JPH0226191Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of an open phase detection circuit for a three-phase power supply.

Conventionally, meter-type devices have been used to detect open phase, but due to their structure, there are limits to miniaturization.
In recent years, so-called stationary devices using semiconductor circuits have come into use. There are various detection methods, and the block configuration of one example is shown in FIGS. 1 and 2.

In Figure 1, 1 is a three-phase AC input terminal, 2 is a transformer circuit, 3 is a positive phase detection circuit, 4 is a negative phase detection circuit, 5 is a comparison circuit, 6 is an output circuit, and 7 is an output terminal. It is. In this method, when the three-phase input is normal, the positive phase component and the negative phase component are balanced, so the output of the comparator circuit 5 is zero, and no signal is output to the output terminal 7. In the event of an open phase or a power outage, a difference occurs between the positive phase component and the negative phase component, and the comparison circuit 5 detects this difference and outputs a signal to the output terminal 7 through the output circuit 6. However, with this method,
Even if all three-phase voltages become low due to a power outage, no signal will be output to the output terminal as long as the positive and negative phase components are the same. However, if there is distortion in each phase voltage of the three-phase voltage, has the disadvantage that even if the voltage is within the normal range, there is a difference between the positive and negative phase components and a signal is output to the output terminal.

Fig. 2 is an example of another method, and in the figure, 1 is a three-phase AC input terminal, 2 is a transformer circuit, 5 is a comparison circuit, 6 is an output circuit, 7 is an output terminal, and 8 is a three-phase AC input terminal. 9 is a smoothing circuit, 10 is a stabilizing circuit, 11 is a reference voltage circuit, and 12 is an integrating circuit. Moreover, FIGS. 3 and 4 show its operating waveforms.

Now, when the three-phase input is normal, the waveform at the output point A of the three-phase full-wave rectifier circuit 8 is as shown in FIG. (hereinafter referred to as reference voltage). in this case,
Since the voltage at point A is higher than the reference voltage, no voltage appears at output point B of comparator circuit 5, and no signal appears at output terminal 7. Now, considering the case of a power outage, the relationship between the voltage at point A and the reference voltage is as shown in FIG. 3b. That is, if the voltage at point A gradually decreases to below the reference voltage due to a power outage, the voltage at output point B of the comparator circuit 5 will be output during that period. This is shown in Figure 3c. This voltage at point B is supplied to the integrating circuit 12, and its output voltage increases during the period when the voltage at point B exists, as shown in FIG. 3d, and decreases during the period when there is no voltage at point B. This is the operation. This voltage is compared by a comparison circuit in the output circuit 6, and when it reaches a certain voltage, it is sent out as an output signal 7. The one-dot chain line in FIG. 3d is the detection level, and is the signal sent to the output terminal 7 in FIG. 3e.

Also, considering the case where the three-phase input has an open phase, the relationship between the voltage at point A and the reference voltage is as shown in FIG. 4a. In the figure, during a period when the voltage at point A is below the reference voltage, the voltage at output point B of the comparator circuit 5 is output. This is shown in FIG. 4b. This B
The voltage at the point is supplied to the integrating circuit 12, and its output voltage gradually increases while continuing to rise and fall as shown in Figure 4c, and when it reaches a predetermined detection level at time _t1 , the output terminal A signal will be sent to 7.

As explained above, the system shown in FIG. 2 has the disadvantage that a signal is sent to the output terminal both during power outage and during phase loss. However, malfunctions due to distortion of the three-phase voltage as in the system shown in FIG. 1 are less likely to occur.

The present invention was made in order to eliminate the above-mentioned drawbacks inherent in the conventional technology. Therefore, the purpose of the present invention is to improve the system shown in FIG. It is an object of the present invention to provide a novel open-phase detection circuit configured to send out an output signal only when the phase is in phase.

In order to achieve the above object, the phase loss detection circuit according to the present invention adds a voltage obtained by full-wave rectification of a three-phase AC voltage and a reference voltage to a comparison circuit, so that the full-wave rectified voltage becomes lower than the reference voltage at the time of phase loss. In an open phase detection circuit that detects rotation and operates an output circuit via an integrating circuit, the main components include an operational amplifier, a timing resistor, and a capacitor between the comparator circuit and the integrating circuit. It is constructed by providing a monostable multivibrator circuit as an element.

Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 5 shows a block configuration of an embodiment of an open phase detection circuit according to the present invention. One embodiment of the present invention is the second
A monostable multivibrator circuit 13 is provided between the comparator circuit 5 and the integrator circuit 12 shown in the figure, and this configuration is intended to eliminate the above-mentioned drawbacks.

FIG. 6 shows an example of a specific circuit configuration of an embodiment of the present invention. The parts surrounded by dotted lines in the figure respectively correspond to the block diagram in FIG. 8 is a three-phase full-wave rectifier circuit, and bridge circuit 1 is composed of six silicon bodies.
Consists of 02. A smoothing circuit 9 includes a silicon body 103 and a capacitor 104. 10 is a stabilizing circuit, which includes a transistor 105 and a resistor 10.
6, consisting of a constant voltage diode 107. A reference voltage circuit 11 includes a resistor 110 and a constant voltage diode 111. Reference numeral 5 denotes a comparator circuit, which includes an operational amplifier 112, which outputs a detection voltage divided by resistors 108 and 109, and a constant voltage diode 111.
is configured to compare a reference voltage which is a terminal voltage of. 13 is a monostable multivibrator circuit, which includes silicon bodies 113, 117, 120, 12
1,126, resistor 114, 115, 118, 1
19, 122, 124, capacitor 116, 12
5 and an operational amplifier 123. 12 is an integrating circuit, which includes a silicon body 127, a resistor 128, 1
30 and a capacitor 129. Reference numeral 6 denotes an output circuit, which includes a resistor 131, a relay 132, and a thyristor 133. 134 is a contact of the relay 132 and is connected to the output terminal 7.

Further, FIGS. 7 and 8 are waveform diagrams illustrating the operation of the circuit according to the present invention. The operation of the present invention will be explained below.

The voltage applied to the three-phase AC input terminal 1 is stepped down by the transformer 101, and is subjected to three-phase full-wave rectification by the silicon body 102. The three-phase full-wave rectified voltage waveform is the seventh
It is shown in Figure a and Figure 8a. This voltage is divided by resistors 108 and 109, and the operational amplifier 11
2 non-inverting input terminals. On the other hand, the three-phase full-wave rectified voltage becomes a DC circuit voltage by the smoothing circuit 9 and the stabilizing circuit 10, which is not affected by fluctuations in the three-phase AC input or phase loss. From this stabilized DC circuit voltage, a reference voltage created by a resistor 110 and a constant voltage diode 111 is applied to the inverting input terminal of the operational amplifier 112 mentioned above.

With this configuration, the output voltage of the operational amplifier 112 becomes low only when the non-inverting input terminal voltage becomes lower than the inverting input terminal voltage (approximately
2V), and under other conditions the output voltage is always approximately the DC voltage value. The output terminal of the operational amplifier 112 is connected via a capacitor 116 to provide a trigger signal for the monostable multivibrator circuit 13. A voltage obtained by dividing the DC circuit voltage by resistors 114 and 118 is applied to the inverting input terminal of the operational amplifier 123 of the monostable multivibrator circuit 13. Moreover, this voltage is divided into approximately 1/2 of the DC circuit voltage. On the other hand, operational amplifier 12
The DC circuit voltage is connected to the non-inverting input terminal of 3 through resistor 1.
A voltage divided by voltages 15 and 119 is applied through the silicon body 120, and this voltage is approximately 2V.
It's getting old. Further, a capacitor 125 is connected to the non-inverting input terminal of the operational amplifier 123 from the output of the operational amplifier 123, and a resistor 122 is connected to the negative pole of the DC circuit voltage. This capacitor 125 and resistor 122 constitute a timing circuit of the monostable multivibrator circuit 13.
Determine the output pulse width. Silicon body 113,1
17 and 121 are for protecting the inverting input terminal and non-inverting input terminal of the operational amplifier 123, and the silicon body 126 is for discharging the timing capacitor 125. Also, resistor 124 is a pull-up resistor.

Here, the operation of the monostable multivibrator circuit 13 will be briefly explained. In a normal state, the inverting input terminal voltage of the operational amplifier 123 is set to be higher than the non-inverting input terminal voltage, so the output voltage of the operational amplifier 123 is low, about 2V. As described above, since the design is such that a voltage of approximately 2V is applied to the non-inverting input terminal, the voltage across the timing capacitor 125 is approximately zero volts. When a negative trigger signal is now applied to the inverting input terminal and becomes lower than the non-inverting input terminal, the output voltage of the operational amplifier 123 increases to approximately the DC circuit voltage. At that point, the voltage across resistor 122, ie, the non-inverting input terminal voltage, increases to near the DC circuit voltage. The inverting input terminal voltage is approximately 1/ of the DC circuit voltage.
2, and even if the trigger signal disappears, the output voltage of the operational amplifier 123 remains high because the non-inverting input terminal voltage is higher than the inverting input terminal voltage. timing capacitor 12
5. As the capacitor 125 is charged by current flowing through the path of the resistor 122, the voltage of the resistor 122, that is, the voltage of the non-inverting input terminal becomes lower. The moment this voltage becomes less than the voltage at the inverting input terminal, the output of the operational amplifier 123 becomes low. From this point on, the charge stored in the capacitor 125 is discharged through the silicon body 126 in preparation for the next trigger signal. By applying the trigger signal momentarily in this manner, the output of the monostable multivibrator circuit 13 appears only for a certain period of time determined by the timing capacitor 125 and the resistor 122.

The output of monostable multivibrator circuit 13 charges capacitor 129 through silicon body 127 and resistor 128. When the output of the monostable multivibrator circuit 13 disappears, the capacitor 129
The charges charged in the resistors 130 and 131 are discharged through the resistors 130 and 131. When the voltage of the capacitor 129 increases and becomes equal to or higher than the gate trigger voltage of the thyristor 133, the thyristor 133 is fired and the relay 13 is activated.
2 will be energized and its contact 134 will be output.

Next, the actual operation during a power outage and an open phase will be explained based on FIGS. 7 and 8. FIG. 7a shows the normal waveforms applied to the inverting input terminal and non-inverting input terminal of the comparator circuit 5, where the dashed line indicates the reference voltage applied to the inverting input terminal, and the solid line indicates the reference voltage applied to the inverting input terminal. Shown is the sense voltage applied to the non-inverting input terminal. Now, assuming that a power outage has occurred, the waveform will change as shown in FIG. 7b. Therefore, as shown in FIG. 7c, the output voltage of the comparator circuit 5 falls only during the period when the detected voltage shown by the solid line in FIG. 7b is lower than the reference voltage shown by the dashed-dotted line. This falling voltage becomes a trigger signal for the monostable multivibrator circuit 13. FIG. 7d shows the output voltage of the monostable multivibrator circuit 13. In this figure, "τ" is the time required to trigger the monostable multivibrator circuit 13, and a shorter trigger signal will not trigger it. Further, "tp" is a constant value determined by the timing circuit. As can be seen from Figure 7c and d, in the event of a power outage, the monostable multivibrator circuit 13
Since the output of is a single pulse, the integration circuit 12
The capacitor 129 in Fig. 7e is not sufficiently charged.
As shown, the gate trigger voltage of the thyristor 133 is not reached as indicated by the dashed line. Therefore, Fig. 7 f
No signal is sent to the output terminal 7 as shown in FIG.

Next, considering the case of an open phase, the situation is as follows. FIG. 8a shows the waveform during normal operation, and FIG. 8b shows the voltage waveform applied to the comparator circuit 5 during phase loss. Therefore, the output of the comparator circuit 5 has a waveform as shown in FIG. In the case of phase loss, this trigger signal is generated continuously, so the monostable multivibrator circuit 13
The output of ``tp'' will also be a continuous voltage with a pulse width of ``tp''. As a result, the capacitor 129 of the integrating circuit 12 is gradually charged while repeating charging and discharging, and reaches the gate trigger voltage of the thyristor 133. At this point, thyristor 133
is fired, energizing relay 132 and sending its contact 134 to the output terminal. The waveforms during this period are shown in FIG. 8 d, e, and f.

As described above, by providing a monostable multivibrator circuit between the comparator circuit and the integrating circuit as in the present invention, a phase loss detection circuit that does not output a signal during a power outage and reliably sends a signal only when a phase loss occurs can be created. Realized.

[Brief explanation of the drawing]

1 and 2 are block diagrams of conventional open phase detection circuits, FIGS. 3 and 4 are operational waveform diagrams of FIG. 2, and FIG. 5 is an example of the open phase detection circuit according to the present invention. FIG. 6 is a detailed block diagram of the open phase detection circuit of the present invention, and FIGS. 7 and 8 are waveform diagrams illustrating the operation of the present invention. 1...Three-phase AC input terminal, 2...Transformer circuit, 3
... Positive phase detection circuit, 4... Negative phase detection circuit, 5
... Comparison circuit, 6 ... Output circuit, 7 ... Output terminal, 8 ... Three-phase full-wave rectifier circuit, 9 ... Smoothing circuit,
10... Stabilization circuit, 11... Reference voltage circuit, 1
2... Integrating circuit, 13... Monostable multivibrator circuit, 101... Transformer, 102... Bridge circuit, 103, 111, 113, 117, 12
0,121,126,127...Silicon body, 1
04,116,125,129...Capacitor,
105...transistor, 106, 108, 10
9,110,114,115,118,119,
122, 124, 128, 130, 131...Resistor, 107... Constant voltage diode, 112,1
23...Operation amplifier, 132...Relay, 133
...thyristor, 134...relay contact.

Claims (1)

[Scope of utility model registration request] A method that adds a voltage obtained by full-wave rectification of three-phase AC voltage and a reference voltage to a comparison circuit, detects that the full-wave rectified voltage is lower than the reference voltage in the event of a phase failure, and activates the output circuit via an integrating circuit. In the phase loss detection circuit, a monostable multivibrator circuit whose main components include an operational amplifier, a timing resistor, and a capacitor is provided between the comparator circuit and the integration circuit. detection circuit.