JPS6137848B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is designed to prevent damage or burnout caused by incorrect connection of the power supply or reverse phase rotation in electrical equipment operated using three-phase alternating current as a power source. This invention relates to antiphase protection devices used to protect electrical equipment that generates.

[Conventional technology]

Generally, many electrical devices that use three-phase alternating current as a power source use a three-phase induction motor as their power source. The rotation direction of this three-phase induction motor is determined by the phase rotation of the power supply, and reversible operation is performed by switching the two phases, but depending on the equipment driven by this motor, The direction of rotation is fixed and cannot be reversed, and if reversed by mistake, it often causes damage or other accidents. Even if the equipment is capable of reversible operation, for example, if the power supply is incorrectly connected to a conduction valve actuator, which is widely used in the process industry, the actuator's limit switch will not operate, causing it to run away and destroy the valve. This may cause an accident that may cause the motor to burn out. Therefore, one of the devices conventionally used to protect these devices from the reverse phase of the power supply is an induction disk type reverse phase relay, in which each phase current is passed through three shaded ring drive magnets. There is a structure that detects phase inversion or phase loss depending on the balance between the operating torque applied to the phase rotation and the suppressing torque due to phase rotation.

[Problem that the invention seeks to solve]

However, the anti-phase protection device has a complicated structure because it requires a rotation mechanism and the like, and has the disadvantage that it is inferior to the electronic 3E relay described later in terms of quick response. In addition, the electronic 3E relay, which is widely used today, converts the load current of each three-phase line into voltage using three current transformers, and processes the voltage with several stages of electronic circuits to connect the protective relay. Since the circuit is designed to output an operating signal, the circuit configuration becomes complicated and three expensive current transformers are required.
It has the disadvantage of being very costly.

This invention was created in view of these problems, and utilizes the time constant of an electronic circuit made of a small number of electronic components without using a complicated rotation mechanism or expensive current transformer, and is small and robust. Can be produced inexpensively,
Moreover, it is an object of the present invention to provide an anti-phase protection device that can accurately detect anti-phase of a three-phase power supply, quickly release a load from the power supply, and prevent damage to the load.

[Means for solving problems]

In order to achieve the above-mentioned object, the anti-phase protection device for a three-phase AC load of the present invention is provided between one line of the three-phase AC circuit connected to the three-phase AC load and the other two lines as the midpoint. In each case, a capacitor-input smoothing circuit consisting of a half-wave rectifying element, a capacitor, and a resistor connected in parallel is connected in such a way that the half-wave rectifying elements are connected in anti-series with each other, and A DC relay comprising a DC relay and another half-wave rectifier connected in series between each series connection point of the wave rectifier and the capacitor input smoothing circuit, and another capacitor connected in parallel to the DC relay. The circuit is connected, and the operating contact of the DC relay is inserted and connected to a switching control circuit of a main switch that connects and disconnects the three-phase AC circuit.

[Effect]

With the above configuration, the two half-wave rectifying elements provided between one line and the other two lines of the three-phase AC circuit are oriented in anti-series, so that there is a The difference voltage between the line voltages generated in the capacitor input type smoothing circuit connected in series with each half-wave rectifying element appears in the capacitor of the connected DC relay circuit. Therefore, when a three-phase AC circuit is connected to the positive phase, the phase difference between the line voltages appearing between the two phases is 120°, and
The voltage difference is less than the rated voltage of the DC relay,
DC relays are not activated. On the other hand, when a three-phase AC circuit is connected to the opposite phase, the phase difference between the line voltages appearing between the two phases becomes 240°, and the voltage difference exceeds the rated voltage of the DC relay, causing the DC relay to drive. Its operating contact is actuated and the main switch interrupts the main circuit to the load.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit configuration diagram of an anti-phase protection device for a three-phase AC load according to an embodiment, where R, S, and T are three-phase AC power lines, for example, 220V. Reference numeral 1 denotes an air circuit breaker that interrupts the electric circuit when a ground fault or correlated short circuit occurs in the electric circuit or the load, 2 is the main switch of the load circuit consisting of an electromagnetic switch, and 3 is its contact. Reference numeral 4 denotes a switching control circuit for the main switch 2, which incorporates a DC relay Ry, which is the output part of the anti-phase protection device 6 of the present invention, and its operating contacts b and b' (normally closed), which are surrounded by a broken line. There is. 5 and 5' are AC power supply terminals of the opening/closing control circuit 4. A voltage regulator or the like may be used for the electric lines R, S, and T, but it is not shown because it is not related to this invention. 6 is the anti-phase protection device of the present invention as described above, and when the phase is positive, the three phases are connected as T' phase - point A, S' phase - point B, R' phase - point C. . D ₁ , D ₂ , and D ₃ are half-wave forward current elements each consisting of a diode, which can withstand a reverse breakdown voltage twice the maximum AC value. C ₁ , C ₂ , C ₃ are smoothing capacitors, and the two capacitors C ₁ and C ₂ are 1 μF in this example, and are connected in anti-series to each other.
Use 20μF for the other capacitor _C3 . Also,
The output resistances R ₁ and R ₂ are 10KΩ, and as shown in the figure, each parallel circuit of each capacitor C ₁ and C ₂ and each output resistance R ₁ and R ₂ is connected in series to the half-wave rectifier D ₁ and D ₂ . They are connected to form a capacitor input type smoothing circuit for the T' and R' phases. As mentioned above, the time constant of this smoothing circuit is set to 10 msec or more and about 20 msec, and the time constant of capacitor _C3 connected in parallel to series relay Ry is set large enough to not reduce the responsiveness of DC relay Ry.

Next, the operation of the embodiment will be explained with reference to FIGS. 2 and 3.

Figures 2A to 2E show the voltage waveforms of various parts when the three phases are in positive phase, and first, v ₁ in Figure 2A is shown in Figure 1.
Line voltage of T′ phase and S′ phase, v ₂ is 120 from line voltage v ₁
゜It is the line voltage of the R' phase and S' phase which are advanced in phase. Figure B shows that after the line voltage v ₂ is rectified by the half-wave rectifier D ₂ , the capacitor C ₂ is charged, and the resistor R ₂
The waveform of the DC voltage V ₂ due to the discharge characteristics at point 9
is + and point 8 is -. Figure C shows the rectified waveform of the line voltage v _1. After the half-wave with the opposite polarity to the line voltage v ₂ is rectified by the half-wave rectifier D ₁ , the capacitor C ₁ is charged and the voltage is applied to the resistor R ₁ . This is due to the discharge characteristics, with point 7 being + and point 8 being -. The same figure D shows the voltage V ₂
and the voltage V ₁ , that is, the differential voltage △V _N ' appearing between points 9 and 7, and assuming that there is no capacitor C ₃ , the half-wave rectifier D ₃ and the DC relay
This is the DC voltage applied to Ry. Figure E is the first
As shown in the figure, the average value of the differential voltage △V _N when capacitors _C3 are connected in parallel is approximately 35V, but since the DC relay Ry has a rating of 100V, the differential voltage △ of the above 35V At _VN , the operating contacts b and b' remain closed and supply power to the load without being energized and without any beat or chattering.

Next, the operation at the time of anti-phase connection will be explained with reference to FIG. For example, as shown by the broken lines in FIG. 1, when the two phases S and T are connected incorrectly to the connection points 12 and 13, the voltage is applied between the connection terminals B and C. The voltage is the line voltage between the R phase and T phase, which is v ₂ ' in the same figure A, and on the other hand,
The voltage applied between connection terminals A and B is T phase and S
The phase line voltage is v ₁ ′, which is 240° behind the line voltage v ₂ ′ mentioned above, and is 120° behind the line voltage v ₁ in Figure 2A. It's getting old. FIG. 3B shows the waveform of the DC voltage V ₂ ' caused by charging the capacitor C ₂ and discharging into the resistor R ₂ after the line voltage V _{2 '} is rectified. moreover,
Figure C shows the waveform of the DC voltage V ₁ ' caused by charging the capacitor C ₁ after the line voltage V ₁ ' has been rectified and discharging it to the resistor R ₁ . Furthermore, Figure D shows the differential voltage between the voltage V ₂ ' and the voltage V ₁ ', that is, the differential voltage △V' appearing between points 9 and 7, when the capacitor C ₃ shown in Figure 1 is connected. This is the waveform of the DC voltage applied to the half-wave rectifier D ₃ and the DC relay Ry when it is assumed that the maximum value △V′ _Bnax
The voltage reaches about 180V, but the generation time is extremely instantaneous, and the average value is about 30V, so the DC relay
Although Ry cannot be activated, by connecting capacitor C ₃ as shown in Figure 1,
As shown in Figure E, the differential voltage △V _B ' is smoothed to an average value of about 100V, and the DC voltage
It lasts until time e when the next half of V ₂ ' appears. Therefore, this smoothed differential voltage △V _B is supplied to the DC relay Ry and its operating contacts b and b' are opened, so the main switch 2 is operated and the load circuit is cut off, resulting in an anti-phase connection. At the same time, the contact b' lights up an alarm indicator light (not shown) attached to the control circuit 4 to warn the operator of the out-of-phase connection.

In addition, when the S phase and T phase based on FIG. If each is incorrectly connected, the line voltage between S phase and R phase will be applied between terminals B and C, and the line voltage between R phase and T phase will be applied between terminals A and B. , the phase difference is 240 degrees, which is the same as the phase difference between the line voltage v ₂ ' and the line voltage v ₁ ' in Figure 3, and the waveforms of each part are the same as in Figures A to E in Figure 3, and the operation is the same as above. to cut off the main circuit. As described above, even if any two phases are reversely connected, the balance between the output voltages of the two sets of capacitor input type smoothing circuits of the device is broken, energizing the DC relay Ry, and the anti-phase protection device is properly activated.

The above embodiments have been explained for AC 220V, but in the case of 440V, DC relay Ry is used as DC relay Ry.
You can use one with a 200V rating, or insert a series resistor equivalent to the internal resistance of a DC relay with a 100V DC rating. In addition, if this DC relay Ry is replaced with a DC keep relay, the contacts will remain open when the phase is out of phase, and the protection function will be further improved by eliminating the out-of-phase phenomenon and resetting when the situation returns to normal. .

〔Effect of the invention〕

Since this invention is configured as described above,
Without inserting an expensive current transformer into each three-phase line to convert the load current into voltage, the reverse phase of the three-phase power supply can be instantly detected using a small number of electronic components, and the load circuit can be changed. can cut off the load,
For example, it is possible to prevent damage or destruction to an electric motor or a valve driven by the electric motor. Moreover, the structure is simple and compact,
This has the advantage of being a convenient and inexpensive device to install.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of an anti-phase protection device for a three-phase AC load according to an embodiment of the present invention, and Figs. 2 A to E are waveform diagrams of various parts for explaining operation when the three phases are positive phases. , and FIGS. 3A to 3E are waveform diagrams of respective parts when two of the three phases are reversely connected. R, S, T...Three-phase AC line, R', S', T'...
...Each line voltage extraction point, 2...Load main switch, 4...
...opening/closing control circuit, 6...reverse phase protection device, D ₁ to _{D 3}
... Half-wave rectifier, C ₁ - C ₃ ... Smoothing capacitor, R ₁ - _{R 2} ... Output resistance, Ry ... DC relay,
b, b'...Same operating contact (normally closed), v ₁ ...S-phase and T-phase line voltage during positive phase, v ₁ '...Above line voltage during anti-phase, v ₂ ... ...Line voltage of R phase and S phase during positive phase, v ₂ ′...Above line voltage during anti-phase, V ₁ , V ₁ ′,
V ₂ , V ₂ ′...Half-wave rectified output voltage of v ₁ , v ₁ ′, v ₂ , v ₂ ′, respectively, △V _N ...Differential voltage applied to relay Ry during positive phase, △V _B ...Differential voltage applied to relay Ry when the phase is out of phase.

Claims (1)

[Claims] 1 A capacitor-input type smoothing device in which a half-wave rectifying element, a capacitor, and a resistor are connected in parallel between one line of a three-phase AC circuit connected to a three-phase AC load and the other two lines as the midpoint. A series circuit with the circuit is connected in such a way that each half-wave rectifying element is connected in anti-series connection with each other, and each series connection point between each half-wave rectifying element and the capacitor input type smoothing circuit is connected. A DC relay circuit in which a DC relay and another half-wave rectifying element are connected in series and another capacitor is connected in parallel to the DC relay is connected between them, and the operating contacts of the DC relay are connected to the three-phase AC A reverse phase protection device for a three-phase AC load, characterized in that it is inserted and connected to the switching control circuit of a main switch that connects and disconnects the circuit.