circuit breaker, at a low range of current through the circuit breaker, and at a low non-linear range of a magnetization curve of the transformer core.