Thermal management of self-powered power sensors
First Claim
1. An apparatus comprising:
- at least one analog section having a current transformer with a transformer core configured to mount around an alternating current (AC) power line making the AC power line a primary winding of the current transformer, the at least one analog section for harvesting energy from a secondary winding wound around the transformer core, and storing harvested energy for use by components of the apparatus and for periodically switching to allow sampling of a current flowing through the current transformer by a sense resistor, wherein a ratio between a first period of time in which the apparatus harvests energy and a total cycle time comprising at least the first period of time plus a second period of time in which the apparatus senses current samples is a duty cycle of the apparatus;
a microcontroller coupled to the at least one analog section to receive harvested energy, to determine at least a value respective of at least an analog signal responsive to the alternating current in the AC power line by the sense resistor, and a time synchronization signal, the time synchronization signal configured to account for an internal drift of a clock of the microcontroller to be smaller than an allowed error in a current to voltage phase measurement;
the microcontroller also repeatedly responsive of at least a current sample which one of a plurality of duty cycles is to be the duty cycle of operation of the apparatus;
a memory coupled to the microcontroller; and
a transmitter enabled to periodically transmit, under the control of the microcontroller, information responsive to power consumption of a load connected to the AC power line that includes at least one of;
the at least the value, or the time synchronization signal;
such that a receiver of the at least the value may use the at least the value for determination of at least an electrical parameter and correction thereof respective of the time synchronization signal.
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Accused Products
Abstract
Apparatus and methods are provided for handling the heating resulting from the operation of a self-powered power sensor (SPPS). The SPPS periodically switches between a sense mode and a harvest mode, each contributing to power dissipation that translates into heat, which may become a safety hazard. A duty cycle that is the ratio between the period in which sensing take place and the total time elapsed between sensing periods defines the duty cycle of the SPPS. In order to prevent overheating of the SPPS it is configured to provide a dynamic duty cycle that is higher for lower currents in the primary power wire and lower, for higher primary currents. This allows for better power dissipation of the SPPS and removing it from operation in unfavorable or dangerous conditions.
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Citations
21 Claims
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1. An apparatus comprising:
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at least one analog section having a current transformer with a transformer core configured to mount around an alternating current (AC) power line making the AC power line a primary winding of the current transformer, the at least one analog section for harvesting energy from a secondary winding wound around the transformer core, and storing harvested energy for use by components of the apparatus and for periodically switching to allow sampling of a current flowing through the current transformer by a sense resistor, wherein a ratio between a first period of time in which the apparatus harvests energy and a total cycle time comprising at least the first period of time plus a second period of time in which the apparatus senses current samples is a duty cycle of the apparatus; a microcontroller coupled to the at least one analog section to receive harvested energy, to determine at least a value respective of at least an analog signal responsive to the alternating current in the AC power line by the sense resistor, and a time synchronization signal, the time synchronization signal configured to account for an internal drift of a clock of the microcontroller to be smaller than an allowed error in a current to voltage phase measurement; the microcontroller also repeatedly responsive of at least a current sample which one of a plurality of duty cycles is to be the duty cycle of operation of the apparatus; a memory coupled to the microcontroller; and a transmitter enabled to periodically transmit, under the control of the microcontroller, information responsive to power consumption of a load connected to the AC power line that includes at least one of;
the at least the value, or the time synchronization signal;such that a receiver of the at least the value may use the at least the value for determination of at least an electrical parameter and correction thereof respective of the time synchronization signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification