JP3614048B2 - Energization information measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an energization information measuring device that measures energization information such as voltage, current, and power of an AC load, and in particular, when a transformer that is housed in the device and connected to a circuit to be measured is energized with a large current in the circuit to be measured. The present invention relates to a voltage measurement value that does not affect an error when affected by a generated magnetic field.
[0002]
[Prior art]
FIG. 5 is a diagram showing a circuit block configuration of a circuit breaker provided with a conventional energization information measurement display device disclosed in, for example, Japanese Patent Application Laid-Open No. 11-008930.
In the figure, 1 is a circuit breaker body, 2 is a main conducting conductor that penetrates the inside of the circuit breaker body 1, and 3 is a switching contact that is operated by a switching mechanism (not shown) to turn on and off the current of the conducting main conductor 2. 4 is a current transformer for detecting the current flowing through each energized main conductor 2, 5 is a rectifier circuit for rectifying the output of the current transformer 4, and 6 is an A / D conversion process by converting the output from the rectifier circuit 5 into a voltage. The peak value conversion circuit 7 detects the instantaneous maximum value of the current flowing through the energized main conductor 2, 7 is an instantaneous time limit circuit that outputs a signal when the output of the peak value conversion circuit 6 exceeds a predetermined value, and 8 is the instantaneous time limit circuit 7. This is a short-timed circuit that outputs a signal by performing an anti-timed operation according to the magnitude of the output of the peak value conversion circuit 6 at a level equal to or lower than the operation output. 9 is an effective value conversion circuit that obtains an output corresponding to the effective value of the current flowing through the energized main conductor 2 by performing voltage conversion, A / D conversion processing, etc. on the output from the rectifier circuit 5, and 10 is a long-time circuit. Depending on the magnitude of the output of the effective value conversion circuit 9, the circuit breaker is not interrupted at the rated current, and the signal is output with the counter-timed operation above the rated current.
[0003]
Reference numeral 11 denotes a trigger circuit, which receives a signal output from any one of the instantaneous time circuit 7, the short time circuit 8, and the long time circuit 10, and the electromagnetic coil 12 turns off the switching contact 3 via a switching mechanism (not shown) to the load. Shut off the power of the. 13 is a measuring current transformer that detects a current flowing in each conductor 2 separately from the current transformer 4 for detecting overcurrent, and 14 is a transformer that detects a voltage between the conductors 2 (phase voltage). The measuring current transformer 13 and the transformer 14 are accommodated integrally in the circuit breaker body 1.
[0004]
20 is an energization information measuring unit, 21 is an A / D conversion circuit that obtains a digital output corresponding to the current flowing through the energizing main conductor 2 by subjecting the output from the measurement current transformer 13 to A / D conversion processing, and the like. Is a voltage A / D conversion circuit that performs an A / D conversion process on the output from the transformer 14 to obtain a digital output corresponding to the interphase voltage. These A / D conversion circuits and processes to be described below are executed by a microprocessor (not shown).
[0005]
Reference numeral 23 denotes a current current value output (I) for each current-carrying main conductor 2 for each phase. Reference numeral 24 denotes a maximum current value storage circuit which stores and holds the latest maximum current value (Imax) from the conductor 2 by peak hold. . 25 is a voltage output (V) between each phase, and 26 is a multiplication circuit that multiplies the outputs of the current A / D conversion circuit 21 and the voltage A / D conversion circuit 22, and obtains an output corresponding to the power (W) of the load. Reference numeral 27 denotes an integration circuit that integrates the outputs from the multiplication circuit 26 to obtain an electric energy (Wh). For the power (W) and the power amount (Wh), a total power value can be obtained in accordance with the wiring form to the load. The output of measurement results of these current current value (I), maximum current value (Imax), interphase voltage (V), power (W), and electric energy (Wh) are items selected via the display content selection means 28. Is input to the display unit 29 and numerically displayed.
[0006]
The energization information measuring apparatus as described above can obtain information on the voltage from the transformer 14 built in the circuit breaker body 1, and using the voltage information, the power supply energization information of the load is not only related to the current but also between the phases. Information such as voltage (V), power (W), and electric energy (Wh) can also be obtained. Operating power including these microprocessors is supplied from a power supply circuit (not shown).
[0007]
[Problems to be solved by the invention]
The conventional energization information measurement and display device as described above samples the values measured by the measurement current transformer 13 and the transformer 14 in the circuit breaker as they are, and performs A / D conversion for calculation and display. Yes. Therefore, when a large current exceeding the rated current flows through the circuit breaker, the secondary output voltage of the transformer 14 is not proportional to the primary voltage under the influence of the magnetic field generated around the energized main conductor 2. Become. For this reason, for example, when a current of 200% of the rated current of the circuit breaker passes through the energizing main conductor 2, the primary voltage of the transformer 14 does not change, but the secondary output produces a voltage of 150% or more than the normal voltage. Or For this reason, the interphase voltage (V), power (W), and electric energy (Wh) while the circuit breaker due to a large current reaches the overcurrent interruption are measured as values including large errors and input to the display unit 29. Large error values are displayed. In particular, the amount of electric power (Wh) is not a temporary instantaneous value but remains as a cumulative value, so the influence is great.
[0008]
In general, if the current-carrying main conductor 2 and the transformer 14 are arranged apart from each other or if the transformer 14 is sufficiently shielded, it is possible to prevent the influence of a magnetic field. In such a limited space, the transformer 14 and the current-carrying main conductor 2 must be arranged close to each other, and a sufficient shield mounting on the transformer 14 hinders downsizing of the apparatus due to an increase in the volume of the transformer 14. There was a problem to do.
[0009]
The present invention has been made in order to solve the above-described problems. Even if the arrangement position of the transformer 14 in the casing and the shield of the transformer 14 are simplified, the current exceeding the rated current of the main conducting conductor 2 is large. Even if the transformer 14 when the current flows is affected by the magnetic field, the measurement values such as the interphase voltage (V), power (W), power amount (Wh), power factor, etc., should not have a large error.
[0010]
[Means for Solving the Problems]
An energization information measurement / display apparatus according to the present invention includes a transformer provided in the casing in proximity to the energizing main conductor for detecting a voltage between the energizing main conductors, a current transformer for detecting a current of the energizing main conductor, and a transformer. Sampling and calculation processing of current and voltage detected by the current transformer and transformer to convert them into measurement signal output of current value, voltage value, power value, and energy, and temporary measurement signal output of voltage value Voltage value storage means for storing and current value determination means for replacing the voltage value measurement signal used for calculation processing with the voltage value measurement signal in the voltage value storage means when the current value measurement signal output is equal to or greater than the threshold value. It is provided.
[0011]
In addition, a zero cross detecting means for detecting the zero cross of each of the current and voltage of the AC circuit and the number N of sampling clocks for a half cycle of the AC circuit waveform are set in the above, and the sampling between the zero cross difference of the current and the voltage is set. Phase difference detecting means for detecting the clock number m and power factor calculating means for calculating the power factor from the sampling clock number N and the sampling clock number m are provided.
[0012]
The number N of sampling clocks during a half cycle of the AC circuit waveform is obtained by counting and detecting the sampling clocks at the zero-cross detection interval of the AC circuit to be measured.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram of a circuit configuration of an energization information measuring apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a flowchart for explaining the operation of Embodiment 1 of the present invention. In the figure, reference numerals 1 to 15 and 20 to 29 are the same as those described in the conventional example.
Here, the current A / D conversion circuit 21 and the voltage A / D conversion circuit 22 output current values and voltage values calculated as effective values. Reference numeral 30 denotes a current value determination unit that determines the magnitude of the current from the current A / D conversion circuit 21 corresponding to the current flowing through the energized main conductor 2. Reference numeral 31 denotes a determination signal. When the current flowing through the energized main conductor 2 is equal to or greater than a predetermined value, for example, “H” is output from the current value determination unit 30. It becomes “L” when the current of the energized main conductor 2 is less than a predetermined value. Reference numeral 32 denotes a voltage value storage circuit.
Reference numeral 33 denotes a change-over switch. When the determination signal 31 is “L”, the voltage measurement signal output corresponding to the interphase voltage from the voltage A / D conversion circuit 22 is directly subjected to downstream processing such as a multiplication circuit 26, an integration circuit 27, The display content selection unit 28 and the display unit 29 are processed. When the determination signal 31 becomes “H”, the voltage measurement signal output of the interphase voltage stored in the voltage value storage circuit 32 is switched to the downstream processing.
[0014]
Next, the operation of the present invention will be described with reference to the flowchart of FIG.
The voltage output value of the voltage A / D conversion circuit 22 is stored in the voltage value storage circuit 32. Then, the current output value of the current A / D conversion circuit 21 is read, and the current value determination unit 30 compares this current output value with a predetermined threshold value. When the current output value <the threshold value, the changeover switch 33 sends the voltage output from the voltage A / D conversion circuit 22 to the downstream process as it is and uses it for the calculation process / display. If the current output value ≧ the threshold value, the changeover switch 33 switches the voltage output value of the voltage A / D conversion circuit 22 previously stored in the voltage value storage circuit 32 to be sent to the downstream processing at that time. Thereafter, while the state of current output value ≧ threshold value continues, the voltage output value stored in the voltage value storage circuit 32 is used to display the interphase voltage (V) and the calculation of power (W) and power amount (Wh). And display. If the current output value <threshold value is restored, then the changeover switch 33 is switched back so that the changeover switch 33 sends the voltage output value of the voltage A / D conversion circuit 22 directly to downstream processing.
[0015]
The threshold value is preferably set to a value just before the magnetic interference to the transformer 14 due to the current passed through the current-carrying main conductor 2 affects the secondary output of the transformer 14. Depending on the degree of magnetic shielding, 150 to 200% of the rated current is adopted.
[0016]
In a general power distribution circuit, the load current (current of the energized main conductor 2) increases and decreases drastically, but the voltage is relatively stable. The present invention uses this point to store in the voltage value storage circuit 32 the voltage value immediately before the secondary output of the transformer 14 affects the current of the current-carrying main conductor 2. In a range where an error occurs in the output, calculation and display are executed with the voltage value held in the voltage value storage circuit 32. Although the voltage value is constrained by the voltage value stored in the voltage value storage circuit 32 over time, the current value is measured every moment, so that the interphase voltage (V), power to be calculated and displayed The (W) and electric energy (Wh) values can be calculated and displayed with an accuracy that does not affect the practical use although there is a slight error corresponding to the voltage change during this period.
[0017]
Embodiment 2. FIG.
The second embodiment enables measurement and display of reactive power (Var) and power factor (Pf) in addition to the interphase voltage (V), active power (W), and electric energy (Wh) of the first embodiment. To do.
FIG. 3 is a block diagram of the circuit configuration of the energization information measuring apparatus showing the second embodiment of the present invention, and FIG. 4 is a diagram for explaining the operation of the second embodiment. In the figure, 2, 13, 14, 21 to 33 are the same as those described in the first embodiment.
Reference numeral 34 denotes a current zero-cross detection circuit, and reference numeral 35 denotes a voltage zero-cross detection circuit. 36 is a phase difference detection circuit, and 37 is a power factor calculation circuit. The phase difference detection circuit 36 performs a voltage / current phase difference from the voltage zero cross detection circuit 35 and the current zero cross detection circuit 34 using a sampling clock for A / D conversion. The counter counts the number of clocks N for sampling the 1/2 cycle of the AC circuit to be measured, and also counts the number of clocks m between the zero-cross detection time difference between the voltage and current, and the power factor Pf of the AC circuit to be measured is calculated from the value. Is obtained by Pf = Cos (π · m / N), and the reactive power factor Pv is obtained by Pv = Sin (π · m / N). By reflecting this result on the multiplication circuit 26, it is possible to calculate and display the active power (W) and the reactive power (Var).
In this method, if the sampling clock frequency is 50 kilohertz or more, the power factor measurement accuracy can ensure a resolution of 0.5 degrees in angle.
[0018]
If the frequency of the AC circuit to be measured and the sampling clock frequency are determined, the number of sampling clocks during a half cycle of the AC circuit can be calculated and set. However, the frequency of the AC circuit to be measured changes (such as 50 Hz) due to changes in the AC circuit to be measured. 60Hz), resetting is necessary.
However, the configuration obtained by counting the number of clocks N of 1/2 cycle of the AC circuit to be measured with a counter is independent of the change in the frequency of the AC circuit to be measured (50 Hz, 60 Hz) and the fluctuation of the sampling clock frequency. The power factor Pf of the AC circuit to be measured can be obtained as it is.
[0019]
In addition, it is obvious that the power factor Pf can be calculated by correcting the number of sampling clocks corresponding to π · 2/3 for the phase difference between the current and voltage of the AC line to be measured (single phase, three phase) and voltage. is there.
[0020]
In each of the above embodiments, the threshold determination of the load current (current of the energized main conductor 2) is performed with the A / D conversion processing performed by the current A / D conversion circuit 21, but this is measured. It is obvious that the same effect can be obtained even if the output of the current transformer 13 is an analog type determination means such as an operational amplifier.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of an energization information measuring apparatus showing a first embodiment of the invention.
FIG. 2 is a flowchart illustrating the operation of the first embodiment of the present invention.
FIG. 3 is a circuit block diagram of an energization information measuring apparatus showing Embodiment 2 of the present invention.
FIG. 4 is a diagram for explaining the operation of the second embodiment of the present invention.
FIG. 5 is a circuit block diagram of a circuit breaker including a conventional energization information measurement display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Circuit breaker main body, 2 Current supply main conductor, 3 Switch contact 13 Current transformer for measurement, 14 Transformer, 20 Current supply information measurement unit 21 Current A / D conversion circuit, 22 Voltage A / D conversion circuit current value output, 25 Voltage output, 26 multiplication circuit, 27 integration circuit display content selection means, 29 display section, 30 current value determination section switching signal, 32 voltage value storage circuit, 33 selector switch 35 zero cross detection circuit, 36 phase difference detection circuit 37 power factor calculation circuit

Claims (3)

A transformer provided in the housing for detecting a voltage between the energized main conductors in proximity to the energized main conductor of the AC circuit, current detecting means for detecting a current of the energized main conductor, the current detecting means and the transformer Sampling and computing the current and voltage detected by, and converting to at least current value, voltage value, power value, and power measurement signal output, and select measurement items from the above measurement signal outputs In the energization information measurement display device that can be,
Voltage value storage means for temporarily storing a voltage value measurement signal output, and a voltage used for calculation processing when the current value measurement signal output is equal to or greater than the threshold value by comparing the current value measurement signal output with a predetermined threshold value. An energization information measurement display device comprising: current value determination means for replacing the value measurement signal with the voltage value measurement signal stored and stored in the voltage value storage means. Zero cross detection means for detecting the zero cross of each of the current and voltage of the AC circuit detected by the current detection means and the transformer, and the number of sampling clocks N during a half cycle of the AC circuit waveform, and the measured current 2. A phase difference detecting means for detecting a sampling clock number m between zero-crossing differences in voltage, and a power factor calculating means for calculating a power factor from the sampling clock number N and the sampling clock number m. 1. An energization information measurement display device according to 1. 3. The energization information measurement display apparatus according to claim 2, wherein the number N of sampling clocks during a half cycle of the AC circuit waveform is obtained by counting and detecting a sampling clock at a zero-cross detection interval of the current or voltage of the circuit to be measured. .

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