JPH0926445A - Method for measuring phase angle, power factor, and power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly calculate phase angle by inputting two signals of AC voltage and AC power supply voltage obtained by converting AC power supply current to a pulse gate circuit between phase angles, and being based on a pulse increase obtained from the output of a pulse counter. SOLUTION: The power supply voltage of a load 2 is stepped down by a transformer 3 and is inputted to a comparator 6. Also, a load current is detected by a current transformer 4 for measuring instrument, a resistor 5 is connected to an output terminal, and the load current is converted into AC voltage and is inputted to a comparator 7. Then, the current is inputted to a pulse gate circuit between phase angles which is constituted of, for example, comparators 6 and 7 which continue only while the phases of two signals deviate, NOT circuits 10 and 12, an AND circuit 11, and a photo coupler 13. Further, a pulse generator 14 and a pulse counter are connected via the pulse gate circuit and a phase angle is calculated based on the pulse increment obtain from the output of the pulse counter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring an AC phase angle, a power factor and an electric power.

[0002]

2. Description of the Related Art Generally, in an apparatus using an AC power source such as a bucket elevator or a trough chain conveyor installed in a cement factory or the like, an abnormal situation such as a drive system failure or an accident involving a person is promptly as soon as possible. Development of a system that detects and responds is desired.

In the case of such an abnormal situation, a sudden overload is usually caused. Therefore, a so-called overload protection device capable of constantly monitoring the power and immediately shutting off the power at the time of overload to prevent serious damage is required. is there.

Conventionally, as a method of monitoring the above-mentioned abnormal situation, a method of monitoring the power factor and active power has been adopted.

However, in the conventional method, the response time is 0.5 to 1 second, which is too long to cope with an abnormal situation and does not have a sufficient monitoring function in view of the measuring principle.

[0006]

SUMMARY OF THE INVENTION The present invention provides a basic AC phase angle, power factor and power measuring method capable of responding to and dealing with the above-mentioned abnormal situation at an extremely high speed. It is provided.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a phase angle between two signals, an AC voltage obtained by converting an AC power supply current into an AC voltage and an AC power supply voltage, is conducted only while the two signals are out of phase. A phase angle characterized by inputting to a pulse gate circuit, further connecting a pulse generator and a pulse counter through the pulse gate circuit, and calculating a phase angle based on the pulse increment obtained from the output of the pulse counter. Is a measuring method. Further, it is a power factor measuring method for calculating a power factor by calculating a cosine of the phase angle. Further, it is a power measuring method for calculating power based on the peak value of each of the two signals of the AC voltage obtained by converting the AC power supply current into the AC voltage and the AC power supply voltage, and the power factor.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing the principle configuration of an embodiment of the present invention.

Reference numeral 1 is a single-phase AC power source. Although a single-phase power circuit is used for the sake of simplicity, it is needless to say that it can be applied to a multi-phase AC power circuit.

Reference numeral 2 is a load, and the power supply voltage of this load is applied to the transformer 3
The voltage is stepped down and is input to the comparator 6.

The load current is detected by the instrument current transformer 4, a resistor 5 is connected to the output terminal, the load current is converted into an AC voltage, and the AC voltage is input to the comparator 7.

In the embodiments described in this specification, a transformer or a current transformer for a meter is used to convert an AC voltage or an AC current into an AC voltage having an appropriate voltage. Any conversion method can be applied.

The output circuits of the comparators 6 and 7 are connected to Zener diodes 8 and 9, respectively, to extract only the positive voltage.

The output voltage of the comparator 7 is the NOT circuit 1
0, and the output of the NOT circuit 10 is the AND circuit 11
Input to one of the input terminals of.

The output of the comparator 6 is input to the other input terminal of the AND circuit 11.

The output of the AND circuit 11 is the NOT circuit 12
Input to (Open collector of NPN transistor),
The photo coupler 13 is connected to the cathode side of the light emitting diode, and a positive voltage is supplied to the anode side through the current limiting resistor 23.

On the other hand, the positive output of the pulse generator 14 is connected to the positive pulse input terminal 19-1 of the programmable controller (hereinafter referred to as PC) 17 through the output transistor of the photocoupler 13, and the negative output of the pulse generator 14 is connected. Is directly connected to the negative pulse input terminal 19-2 of the PC 17.

The pulse generator 14 always generates a pulse and its frequency is fixed.

The output circuit of the comparator 7 is connected to the anode of the light emitting diode of the photocoupler 15 via the resistor 16.

The output transistor of the photocoupler 15 is
It is connected to the digital input terminals 18-1 and 18-2 of the PC 17.

Reference numerals 21-1, 21-2 are power supply terminals.

FIG. 2 shows a waveform chart of each part when configured as shown in FIG.

Although the embodiment of FIG. 1 describes the method of measuring the lagging power factor, it is also possible to measure the leading power factor in principle.

The following description is based on FIGS. 1 and 2.

Reference numeral 31 is an AC power supply voltage waveform input to the comparator 6, and the output waveform is as shown by 33.

Reference numeral 32 is a load current waveform input to the comparator 7, and the output waveform is as 34.

The output waveform 34 is input to the NOT circuit 10 and the output waveform becomes as shown by 35.

When the output waveform 33 of the comparator 6 and the output waveform of the NOT circuit 10 are input to the AND circuit 11, the output waveform becomes 36.

As is apparent from FIG. 2, the AND circuit 11
It can be seen that the width of the waveform of the output waveform 36 is equal to the phase angle of the AC power supply voltage and the load current.

Since the output waveform 36 is input to the NOT circuit, the output transistor of the photocoupler 13, which is a pulse gate, outputs the pulse of the pulse generator 14 only while the voltage of the output waveform 36 is high, that is, during the phase angle. Is input to the pulse input terminals 19-1 and 19-2 of the PC 17.

Therefore, a circuit composed of the comparators 6 and 7, the NOT circuits 10 and 12, the AND circuit 11 and the photocoupler 13 is defined as a pulse gate circuit between phase angles.

Since the comparators 6 and 7 are simply used to increase the voltage between the zero crosses of the sine wave alternating current and extract it as a rectangular wave, it goes without saying that other methods such as a zero cross detection circuit can be used. Is.

As the photocoupler 13 used for the pulse gate, any element having a switching function such as a switching transistor can be applied.

Further, in this embodiment, the NOT circuit is connected to the output side of the comparator 7, but this may be connected to the output side of the comparator 6 without any problem.

In short, any combination of logic circuits can be applied in which the pulse gate is opened only when the phases of the two alternating current inputs to the phase angle pulse gate circuit are shifted.

Pulse input terminals 19-1 and 19 of the PC 17
-2, the photocoupler 15 becomes conductive when the pulse is completely input to the digital input terminals 18-1 and 18-2 of the PC 17.
Is conducted, and the PC 17 detects the rise of this conduction and executes the following power factor calculation.

The power factor calculation method will be described below.

The frequency of the pulse generator is fixed and known, and is K (Hz), and the frequency of the AC power supply 1 is F (Hz).

The pulse increment input to the PC 17 is N
Assuming that (P), the time of one cycle of AC T = 1 / F (second) The time per pulse t = 1 / K (second / P) The angle of one cycle of AC = 360 (degree) Therefore, the phase angle θ (degree ) Is calculated by the following formula.

Q = 360 tN / T = 360 FN / K (degrees) The PC 17 calculates the cosine of this phase angle θ to obtain the power factor.

The PC 17 converts the obtained power factor into an analog output and outputs the analog output to the analog output terminals 20-1 and 20-2. Reference numeral 22 is a power factor indicator (which can indicate a delay / advance power factor).

Of course, the power factor obtained by using the communication function of the PC 17 can be transmitted as communication data.

Since the PC 17 executes this processing every AC cycle, it is possible to measure the power factor with an extremely high speed response.

In this embodiment, the power factor is measured for each cycle of alternating current, but if the exclusive OR circuit of the output waveform 33 and the output waveform 35 of the comparator 6 is used, the pulse gate is opened and closed every half cycle. Since it is possible, the power factor can be measured every half cycle.

The curves indicated by the reference numerals 37 and 38 are respectively
The voltage peak value and the current peak value are shown.

FIG. 3 shows an embodiment of the present invention capable of measuring the delay power factor and the advance power factor.

Hereinafter, description will be given with reference to FIGS. 3, 4 and 5.

An AC power supply voltage signal is input to the comparator 41, and an AC load current is converted into an AC voltage and input to the comparator 42.

Output of comparator 41 and comparator 4
The output of 2 is input to an exclusive OR circuit (hereinafter referred to as an EOR circuit) 43, and the output of this EOR circuit 43 is ANDed.
Input to one of the inputs of circuits 44-1 and 44-2.

The output of the comparator 41 is input to the other input of the AND circuit 44-1 and the AND circuit 44-2 is used.
The output of the comparator 42 is input to the other input of the.

In FIG. 3, 48-2 is an AND circuit,
24 is a NOT circuit and 30 is a resistor.

Now, in the case of the delay power factor, that is, when the input phase of the comparator 42 is behind the input of the comparator 41, the waveform chart of each part is as follows.

FIG. 4 showing a waveform chart in the case of a delay power factor.
In FIG. 5, 51 is an input waveform of the comparator 41, 52 is an input waveform of the comparator 42, 53 is an output waveform of the comparator 41, and 54 is an output waveform of the comparator 42.

Further, 53 and 54 are input to the EOR circuit 43, and the output waveform thereof is 55.

The output waveform of the AND circuit 104-1 into which the output waveform 55 and the output waveform 53 of the comparator 41 are input is as 56.

As a result, the photocoupler 45, which is a pulse gate, conducts only during the phase angle between the input of the comparator 41 and the comparator 42, and the pulse generator 46 only during this period.
From the pulse input terminals 19-1, 1 of PC17
It will be input to 9-2. On the other hand, the timing for starting the power factor calculation based on the input pulse is obtained by the following mechanism.

The output of the comparator 41 becomes a positive potential at the same time that its input voltage becomes negative and is input to one of the inputs of the AND circuit 47-1 (hereinafter referred to as ON), and the other input terminal is the comparator. Since the output of 2 is not turned on, the AND circuit 47-2 is turned off, and N
Since the output of the OT circuit 50-2 is turned on, the AND circuit 47
The output of -1 is turned on, is input to one of the inputs of the AND circuit 48-1, and waits until the output of the comparator 42 is turned on, and the output of the AND circuit 47-2 is turned on by the NOT circuit 50-1. Interlock so as not to.

The output of the comparator 42 is turned on with a delay of the phase angle, as a result, the output of the AND circuit 48-1 is turned on, the photocoupler 49-1 is turned on, and the PC 17 is turned on.
The digital input terminals 18-1 and 18-2 are turned on.

When the PC 17 detects the rising edge of the digital input, the PC 17 calculates the delay power factor based on the pulse increment input from the pulse input terminals 19-1 and 19-2, and outputs the power factor indicator 22 (delay).・ Progress power factor can be indicated.) Is analog output.

In the case of the advance power factor, the photocoupler 49-2 conducts in the opposite manner to the delay power factor, the PC 17 calculates the advance power factor, and outputs it to the power factor indicator 22 in an analog manner.

FIG. 5 is a diagram corresponding to FIG. 4 in the case of the advance power factor.

FIG. 6 shows an example of an embodiment for measuring power factor and electric power to which the present invention is applied.

In order to detect the peak value of the AC power supply voltage and the AC current in the embodiment of FIG.
9, 40, etc. are added.

The mechanism of power measurement will be described below.

The AC power supply voltage is input to the peak value detector 39, and the AC current is input to the peak value detector 40. The peak value when the voltage is positive is held and the analog input terminal 25 of the PC 17 is held. -1, 25-2 and 27
-1, 27-2 are input.

Assuming that the peak value converted into the AC power supply voltage is E _m , the peak value converted into the AC load current is I _m , and the power factor is PF, the power consumption P of the load 2 in FIG. 6 is P = The voltage effective value × current effective value × PF.

Here, the voltage effective value = E _m / √2 and the current effective value = I _m / √2 Therefore, the formula for calculating the power consumption P is P = (E _m / √2) × (I _m / √2) × It becomes PF.

After calculating the power factor, the PC 17 outputs the voltage peak value and the current peak value to the analog input terminals 25-1 and 25-2, respectively.
Digital output terminals 24-1, 24-2 and 26-1, 2 to read from 5-2 and 27-1, 27-2 and reset the voltage and the peak value of the power source by performing the above-mentioned calculation.
Turn on the digital output that shorts 6-2.

The PC 17 analog-outputs the obtained power factor and electric power for each cycle, and instructs the power factor indicator 22 and the electric power indicator 28 on the measured values.

In this embodiment, the PC is used for the arithmetic processing, but it is not limited to the PC.

Although the present embodiment measures the single-phase AC power factor and power, it is possible to measure even the balanced three-phase load, and the AC power supply voltage and the AC load current can be detected by one point each. .

With a three-phase AC unbalanced load, it is possible to measure the AC power supply voltage and the AC load current at two points each by the so-called two-power meter method.

[0074]

[Effect] As described above, the present invention is characterized in that the AC phase angle, the power factor, and the electric power can be measured every one week.

Taking advantage of this feature, in the case of a load such as a transport machine such as a bucket elevator or a trough chain conveyor that causes a sudden overload due to an internal failure, the power is constantly monitored and the power is immediately shut off when the overload occurs. It is ideal for so-called overload protection devices that can prevent serious damage.

As described above, the present invention can measure not only the phase angle and power factor of the power circuit but also the power at an ultra-high speed, so that it is effective for transient phenomenon analysis of the power circuit and overload protection of the motor drive equipment. It is a very useful invention.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a measuring method according to the present invention.

FIG. 2 is a diagram showing a waveform chart of each part in FIG.

FIG. 3 is a principle configuration diagram of a power factor measuring method according to the present invention capable of measuring delay and advance power factors.

FIG. 4 is a drawing showing a waveform chart of each part in FIG. 3 in the case of a delay power factor.

FIG. 5 is a drawing showing a waveform chart of each part in FIG. 3 in the case of a forward power factor.

FIG. 6 is a principle configuration diagram of a power factor and power measuring method of the present invention.

[Explanation of symbols]

1 AC power supply 2 Load 3 Transformer 4 Current transformer for instrument 5 Resistor 6,7 Comparator 8,9 Zener diode 10,12 NOT circuit 11 AND circuit 13,15 Photocoupler 14 Pulse generator 16 Resistor 17 Programmable controller 18 -1, 18-2 Digital input terminal 19-1 Positive pulse input terminal 19-2 Negative pulse input terminal 20-1, 20-2 Analog output terminal 21-1, 21-2 Power supply terminal 22 Power factor indicator 23 Current limiting Resistors 24-1, 24-2, 26-1, 26-2 Digital output terminals 25-1, 25-2, 27-1, 27-2 Analog input terminals 28 Power indicator 29 NOT circuit 30 Resistor 31 Comparator AC power supply voltage waveform 32 input to 6 load current waveform 33 input to comparator 7 Comparator 6 Output waveform from 34 Output waveform from comparator 35 Output waveform from NOT circuit 36 Output waveform from AND circuit 37 Voltage peak value 38 Current peak value 39, 40 Peak value detector 41, 42 Comparator 43 Exclusive logic AND circuit 44-1, 44-2 AND circuit 45 Photocoupler 46 Pulse generator 47-1, 47-2, 48-1, 48-2 AND circuit 49-1, 49-2 Photocoupler 50-1, 50- 2 NOT circuit 51 Input waveform of comparator 41 52 Input waveform of comparator 42 53 Output waveform of comparator 41 54 Output waveform of comparator 42 55 Output waveform of EOR circuit 43 56 Output waveform of AND circuit 44-1

Claims (3)

[Claims] 1. A two-phase signal, an AC voltage obtained by converting an AC power supply current into an AC voltage and an AC power supply voltage, is input to a phase-angle pulse gate circuit that conducts only while the two signals are out of phase, and further, A method for measuring a phase angle, characterized in that a pulse generator and a pulse counter are connected via the pulse gate circuit, and the phase angle is calculated based on the pulse increment obtained from the output of the pulse counter. 2. A method of measuring a power factor, which is characterized by calculating a cosine of the phase angle calculated in claim 1 to calculate a power factor. 3. The power is calculated based on the peak value of each of the two signals of the AC voltage and the AC power supply voltage obtained by converting the AC power supply current into the AC voltage and the power factor calculated in claim 2. And how to measure the power.