Monitoring power-related parameters in a power distribution unit

• US 8,321,163 B2
• Filed: 03/04/2010
• Issued: 11/27/2012
• Est. Priority Date: 03/04/2009
• Status: Active Grant

• Current Assignee: Legrand DPC LLC (Legrand SA)
• Original Assignee: Server Technology Incorporated (Legrand SA)
• Inventors: Ewing, Carrel W., Maskaly, James P., Auclair, Brian, McGlumphy, Dennis
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US12/717,879
• Publication Number:
  US 20100280774A1
• Time in Patent Office: 999 Days
• Field of Search: 702/60, 361/622
• 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;

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 a respective electrical load;

a plurality of current sensors, each in electrical communication with one of the power outputs; and

a power monitoring section having 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;

wherein the ADC is responsive to signals provided by the sensors to sample the signals and obtain samples of voltage and current over more than one cycle of input power;

wherein the processing logic is configured to (1) calculate raw RMS values of voltage and current from the samples, (2) scale the raw RMS values according to a predetermined calibration factor to obtain calibrated RMS voltage and current values, and (3) compare samples of voltage and current obtained with respect to at least one of the electrical loads during a first cycle of input power with respective samples of voltage and current obtained with respect to the at least one of the electrical loads during a second cycle of input power and generate an alert signal if there is a difference of at least a predetermined magnitude therebetween; and

wherein the memory stores at least the samples of voltage and current.

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 calibrated RMS voltage and current values.

6. 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.

7. A power distribution unit as in claim 6 wherein the power monitoring section is responsive to the timing sensor to calculate a frequency of the input power.

8. A power distribution unit as in claim 7 wherein the power monitoring section uses the calculated frequency to compensate for errors in an internal processor time base.

9. A power distribution unit as in claim 6 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.

10. 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.

11. 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.

12. A power distribution unit comprising:

a power distribution unit housing;

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 a respective electrical load;

a plurality of current sensors, each in electrical communication with one of the power outputs; and

a power monitoring section having 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;

wherein the ADC is responsive to signals provided by the sensors to sample the signals and obtain samples of voltage and current during a cycle of input power;

wherein the processing logic is configured to (1) calculate raw RMS values of voltage and current from the samples, (2) scale the raw RMS values according to a predetermined calibration factor to obtain calibrated RMS voltage and current values, and (3) compare model waveform samples for at least one of the electrical loads with respective samples obtained with respect to the one of the electrical loads during the cycle of input power and generate an alert signal if there is a difference of at least a predetermined magnitude therebetween;

wherein the memory stores at least the samples of voltage and current.

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

sampling voltage across and current flowing through each of the electrical loads repeatedly during a cycle of input power;

calculating raw RMS values of voltage and current from the samples;

scaling the raw RMS values according to a predetermined calibration factor to obtain calibrated RMS voltage and current values for each of the electrical loads; and

comparing samples of voltage and current obtained with respect to at least one of the electrical loads during a first cycle of input power with respective samples of voltage and current obtained with respect to the at least one of the electrical loads during a second cycle of input power, and generating an alert signal if there is a difference of at least a predetermined magnitude therebetween.

14. A method as in claim 13 and further comprising storing the samples of voltage and current.

15. A method as in claim 14 wherein storing the samples comprises storing samples of voltage and current obtained over more than one cycle of input power.

16. A method as in claim 13 and further comprising storing the calibrated RMS voltage and current values.

17. A method as in claim 13 and further comprising calculating for each electrical 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 electrical load, and energy consumed over an interval longer than one cycle of input power by the electrical load.

18. A method as in claim 13 and further comprising sensing a zero crossing of a cycle of input power.

19. A method as in claim 18 and further comprising calculating a frequency of the input power.

20. A method as in claim 19 and further comprising compensating an internal time base according to the frequency.

21. A method as in claim 18 and further comprising calculating a reload value;

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

22. A method as in claim 13 and further comprising communicating the calibrated RMS voltage and current values to a remotely located network power manager.

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

sampling voltage across and current flowing through each of the electrical loads repeatedly during a cycle of input power;

calculating raw RMS values of voltage and current from the samples;

scaling the raw RMS values according to a predetermined calibration factor to obtain calibrated RMS voltage and current values for each of the electrical loads; and

comparing model waveform samples for at least one of the electrical loads with respective samples of voltage and current obtained with respect to the at least one of the electrical loads during the cycle of input power, and generating an alert signal if there is a difference of at least a predetermined magnitude therebetween.

24. A power distribution unit comprising:

a power distribution unit housing;

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 a respective electrical load;

a plurality of current sensors, each in electrical communication with a respective one of the power outputs; and

a power monitoring circuit in electrical communication with the voltage sensor and the current sensors and responsive to signals provided by the sensors to generate and compare samples of voltage and current obtained with respect to at least one of the electrical loads during a first cycle of input power with respective samples of voltage and current obtained with respect to the at least one of the electrical loads during a second cycle of input power and generate an alert signal if there is a difference of at least a predetermined magnitude therebetween.

25. A power distribution unit as in claim 24 wherein the power monitoring circuit stores the samples of voltage and current.

26. A power distribution unit as in claim 24 wherein the power monitoring circuit calculates for each electrical load at least one of average active power, average apparent power, power factor, and input current crest factor.

27. A power distribution unit as in claim 24 wherein the power monitoring circuit calculates a phase angle between the voltage across and the current flowing through each electrical load.

28. A power distribution unit as in claim 24 wherein the power monitoring circuit calculates energy consumed by each electrical load over an interval longer than one cycle of input power.

29. A power distribution unit as in claim 24, wherein the power monitoring circuit comprises a processor to compare said samples.

30. A power distribution unit comprising:

a power distribution unit housing;

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 a respective electrical load;

a plurality of current sensors, each in electrical communication with a respective one of the power outputs; and

a power monitoring circuit in electrical communication with the voltage sensor and the current sensors and responsive to signals provided by the sensors to generate and compare samples of voltage and current obtained with respect to at least one of the electrical loads during a cycle of input power with respective model waveform samples for the at least one of the electrical loads and generate an alert signal if there is a difference of at least a predetermined magnitude therebetween.

31. A power distribution unit as in claim 30, wherein the power monitoring circuit comprises a processor to compare said samples.