Smart current transformer system
A smart current transformer for determining primary current or power consumption, by stepping down the primary current to a secondary current for subsequent measurement by a connected meter. The current transformer is provided with a connected non-volatile memory for storing calibration data (and optionally identification data) regarding that particular current transformer. The calibration data can include the gain error and/or phase delay for the current transformer, as determined from prior calibration testing of the current transformer. The calibration data may be communicated to or otherwise determined by the meter, and used to calibrate the measurement of the secondary current, in order to determine the primary current or power consumption. Also disclosed is a system and method utilizing such a smart current transformer.
1. A device for determining a current or power consumption at a primary wire, the device comprising:
a current transformer, having a turns ratio and provided with a secondary wire, the current transformer adapted to be installed upon the primary wire in order to step-down a primary current at the primary wire to a secondary current at the secondary wire according to the turns ratio; and
a non-volatile memory connected to the current transformer, wherein the non-volatile memory is configured to store calibration data across a range of load currents wherein bytes of a calibration block are mapped to specific calibration values,
wherein the current transformer is connectable to a downstream meter for measuring a measured secondary current or a measured power consumption at the secondary wire, and wherein the current transformer is configured to communicate the calibration data to the meter, in order to calibrate the measured secondary current so as to determine the primary current or to calibrate the measured power consumption so as to determine the power consumption.
2. The device of claim 1 , wherein the non-volatile memory is an EEPROM microchip.
3. The device of claim 1 , wherein the current transformer is provided with an interface connected to the current transformer via the secondary wire, wherein the interface is configured to enable connection of the current transformer with the downstream meter.
4. The device of claim 3 , wherein the non-volatile memory is embedded within the interface.
5. The device of claim 1 , wherein the non-volatile memory is integrated with the current transformer.
6. The device of claim 1 , wherein the current transformer is a clamp-style transformer actuable between an open position and a closed position, wherein in the open position, the current transformer may be installed around the primary wire, and secured upon the primary wire in the closed position.
7. The device of claim 1 , wherein the calibration data includes at least one of: gain error data, phase delay data, and current transformer identification data.
8. The device of claim 7 , wherein the calibration data comprises a range of values according to the primary current.
9. A system for determining current or power consumption at a primary wire, comprising:
a current transformer, having a turns ratio and provided with a secondary wire, the current transformer adapted to be installed upon the primary wire in order to step-down a primary current at the primary wire to a secondary current at the secondary wire according to the turns ratio;
a non-volatile memory connected to the current transformer, wherein the non-volatile memory stores calibration data across a range of load currents, wherein bytes of a calibration block are mapped to specific calibration values; and
a downstream meter in connection with the secondary wire, for measuring at the secondary wire a measured secondary current or a measured power consumption and wherein the current transformer is configured to communicate the calibration data to the meter, in order to calibrate the measured secondary current so as to determine the primary current or to calibrate the measured power consumption so as to determine the power consumption.
10. The system of claim 9 , wherein the non-volatile memory is an EEPROM microchip.
11. The system of claim 9 , wherein the current transformer is provided with an interface connected to the current transformer via the secondary wire, wherein the interface is configured to enable connection of the current transformer with the downstream meter.
12. The system of claim 11 , wherein the non-volatile memory is embedded within the interface.
13. The system of claim 9 , wherein the current transformer is a clamp-style transformer actuable between an open position and a closed position, wherein in the open position, the current transformer may be installed around the primary wire, and secured upon the primary wire in the closed position.
14. The system of claim 9 , wherein the calibration data includes at least one of:
gain error data, phase delay data and current transformer identification data.
15. A method for determining a primary current or a power consumption at a primary wire, comprising:
installing at the primary wire, a device comprising:
a current transformer, having a turns ratio and provided with a secondary wire, the current transformer adapted to step-down the primary current at the primary wire to a secondary current at the secondary wire according to the turns ratio; and
a non-volatile memory connected to the current transformer, wherein the non-volatile memory stores calibration data across a range of load currents, wherein bytes of a calibration block are mapped to specific calibration values;
connecting a downstream meter with the current transformer via the secondary wire,
measuring using the meter a measured secondary current or a measured power consumption at the secondary wire, and
at the meter:
receiving the calibration data, and
calibrating, using the calibration data, the measured secondary current so as to determine the primary current or calibrating the measured power consumption so as to determine the power consumption.
16. The method of claim 15 , wherein the non-volatile memory is an EEPROM microchip.
17. The method of claim 15 , wherein the current transformer is provided with an interface connected to the current transformer via the secondary wire, wherein the interface is configured to enable connection of the current transformer with the downstream meter.
18. The method of claim 17 , wherein the non-volatile memory is embedded within the interface.
19. The method of claim 15 , wherein the current transformer is a clamp-style transformer actuable between an open position and a closed position, wherein in the open position, the current transformer may be installed around the primary wire, and secured upon the primary wire in the closed position.
20. The method of claim 15 , wherein the calibration data includes at least one of: gain error data, phase delay data and current transformer identification data.
21. The method of claim 15 , wherein prior to installing the device, the calibration data for the current transformer is determined, and stored in the non-volatile memory.