Monitoring power-related parameters in a power distribution unit

Patent metadata

Field	Value
Publication number	US-9952261-B2
Application number	US-201414247900-A
Country	US
Kind code	B2
Filing date	Apr 8, 2014
Priority date	Mar 4, 2009
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

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.

First claim

We claim:

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 mountable;
a power input penetrating the housing configured to provide an alternating current (AC) power input to a plurality of power outputs;
the plurality of power outputs disposed in the housing, each in electrical communication with the power input and each connectable to an electrical load;
a voltage sensor for sensing a voltage at the power input or at one of the plurality of power outputs;
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 current sensors and the voltage sensor to calculate energy with respect to at least one of the plurality of power outputs, wherein:
the energy that is calculated corresponds to an interval longer than one cycle of AC input power, and
the energy is calculated by accumulating instantaneous power values, obtained by multiplying a voltage value sensed by the voltage sensor with a current value sensed by at least one of the plurality of current sensors, over the interval.

2. The 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. The power distribution unit as in claim 1 and further comprising a numeric display.

4. The 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. The 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.

6. The 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.

7. The 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.

8. The power distribution unit as in claim 7 wherein samples of voltage and current obtained over more than one cycle of AC input power are stored in the memory.

9. The power distribution unit as in claim 8 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.

10. The power distribution unit as in claim 7 and further comprising, stored in the memory, model samples of voltage and current representing one of the loads.

11. The power distribution unit as in claim 10 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.

12. The 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.

13. The power distribution unit as in claim 12 wherein the power monitoring section is responsive to the timing sensor to calculate a frequency of the AC input power.

14. The power distribution unit as in claim 13 wherein the power monitoring section uses the calculated frequency to compensate for errors in an internal processor time base.

15. The power distribution unit as in claim 12 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.

16. The 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.

17. The 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.

18. The power distribution unit as in claim 1 wherein the calculation comprises (1) computing the product of an instantaneous voltage and an instantaneous current for the at least one output and (2) integrating the computed product over an interval longer than one cycle of AC input power.

19. The power distribution unit as in claim 18 wherein the calculation is performed with respect to each of the plurality of power outputs.

20. The power distribution unit as in claim 1 wherein the energy consumed is calculated with respect to each of the plurality of power outputs.

21. The power distribution unit as in claim 1 wherein the power monitoring section (1) samples the signals to obtain samples of voltage and current at each of the plurality of power outputs during one cycle of AC input power, (2) calculates raw RMS values of voltage and current from the samples, and (3) scales 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.

22. The power distribution unit as in claim 21 wherein the power monitoring section stores the samples of voltage and current.

23. The power distribution unit as in claim 21 wherein the power monitoring section stores the corrected RMS voltage and current values.

24. The power distribution unit as in claim 1 wherein the energy calculation includes:
measuring a first time from a first source and a second time from a second source; and
upon determining a discrepancy between the first time and the second time, verifying the energy calculations.

25. The power distribution unit as in claim 24 wherein the first source and the second source are a microcontroller and a network controller.

26. The power distribution unit as in claim 1 wherein the energy calculation includes:
measuring a first time from a first source and a second time from a second source;
upon determining a discrepancy between the first time and the second time, adjusting the energy calculations with a correction.

27. The power distribution unit as in claim 26 wherein the first source and the second source are a microcontroller and a network controller.

28. A method of managing a plurality of electrical loads each drawing electrical power from a power distribution unit, the method comprising:
providing an alternating current (AC) power input to at least one of the plurality of loads;
receiving, from one or more sensors disposed within the power distribution unit, one or more signals corresponding to voltage across and current flowing through at least one of the plurality of loads o

Assignees

• Server Tech Inc

Inventors

• Ewing Carrel W
• Maskaly James P
• Auclair Brian P
• Mcglumphy Dennis W

Classifications

• H02B1/011

  Open support bases · CPC title

• G06F2200/261

  PC controlled powerstrip · CPC title

• G01R21/005

  Measuring apparent power · CPC title

• G01R35/005

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title

• H04Q2209/84

  Measuring functions · CPC title