Monitoring power-related parameters in a power distribution unit

• US 8,694,272 B2
• Filed: 11/27/2012
• Issued: 04/08/2014
• Est. Priority Date: 03/04/2009
• Status: Active Grant

• Current Assignee: Server Technology Incorporated (Legrand SA)
• Original Assignee: Server Technology Incorporated (Legrand SA)
• Inventors: Ewing, Carrel W., Maskaly, James P., Auclair, Brian P., McGlumphy, Dennis W.
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US13/686,685
• Publication Number:
  US 20130090869A1
• Time in Patent Office: 497 Days
• Field of Search: 702/60
• US Class Current: 702/60
• CPC Class Codes: G01R 21/005 Measuring apparent power
• CPC Class Codes: G01R 21/006 Measuring power factor
• CPC Class Codes: G01R 21/10 by using square-law characteristics of circuit elements, e.g. diodes, to measure power absorbed by loads of known impedance G01R21/02 takes precedence
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: G06F 2200/261 PC controlled powerstrip
• CPC Class Codes: H01R 25/006 the coupling part being secured to apparatus or structure, e.g. duplex wall receptacle
• CPC Class Codes: H02B 1/011 Open support bases
• CPC Class Codes: H04Q 2209/60 for transmitting utility meters data, i.e. transmission of data from the reader of the utility meter
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 2209/84 Measuring functions
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A power distribution unit (PDU) disposable in an electrical equipment rack. The PDU has a housing, a power input penetrating the housing, outlets in the housing, a processor disposed in the housing, voltage and current sensors, and a voltage calculation procedure communicable with the processor. The processor samples voltage and current waveforms and calculates RMS values and other power parameters. A method of managing electrical loads each drawing electrical power from a PDU includes repeatedly sampling voltage across and current flowing through each of the loads, calculating raw RMS values of voltage and current, and scaling the raw RMS values to obtain corrected RMS voltage and current values and other power parameters.

Claims

1. A power distribution unit comprising:

a power distribution unit housing disposable in an electrical equipment rack of the type in which a plurality of electrical components are removably mountable;

a power input penetrating the housing;

a voltage sensor;

a plurality of power outputs disposed in the housing, each in electrical communication with the power input and each connectable to an electrical load;

a plurality of current sensors each in electrical communication with one of the power outputs to sense current through each of the plurality of the power outputs, the plurality of current sensors disposed within the housing; and

a power monitoring section in electrical communication with the voltage sensor and the current sensors and responsive to signals provided by the sensors to (1) sample the signals to obtain samples of voltage and current at each of the plurality of power outputs during one cycle of input power, (2) calculate raw RMS values of voltage and current from the samples, and (3) scale the raw RMS values according to a predetermined calibration factor to obtain corrected RMS voltage and current values for the load connected to each power output.

2. A power distribution unit as in claim 1 wherein the power distribution unit housing is adapted for mounting within an electrical equipment rack in a vertical orientation.

3. A power distribution unit as in claim 1 and further comprising a numeric display.

4. A power distribution unit as in claim 3 wherein the voltage sensor, the current sensors, the numeric display and the power monitoring section are disposed in the power distribution unit housing.

5. A power distribution unit as in claim 1 wherein the power monitoring section stores the samples of voltage and current.

6. A power distribution unit as in claim 1 wherein the power monitoring section stores the corrected RMS voltage and current values.

7. A power distribution unit as in claim 1 wherein the power monitoring section calculates for each load at least one of average active power, average apparent power, power factor, and input current crest factor.

8. A power distribution unit as in claim 1 wherein the power monitoring section calculates a phase angle between the voltage across and the current flowing through each load.

9. A power distribution unit as in claim 1 wherein the power monitoring section calculates energy consumed over an interval longer than one cycle of input power by each load.

10. A power distribution unit as in claim 1 wherein the power monitoring section comprises an analog-to-digital converter (ADC) in electrical communication with the voltage sensor and the current sensors, processing logic in electrical communication with the ADC, and a memory in electrical communication with the processing logic.

11. A power distribution unit as in claim 10 wherein samples of voltage and current obtained over more than one cycle of input power are stored in the memory.

12. A power distribution unit as in claim 11 wherein the processing logic compares samples of voltage and current obtained with respect to one of the loads during a first voltage cycle with samples of voltage and current obtained with respect to the same load during a second voltage cycle and generates an alert signal if there is a difference of predetermined magnitude therebetween.

13. A power distribution unit as in claim 10 and further comprising, stored in the memory, model samples of voltage and current representing one of the loads.

14. A power distribution unit as in claim 13 wherein the processing logic compares the model samples with samples obtained with respect to the same load during a voltage cycle and generates an alert signal if there is a difference of predetermined magnitude therebetween.

15. A power distribution unit as in claim 1 and further comprising a timing sensor in electrical communication with the power input and the power monitoring section.

16. A power distribution unit as in claim 15 wherein the power monitoring section is responsive to the timing sensor to calculate a frequency of the input power.

17. A power distribution unit as in claim 16 wherein the power monitoring section uses the calculated frequency to compensate for errors in an internal processor time base.

18. A power distribution unit as in claim 15 wherein the power monitoring section is responsive to the timing sensor to calculate a reload value and to use the reload value to determine sampling intervals for sampling the voltage and current.

19. A power distribution unit as in claim 1 and further comprising a communication section for establishing communication between the power monitoring section and a remotely located network power manager.

20. A power distribution unit as in claim 1 wherein the power distribution unit housing is adapted for mounting within an electrical equipment rack in a horizontal orientation.

21. A power distribution unit comprising:

a power distribution unit housing disposable in an electrical equipment rack in which a plurality of electrical components are removably mountable;

a power input penetrating the housing;

a plurality of power outputs disposed in the housing to distribute power to the plurality of electrical components;

a voltage sensor communicable with the power outputs;

a plurality of current sensors each communicable with one of the power outputs to detect current flow through each of the power outputs;

a processor disposed in the housing and communicably coupled to the voltage sensor and to the plurality of current sensors; and

a memory associated with the processor and configured to store at least one of;

historic voltage waveform data,

historic current waveform data, and

historic power metric data other than the historic voltage waveform data and historic current waveform data,

the processor configured to determine or receive a corresponding at least one of;

present voltage waveform data from the voltage sensor,

present current waveform data from the current sensors, and

present power metric data other than the present voltage waveform data and the present current waveform data,

the processor configured to compare at least one of;

magnitudes of the historic voltage waveform data to magnitudes of the present voltage waveform data,

magnitudes of the historic current waveform data to magnitudes of the present current waveform data, and

the historic power metric data to the present power metric data,

wherein the historic voltage waveform data and the historic current waveform data exclude the present voltage waveform data and the present current waveform data, wherein the processor generates a notification if the voltage comparisons, the current comparisons, or the other power metric comparisons exceed associated predetermined thresholds.

22. A power distribution unit as in claim 21 and further comprising a storage unit communicable with the processor.

23. A power distribution unit as in claim 21 wherein the power distribution unit housing is adapted for mounting within an electrical equipment rack in a vertical orientation.

24. A power distribution unit as in claim 21 and further comprising a numeric display.

25. A power distribution unit as in claim 24 wherein the voltage sensor, the current sensors, and the numeric display are disposed in the power distribution unit housing.

26. A power distribution unit as in claim 21 wherein the historic and present power metric data include one or more of:

an RMS calculation, an average active power calculation, an average apparent power calculation, a power factor calculation, an input current crest factor calculation, a voltage-to-current phase angle calculation, and an energy usage calculation.

27. A power distribution unit as in claim 21 wherein the processor comprises an analog-to-digital converter and an arithmetic logic unit.

28. A power distribution unit as in claim 21 and further comprising a timing sensor communicable with the power input.

29. A power distribution unit as in claim 21 and further comprising a communication section communicable with the processor and with a communication network external of the housing.

30. A power distribution unit as in claim 21 wherein the power distribution unit housing is adapted for mounting within an electrical equipment rack in a horizontal orientation.

31. A method of managing a plurality of electrical loads each drawing electrical power from a power distribution unit, the method comprising:

sampling, with a plurality of sensors disposed within the power distribution unit, voltage across and current flowing through each of the loads repeatedly during one cycle of input power;

calculating, with a processor disposed within the power distribution unit, raw RMS values of voltage and current from the samples;

scaling, with the processor, the raw RMS values according to a predetermined calibration factor to obtain corrected RMS voltage and current values for each of the loads;

storing model samples of voltage and current representative of one of the loads;

comparing the stored model samples with samples of voltage and current obtained with respect to the same load during the one cycle of input power; and

generating an alert signal if there is a difference of a predetermined magnitude therebetween.

32. A method as in claim 31 and further comprising storing the samples of voltage and current.

33. A method as in claim 32 wherein storing the samples comprises storing samples of voltage and current obtained over more than one voltage cycle.

34. A method as in claim 31 and further comprising storing the corrected RMS voltage and current values.

35. A method as in claim 31 and further comprising calculating for each load at least one of average active power, average apparent power, power factor, input current crest factor, phase angle between voltage across and current flowing through the load, and energy consumed over an interval longer than one cycle of input power by the load.

36. A method as in claim 31 and further comprising:

comparing samples of voltage and current obtained with respect to one of the loads during a first voltage cycle with samples of voltage and current obtained with respect to the same load during a second voltage cycle; and

generating an alert signal if there is a difference of predetermined magnitude therebetween.

37. A method as in claim 31 and further comprising sensing a zero crossing of a cycle of input power.

38. A method as in claim 37 and further comprising calculating a frequency of the input power.

39. A method as in claim 38 and further comprising compensating an internal time base according to the frequency.

40. A method as in claim 37 and further comprising calculating a reload value;

and determining sampling intervals for sampling the voltage and current according to the reload value.

41. A method as in claim 31 and further comprising communicating the corrected RMS voltage and current values to a remotely located network power manager.