JP2009098060A - Current-measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure and record currents for respective current sensors which are sent from the current sensors disposed in a power supply system and which vary dynamically. <P>SOLUTION: A plurality of sensor units 11 are disposed in a power supply system of IT equipment in a data center. Each of the sensor units 11 comprises an AC current sensor 12 installed in the power supply system; a rectifying part 13 for rectifying the output of the sensor 12; an A/D converter 14 for digitally converting output of the rectifying part 13; and an interface part 15 for sending the output of the A/D converter 14, to a higher-level device. A sensor control unit 21 comprises interface parts 22a-22n for receiving signals from the plurality of sensor units 11; a selection part 23 for selecting signals from the interface parts; a higher-level interface part 24 for receiving instructions and data from the higher-level device and sending data, corresponding to the instructions, to the higher-level device; and a microprocessor 27 for connecting a nonvolatile memory 25 to a clock transmitter 26. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a current measuring apparatus that individually measures and records currents flowing through a plurality of IT devices (servers, network devices, hard disks, etc.) installed in a data center or a machine room in a company.

  In recent years, a plurality of IT devices have been installed in machine rooms in data centers and companies. For example, 200 to 1000 cases (rack) are installed in the machine room of the data center. Various IT devices are mounted per case. In one housing, the feeding system is usually divided into 1/4 housing, 1/2 housing, or housing unit, and it has become necessary to measure the current flowing through the feeding system.

  Previously, it was only necessary to measure the total power consumption of the entire data center, but with the revision of the Energy Conservation Law, regulations for buildings with a total floor area exceeding 2000 square meters have become more restrictive. The need to measure current has arisen.

  In order to measure the current, a means is adopted in which a current sensor is installed in the power feeding system and a signal from the sensor is measured by a measuring instrument. In this case, when there are a plurality of power feeding systems as well as a single sensor, a plurality of current sensors are used. To increase the accuracy by recognizing waveforms from the zero cross point for a plurality of sensors, Circuit is required (see Patent Document 1).

  There is also a measurement of a means for sampling an alternating current waveform and taking out a current signal. Usually, since sampling is performed at a high rate of 20 times or more for one cycle of the alternating current waveform, the sampling time interval is 488 μS. In a second, 2049 samplings are performed (see Patent Document 2).

In addition to the above, when performing sampling, there are some which perform considerable program processing to recognize 50HZ and 60HZ (see Patent Document 3).
JP 2003-254999 A JP 2007-155616 A Japanese Patent Laid-Open No. 11-304852

  In order to measure the current flowing through IT equipment such as a data center as described above, a plurality of current sensors are installed in each power supply system (for example, 30 to 50), and the dynamically changing AC detected by these current sensors is used. It is necessary to process and measure the current simultaneously. However, it is very difficult to process and measure currents from a plurality of sensors at the same time, and even if there is a measuring instrument, it becomes very expensive and economically disadvantageous.

  This is because, unlike the DC current, the AC current itself is a fluctuating current, and therefore it is necessary to always grasp the envelope of the AC current or the effective value for each sensor. As described above, there are several tens of sampling methods for one cycle of AC current. However, if this processing is performed on several tens sensors at the same time by one processing unit, the sampling timing is shifted. There is a problem with difficulty.

  The present invention has been made in view of the above circumstances, and accurately measures and records a current for each dynamically changing current sensor detected and sent by a current sensor installed in several tens or more of a power supply system. An object of the present invention is to provide a current measuring device capable of

  In order to achieve the above object, the present invention provides a plurality of power feeding systems, AC current sensors respectively installed in these power feeding systems, a rectifying unit that rectifies an output detected by the sensors, and an output of the rectifying unit. A plurality of installed current sensor units having an AD conversion unit for digital conversion, an interface unit for sending the output of the AD conversion unit to a host device, and a plurality of interface units for receiving signals from the plurality of installed current sensor units, these Selection unit for selecting a signal from the interface unit, upper interface unit capable of receiving a command and data from the host device and sending data corresponding to the command to the host device, a transmitter for the non-volatile memory and the clock And a current sensor with a microprocessor that calculates and measures the current value from the signal selected by the selector. Characterized in that it consists of a control unit.

  In addition, the current sensor control unit is configured to determine that the frequency of the commercial power source is stable, the program processing of the method utilizing the sampling theorem, that there is no co-divisor for 50HZ and 60HZ, and the current fluctuation speed of the measurement target. Multiple AC currents installed simultaneously using a program that processes sense data from each sensor at a sampling rate of 1 second under the condition that it is at least twice that frequency in terms of frequency, using 1 second or multiples of that time. It is characterized by grasping a dynamically changing current sent from a sensor and measuring and recording a current for each sensor.

  According to the present invention, there is an advantage that a dynamically changing AC current detected and sent by a large number of AC current sensors installed in a large quantity of several tens or more can be accurately measured and recorded for each sensor. is there.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention, in which 11 is a current sensor unit, and a plurality of sensor units 11 are installed in a power supply system of IT equipment such as a data center. These sensor units 11 include a plurality of commercially available AC current sensors 12 installed in the power supply system, a rectifier 13 that rectifies the output of the sensor 12, an AD converter 14 that digitally converts the output of the rectifier 13, It comprises an interface unit 15 that sends the output of the AD conversion unit 14 to a host device (not shown). A smoothing unit may be added behind the rectifying unit 13 as necessary.

  Reference numeral 21 denotes a current sensor control unit. The sensor control unit 21 includes interface units 22a to 22n that receive signals from a plurality of installed sensor units 11, a selection unit 23 that selects signals from the interface units 22a to 22n, A microprocessor for receiving a command and data from a host device (not shown) and sending a data corresponding to the command to the host device, a non-volatile memory 25 and a microprocessor 26 for connecting to a clock 27.

  In the embodiment configured as described above, the frequency of the commercial power source is stable, and the program processing is a method utilizing the sampling theorem, and has no co-divisor for 50HZ and 60HZ. is there.

  Then, the current fluctuation speed of the object to be measured is converted into a frequency, and a program that processes the sense data from each sensor with the number of samplings per second under the condition that it is twice or more of the frequency uses one second or a multiple of that time. At the same time, it grasps dynamically changing currents sent from a plurality of AC current sensors and measures and records the current for each sensor.

  FIG. 2 is an output waveform diagram in which a 50 Hz current that does not change is sensed by the AC current sensor 12 for 1 second. FIG. 3 is a waveform diagram obtained by full-wave rectification using a diode bridge. FIG. 4 is an enlarged waveform diagram of the output of 6 cycles of FIG. 3 (there are 12 peaks for full-wave rectification).

  4, 2, 3, 4, 5 and 6 show the locations and sampling values when sampling 49 times per second. FIG. 5 is a waveform diagram obtained by sampling 49 times per second, which is the same shape as the waveform of one cycle in FIG. In order to obtain the current value, the average value obtained by accumulating 49 sample values and dividing by 49 may be multiplied by a constant.

  1 in FIG. 4 is an example in which the position of the sample start is the first in the waveform. Actually, however, the waveform of one cycle is obtained after 1 second from any position. For example, if sampling is performed 49 times per second from 4 locations, it will reach the 3rd position of the next cycle, which is also equivalent to 1 cycle. This means that in the plurality of current sensor units 11, it is not necessary to be constrained by the sampling start location for the current waveform, and it is only necessary to perform 49 samplings per second for each sensor at equal time intervals. It shows that.

  This method does not require high-speed processing for the microprocessor 27 per current sensor unit 21, and accordingly, processing for a plurality of current sensor units 21 is possible. This embodiment is a method utilizing the fact that the frequency of the commercial power supply is stable. If the number of times of sampling is set to “59” for 60 Hz, the same diagram as for 50 Hz is obtained.

  However, if the same 49 sampling times are used for 60 Hz, it will not be gradually sampled at each shift timing as shown in FIG. 4, but after 1 second, even for a 60 Hz waveform at equal intervals. Sampling will be done. Therefore, in order to obtain the current value, it is only necessary to multiply the average value obtained by accumulating the 49 sampling values and dividing by 49 as in the case of 50 Hz.

However, when the sampling values are arranged in the order of sampling, the same smooth figure can be obtained by rearranging although the waveform does not become smooth as shown in FIG.
FIG. 6 is a waveform diagram showing that the current has changed to 1/2 in one second. FIG. 7 is a waveform diagram obtained by sampling 49 times per second with respect to the current change of FIG. In this case as well, the current value obtained by multiplying the average value obtained by accumulating the 49 sampling values and dividing by “49” is equal to the actual value.

  However, the current change speed cannot be sufficiently tracked unless the current change speed is converted into a frequency and the sampling frequency is twice or more. Here, assuming the current consumption of a general IT device as a measurement target, the frequency of current change is set to 20 HZ or less, and “49” that is twice or more is selected. If the current change frequency is high, a high sampling frequency may be selected.

  The selection condition of the sampling frequency may be a number that is at least twice the frequency of the current change and does not have a common divisor for 50HZ and 60HZ. For example, a prime number can be easily selected because it meets the condition.

Next, the operation of the above embodiment will be described with reference to the processing flowcharts of FIGS. In this case, 32 sensors were used and the number of samplings was “49”.
8 and 9, the recycle counter is set to “0” in step S1, and each write area of the memory corresponding to the current sensors from “0” to “31” is cleared in step S2. Thereafter, the 1/49 second timer is called in step S3, and it is determined in step S4 whether 1/49 second has elapsed. If "YES", the process proceeds to step S5 to set the timer. If “NO” in the step S4, the process returns to the process of the step S3.

  If the timer is set in step S5, "0" is set in the current sensor address register in the process of step S6, and the process of reading the contents of the register is performed in step S7. Thereafter, in step S8, the correction value corresponding to the current sensor at the address is read from the nonvolatile memory, and the current sensor signal at the address is selected in step S9.

  The numerical value and the correction value indicated by the selected signal are added in step S10, and this added value is added to the value read from the writing area of the current sensor in the memory, and overwritten by the process in step S11. Then, the contents of the current sensor address register are read in step S12. Whether the content is “31” or not is determined in step S13. If “NO”, the content of the current sensor address register is written “+1” in step S14, and the process returns to step S7.

  On the other hand, if “YES” in the step S13, the recycle counter is read in a step S15, and it is determined whether or not the numerical value is “49” in a step S16. If “NO”, “+1” is added to the content of the recycle counter in a step S17. After writing, the process returns to step 3. If “YES” in the step S16, the process of a step S18 is performed. The process reads out the data of each current sensor area of the memory for the current sensors of “0” to “31”, divides the value by “49”, and the measurement result area for each current sensor of the memory To finish the process.

  In the above embodiment, when the current sensor unit 11 and the current sensor control unit 21 are connected by a cable, the cable length is long (for example, 100 m) because the digital interface is provided between the units 11 and 21. However, it is possible to prevent mixing of noise and the like that cause an error.

  In this embodiment, 32 sensors are processed by one microprocessor. However, in a method of sampling one cycle at a high speed as in a conventional current sensor, it is less than one digit. Only the sensor can be processed. However, in this embodiment, a plurality of sensors can be processed by the same processor by the method of recognizing the waveform for one cycle. That is, in this embodiment, sampling is performed 49 times per second.

  Conventionally, sampling is performed approximately 2500 times per second, and in order to perform sampling approximately 2500 times for a large number of sensors, it is extremely difficult to realize by switching the sensors and communication processing.

  In the above description, 49 samplings per second have been described. However, if “47”, “49”, “53”, “59”, “61”... On the other hand, even if the waveform at the sampling start time is different, the waveform for one cycle can be recognized for each sensor after 1 second. The waveform can be recognized, that is, the accuracy is high. Thus, in this embodiment, sense data is added and divided by the number of samplings on the premise that the waveform can be recognized.

  When sampling for 1 second with the number as described above, the value of the sensor at the sampling point draws an envelope of the waveform for one cycle for 50 Hz and 60 Hz. Since there is one period, there is an effect that the starting point of sampling does not become a problem.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a current measuring device that individually measures and records currents flowing through a plurality of IT devices (servers, network devices, hard disks, etc.) installed in a data center or a machine room in a company.

The structure explanatory view showing the embodiment of the invention. The output waveform figure which sensed the electric current of 50HZ which does not change for 1 second with the AC current sensor. Waveform diagram after full-wave rectification using a diode bridge. FIG. 4 is a waveform diagram in which outputs for six cycles in FIG. 3 are enlarged. Waveform diagram sampled 49 times per second. The wave form diagram which shows that the electric current changed to 1/2 in 1 second. The wave form diagram sampled 49 times per second with respect to the electric current change of FIG. Processing flowchart. Processing flowchart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Current sensor unit 12 ... AC current sensor 13 ... Rectification part 14 ... AD conversion part 15 ... Interface part 21 ... Current sensor control unit 22a-22n ... Interface part 23 ... Selection part 24 ... High-order interface part 25 ... Non-volatile memory 26 ... Transmitter 27 ... Microprocessor

Claims (2)

A plurality of power supply systems;
An AC current sensor installed in each of these power supply systems, a rectifier that rectifies the output detected by this sensor, an AD converter that digitally converts the output of this rectifier, and an interface that sends the output of this AD converter to the host device A plurality of installed current sensor units having a section;
A plurality of interface units that receive signals from the plurality of installed current sensor units, a selection unit that selects signals from these interface units, commands and data from the host device, and data corresponding to the commands to the host device Connected to a non-volatile memory and a clock transmitter, and a current sensor control unit having a microprocessor that calculates and measures the current value from the signal selected by the selection unit. A current measuring device.   The current sensor control unit has the frequency of the commercial power supply to be stable, the program processing of the system utilizing the sampling theorem, no co-divisor for 50HZ and 60HZ, and the current fluctuation speed of the measurement object as the frequency For conversion, a microprocessor that processes the sense data from each sensor with the number of samplings per second under the condition of at least twice that frequency uses one second or a multiple of that time, and from multiple AC current sensors installed at the same time. 2. A current measuring apparatus according to claim 1, wherein a current change for each sensor is grasped and a current for each sensor is measured and recorded.

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