JP4793395B2 - Overvoltage protection circuit - Google Patents

Description

  The present invention relates to an overvoltage protection circuit.

  An overvoltage protection circuit has been put into practical use as a protection circuit against overvoltage in a circuit using a multiphase power supply. Such a technique is disclosed in the following Patent Documents 1 and 2. Causes of overvoltage include when the voltage of all phases rises to cause overvoltage, opening of the midpoint (hereinafter also simply referred to as “neutral phase of neutral point” or “N-phase phase loss”) and phase voltage In some cases, the voltage of each phase becomes non-equilibrium due to an open phase, and an overvoltage is caused.

  FIG. 3A is a schematic diagram of a three-phase four-wire AC power source in a normal state (no voltage increase in all phases and no phase loss). Taking a three-phase four-wire AC power source as an example, the neutral point corresponds to the center point N0 of the equilateral triangle, and each of the vectors going from the center point to each vertex of the equilateral triangle has three phase voltages L1. , L2 and L3. Here, since the magnitude of each vector is equal to the voltage value of the phase voltage, all the phase voltages of each phase are equal in a normal state.

  FIG. 3B is a schematic diagram showing a state transitioned from FIG. 3A when the N phase is lost. For example, if the N phase is lost, the lengths of the vectors are not uniform as shown in FIG. 3B, so that the voltages of the phases become unbalanced and cause overvoltage. In FIG. 3 (b), the voltage increases (in other words, the vector becomes longer) and the voltage decreases (in other words, the vector becomes shorter) than in the state of FIG. 3 (a). A) The phase voltage is shown finely. That is, when the N phase is lost and the base point N1 of the three vectors is positioned closer to the L3 phase, the phase voltages of the L1 phase and the L2 phase increase, and the phase voltage of the L3 phase decreases.

  FIG. 4A is a schematic diagram showing a conventional example of the arrangement of the control power supply and the load with respect to the multiphase power supply. Power is supplied to the load from each phase. The control power supply receives a phase voltage between the L2 phase and the N phase which is a neutral point, and generates a power supply for control, for example, an overvoltage protection circuit (not shown) based on this phase voltage. FIG. 4B is a schematic diagram equivalently showing the configuration of FIG. 4A when the N phase is lost.

  As a control power source for controlling the overvoltage protection circuit in a circuit using a multiphase power source, as shown in FIG. 4A as an example, a technique using the phase voltage of the multiphase power source has been proposed. When the N phase is lost, the control power supply cannot receive the phase voltage as shown in FIG. 4B, and the control power supply cannot be generated.

  FIG. 5A is a schematic diagram showing another conventional example of the arrangement of the control power supply and the load with respect to the multiphase power supply. In this example, the control power supply receives a line voltage between the L2 phase and the L3 phase, and generates a control power supply based on the line voltage. FIG. 5B is a schematic diagram equivalently showing the configuration of FIG. 5A when the L3 phase is lost.

  As another example of the generation of the control power supply, a technique using the line voltage of the multiphase power supply as shown in FIG. 5 (a) has been proposed. As shown in FIG. 5 (b), the control power supply cannot receive the line voltage and cannot generate a control power supply.

  Further, when the four conductors are disconnected and connected in a circuit breaker connected to a three-phase four-wire AC power source, an N-phase phase loss may occur due to a time shift in the interruption and connection of each conductor. . When the neutral line that bears the N phase is branched into three on the branch stand that is closer to the load than the circuit breaker, when such an open phase occurs, each power line that bears the three phases Stay connected. Therefore, for example, a closed circuit such as the first phase power line → load → neutral line → branch stand → neutral line → load → second phase power line is formed, and an excessive voltage is applied to the load. End up. In order to cope with such a phase loss, Patent Document 3 listed below proposes a technique for avoiding the formation of the closed circuit formed when the N phase is lost.

  Patent Documents 4 to 9 listed below include a switch that transitions from a conducting state to a non-conducting state when a phase loss occurs in a phase power supply including the N phase, and the switch is brought into a non-conducting state. In some cases, a technique is disclosed in which the relay does not perform the relay operation.

JP-A-4-161743 JP-A-11-218346 JP 2002-268195 A JP 2006-033999 A JP 2006-141114 A JP 2006-262660 A JP 2007-104858 A JP 2007-155256 A JP 2007-244019 A

  However, all of the techniques disclosed in Patent Documents 3 to 9 are intended to protect the circuit against an open phase, and are not intended to protect the load by detecting an overvoltage. It cannot cope with overvoltage caused by rising.

  In order to protect the load against overvoltage due to voltage increase in all phases and overvoltage due to phase loss, it is important to secure a control power source that controls the overvoltage protection circuit even in the case of phase loss.

  In view of the above problems, an object of the present invention is to provide a technique capable of dealing with both overvoltage due to voltage increase in all phases and overvoltage due to phase loss.

  In order to solve the above-mentioned problem, the first invention is the relay (14) relaying from the multiphase power supply (12) to the load (16), and the phase voltage of the multiphase power supply exceeds a predetermined voltage threshold. An overvoltage detection circuit (22) for detecting an overvoltage of the multi-phase power supply, a relay drive unit (24) for causing the relay to perform a cut-off operation when the overvoltage is detected, and more than the relay It is an overvoltage protection circuit (10) provided with the control power supply part (26) which produces | generates the electric power supplied to the said overvoltage detection circuit and the said relay drive part based on the said phase voltage by the side near the said multiphase power supply.

  2nd invention is 1st invention, Comprising: As said multiphase power supply, 1st phase power supply (31), 2nd phase power supply (32), 3rd phase power supply (33), and neutral point A three-phase four-wire AC power supply (12) having (34) is adopted, and is connected to the first phase power supply line (41) connected to the first phase power supply and the second phase power supply. A second phase power supply line (42), a third phase power supply line (43) connected to the third phase power supply, and a neutral point power supply line (44) connected to the neutral point And the control power supply unit (26) has one phase power supply line connected to the relay on the side closer to the three-phase four-wire AC power supply than the relay, the neutral point power supply line, A first control power supply (261) that generates a first power supply using a voltage between the relay and the relay closer to the three-phase four-wire AC power supply than the relay. And a second control power source (262) that generates a second power source using a voltage between the other phase power source line connected to the neutral point power source line and the neutral point power source line. The power supply unit supplies power to the overvoltage detection circuit (22) and the relay drive unit (24) using a combined voltage of the output voltage of the first control power supply and the output voltage of the second control power supply. .

  3rd invention is 2nd invention, Comprising: The said overvoltage detection circuit (22) is a said 1st phase power supply between the said 3 phase 4 wire type AC power supply (12) and the said relay (14). A first rectifier element (51) connected to a line (41) and rectifying a phase voltage of the first phase power source (31); and between the three-phase four-wire AC power source and the relay. A second rectifier element (52) connected to a second phase power supply line (42) and rectifying a phase voltage of the second phase power supply (32); the three-phase four-wire AC power supply; the relay the relay And a third rectifier element (53) connected to the third phase power supply line (43) for rectifying the phase voltage of the third phase power supply (33), and the first rectifier element to A combined voltage obtained by combining output voltages from the third rectifier elements and a comparator (55) for comparing the reference voltage When the combined voltage is higher than the reference voltage, the comparator determines that it is the overvoltage and sends a detection signal to the relay drive unit (24), and the relay drive unit receives the signal. If it does, the relay (14) is cut off.

  According to the first aspect of the present invention, the control power supply for overvoltage detection and load protection operation (overvoltage protection operation) is provided on the side closer to the power supply than the relay relaying to protect the load. The overvoltage protection operation can be performed without making the side near the load correspond to the overvoltage.

  According to the second aspect, the control power supply can be generated even when any one of the first to third phase power supplies and the neutral point is lost.

  According to the third invention, it contributes to overvoltage detection.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In the following drawings including FIG. 1, only elements related to the present invention are shown.

<Circuit configuration between power supply and load>
FIG. 1 is a diagram illustrating a circuit configuration of an overvoltage protection circuit 10 according to an embodiment of the invention. The overvoltage protection circuit 10 supplies power from the three-phase four-wire AC power supply 12 via the relay 14 to operate the load 16. In the present embodiment, the load 16 includes a diode bridge 13, a capacitor 15, and an inverter 17.

  The three-phase four-wire AC power supply 12 includes a first phase power supply 31, a second phase power supply 32, a third phase power supply 33, and a neutral point 34. A second phase power line 42, a third phase power line 43, and a neutral point power line 44 are connected.

  The first phase power supply line 41 to the third phase power supply line 43 are connected to the diode bridge 13 via the relay 14, and the neutral point power supply line 44 is directly connected to the diode bridge 13. The voltage of the three-phase four-wire AC power supply 12 connected to the diode bridge 13 is smoothed and applied to the inverter 17 by the cooperation of the diode bridge 13 and the capacitor 15.

  One power supply line (for example, the second phase power supply line 42) connected to the relay 14 is provided with a first control power supply 261 that obtains a first phase voltage with respect to the neutral point power supply line 44. A second control power source 262 that obtains a second phase voltage with respect to the neutral point power source line 44 is provided in the other power source line (for example, the third phase power source line 43). The first and second control power supplies 261 and 262 have an ability to generate a predetermined voltage when at least half of the phase voltage is supplied. A circuit configuration having such a capability is well known to those skilled in the art, and details thereof are omitted. The voltage combiner 265 combines the voltages of both control power supplies 261 and 262 to generate a combined voltage. Since the circuit configuration for realizing the voltage synthesizer 265 is also a well-known technique for those skilled in the art, the details are omitted. The first and second control power sources 261 and 262 and the voltage synthesis unit 265 constitute the control power source unit 26. The control power supply unit 26 supplies electric power to an overvoltage protection circuit, which will be described later, specifically, an overvoltage detection circuit 22 and a relay drive unit 24.

  By providing the control power supply unit 26 in this way, for example, when the neutral point 34 is out of phase, the first control power supply 261 and the second control power supply 262 are connected, and the second phase power supply is connected. A control power supply can be generated from the line voltage between the line 42 and the third phase power supply line 43. Further, for example, when the third phase power supply 33 is lost, the first control power supply 261 is output as the control power supply for the overvoltage detection circuit 22 and the relay drive unit 24. This is because the voltage generated by the second control power supply 262 is very low when the power supply third phase power supply 33 is lost in phase.

  As described above, on the side closer to the three-phase four-wire AC power supply 12 than the relay 14 that relays the load 16 to operate, the control power supply unit used for overvoltage detection and load 16 protection operation (overvoltage protection operation). 26, the overvoltage protection operation can be performed without making the side closer to the load 16 than the relay 14 correspond to the overvoltage.

<Circuit Configuration of Overvoltage Detection Circuit 22 and Relay Drive Unit 24>
The configuration of the overvoltage detection circuit 22 of the overvoltage protection circuit that is driven by receiving power supply from the control power supply unit 26 is as follows. The control power supply unit 26 and the components shown below have specifications that can sufficiently cope with an overvoltage assumed in the overvoltage protection circuit 10.

  The first phase power supply line 41 branches at a position P1 closer to the three-phase four-wire AC power supply 12 than the relay 14, and the branched power supply line 41a rectifies the phase voltage of the first phase power supply 31. 1 rectifier element 51. The second phase power supply line 42 branches at a position P2 closer to the three-phase four-wire AC power supply 12 than the relay 14, and the branched power supply line 42a rectifies the phase voltage of the second phase power supply 32. Connected to the second rectifying element 52. The third phase power supply line 43 branches at a position P3 closer to the three-phase four-wire AC power supply 12 than the relay 14, and the branched power supply line 43a rectifies the phase voltage of the third phase power supply 33. Connected to the third rectifying element 53. The first to third rectifying elements 51 to 53 synthesize phase voltages of the rectified phases.

  The neutral point power supply line 44 branches at a position P4 closer to the three-phase four-wire AC power supply 12 than the relay 14. The difference between the voltage of the branched power line 44a and the synthesized voltage VJ synthesized by the rectifying elements 51 to 53 is divided by using the resistors R1 and R2, and the voltage VK is obtained.

  The voltage VK is compared with the voltage value ref1 of the reference voltage 61, which is a criterion for overvoltage, by the high-voltage side comparator 55. When the voltage VK is higher than the voltage value ref 1 of the reference voltage 61, the high voltage side comparator 55 determines that an overvoltage has occurred and sends an overvoltage detection signal to the determination unit 56. The determination unit 56 causes the relay drive unit 24 to shut off the relay 14 when the overvoltage detection signal is continuously active for a predetermined time, and suppresses malfunction.

  The voltage VK is also input to the low voltage side comparator 57 via a low pass filter LF including a resistor R3 and a capacitor C1. The low voltage side comparator 57 is also supplied with the voltage value ref2 of the reference voltage 62 that is a criterion for determining the insufficient voltage. The low voltage side comparator 57 is insufficient when the voltage VK is lower than the voltage value ref2 of the reference voltage 62. It is determined that a voltage has been generated, and an undervoltage detection signal is sent to the determination unit 56. The determination unit 56 causes the relay drive unit 24 to shut off the relay 14 when the undervoltage detection signal is active for a predetermined time, thereby suppressing malfunction.

  The relay drive unit 24 that is driven by receiving power supply from the control power supply unit 26 controls the energization of the excitation coil 14 a under the control of the determination unit 56 that has received the overvoltage detection signal or the undervoltage detection signal, Performs a shut-off operation.

  The voltage VK is obtained by dividing the combined voltage VJ, and the combined voltage VJ is obtained by rectifying and combining each phase voltage as described above. Therefore, comparing the voltage VK with the reference voltage 61 to obtain the overvoltage detection signal as described above indirectly detects the overvoltage of the multiphase power supply when the phase voltage exceeds a predetermined voltage threshold. become.

<Operation of overvoltage protection circuit>
FIG. 2 is a diagram for explaining the operation of the present invention. The operation of the overvoltage protection circuit 10 having the above configuration will be described.

  When the three-phase four-wire AC power supply 12 is turned on, processing according to the flowchart of FIG. 2 is started, and the first control power supply 261 is supplied from the second phase power supply line 42 and the neutral point power supply line 44. The control power source is generated from the phase voltage, and the second control power source 262 generates the control power source from the phase voltage supplied from the third phase power source line 43 and the neutral point power source line 44 (step) S11).

  Further, the rectifying elements 51 to 53 connected to the power supply lines 41a to 43a branched from the first phase power supply line 41 to the third phase power supply line 43 perform half-wave rectification and half-wave rectification of each phase voltage. The phase voltages are combined to obtain a combined voltage VJ (steps S12 and S13).

  The combined voltage VJ is compared with the respective voltage values of the reference voltages 61 and 62 in the overvoltage detection circuit 22, specifically, the high voltage side comparator 55 and the low voltage side comparator 57, and it is determined whether or not an overvoltage or undervoltage has occurred. (Step S14).

  The high-voltage side comparator 55 compares the voltage value ref1 of the reference voltage 61 with the voltage VK obtained by dividing the composite voltage VJ to determine whether or not an overvoltage has occurred, and if a positive result is obtained, an overvoltage detection signal Is sent to the determination unit 56 (steps S15 and S16). When a negative result is obtained in the high-voltage side comparator 55, the low-voltage side comparator 57 compares the voltage value ref2 of the reference voltage 62 with the voltage VK to determine whether or not an undervoltage has occurred, and a positive result Is output, an undervoltage detection signal is sent to the determination unit 56 (steps S17 and S18).

  If a negative result is obtained in either the high-voltage side comparator 55 or the low-voltage side comparator 57, the relay 14 is driven and relayed, and the process returns to step S12 to repeat a series of processes (step S19).

  The determination unit 56 that has received the overvoltage detection signal or the undervoltage detection signal causes the relay drive unit 24 to perform a blocking process when the period during which each is active is longer than the predetermined period. Specifically, the relay drive unit 24 is controlled to control the energization to the excitation coil 14a, and the relay 14 is made to perform a cutoff operation (step S20). Thereafter, the process returns to step S12, and a series of processes are repeated. When the three-phase four-wire AC power supply 12 is turned off, the process is terminated.

It is a figure which illustrates the circuit structure of the overvoltage protection circuit which concerns on embodiment of this invention. It is operation | movement explanatory drawing of this invention. (A) It is a schematic diagram of the three-phase four-wire type AC power supply in a normal state. FIG. 3B is a schematic diagram showing a state transitioned from FIG. 3A when the N phase is lost. (A) It is the schematic which shows one conventional example of arrangement | positioning of the control power supply and load with respect to a multiphase power supply. FIG. 4B is a schematic diagram equivalently showing the configuration of FIG. 4A when the N phase is lost. (A) It is the schematic which shows other conventional examples of arrangement | positioning of the control power supply and load with respect to a multiphase power supply. FIG. 5B is a schematic diagram equivalently showing the configuration of FIG. 5A when the L3 phase is lost.

Explanation of symbols

10 Overvoltage protection circuit 12 3-phase 4-wire AC power supply (multi-phase power supply)
DESCRIPTION OF SYMBOLS 14 Relay 16 Load 22 Overvoltage detection circuit 24 Relay drive part 26 Control power supply part 261,262 Control power supply 262 2nd control power supply 31-33 Phase power supply 34 Neutral point 41-43 Phase power supply line 44 Neutral point power supply line 51- 53 Rectifier 55 High side comparator

Claims (3)

A relay (14) for relaying from the multiphase power source (12) to the load (16);
An overvoltage detection circuit (22) for detecting an overvoltage of the multiphase power supply when a phase voltage of the multiphase power supply exceeds a predetermined voltage threshold;
A relay drive unit (24) for causing the relay to perform a cut-off operation when the overvoltage is detected;
An overvoltage protection circuit (10) comprising: a control power supply unit (26) that generates electric power to be supplied to the overvoltage detection circuit and the relay drive unit based on the phase voltage on a side closer to the multiphase power supply than the relay. . An overvoltage protection circuit (10) according to claim 1,
As the multiphase power supply, a three-phase four-wire AC power supply (12) having a first phase power supply (31), a second phase power supply (32), a third phase power supply (33), and a neutral point (34). )
A first phase power supply line (41) connected to the first phase power supply;
A second phase power supply line (42) connected to the second phase power supply;
A third phase power supply line (43) connected to the third phase power supply;
A neutral point power line (44) connected to the neutral point;
The control power supply unit (26)
On the side closer to the three-phase four-wire AC power source than the relay, a first power source using a voltage between the one phase power source line connected to the relay and the neutral point power source line A first control power supply (261) for generating
On the side closer to the three-phase four-wire AC power source than the relay, a second power source is used by using a voltage between the other phase power source line connected to the relay and the neutral point power source line. A second control power supply (262) for generating
The control power supply unit uses the combined voltage of the output voltage of the first control power supply and the output voltage of the second control power supply to supply power to the overvoltage detection circuit (22) and the relay drive unit (24). Supply overvoltage protection circuit. An overvoltage protection circuit (10) according to claim 2,
The overvoltage detection circuit (22)
Connected to the first phase power supply line (41) between the three-phase four-wire AC power supply (12) and the relay (14), and rectifies the phase voltage of the first phase power supply (31). A first rectifying element (51);
A second rectifying element (rectifier connected to the second phase power supply line (42) between the three-phase four-wire AC power supply and the relay to rectify the phase voltage of the second phase power supply (32) ( 52),
A third rectifying element (rectifier connected to the third phase power supply line (43) between the three-phase four-wire AC power supply and the relay to rectify the phase voltage of the third phase power supply (33) ( 53)
A comparator (55) that compares a synthesized voltage obtained by synthesizing output voltages from each of the first rectifier element to the third rectifier element with a reference voltage;
When the combined voltage is higher than the reference voltage, the comparator determines that the overvoltage is the overvoltage, and sends a detection signal to the relay driving unit (24).
An overvoltage protection circuit for causing the relay (14) to perform a cut-off operation when the relay driving unit receives the signal.

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