Contact arc extinction three-phase circuit

Abstract

The utility model provides a three-phase circuit for contact arc extinction. The three-phase circuit comprises a contact delay circuit and three trigger circuits, the contact delay circuit comprises a coil MJ; the three trigger circuits are respectively and correspondingly arranged on an A-phase circuit, a B-phase circuit and a C-phase circuit of the power distribution system; each trigger circuit is connected with the three-phase circuit corresponding to each trigger circuit through two terminals; a contact switch KM1 is arranged between the two terminals; the contact switches KM1 of the A-phase circuit, the B-phase circuit and the C-phase circuit correspond to the coil MJ in position; when the three-phase circuit carries out power supply, the three trigger circuits are conducted before the contact delay circuit, and after the contact delay circuit is conducted, the coil MJ can close the contact switch KM1 of the A-phase circuit, the B-phase circuit and the C-phase circuit. According to the embodiment of the invention, the contact switch KM1 of the A-phase circuit, the B-phase circuit and the C-phase circuit can be delayed to be closed through the contact delay circuit, and the conversion from soft switching to hard switching of the three-phase circuit is realized through the three trigger circuits, so that the arc discharge phenomenon is eliminated.

Description

Technical Field

[0001] This application relates to the field of arc suppression technology, specifically to a three-phase circuit for contact arc suppression. Background Technology

[0002] An electric arc is a gas discharge phenomenon, a momentary spark produced when current passes through certain insulating media (such as air). Most of its charge carriers are electrons generated by primary electron emission. Electric arcs can be divided into good arcs and bad arcs. Good arcs are generated during normal operation, such as those in fluorescent lamps and arc welding, while bad arcs can cause circuit fires or affect the normal operation of equipment; these are usually referred to as faulty arcs.

[0003] To reduce the harm caused to humans by fault arcs, people use arc extinguishing methods such as mechanical arc extinguishing, ceramic hammer arc extinguishing, and grid arc extinguishing. However, when using these arc extinguishing methods, regardless of which method is used, an arc has already been generated, and potential dangers may also arise. The arc may still cause harm to people or damage to equipment. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model discloses a three-phase circuit for contact arc extinguishing, which can solve the technical problem that in the prior art, when using these arc extinguishing methods, no matter which arc extinguishing method is used, an electric arc has already been generated, and potential dangers may also accompany it, and the electric arc may still cause harm to people or damage to equipment.

[0005] To achieve the above objectives, this application provides a three-phase circuit for contact arc suppression, which includes a contact delay circuit and three trigger circuits.

[0006] The contact delay circuit includes a coil MJ;

[0007] The three triggering circuits are respectively set on the A, B, and C phase circuits of the power distribution system; each triggering circuit is connected to the corresponding three-phase circuit through two terminals; a contact switch KM1 is set between the two terminals of each triggering circuit; the contact switches KM1 of the A, B, and C phase circuits are all corresponding to the positions of the coil MJ.

[0008] When power is supplied to the three-phase circuits A, B, and C, the three trigger circuits are turned on before the contact delay circuits are turned on, and after the contact delay circuits are turned on, the coil MJ can close the contact switch KM1 of the three-phase circuits A, B, and C.

[0009] In one possible embodiment, the contact delay circuit includes a delay circuit;

[0010] The delay circuit includes coil AJ1, diode D6, contact switch KA1, capacitor C10, and diode D5;

[0011] One end of coil AJ1 is electrically connected to the power supply terminal of the contact delay circuit, and the other end of coil AJ1 is electrically connected to the positive terminal of diode D6; the negative terminal of diode D6 is electrically connected to the base of the first transistor Q1.

[0012] The contact switch KA1 and other units of the delay circuit are set separately; the position of the contact switch KA1 corresponds to the position of the coil AJ1, and the contact switch KA1 can be electrically connected to the coil MJ to form an independent circuit;

[0013] The positive terminal of diode D5 is electrically connected to the power supply terminal of the contact delay circuit, and the negative terminal of diode D5 is grounded.

[0014] One end of capacitor C10 is electrically connected to the negative terminal of diode D5, and the other end of capacitor C10 is grounded;

[0015] When power is supplied to the three-phase circuit A, B, and C, the base potential of the first transistor Q1 rises from zero to the conduction value of the first transistor Q1. The first transistor Q1 conducts, causing the coil AJ1 to close the contact switch KA1, thereby causing the coil MJ to close the contact switch KM1 of the three-phase circuit A, B, and C.

[0016] In one possible embodiment, a resistor R20 is connected in parallel across the two ends of capacitor C10.

[0017] In one possible embodiment, each trigger circuit includes a low-voltage power supply circuit and a signal trigger circuit; the low-voltage power supply circuit is electrically connected to the signal trigger circuit and is used to supply power to the signal trigger circuit;

[0018] The signal triggering circuit includes a bidirectional thyristor; the two ends of the bidirectional thyristor are electrically connected to the two ends of the contact switch KM1 corresponding to each triggering circuit; when the signal triggering circuit triggers a signal, the bidirectional thyristor is turned on.

[0019] In one possible embodiment, after the signal triggering circuit triggers the signal, the bidirectional thyristor is turned on before the first transistor Q1 is turned on; after the first transistor Q1 is turned on, the contact switch KM1 corresponding to each triggering circuit is turned on.

[0020] In one possible embodiment, the low-voltage power supply circuit includes an energy storage capacitor;

[0021] One end of the energy storage capacitor is electrically connected to the power supply terminal of the low-voltage power supply circuit, and the other end of the energy storage capacitor is electrically connected to the ground terminal of the low-voltage power supply circuit; the energy storage capacitor can delay the disconnection of the bidirectional thyristor when the contact switch KM1 corresponding to each trigger circuit is opened.

[0022] In one possible embodiment, the signal triggering circuit includes a photoelectric driver; the low-voltage power supply circuit includes a second resistor;

[0023] The first end of the second resistor is electrically connected to the power supply terminal of the low-voltage power supply circuit, and the second end of the second resistor is electrically connected to the first port of the input terminal of the photoelectric driver.

[0024] In one possible embodiment, the low-voltage power supply circuit includes a voltage regulator circuit; a second diode is provided between the second resistor and the power supply terminal of the low-voltage power supply circuit;

[0025] The voltage regulator circuit includes a first voltage divider resistor, a second voltage divider resistor, and a three-terminal regulator; the first voltage divider resistor, the second voltage divider resistor, and the three-terminal regulator are connected in series in sequence.

[0026] The first voltage divider resistor is electrically connected to the second diode; the three-terminal regulator is electrically connected to the second port of the input terminal of the photoelectric driver.

[0027] In one possible embodiment, a filter capacitor is connected in parallel across the two ends of the three-terminal regulator;

[0028] An anti-interference capacitor and an anti-interference resistor are connected in parallel across the two ends of the three-terminal regulator and the second voltage divider resistor.

[0029] In one possible embodiment, the three-phase circuit for arc suppression by the contact also includes an AC / DC power conversion circuit.

[0030] The AC / DC power conversion circuit is electrically connected to the A, B, and C phase circuits of the power distribution system, and is used to supply power to the contact delay circuit and the three trigger circuits.

[0031] The technical solution provided in this application has the following technical effects:

[0032] In the embodiments of this application, when the three-phase circuits A, B, and C are powered, the three trigger circuits conduct before the contact delay circuits. After the contact delay circuits conduct, the coil MJ can close the contact switches KM1 of the three-phase circuits A, B, and C. When the three trigger circuits are triggered and the contact switches KM1 of the three-phase circuits A, B, and C are not closed, the three trigger circuits supply power to the load, at which time the soft switches of the three contact circuits can be connected to supply power. When the contact switches KM1 of the three-phase circuits A, B, and C are closed, the three-phase circuits A, B, and C supply power to the load, at which time the hard switches of the three-phase circuits A, B, and C can be connected to supply power. This realizes the transformation of the soft switches of the three-phase circuits to hard switches for contact arc suppression, and avoids the arc discharge generated when the contact switches are directly connected when the three-phase circuits A, B, and C are powered, thus eliminating the arc discharge phenomenon. Attached Figure Description

[0033] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the main circuit of a three-phase circuit for contact arc suppression provided in an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of a contact delay circuit for a three-phase circuit with contact arc suppression provided in an embodiment of this application;

[0036] Figure 3 This is a circuit diagram of the trigger circuit for a three-phase circuit with contact arc suppression provided in an embodiment of this application. Figure 1 ;

[0037] Figure 4 This is a circuit diagram of the trigger circuit for a three-phase circuit with contact arc suppression provided in an embodiment of this application. Figure 2 ;

[0038] Figure 5 This is a circuit diagram of the trigger circuit for a three-phase circuit with contact arc suppression provided in an embodiment of this application. Figure 3 ;

[0039] Figure 6 This is a circuit diagram of a power supply circuit for a three-phase circuit with contact arc suppression provided in an embodiment of this application. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0041] It should be noted that the term "an embodiment" or "embodiment" in the specification of the embodiments of this application refers to a specific feature, structure, or characteristic that can be included in at least one implementation of this application. It should be understood that in the specification, claims, and accompanying drawings of the embodiments of this application, the terms "upper," "lower," "top," "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0042] like Figures 1 to 6 As shown, this application discloses a three-phase circuit for contact arc suppression, which includes a contact delay circuit and three trigger circuits. The contact delay circuit includes a coil MJ.

[0043] Optionally, the three trigger circuits are respectively installed on the A, B, and C phase circuits of the power distribution system. Each trigger circuit is connected to its corresponding three-phase circuit via two terminals, and a contact switch KM1 is installed between the two terminals of each trigger circuit. The A, B, and C phase circuits of the power distribution system can be 380V three-phase power for industrial production. The three phases can include three 220V live wires and one neutral wire, and the three phases are all 120 degrees apart.

[0044] In this circuit, the contact switches KM1 of the three-phase circuits A, B, and C are all located corresponding to the coil MJ. The contact switches KM1 of the three-phase circuits A, B, and C can all be set near the coil MJ. When the state of the coil MJ changes, the contact switches KM1 of the three-phase circuits A, B, and C can be opened or closed.

[0045] When power is supplied to the three-phase circuit A, B, and C, the three trigger circuits conduct before the contact delay circuit. After the contact delay circuit conducts, the coil MJ can close the contact switch KM1 of the three-phase circuit A, B, and C. Therefore, the triggering priority of the three trigger circuits is higher than that of the contact switch KM1 of the three-phase circuit A, B, and C. When the three trigger circuits are triggered and the contact switch KM1 of the three-phase circuit A, B, and C is not closed, the three trigger circuits supply power to the load, at which point the soft switches of the three contact circuits can be activated. When the contact switch KM1 of the three-phase circuit A, B, and C is closed, the three-phase circuit A, B, and C supplies power to the load, at which point the hard switches of the three-phase circuit A, B, and C can be activated. This realizes the transformation from soft switching to hard switching in the three-phase circuit for contact arc suppression, thereby eliminating the arc discharge phenomenon.

[0046] It is worth noting that the resistance of the contact switch KM1 in this application is negligible. In other embodiments of the prior art, some embodiments use electrical components or circuit modules capable of eliminating electric arcs to replace the contact switch KM1. However, these electrical components or circuit modules often have a certain resistance, which leads to energy loss and continuous energy waste when the three-phase circuit of the power distribution system is powered. The three-phase arc-extinguishing circuit in this application uses the coil MJ to close the contact switch KM1 of the three-phase circuit to conduct the three-phase circuit, that is, it still uses the contact switch KM1. Since the resistance of the contact switch KM1 in this application is negligible, the three-phase arc-extinguishing circuit in this application does not cause energy waste and achieves energy saving and environmental protection.

[0047] In one possible embodiment, the contact delay circuit includes a delay circuit. The delay circuit may include a coil AJ1, a diode D6, a contact switch KA1, a capacitor C10, and a diode D5.

[0048] Optionally, one end of coil AJ1 can be electrically connected to the power supply terminal of the contact delay circuit, and the other end of coil AJ1 can be electrically connected to the positive terminal of diode D6. The negative terminal of diode D6 can be electrically connected to the base of the first transistor Q1. A resistor R19 can be provided at the connection between the negative terminal of diode D6 and the first transistor Q1. Diode D6 can be a bleeder diode.

[0049] Optionally, the contact switch KA1 and other units of the delay circuit can be separated, and the contact switch KA1 can be electrically connected to the coil MJ to form an independent circuit. Specifically, Figure 1 The kai port connected to the coil MJ and Figure 2The kai port is connected to the contact switch KA1. The position of the contact switch KA1 corresponds to the position of the coil AJ1. When the state of the coil AJ1 changes, the coil AJ1 can be opened or closed.

[0050] Optionally, the positive terminal of diode D5 is electrically connected to the power supply terminal of the contact delay circuit, and the negative terminal of diode D5 is grounded. A diode D4 can also be provided between diode D5 and the power supply terminal of the contact delay circuit. Diodes D4 and D5 are used to make the current flowing through diodes D4 and D5 conduct unidirectionally, thereby controlling the current flow direction in the contact delay circuit.

[0051] Optionally, one end of capacitor C10 is electrically connected to the negative terminal of diode D5, and the other end of capacitor C10 is grounded. Capacitor C10 and resistor R19 can be used to form the time constant of the contact delay circuit.

[0052] When the three-phase circuits A, B, and C are powered, the base potential of the first transistor Q1 can rise from zero to the conduction value of the first transistor Q1. The first transistor Q1 conducts so that the coil AJ1 closes the contact switch KA1, thereby causing the coil MJ to close the contact switch KM1 of the three-phase circuits A, B, and C.

[0053] The time it takes for the base potential of the first transistor Q1 to rise to the conduction value can be an adjustable time. This time can be determined by the capacitor C10 and the resistor R19. Generally, this time can be less than 50 milliseconds. The operator can increase or decrease this time by adjusting the resistance values ​​of the capacitor C10 and the resistor R19.

[0054] In one possible embodiment, a resistor R20 is connected in parallel across the capacitor C10. The resistor R20 and diode D5 are configured to prevent the contact switch KA1 from closing delayed due to the action of capacitor C10 when the power supply to the three-phase circuits A, B, and C is turned off. Therefore, when the contact delay circuit is de-energized, resistor R20 and diode D5 provide a safe discharge path for C10, preventing residual charge from causing AJ1 to remain attracted to KA1, and also preventing residual charge from causing safety hazards.

[0055] In one possible embodiment, each trigger circuit includes a low-voltage power supply circuit and a signal trigger circuit. The low-voltage power supply circuit is electrically connected to the signal trigger circuit and supplies power to the signal trigger circuit, thereby triggering a signal. In the trigger circuit of this application, the time interval between supplying power from the low-voltage power supply circuit to the signal trigger circuit and the signal trigger circuit triggering the signal is negligible.

[0056] Optionally, the signal triggering circuit includes a bidirectional thyristor, with its two ends electrically connected to the two ends of a contact switch KM1 corresponding to each triggering circuit. That is, the bidirectional thyristor of each triggering circuit can be connected in parallel with the contact switch KM1 corresponding to each triggering circuit. When the signal triggering circuit triggers a signal, the bidirectional thyristor immediately conducts. The bidirectional thyristor can be connected in parallel with the contact switch KM1 corresponding to each triggering circuit. Figures 3 to 5 BT1, BT2, and BT3.

[0057] In one possible embodiment, after the signal trigger circuit triggers the signal, the bidirectional thyristor is turned on before the first transistor Q1 is turned on. After the first transistor Q1 is turned on, the contact switch KM1 corresponding to each trigger circuit is turned on. Thus, in the time from the signal trigger circuit triggering the signal to the first transistor Q1 being turned on, the three-phase circuit for contact arc suppression is in a soft-switching state with the bidirectional thyristors of the three trigger circuits turned on. After the first transistor Q1 is turned on, the three-phase circuit for contact arc suppression is in a hard-switching state with the contact switch KM1 turned on.

[0058] In one possible embodiment, the low-voltage power supply circuit includes an energy storage capacitor. One end of the energy storage capacitor is electrically connected to the power supply terminal of the low-voltage power supply circuit, and the other end of the energy storage capacitor is grounded. The energy storage capacitor can delay the disconnection of the bidirectional thyristor when the contact switch KM1 corresponding to each trigger circuit is opened. The energy storage capacitor can be respectively corresponding to... Figures 3 to 5 C1, C4, and C7 in the text.

[0059] Therefore, when the A, B, and C phase circuits are de-energized, the contact delay circuit immediately de-energizes, and the contact switch KM1 immediately closes. At this time, the energy stored in the energy storage capacitors in the three trigger circuits still maintains the bidirectional thyristor briefly on, thus delaying its disconnection. The specific time of the bidirectional thyristor's delayed disconnection can be adjusted by adjusting the amount of energy that the energy storage capacitor can store. After the energy stored in the capacitor is completely released, the bidirectional thyristor also disconnects and shuts off the power supply in a high-resistance state, thereby preventing arc discharge when the A, B, and C phase circuits are de-energized.

[0060] In one possible embodiment, the signal triggering circuit includes a photoelectric driver, and the low-voltage power supply circuit includes a second resistor. The photoelectric driver can correspond to... Figures 3 to 5 In the diagram, U1, U2, and U3, the second resistor can correspond to... Figures 3 to 5 R2, R8, and R14 are used in the circuit. The input terminals of the photoelectric driver may include a first port and a second port, and the output terminals of the photoelectric driver may include a third port and a fourth port. When the fourth port detects a zero-crossing phase, the third port can send a trigger signal to turn on the bidirectional thyristor.

[0061] Optionally, the first end of the second resistor is electrically connected to the power supply terminal of the low-voltage power supply circuit, and the second end of the second resistor is electrically connected to the first port of the input terminal of the photoelectric driver.

[0062] In one possible embodiment, the low-voltage power supply circuit includes a voltage regulator circuit, and a second diode is provided between the second resistor and the power supply terminal of the low-voltage power supply circuit. The second diode can correspond to... Figures 3 to 5 D1, D2, and D3 in the diagram.

[0063] Optionally, the voltage regulator circuit includes a first voltage divider resistor, a second voltage divider resistor, and a three-terminal regulator, which are connected in series. The first and second voltage divider resistors provide voltage division to the three-terminal regulator, thereby stabilizing its operating voltage. The first voltage divider resistor can be respectively connected to... Figures 3 to 5 R3, R9, and R15 in the diagram, the second voltage divider resistors can be respectively... Figures 3 to 5 R6, R12, and R18 in the three-terminal voltage regulator can respectively correspond to Figures 3 to 5 U4, U5, and U6.

[0064] Optionally, the first voltage divider resistor is electrically connected to the second diode, and the three-terminal regulator is electrically connected to the second port of the input terminal of the photoelectric driver. The three-terminal regulator can stabilize the operating voltage of the photoelectric driver.

[0065] In one possible embodiment, filter capacitors are connected in parallel across the two ends of the three-terminal regulator, and the filter capacitors can be respectively connected to... Figures 3 to 5 C2, C5, and C8 are used as filter capacitors to provide filtering for the three-terminal voltage regulator. An anti-interference capacitor and an anti-interference resistor are connected in parallel across the three-terminal voltage regulator and the second voltage divider resistor. These two capacitors are connected in series and work together to maintain the stability of the low-voltage power supply circuit and prevent signal interference. The anti-interference capacitors can be respectively... Figures 3 to 5 C3, C6, and C9 in the diagram. The anti-interference resistors can be respectively... Figures 3 to 5 R5, R11, and R18 in the equation.

[0066] In one possible embodiment, the three-phase circuit for contact arc suppression further includes an AC / DC power conversion circuit. The AC / DC power conversion circuit is electrically connected to the A, B, and C phase circuits of the power distribution system, and is used to supply power to the contact delay circuit and the three trigger circuits.

[0067] Specifically, the contact delay circuit and the three trigger circuits can all be powered by low-voltage DC. The AC / DC power conversion circuit can convert the three-phase AC power of the power distribution system into low-voltage DC power, thereby powering the contact delay circuit and the three trigger circuits in this application. Optionally, the contact delay circuit and the three trigger circuits in this application can be powered by low-voltage 5V.

[0068] It is worth noting that the three-phase circuit for contact arc suppression in this application includes three triggering circuits for connecting to the A, B, and C phase circuits of the power distribution system. The A, B, and C phase circuits of the power distribution system may not be within the protection scope of this application. That is, the three-phase circuit for contact arc suppression in this application may be a separate circuit module for connecting to the three-phase circuits of the power distribution system.

[0069] The three-phase circuit for contact arc suppression in this application is based on the following working principle:

[0070] When the A, B, and C phase circuits of the power distribution system are powered, the contact delay circuit and the three trigger circuits are simultaneously energized by the voltage conversion of the AC / DC power conversion circuit. Due to the setting of the circuit time constant, the three trigger circuits are triggered before the contact switch KM1 corresponding to each trigger circuit. The bidirectional thyristors of the three trigger circuits are turned on first with a sinusoidal 120° phase angle and supply power to the load. At this time, the base potential of the first transistor Q1 gradually rises under the setting of the time constant. And when the base potential rises to the conduction value, the contact switch KA1 drives KM1 to turn on. At this time, the bidirectional thyristors of each trigger circuit are bypassed by the contact switch KM1 corresponding to each trigger circuit. The holding voltages of the ai and ao ports in the A-phase trigger circuit, the bi and bo ports in the B-phase trigger circuit, and the ci and co ports in the C-phase trigger circuit are all reduced and cut off, thereby realizing the switch from power supply by the bidirectional thyristors of each trigger circuit to power supply by the contact switch KM1 corresponding to each trigger circuit, realizing the change from soft switching to hard switching.

[0071] When the A, B, and C phase circuits of the power distribution system are de-energized, the contact delay circuit and the three trigger circuits are simultaneously de-energized. The contact switch KM1 corresponding to each trigger circuit immediately closes. At this time, the energy stored in the energy storage capacitors of the three trigger circuits can still maintain the switching on of the bidirectional thyristors. When the energy stored in the energy storage capacitors of the three trigger circuits is depleted, the bidirectional thyristors of the three trigger circuits are turned off, and the power supply is shut off in a high-impedance state (greater than 3MΩ).

[0072] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

Claims

1. A three-phase circuit with contact arc suppression, characterized in that, The contact delay circuit comprises a coil MJ, and three trigger circuits; The contact delay circuit comprises a coil MJ, and three trigger circuits; The three trigger circuits are respectively arranged on A, B and C three-phase circuits of a power distribution system; each trigger circuit is connected with the corresponding three-phase circuit through two terminals; a contact switch KM1 is arranged between the two terminals of each trigger circuit; the contact switches KM1 of the A, B and C three-phase circuits correspond to the position of the coil MJ; When the A, B and C three-phase circuits are powered, the three trigger circuits are turned on before the contact delay circuit, and after the contact delay circuit is turned on, the coil MJ can close the contact switches KM1 of the A, B and C three-phase circuits.

2. The contact-arc mitigating three-phase circuit of claim 1, wherein, The contact delay circuit comprises a delay circuit; The delay circuit comprises a coil AJ1, a first transistor Q1, a diode D6, a contact switch KA1, a capacitor C10 and a diode D5; One end of the coil AJ1 is electrically connected with a power supply terminal of the contact delay circuit, and the other end of the coil AJ1 is electrically connected with a positive terminal of the diode D6; a negative terminal of the diode D6 is electrically connected with a base of the first transistor Q1; The contact switch KA1 and other units of the delay circuit are separately arranged; the contact switch KA1 corresponds to the position of the coil AJ1, and the contact switch KA1 can be electrically connected with the coil MJ to form an independent circuit; A positive terminal of the diode D5 is electrically connected with the power supply terminal of the contact delay circuit, and a negative terminal of the diode D5 is grounded; One end of the capacitor C10 is electrically connected with the negative terminal of the diode D5, and the other end of the capacitor C10 is grounded; When the A, B and C three-phase circuits are powered, the base potential of the first transistor Q1 rises from zero to the conduction value of the first transistor Q1, the first transistor Q1 is turned on to make the coil AJ1 close the contact switch KA1, so that the coil MJ closes the contact switches KM1 of the A, B and C three-phase circuits.

3. The contact-arc mitigating three-phase circuit of claim 2, wherein, The capacitor C10 is connected in parallel with a resistor R20.

4. The contact-arc mitigating three-phase circuit of claim 2, wherein, Each trigger circuit comprises a low-voltage power supply circuit and a signal trigger circuit; the low-voltage power supply circuit is electrically connected with the signal trigger circuit, and the low-voltage power supply circuit is used for supplying power to the signal trigger circuit; The signal trigger circuit comprises a bidirectional thyristor; two ends of the bidirectional thyristor are respectively electrically connected with two ends of the contact switch KM1 corresponding to each trigger circuit; when the signal trigger circuit triggers a signal, the bidirectional thyristor is turned on.

5. The contact-arc mitigating three-phase circuit of claim 4, wherein, When the signal trigger circuit triggers a signal, the bidirectional thyristor is turned on before the first transistor Q1 is turned on; after the first transistor Q1 is turned on, the contact switch KM1 corresponding to each trigger circuit is turned on.

6. The contact-arc mitigating three-phase circuit of claim 4, wherein, The low-voltage power supply circuit comprises an energy storage capacitor; One end of the energy storage capacitor is electrically connected with the power supply end of the low-voltage power supply circuit, and the other end of the energy storage capacitor is grounded; the energy storage capacitor can make the bidirectional triode delay to be disconnected when the corresponding contact switch KM1 of each trigger circuit is disconnected.

7. The contact-arc mitigating three-phase circuit of claim 4, wherein, The signal trigger circuit comprises a photoelectric driver; the low-voltage power supply circuit comprises a second resistor; A first end of the second resistor is electrically connected with the power supply end of the low-voltage power supply circuit, and a second end of the second resistor is electrically connected with a first port of an input end of the photoelectric driver.

8. The contact-arc mitigating three-phase circuit of claim 7, wherein, The low-voltage power supply circuit comprises a voltage stabilizing circuit; a second diode is arranged between the second resistor and the power supply end of the low-voltage power supply circuit; The voltage stabilizing circuit comprises a first voltage dividing resistor, a second voltage dividing resistor and a three-terminal voltage stabilizer; the first voltage dividing resistor, the second voltage dividing resistor and the three-terminal voltage stabilizer are connected in series; The first voltage dividing resistor is electrically connected with the second diode; the three-terminal voltage stabilizer is electrically connected with a second port of the input end of the photoelectric driver.

9. The contact-arc mitigating three-phase circuit of claim 8, wherein, Filtering capacitors are arranged in parallel at two ends of the three-terminal voltage stabilizer; Anti-interference capacitors and anti-interference resistors are arranged in parallel at two ends of the three-terminal voltage stabilizer and the second voltage dividing resistor.

10. The contact-arc mitigating three-phase circuit of claim 1, wherein, An AC / DC power supply conversion circuit is further included; The AC / DC power supply conversion circuit is electrically connected with A, B and C three-phase circuits of the power distribution system, and the AC / DC power supply conversion circuit is used for supplying power to the contact delay circuit and the three trigger circuits.

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