Power measurement in a two-wire load control device

Patent metadata

Field	Value
Publication number	US-9250669-B2
Application number	US-201313793308-A
Country	US
Kind code	B2
Filing date	Mar 11, 2013
Priority date	Sep 14, 2012
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

A two-wire load control device may be configured to compute an accurate estimate of real-time power consumption by a load that is electrically connected to, and controlled by, the two-wire load control device. The load control device may be adapted to measure a voltage drop across the device during a first portion of a half-cycle of an AC waveform provided to the device. The device may be further configured to estimate a voltage drop across the load during the second portion of the half-cycle. The estimated voltage drop may be based on the measured voltage drop. The device may be further configured to measure a current supplied to the load during a second portion of the half-cycle. The device may be configured to estimate power consumed by the load based on the measured current and the estimated voltage drop.

First claim

What is claimed:

1. A two-wire load control device for controlling an amount of power delivered from an AC power source to an electrical load, the load control device comprising:
a controllably conductive device that operates in a non-conductive state during a first portion of a half-cycle of an alternating current (AC) waveform and in a conductive state during a second portion of the half-cycle;
a voltage measuring circuit that measures a voltage across the two-wire load control device during the first portion of the half-cycle;
a signal generator that generates a complementary voltage waveform that approximates a voltage across the load during the second portion of the half-cycle, wherein the complementary voltage waveform is based on the voltage measured across the two-wire load control device during the first portion of the half-cycle;
a current measuring circuit that measures a current supplied to the load from the two-wire load control device during the second portion of the half-cycle; and
a control circuit that computes an estimated amount of power consumed by the load based on the complementary voltage waveform and the current supplied to the load during the second portion of the half-cycle.

2. The two-wire load control device of claim 1 , wherein the voltage measuring circuit comprises a voltage divider.

3. The two-wire load control device of claim 1 , wherein the current measuring circuit comprises a micro-ohm resistor.

4. The two-wire load control device of claim 1 , wherein the control circuit is configured to report the estimated amount of power consumed by the load.

5. The two-wire load control device of claim 4 , further comprising a communication circuit, wherein the control circuit is configured to report the estimated amount of power consumed by the load via the communication circuit.

6. The two-wire load control device of claim 4 , wherein the control circuit is configured to periodically report the estimated amount of power consumed by the load.

7. The two-wire load control device of claim 4 , further comprising a user interface having a display, wherein the control circuit is configured to report the estimated amount of power consumed by the load via the display.

8. The two-wire load control device of claim 1 , wherein the complementary voltage waveform comprises a step-sine wave.

9. The two-wire load control device of claim 1 , wherein the complementary voltage waveform comprises a square wave.

10. A two-wire load control device for controlling an amount of power delivered from an AC power source to an electrical load, the load control device comprising:
a controllably conductive device that operates in a non-conductive state during a first interval of a half-cycle of an alternating current (AC) waveform and a conductive state during a second interval of the half-cycle; and
a control circuit adapted to:
measure a voltage across the two-wire load control device during a first portion of the half-cycle;
compute an estimated voltage across the load during a second portion of the half-cycle based on the voltage measured across the two-wire load control device during the first interval of the half-cycle;
measure a current supplied to the load during the second portion of the half-cycle; and
compute, based on the estimated voltage and the measured current, an estimated power consumed by the load during the second portion of the half-cycle.

11. The two-wire load control device of claim 10 , wherein the controllably conductive device operates in the non-conductive state during the first portion of the half-cycle and in the conductive state during the second portion of the half-cycle.

12. The two-wire load control device of claim 10 , wherein the control circuit is further adapted to report the estimated power consumed by the load via a communication circuit.

13. The two-wire load control device of claim 10 , further comprising a drive circuit that is configured to trigger the controllably conductive device to switch from the non-conductive state to the conductive state at a certain point during the half-cycle.

14. The two-wire load control device of claim 10 , wherein the estimated voltage has a step-sine waveform.

15. The two-wire load control device of claim 10 , wherein the estimated voltage has a square waveform.

16. A two-wire load control device for controlling an amount of power delivered from an AC power source to an electrical load, the load control device comprising:
a controllably conductive device electrically configured to allow an alternating current to be delivered from the AC power source to the load during a portion of a half-cycle of an AC waveform provided from the AC power source to the load control device; and
a control circuit configured to compute an estimated amount of power consumed by the load based on a current supplied to the load during the portion of the half-cycle and an estimated voltage across the load during the portion of the half-cycle.

17. The two-wire load control device of claim 16 , wherein the control circuit is further configured to measure a voltage drop across the two-wire load control device during a portion of the half-cycle during which current is not supplied to the load.

18. The two-wire load control device of claim 17 , wherein the estimated voltage is based on the measured voltage.

19. The two-wire load control device of claim 17 , wherein the measured voltage has a waveform, and the estimated voltage has a waveform that is complementary to the waveform of the measured voltage.

20. The two-wire load control device of claim 19 , wherein the waveform of the estimated voltage comprises a step-sine wave.

21. The two-wire load control device of claim 19 , wherein the waveform of the estimated voltage comprises a square wave.

22. The two-wire load control device of claim 19 , wherein the waveform of the estimated voltage is generated by a signal generator that is in communication with the control circuit.

23. The two-wire load control device of claim 16 , wherein the control circuit is further configured to report the amount of power consumed by the load.

24. A method for estimating power consumption of an electrical load in a load control system, the load control system including a two-wire load control device for controlling an amount of power delivered from an AC power source to the electrical load, the load control device having a controllably conductive device that operates in a non-conductive state during a first portion of a half-cycle of an alternating current (AC) waveform supplied to the two-wire load control device and in a conductive state during a second portion of the half-cycle, the method comprising:
measuring a voltage across the two-wire load control device during the first portion of the half-cycle;
generating a complementary voltage waveform that approximates a voltage across the load during the second portion of the half-cycle, wherein the complementary voltage waveform is based on the voltage measured across the two-wire load control device during the first portion of the half-cycle;
measuring a current supplied to the load from the two-wire load control device during the second portion of the half-cycle; and
computing an estimated amount of power consumed by the load based on the complementary voltage waveform and the current supplied to the load during the second portion of the half-cycle.

25. The method of claim 24 , furt

Assignees

• Lutron Electronics Co

Inventors

• Blakeley Matthew Robert
• Zotter William

Classifications

• G01R21/133

  by using digital technique · CPC title

• G05B15/02

  electric · CPC title

• H05B39/04

  Controlling · CPC title

• G05F1/66 Primary

  Regulating electric power · CPC title

• G06F1/26 Primary

  Power supply means, e.g. regulation thereof (for memories G11C) · CPC title