Soft starter with thyristor triggering abnormal protection

Abstract

A soft starter with thyristor triggered abnormal protection comprises a microprocessor, a thyristor drive circuit and a fault detection circuit, wherein the input end of the thyristor drive circuit is connected to the microprocessor for receiving a trigger signal sent by the microprocessor, the output end of the thyristor drive circuit is connected to a three-phase asynchronous motor 3M for driving the three-phase asynchronous motor 3M to start, and the input end and the output end of the fault detection circuit are respectively connected to the thyristor drive circuit and the microprocessor for detecting whether the thyristor component of the thyristor drive circuit is turned on and feeding back to the microprocessor. The present invention forms a closed-loop control system with a thyristor triggered abnormal protection function by arranging a fault detection circuit with a feedback function in the soft starter, which enables the microprocessor to detect whether the thyristor component of the thyristor drive circuit is turned on according to the feedback information of the fault detection circuit, thereby protecting the safety of the circuit.

Description

Technical Field

[0001] The invention relates to the fields of electronic power, automation and motor control, in particular to a soft starter with thyristor triggered abnormal protection. Background Art

[0002] When a three-phase asynchronous motor is started directly, the current usually reaches 5 to 8 times, or even greater, generating a large impact current, causing large fluctuations in the power grid in the same system, and having adverse effects on the entire transmission system and equipment. By connecting the soft starter in series between the three-phase asynchronous motor and the three-phase power grid and triggering and driving the thyristor of the soft starter, the starting current can be set and limited to achieve smooth starting of the motor.

[0003] In the existing soft starter, there are two ways to trigger the thyristor, one of which is to use a pulse transformer trigger circuit, and the other is to use an optocoupler anode trigger circuit. However, in the optocoupler anode trigger circuit, open-loop control is generally used, and there is no thyristor trigger abnormal protection, that is, when the thyristor sends a trigger signal, the soft starter fails to detect and feedback whether the thyristor is turned on in time. When the thyristor cannot be turned on or cannot be turned on in time after the trigger signal is sent, that is, when the thyristor is triggered abnormally, the output current of the optocoupler anode trigger circuit will be greater than the rated on-state output current of the optocoupler element for a long time, which will cause the optocoupler element to fail or the charging resistor to burn out.

[0004] In addition, in the existing soft starters, according to the bypass mode, they are divided into external bypass type, built-in bypass type and online type. Among them, the built-in bypass type soft starter realizes bypass by closing the built-in bypass switch after starting. The built-in bypass switch is inside the product body, and the bypass switch generally uses a switch without an arc extinguishing device. However, in the existing built-in bypass type soft starter, a built-in bypass switch without an arc extinguishing device is used. When the bypass operation conditions are met, only a closing signal is applied to the bypass switch, but it is not possible to detect whether the bypass switch is closed normally. Once the bypass is in operation, if the bypass switch is not closed reliably or not closed, the load current will flow through the thyristor, causing the thyristor to overheat or fail. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a soft starter with closed-loop control, timely detection, safety and reliability and thyristor-triggered abnormal protection.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A soft starter with thyristor triggering abnormal protection comprises a microprocessor 1, a thyristor drive circuit 2 and a fault detection circuit 3, wherein the input end of the thyristor drive circuit 2 is connected to the microprocessor 1 for receiving a trigger signal sent by the microprocessor 1, the output end of the thyristor drive circuit 2 is connected to a three-phase asynchronous motor 3M for driving the three-phase asynchronous motor 3M to start, and the input end and the output end of the fault detection circuit 3 are respectively connected to the thyristor drive circuit 2 and the microprocessor 1 for detecting whether the thyristor component of the thyristor drive circuit 2 is turned on and feeding back to the microprocessor 1.

[0008] Preferably, the fault detection circuit 3 includes a U-phase detection circuit, a V-phase detection circuit and a W-phase detection circuit, the input end of the U-phase detection circuit is connected to the output end of the U-phase thyristor drive circuit of the thyristor drive circuit 2, the output end of the U-phase detection circuit is connected to the microprocessor 1, the input end of the V-phase detection circuit is connected to the output end of the V-phase thyristor drive circuit of the thyristor drive circuit 2, the output end of the V-phase detection circuit is connected to the microprocessor 1, the input end of the W-phase detection circuit is connected to the output end of the W-phase thyristor drive circuit of the thyristor drive circuit 2, and the output end of the W-phase detection circuit is connected to the microprocessor 1.

[0009] Preferably, the thyristor drive circuit 2 includes an optocoupler anode trigger circuit and a motor soft start circuit, the input end of the optocoupler anode trigger circuit is connected to the microprocessor 1, the output end of the optocoupler anode trigger circuit is connected to the input end of the motor soft start circuit to trigger the thyristor component of the motor soft start circuit, and the output end of the motor soft start circuit is respectively connected to the input end of the fault detection circuit 3 and the three-phase asynchronous motor 3M.

[0010] Preferably, the thyristor drive circuit 2 includes an optocoupler component and a thyristor component, the input end of the optocoupler component is connected to the microprocessor 1, the output end of the optocoupler component is connected to the input end of the thyristor component, the output end of the thyristor component is respectively connected to the optical isolation of the fault detection circuit 3 and the three-phase asynchronous motor 3M for detecting whether the thyristor component is turned on and soft-started, and the output end of the optical isolation is connected to the microprocessor 1 for feeding back detection information to the microprocessor 1.

[0011] Preferably, the optocoupler anode trigger circuit includes a U-phase optocoupler trigger circuit, a V-phase optocoupler trigger circuit and a W-phase optocoupler trigger circuit, each phase optocoupler trigger circuit includes an optocoupler component formed by an optocoupler, the input end of each phase optocoupler trigger circuit is respectively connected to the microprocessor 1, and the output end of each phase optocoupler trigger circuit is connected to the motor soft start circuit, the motor soft start circuit includes a U-phase thyristor drive circuit, a V-phase thyristor drive circuit and a W-phase thyristor drive circuit, each phase thyristor drive circuit includes a thyristor component formed by thyristors, the input end of each phase thyristor drive circuit is connected to the optocoupler anode trigger circuit, and the output end of each phase thyristor drive circuit is respectively connected to the fault detection circuit 3 and the three windings of the three-phase asynchronous motor 3M.

[0012] Preferably, the U-phase detection circuit includes a bridge DB400, an optical barrier U403 and a U-phase rectifier circuit, the input end of the bridge DB400 is connected to the cathode K1 of the thyristor SCR1 of the U-phase thyristor drive circuit and the cathode K2 of the thyristor SCR2 of the U-phase thyristor drive circuit, the output end of the bridge DB400 is connected to the input end of the optical barrier U403, the output end of the optical barrier U403 is connected to the input end of the U-phase rectifier circuit, the output end of the U-phase rectifier circuit is connected to the microprocessor 1 through a Ui p interface, and the structures of the V-phase detection circuit and the W-phase detection circuit are the same as the structure of the U-phase detection circuit.

[0013] Preferably, the cathode K1 of the thyristor SCR1 is connected to the first pin of the bridge DB400, and resistors R421, R422 and R423 are connected in series between the cathode K1 of the thyristor SCR1 and the bridge DB400, the cathode K2 of the thyristor SCR2 is connected to the second pin of the bridge DB400, a capacitor C410 is connected in parallel between the first pin of the bridge DB400 and the second pin of the bridge DB400, and the third pin of the bridge DB400 and the fourth pin of the bridge DB400 are connected to the second pin of the optical isolation U403 and the optical isolation U403 respectively. The third pin of the optical isolator U403 is connected to the third pin of the optical isolator U403, a capacitor C409 is connected in series between the first pin of the bridge DB400 and the third pin of the bridge DB400, a capacitor C411 is connected in series between the first pin of the bridge DB400 and the fourth pin of the bridge DB400, the U-phase rectifier circuit includes a resistor R424, a resistor R425, a resistor R426, a resistor R427, a capacitor C413 and a capacitor C414, the fifth pin of the optical isolator U403 is grounded, the sixth pin of the optical isolator U403 is connected to one end of the resistor R426, and the other end of the resistor R426 is connected to the optical isolator U403 through the Ui The p interface is connected to the microprocessor 1, the seventh pin of the optical isolation U403 is connected in series with the resistor R427 and then grounded, the eighth pin of the optical isolation U403 is connected in series with the resistor R424 and then connected to the power supply VCC end, one end of the resistor R425 is connected to the power supply VCC, and the other end is connected to the sixth pin of the optical isolation U403, the capacitor C413 is connected in parallel between the eighth pin of the optical isolation U403 and the fifth pin of the optical isolation U403 and grounded, the other end of the capacitor C414 is connected to the microprocessor 1 through the Ui p interface and is grounded, and the structures of the V phase detection circuit and the W phase detection circuit are the same as the structure of the U phase detection circuit.

[0014] Preferably, the U-phase optocoupler trigger circuit includes an optocoupler U7, an optocoupler U8, an optocoupler U9, a varistor RV7, a varistor RV8 and a varistor RV9, the first pin of the optocoupler U7 is connected to the power supply, the second pin of the optocoupler U7 and the third pin of the optocoupler U7 are connected in parallel to the first pin of the optocoupler U8, the fourth pin of the optocoupler U7 is connected to the sixth pin of the optocoupler U8, the sixth pin of the optocoupler U7 is connected to one end of the resistor R15, the first pin of the optocoupler U8 is connected to the optocoupler U7, the second pin of the optocoupler U8 is connected to the optocoupler U7, and the The third pin of U8 is connected in parallel with the first pin of the optocoupler U9, the fourth pin of the optocoupler U8 is connected to the sixth pin of the optocoupler U9, the sixth pin of the optocoupler U8 is connected to the optocoupler U7, the first pin of the optocoupler U9 is connected to the optocoupler U8, the second pin of the optocoupler U9 and the third pin of the optocoupler U9 are connected in parallel and connected to the microprocessor 1 through the resistor R20, the fourth pin of the optocoupler U9 is connected to one end of the resistor R21, the sixth pin of the optocoupler U9 is connected to the optocoupler U8, the two ends of the varistor RV7 are respectively connected to the fourth pin and the third pin of the optocoupler U7. The sixth pin of the optocoupler U7 is connected, the two ends of the varistor RV8 are respectively connected to the fourth pin of the optocoupler U8 and the sixth pin of the optocoupler U8, the two ends of the varistor RV9 are respectively connected to the fourth pin of the optocoupler U9 and the sixth pin of the optocoupler U9, a capacitor C8 is also connected in series between the first pin of the optocoupler U7 and the third pin of the optocoupler U9, the other end of the resistor R15 is connected to one end of the resistor R17, the other end of the resistor R17 is respectively connected to the motor soft start circuit and one end of the resistor R16, the other end of the resistor R16 is The first end of the resistor R21 is connected to the motor soft start circuit, and the two ends of the resistor R16 are sequentially connected in parallel with a capacitor C7 and a reverse diode D5. The other end of the resistor R21 is connected to one end of the resistor R18. The other end of the resistor R18 is respectively connected to the motor soft start circuit and one end of the resistor R19. The other end of the resistor R19 is connected to the motor soft start circuit, and the two ends of the resistor R19 are sequentially connected in parallel with a capacitor C9 and a reverse diode D6. The structures of the V-phase optocoupler trigger circuit and the W-phase optocoupler trigger circuit are the same as that of the U-phase optocoupler trigger circuit.

[0015] Preferably, the U-phase thyristor drive circuit includes a thyristor SCR1, a thyristor SCR2 and a bypass switch S1. The thyristor SCR1 and the thyristor SCR2 are arranged in reverse parallel and are controlled by the trigger signal Mu of the microprocessor 1 to form a U-phase thyristor assembly. The bypass switch S1 is connected in parallel between the cathode K1 and the anode of the thyristor SCR1. The cathode K1 of the thyristor SCR1 serves as a network point and is connected to the U-phase input terminal of the three-phase asynchronous motor 3M. The thyristor SCR1 and the thyristor SCR2 are connected in parallel at one end and the thyristor SCR2. The gate G1 of the silicon SCR1 is respectively connected to the RC charging and discharging circuit composed of the capacitor C7 and the resistor R16 of the optocoupler anode trigger circuit, the cathode K2 of the thyristor SCR2 is a network point and is connected to the U-phase power grid, the other end of the thyristor SCR1 and the thyristor SCR2 after being connected in parallel and the gate G2 of the thyristor SCR2 are respectively connected to the RC charging and discharging circuit composed of the capacitor C9 and the resistor R19 of the optocoupler anode trigger circuit, and the structure of the V-phase thyristor drive circuit and the W-phase thyristor drive circuit is the same as that of the U-phase thyristor drive circuit.

[0016] Preferably, after the microprocessor 1 sends a U-phase trigger signal, if the microprocessor 1 detects that the output end of the U-phase detection circuit flips from a low level to a high level within a preset time, it is considered that the thyristor corresponding to the U-phase is normally turned on. If the microprocessor 1 detects that the level of the output end of the U-phase detection circuit has not changed within the preset time, it is considered that the thyristor SCR1 or thyristor SCR2 corresponding to the U-phase is not turned on or is not turned on in time. The principles of the V-phase detection circuit and the W-phase detection circuit are the same as the principles of the U-phase detection circuit.

[0017] The soft starter with thyristor triggered abnormal protection of the present invention forms a closed-loop control system with thyristor triggered abnormal protection function by arranging a fault detection circuit with feedback function between the thyristor drive circuit and the microprocessor of the soft starter. The closed-loop control system has strong anti-interference ability and can perform effective control, so that the microprocessor can detect whether the thyristor component of the thyristor drive circuit is turned on according to the feedback information of the fault detection circuit. If the thyristor component fails to turn on in time or fails to turn on, the microprocessor immediately stops sending the trigger signal, thereby protecting the safety of the circuit. In addition, the present invention adopts a closed-loop control system composed of a microprocessor, a thyristor drive circuit and a fault detection circuit, so that during the soft starting process of the motor, when the thyristor component sends a trigger signal, the microprocessor can detect whether the thyristor component of the corresponding phase is turned on within a time of 0 microseconds to 1000 microseconds, thereby avoiding the failure of the optical coupling component or other circuit elements caused by too long detection time, and also avoiding the abnormal protection of the thyristor component triggered due to too short detection time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a functional structure block diagram of the present invention;

[0019] Figure 2 It is a work flow chart of the thyristor trigger detection of the present invention;

[0020] Figure 3 It is a schematic diagram of the U-phase optocoupler trigger circuit of the present invention;

[0021] Figure 4 It is a schematic diagram of the V-phase optocoupler trigger circuit of the present invention;

[0022] Figure 5 It is a schematic diagram of the W-phase optocoupler trigger circuit of the present invention;

[0023] Figure 6 It is a schematic diagram of the motor soft starting circuit of the present invention;

[0024] Figure 7 It is a schematic diagram of the U-phase detection circuit of the present invention;

[0025] Figure 8 It is a schematic diagram of the V-phase detection circuit of the present invention;

[0026] Fig. 9 It is a schematic diagram of the W-phase detection circuit of the present invention;

[0027] Fig.10 It is a schematic diagram of the bypass switch fault detection principle within the first 10 seconds after the soft starter of the present invention switches to bypass operation;

[0028] Fig.11 The diagram is a schematic diagram of the bypass switch fault detection principle 10 seconds after the soft starter of the present invention switches to bypass operation. DETAILED DESCRIPTION

[0029] The following is combined with Figures 1 to 11 The embodiments of the present invention are given to further illustrate the specific implementation of the soft starter with thyristor triggered abnormal protection of the present invention. The soft starter with thyristor triggered abnormal protection of the present invention is not limited to the description of the following embodiments.

[0030] like Figure 1As shown, the soft starter with thyristor triggered abnormal protection of the present invention includes a microprocessor 1, a thyristor drive circuit 2 and a fault detection circuit 3, the input end of the thyristor drive circuit 2 is connected to the microprocessor 1 for receiving a trigger signal sent by the microprocessor 1, the output end of the thyristor drive circuit 2 is connected to the three-phase asynchronous motor 3M for driving the three-phase asynchronous motor 3M to start, the input end and the output end of the fault detection circuit 3 are respectively connected to the thyristor drive circuit 2 and the microprocessor 1 for detecting whether the thyristor component of the thyristor drive circuit 2 is turned on and fed back to the microprocessor 1, and the microprocessor 1 controls the sending or termination of the trigger signal according to the feedback information. The present invention forms a closed-loop control system with a thyristor triggering abnormal protection function by arranging a fault detection circuit 3 with a feedback function between a thyristor drive circuit 2 and a microprocessor 1 of a soft starter, so that a control subject of the closed-loop control system can discover and correct deviations in the operation of a controlled object according to feedback information, has a strong anti-interference ability, and can perform effective control, thereby ensuring the realization of a predetermined goal, that is, the microprocessor 1 can detect whether a thyristor component of the thyristor drive circuit 2 is turned on according to the feedback information of the fault detection circuit 3. If the thyristor has been turned on in time, it means that the thyristor component is triggered normally, and the soft starter continues to run; if the thyristor component fails to be turned on in time or fails to be turned on, it means that the thyristor is triggered abnormally, and the microprocessor 1 immediately stops sending a trigger signal, thereby protecting the safety of the circuit.

[0031] In addition, the input end and the output end of the fault detection circuit 3 are respectively connected to the thyristor drive circuit 2 and the microprocessor 1 and can also be used to detect whether the bypass switch of the soft starter has a fault, that is, after the bypass operation, when the number of falling edges or rising edges of the detection signal of the fault detection circuit 3 received by the microprocessor within the preset bypass detection cycle exceeds the preset fault threshold, the bypass switch fault is determined. The present invention forms a closed-loop control system with a bypass switch fault protection function by arranging a fault detection circuit 3 with a feedback function between the microprocessor 1 and the thyristor drive circuit 2 of the soft starter, that is, the microprocessor 1 can detect whether the bypass switch of the soft starter is closed according to the feedback information of the fault detection circuit 3. If it is detected that the bypass switch is unreliable or not closed, the soft starter will report the bypass switch fault protection and shut down, thereby preventing the risk of overheating or damage of the thyristor element in the thyristor drive circuit 2, and ensuring the safety and reliability of the soft starter.

[0032] The thyristor drive circuit 2 includes an optocoupler component (i.e., a photoelectric bidirectional thyristor driver) and a thyristor component. The input end of the optocoupler component is connected to the microprocessor 1 for receiving a trigger signal from the microprocessor 1. The output end of the optocoupler component is connected to the input end of the thyristor component for providing a trigger signal to the thyristor component. The output end of the thyristor component is respectively connected to the optical isolation of the fault detection circuit 3 and the three-phase asynchronous motor 3M for detecting whether the thyristor component is turned on and soft-started. The output end of the optical isolation is connected to the microprocessor 1 for feeding back the detection information to the microprocessor 1. Figure 2 As shown, when the main circuit of the soft starter is started, the microprocessor 1 detects the conduction status of the thyristor component in real time through the fault detection circuit 3 and feeds back to the microprocessor 1. When the microprocessor 1 sends a trigger signal to the thyristor component, the optocoupler component of the corresponding phase will be turned on (generally, the conduction lag time is less than 100 microseconds). At the same time, the microprocessor 1 will detect whether the thyristor component of the corresponding phase has been turned on within 0 microseconds to 1000 microseconds. If it has been turned on, it is considered that the thyristor is triggered normally and the soft starter continues to work; if it is not turned on, it is considered that the thyristor component is triggered abnormally, and the soft starter will stop working due to fault protection to prevent the optocoupler component or other circuit components from failing. The present invention adopts a closed-loop control system composed of a microprocessor 1, a thyristor drive circuit 2 and a fault detection circuit 3, so that during the soft starting process of the motor, when the thyristor component sends a trigger signal, the microprocessor 1 can detect whether the thyristor component of the corresponding phase is turned on within a time of 0 microseconds to 1000 microseconds, thereby avoiding the failure of the optical coupler component or other circuit elements due to too long detection time, and also avoiding the abnormal protection of the thyristor component triggered due to too short detection time.

[0033] In addition, during the bypass start of the soft starter, the fault threshold and / or bypass detection cycle for determining the bypass switch fault by the microprocessor 1 are different in different time periods after the bypass operation. The bypass detection cycle includes a first bypass detection cycle and a second bypass detection cycle, and the fault threshold includes a first fault threshold and a second fault threshold. In the first time period after the bypass operation, if the number of falling edges or rising edges of the detection signal of the fault detection circuit 3 received by the microprocessor 1 in the first bypass detection cycle exceeds the preset first fault threshold, the bypass switch fault is determined; after the first time period after the bypass operation, if the number of falling edges or rising edges of the detection signal of the fault detection circuit 3 received by the microprocessor 1 in the second bypass detection cycle exceeds the preset second fault threshold, the bypass switch fault is determined, wherein the second bypass detection cycle is greater than the first bypass detection cycle and / or the second fault threshold is less than the first fault threshold. The present invention divides bypass switch fault detection into two time periods during bypass operation, namely, within the first time period after the soft starter is switched to bypass operation and after the first time period after the soft starter is switched to bypass operation, such as within 10 seconds after bypass operation and after 10 seconds. Therefore, during factory inspection of the soft starter of the present invention, the test time of the bypass switch fault detection item can be greatly shortened by adopting the detection method within the first 10 seconds after bypass operation, thereby improving production efficiency.

[0034] Preferably, the first time period is 10s, the first bypass detection cycle is 10s, and the first fault threshold is 250-500; the second bypass detection cycle is 300S, and the second fault threshold is 250-500. Setting the fault threshold at 250-500 can effectively avoid misjudgment. Of course, the fault threshold can also be set to be smaller or larger as needed. The time of the bypass detection cycle must match the corresponding fault threshold. The 10s time is obtained in combination with actual tests. If the time is too short, there is a risk of false alarm of bypass switch failure; if the time is too long, there is a risk of greater heating of the thyristor when the bypass switch is not closed.

[0035] A specific embodiment of the present invention is that the thyristor drive circuit 2 includes an optocoupler anode trigger circuit and a motor soft start circuit, the input end of the optocoupler anode trigger circuit is connected to the microprocessor 1 for receiving a trigger signal sent by the microprocessor 1, the output end of the optocoupler anode trigger circuit is connected to the input end of the motor soft start circuit for triggering the thyristor component of the motor soft start circuit, the output end of the motor soft start circuit is respectively connected to the input end of the fault detection circuit 3 and the three-phase asynchronous motor 3M for fault detection and soft starting, and the output end of the fault detection circuit 3 is connected to the microprocessor 1 for feeding back detection information to the microprocessor 1.

[0036] The optocoupler anode trigger circuit is composed of a three-phase optocoupler trigger circuit, namely, a U-phase optocoupler trigger circuit, a V-phase optocoupler trigger circuit and a W-phase optocoupler trigger circuit. Each phase of the optocoupler trigger circuit includes an optocoupler component formed by an optocoupler. The input end of each phase of the optocoupler trigger circuit is respectively connected to the microprocessor 1 for receiving a trigger signal, and the output end of each phase of the optocoupler trigger circuit is connected to the motor soft start circuit.

[0037] The motor soft start circuit includes a three-phase thyristor drive circuit, namely, a U-phase thyristor drive circuit, a V-phase thyristor drive circuit and a W-phase thyristor drive circuit, each phase thyristor drive circuit includes a thyristor assembly formed by thyristors, the input end of each phase thyristor drive circuit is connected to the optical coupler through the anode trigger circuit and the three-phase power grid, and the output end of each phase thyristor drive circuit is respectively connected to the fault detection circuit 3 and the three windings of the three-phase asynchronous motor 3M, that is, the input end of the U-phase thyristor drive circuit is connected to the three The U-phase power grid of the three-phase power grid is connected, the output end of the U-phase thyristor drive circuit is connected to the U-phase input end of the three-phase asynchronous motor 3M, the input end of the V-phase thyristor drive circuit is connected to the V-phase power grid of the three-phase power grid, the output end of the V-phase thyristor drive circuit is connected to the V-phase input end of the three-phase asynchronous motor 3M, the input end of the W-phase thyristor drive circuit is connected to the W-phase power grid of the three-phase power grid, and the output end of the W-phase thyristor drive circuit is connected to the W-phase input end of the three-phase asynchronous motor 3M.

[0038] The fault detection circuit 3 includes a three-phase detection circuit, namely a U-phase detection circuit, a V-phase detection circuit and a W-phase detection circuit. The input end of the U-phase detection circuit is connected to the output end of the U-phase thyristor drive circuit of the motor soft start circuit, and the output end of the U-phase detection circuit is connected to the microprocessor 1 for feeding back the detection information to the microprocessor 1; the input end of the V-phase detection circuit is connected to the output end of the V-phase thyristor drive circuit of the motor soft start circuit, and the output end of the V-phase detection circuit is connected to the microprocessor 1 for feeding back the detection information to the microprocessor 1; the input end of the W-phase detection circuit is connected to the output end of the W-phase thyristor drive circuit of the motor soft start circuit, and the output end of the W-phase detection circuit is connected to the microprocessor 1 for feeding back the detection information to the microprocessor 1.

[0039] Specifically, Figure 3As shown, the U-phase optocoupler trigger circuit includes an optocoupler U7, an optocoupler U8, an optocoupler U9, a varistor RV7, a varistor RV8 and a varistor RV9, the first pin of the optocoupler U7 is connected to a 15V power supply, the second pin of the optocoupler U7 and the third pin of the optocoupler U7 are connected in parallel to the first pin of the optocoupler U8, the fourth pin of the optocoupler U7 is connected to the sixth pin of the optocoupler U8, the fifth pin of the optocoupler U7 is suspended, the sixth pin of the optocoupler U7 is connected to one end of the resistor R15, the first pin of the optocoupler U8 is connected to the optocoupler U7, the second pin of the optocoupler U8 and the third pin of the optocoupler U8 are connected in parallel to the first pin of the optocoupler U9, and the optocoupler U The fourth pin of 8 is connected to the sixth pin of the optocoupler U9, the fifth pin of the optocoupler U8 is suspended, the sixth pin of the optocoupler U8 is connected to the optocoupler U7, the first pin of the optocoupler U9 is connected to the optocoupler U8, the second pin of the optocoupler U9 and the third pin of the optocoupler U9 are connected in parallel and connected to the microprocessor 1 through the resistor R20 and controlled by the network point Mu (i.e., the trigger signal), the fourth pin of the optocoupler U9 is connected to one end of the resistor R21, the fifth pin of the optocoupler U9 is suspended, and the sixth pin of the optocoupler U9 is connected to the optocoupler U8. The optocouplers U7, U8 and U9 can isolate the strong and weak electricity in the circuit, and the rear end can withstand the strong voltage in the power grid; the varistor RV7 The two ends of the varistor RV8 are respectively connected to the fourth pin of the optocoupler U7 and the sixth pin of the optocoupler U7, thereby being connected in parallel at the rear end of the optocoupler U7. The two ends of the varistor RV9 are respectively connected to the fourth pin of the optocoupler U9 and the sixth pin of the optocoupler U9, thereby being connected in parallel at the rear end of the optocoupler U9. By connecting a varistor in parallel to the rear end of each optocoupler, the surge voltage on the phase circuit or the back electromotive force of the motor can be absorbed. At the same time, at normal voltage, the varistor RV7, the varistor RV8 and the varistor RV9 are in a high-resistance state, with only microamperes. Leakage current, a capacitor C8 is also connected in series between the first pin of the optocoupler U7 and the third pin of the optocoupler U9; the other end of the resistor R15 is connected to one end of the resistor R17, the other end of the resistor R17 is respectively connected to the motor soft start circuit and one end of the resistor R16, the other end of the resistor R16 is connected to the motor soft start circuit, and the capacitor C7 and the reverse diode D5 are sequentially connected in parallel at both ends of the resistor R16, the capacitor C7 and the resistor R16 form an RC charge and discharge circuit, the reverse diode D5 is used for unidirectional conduction, when the U phase voltage is in the negative half cycle and the optocoupler U7, the optocoupler U8 and the optocoupler U9 are turned on, the current flows through the reverse diode D5;The other end of the resistor R21 is connected to one end of the resistor R18, and the other end of the resistor R18 is respectively connected to the motor soft start circuit and one end of the resistor R19, and the other end of the resistor R19 is connected to the motor soft start circuit, and the capacitor C9 and the reverse diode D6 are sequentially connected in parallel at both ends of the resistor R19, and the capacitor C9 and the resistor R19 form an RC charge and discharge circuit, and the reverse diode D6 is used for unidirectional conduction. When the U phase voltage is in the positive half cycle and the optocoupler U7, the optocoupler U8 and the optocoupler U9 are turned on, the current flows through the reverse diode D6. ;

[0040] like Figure 4As shown, the V-phase optocoupler trigger circuit includes an optocoupler U4, an optocoupler U5, an optocoupler U6, a varistor RV4, a varistor RV5 and a varistor RV6, the first pin of the optocoupler U4 is connected to a 15V power supply, the second pin of the optocoupler U4 is connected in parallel with the third pin of the optocoupler U4 and then connected to the first pin of the optocoupler U5, the fourth pin of the optocoupler U4 is connected to the sixth pin of the optocoupler U5, the fifth pin of the optocoupler U4 is suspended, the sixth pin of the optocoupler U4 is connected to one end of the resistor R8, the first pin of the optocoupler U5 is connected to the optocoupler U4, the second pin of the optocoupler U5 is connected in parallel with the third pin of the optocoupler U5 and then connected to the first pin of the optocoupler U6, the optocoupler The fourth pin of U5 is connected to the sixth pin of the optocoupler U6, the fifth pin of the optocoupler U5 is suspended, the sixth pin of the optocoupler U5 is connected to the optocoupler U4, the first pin of the optocoupler U6 is connected to the optocoupler U5, the second pin of the optocoupler U6 and the third pin of the optocoupler U6 are connected in parallel and connected to the microprocessor 1 through the resistor R13 and are controlled by the network point Mv (i.e., the trigger signal), the fourth pin of the optocoupler U6 is connected to one end of the resistor R14, the fifth pin of the optocoupler U6 is suspended, and the sixth pin of the optocoupler U6 is connected to the optocoupler U5. The optocouplers U4, U5 and U6 can isolate the strong and weak electricity in the circuit, and the rear end can withstand the strong voltage in the power grid; the varistor R The two ends of V4 are respectively connected to the fourth pin of the optocoupler U4 and the sixth pin of the optocoupler U4, and are thus connected in parallel at the rear end of the optocoupler U4. The two ends of the varistor RV5 are respectively connected to the fourth pin of the optocoupler U5 and the sixth pin of the optocoupler U5, and are thus connected in parallel at the rear end of the optocoupler U5. The two ends of the varistor RV6 are respectively connected to the fourth pin of the optocoupler U6 and the sixth pin of the optocoupler U6, and are thus connected in parallel at the rear end of the optocoupler U6. By connecting a varistor in parallel to the rear end of each optocoupler, the surge voltage on the phase circuit or the back electromotive force of the motor can be absorbed. At the same time, at normal voltage, the varistor RV4, the varistor RV5 and the varistor RV6 are in a high-resistance state, and only A capacitor C5 is connected in series between the first pin of the optocoupler U4 and the third pin of the optocoupler U6 to reduce the leakage current of the microampere level; the other end of the resistor R8 is connected to one end of the resistor R10, and the other end of the resistor R10 is respectively connected to the motor soft start circuit and one end of the resistor R9, and the other end of the resistor R9 is connected to the motor soft start circuit, and a capacitor C4 and a reverse diode D3 are sequentially connected in parallel at both ends of the resistor R9, and the capacitor C4 and the resistor R9 form an RC charge and discharge circuit, and the reverse diode D3 is used for unidirectional conduction. When the V phase voltage is in the negative half cycle and the optocoupler U4, the optocoupler U5 and the optocoupler U6 are turned on, the current flows through the reverse diode D3;The other end of the resistor R14 is connected to one end of the resistor R11, and the other end of the resistor R11 is respectively connected to the motor soft start circuit and one end of the resistor R12, and the other end of the resistor R12 is connected to the motor soft start circuit, and the capacitor C6 and the reverse diode D4 are sequentially connected in parallel at both ends of the resistor R12, and the capacitor C6 and the resistor R12 form an RC charge and discharge circuit, and the reverse diode D4 is used for unidirectional conduction. When the V phase voltage is in the positive half cycle and the optocoupler U4, the optocoupler U5 and the optocoupler U6 are turned on, the current flows through the reverse diode D4. ;

[0041] like Figure 5As shown, the W-phase optocoupler trigger circuit includes an optocoupler U1, an optocoupler U2, an optocoupler U3, a varistor RV1, a varistor RV2 and a varistor RV3, the first pin of the optocoupler U1 is connected to a 15V power supply, the second pin of the optocoupler U1 and the third pin of the optocoupler U1 are connected in parallel to the first pin of the optocoupler U2, the fourth pin of the optocoupler U1 is connected to the sixth pin of the optocoupler U2, the fifth pin of the optocoupler U1 is suspended, the sixth pin of the optocoupler U1 is connected to one end of the resistor R1, the first pin of the optocoupler U2 is connected to the optocoupler U1, the second pin of the optocoupler U2 and the third pin of the optocoupler U2 are connected in parallel to the first pin of the optocoupler U3, and the optocoupler U3 is connected to the first pin of the optocoupler U3. The fourth pin of the optocoupler U2 is connected to the sixth pin of the optocoupler U3, the fifth pin of the optocoupler U2 is suspended, the sixth pin of the optocoupler U2 is connected to the optocoupler U1, the first pin of the optocoupler U3 is connected to the optocoupler U2, the second pin of the optocoupler U3 and the third pin of the optocoupler U3 are connected in parallel and connected to the microprocessor 1 through a resistor R6 and are controlled by the network point Mw (i.e., a trigger signal), the fourth pin of the optocoupler U3 is connected to one end of the resistor R7, the fifth pin of the optocoupler U3 is suspended, and the sixth pin of the optocoupler U3 is connected to the optocoupler U2. The optocoupler U1, the optocoupler U2 and the optocoupler U3 can isolate the strong and weak electricity in the circuit, and the back end can withstand the strong voltage in the power grid; the varistor R The two ends of V1 are respectively connected to the fourth pin of the optocoupler U1 and the sixth pin of the optocoupler U1, thereby being connected in parallel to the rear end of the optocoupler U1; the two ends of the varistor RV2 are respectively connected to the fourth pin of the optocoupler U2 and the sixth pin of the optocoupler U2, thereby being connected in parallel to the rear end of the optocoupler U2; the two ends of the varistor RV3 are respectively connected to the fourth pin of the optocoupler U3 and the sixth pin of the optocoupler U3, thereby being connected in parallel to the rear end of the optocoupler U3; by connecting a varistor in parallel to the rear end of each optocoupler, the surge voltage on the phase circuit or the back electromotive force of the motor can be absorbed; at the same time, at normal voltage, the varistor RV1, the varistor RV2 and the varistor RV3 are in a high-resistance state, and only There is a leakage current of microampere level, and a capacitor C2 is connected in series between the first pin of the optocoupler U1 and the third pin of the optocoupler U3; the other end of the resistor R1 is connected to one end of the resistor R3, and the other end of the resistor R3 is respectively connected to the motor soft start circuit and one end of the resistor R2, and the other end of the resistor R2 is connected to the motor soft start circuit, and the capacitor C1 and the reverse diode D1 are sequentially connected in parallel at both ends of the resistor R2, and the capacitor C1 and the resistor R2 form an RC charge and discharge circuit, and the reverse diode D1 is used for unidirectional conduction. When the W phase voltage is in the negative half cycle and the optocoupler U1, the optocoupler U2 and the optocoupler U3 are turned on, the current flows through the reverse diode D1;The other end of the resistor R7 is connected to one end of the resistor R4, and the other end of the resistor R4 is respectively connected to the motor soft start circuit and one end of the resistor R5, and the other end of the resistor R5 is connected to the motor soft start circuit, and the capacitor C3 and the reverse diode D2 are sequentially connected in parallel at both ends of the resistor R5, and the capacitor C3 and the resistor R5 form an RC charge and discharge circuit, and the reverse diode D2 is used for unidirectional conduction. When the W phase voltage is in the positive half cycle and the optocoupler U1, the optocoupler U2 and the optocoupler U3 are turned on, the current flows through the reverse diode D2. ;

[0042] like Figure 6 As shown, the U-phase thyristor drive circuit includes thyristors SCR1, SCR2 and a bypass switch S1 without an arc extinguishing device (such as a magnetic latching switch and a stand-alone contactor, etc.), the thyristors SCR1 and SCR2 are reversely connected in parallel and controlled by a trigger signal Mu of a microprocessor 1 to form a U-phase thyristor assembly, the bypass switch S1 is connected in parallel between the cathode K1 and the anode of the thyristor SCR1, the cathode K1 of the thyristor SCR1 serves as a network point and is connected to the U-phase input of the three-phase asynchronous motor 3M. The input end is connected, one end of the thyristor SCR1 and the thyristor SCR2 connected in parallel and the gate G1 of the thyristor SCR1 are respectively connected to the RC charge and discharge circuit composed of the capacitor C7 and the resistor R16 of the optocoupler anode trigger circuit, the cathode K2 of the thyristor SCR2 is the network point and is connected to the U-phase power grid, and the other end of the thyristor SCR1 and the thyristor SCR2 connected in parallel and the gate G2 of the thyristor SCR2 are respectively connected to the RC charge and discharge circuit composed of the capacitor C9 and the resistor R19 of the optocoupler anode trigger circuit.

[0043] The V-phase thyristor drive circuit includes a thyristor SCR3, a thyristor SCR4 and a bypass switch S2. The thyristor SCR3 and the thyristor SCR4 are arranged in reverse parallel to form a V-phase thyristor assembly. The bypass switch S2 is connected in parallel between the cathode K3 and the anode of the thyristor SCR3. The cathode K3 of the thyristor SCR3 is a network point and is connected to the V-phase input end of the three-phase asynchronous motor 3M. One end of the thyristor SCR3 and the thyristor SCR4 connected in parallel and the gate G3 of the thyristor SCR3 are respectively connected to the RC charge and discharge circuit composed of the capacitor C4 and the resistor R9 of the optocoupler anode trigger circuit. The cathode K4 of the thyristor SCR4 is a network point and is connected to the V-phase power grid. The other end of the thyristor SCR3 and the thyristor SCR4 connected in parallel and the gate G4 of the thyristor SCR4 are respectively connected to the RC charge and discharge circuit composed of the capacitor C6 and the resistor R12 of the optocoupler anode trigger circuit.

[0044] The W-phase thyristor drive circuit includes a thyristor SCR5, a thyristor SCR6 and a bypass switch S3. The thyristor SCR5 and the thyristor SCR6 are arranged in reverse parallel to form a W-phase thyristor assembly. The bypass switch S3 is connected in parallel between the cathode K5 and the anode of the thyristor SCR5. The cathode K5 of the thyristor SCR5 is a network point and is connected to the W-phase input end of the three-phase asynchronous motor 3M. One end of the thyristor SCR5 and the thyristor SCR6 connected in parallel and the gate G5 of the thyristor SCR5 are respectively connected to the RC charge and discharge circuit composed of the capacitor C1 and the resistor R2 of the optocoupler anode trigger circuit. The cathode K6 of the thyristor SCR6 is a network point and is connected to the W-phase power grid. The other end of the thyristor SCR5 and the thyristor SCR6 connected in parallel and the gate G6 of the thyristor SCR6 are respectively connected to the RC charge and discharge circuit composed of the capacitor C3 and the resistor R5 of the optocoupler anode trigger circuit.

[0045] like Figure 7As shown, the U-phase detection circuit includes a bridge DB400, a light barrier U403 and a U-phase rectifier circuit. The input end of the bridge DB400 is connected to the cathode K1 (network point) of the thyristor SCR1 of the U-phase thyristor drive circuit and the cathode K2 (network point) of the thyristor SCR2 of the U-phase thyristor drive circuit for converting the AC voltage signals of the cathode and anode of the thyristor element into a DC pulse voltage signal. The output end of the bridge DB400 is connected to the input end of the light barrier U403 for trigger detection of the thyristor element. The output end of the light barrier U403 is connected to the input end of the U-phase rectifier circuit for rectification and filtering. The output end of the U-phase rectifier circuit is connected to the microprocessor 1 through the Ui p interface for feeding back detection information to the microprocessor 1. Specifically, the cathode K1 of the thyristor SCR1 is connected to the first pin of the bridge DB400, and resistors R421, R422 and R423 are connected in series between the cathode K1 of the thyristor SCR1 and the bridge DB400, the cathode K2 of the thyristor SCR2 is connected to the second pin of the bridge DB400, a capacitor C410 is connected in parallel between the first pin of the bridge DB400 and the second pin of the bridge DB400, the third pin of the bridge DB400 and the fourth pin of the bridge DB400 are connected to the second pin of the optical isolation U403 and the third pin of the optical isolation U403 respectively, a capacitor C409 is connected in parallel between the first pin of the bridge DB400 and the third pin of the bridge DB400, and a capacitor C411 is connected in parallel between the first pin of the bridge DB400 and the fourth pin of the bridge DB400, and the U-phase rectifier circuit includes a resistor R4 24. Resistor R425, resistor R426, resistor R427, capacitor C413 and capacitor C414. The fifth pin of optical isolation U403 is grounded. The sixth pin of optical isolation U403 is connected to one end of resistor R426. The other end of resistor R426 is connected to microprocessor 1 through Uip interface. The seventh pin of optical isolation U403 is connected in series with resistor R427 and then grounded. The eighth pin of optical isolation U403 is connected in series with resistor R424 and then connected to power supply VCC. One end of resistor R425 is connected to power supply VCC, and the other end is connected to the sixth pin of optical isolation U403. The capacitor C413 is connected in parallel between the eighth pin of optical isolation U403 and the fifth pin of optical isolation U403 and grounded. The other end of capacitor C414 is connected to microprocessor 1 through Uip interface and grounded. The first pin of optical isolation U403 and the fourth pin of optical isolation U403 are suspended. When working, when V K2K1 When it is 0V or less than a certain voltage value (usually around 30V), the optocoupler is not conducting, Uip is high level, and when V K2K1 When the voltage is greater than a certain value (generally around 30V), the optocoupler is turned on and Uip is at a low level.

[0046] like Figure 8As shown, the V-phase detection circuit includes a bridge DB401, an optical isolator U404 and a V-phase rectifier circuit. The input end of the bridge DB401 is connected to the cathode K3 (network point) of the thyristor SCR3 of the V-phase thyristor drive circuit and the cathode K4 (network point) of the thyristor SCR4 of the V-phase thyristor drive circuit for converting the AC voltage signals of the cathode and anode of the thyristor element into a DC pulse voltage signal. The output end of the bridge DB401 is connected to the input end of the optical isolator U404 for trigger detection of the thyristor element. The output end of the optical isolator U404 is connected to the input end of the V-phase rectifier circuit for rectification and filtering. The output end of the V-phase rectifier circuit is connected to the microprocessor 1 through the Vip interface for feeding back detection information to the microprocessor 1. Specifically, the cathode K3 of the thyristor SCR3 is connected to the first pin of the bridge DB401, and resistors R428, R429 and R430 are connected in series between the cathode K3 of the thyristor SCR3 and the bridge DB401, the cathode K4 of the thyristor SCR4 is connected to the second pin of the bridge DB401, a capacitor C416 is connected in parallel between the first pin of the bridge DB401 and the second pin of the bridge DB401, the third pin of the bridge DB401 and the fourth pin of the bridge DB401 are connected to the second pin of the optical isolation U404 and the third pin of the optical isolation U404 respectively, a capacitor C415 is connected in parallel between the first pin of the bridge DB401 and the third pin of the bridge DB401, and a capacitor C417 is connected in parallel between the first pin of the bridge DB401 and the fourth pin of the bridge DB401, and the V-phase rectifier circuit includes resistor R43 1. Resistor R432, resistor R433, resistor R434, capacitor C419 and capacitor C420. The fifth pin of optical isolation U404 is grounded. The sixth pin of optical isolation U404 is connected to one end of resistor R433. The other end of resistor R433 is connected to microprocessor 1 through Vip interface. The seventh pin of optical isolation U404 is connected in series with resistor R434 and then grounded. The eighth pin of optical isolation U404 is connected in series with resistor R431 and then connected to power supply VCC. One end of resistor R432 is connected to power supply VCC, and the other end is connected to the sixth pin of optical isolation U404. The capacitor C419 is connected in parallel between the eighth pin of optical isolation U404 and the fifth pin of optical isolation U404 and grounded. One end of capacitor C420 is connected to microprocessor 1 through Vip interface and the other end is grounded. The first pin of optical isolation U404 and the fourth pin of optical isolation U404 are suspended. When working, when V K4K3 When it is 0V or less than a certain voltage value (usually around 30V), the optocoupler is not conducting, Vip is high level, and when V K4K3 When the voltage is greater than a certain value (usually around 30V), the optocoupler is turned on and Vip is at a low level.

[0047] like Fig. 9As shown, the W-phase detection circuit includes a bridge DB402, a light barrier U405 and a W-phase rectifier circuit. The input end of the bridge DB402 is connected to the cathode K5 (network point) of the thyristor SCR5 of the W-phase thyristor drive circuit and the cathode K6 (network point) of the thyristor SCR6 of the W-phase thyristor drive circuit for converting the AC voltage signals of the cathode and anode of the thyristor element into a DC pulse voltage signal. The output end of the bridge DB402 is connected to the input end of the light barrier U405 for triggering detection of the thyristor element. The output end of the light barrier U405 is connected to the input end of the W-phase rectifier circuit for rectification and filtering. The output end of the W-phase rectifier circuit is connected to the microprocessor 1 through the Wip interface for feeding back detection information to the microprocessor 1. Specifically, the cathode K5 of the thyristor SCR5 is connected to the first pin of the bridge DB402, and a resistor R435, a resistor R436 and a resistor R437 are connected in series between the cathode K5 of the thyristor SCR5 and the bridge DB402, the cathode K6 of the thyristor SCR6 is connected to the second pin of the bridge DB402, a capacitor C422 is connected in parallel between the first pin of the bridge DB402 and the second pin of the bridge DB402, the third pin of the bridge DB402 and the fourth pin of the bridge DB402 are connected to the second pin of the optical isolation U405 and the third pin of the optical isolation U405 respectively, a capacitor C421 is connected in parallel between the first pin of the bridge DB402 and the third pin of the bridge DB402, and a capacitor C423 is connected in parallel between the first pin of the bridge DB402 and the fourth pin of the bridge DB402, and the W-phase rectifier circuit includes a resistor R438, resistor R439, resistor R440, resistor R441, capacitor C425 and capacitor C426, the fifth pin of optical partition 405 is grounded, the sixth pin of optical partition 405 is connected to one end of resistor R440, the other end of resistor R440 is connected to microprocessor 1 through Wip interface, the seventh pin of optical partition 405 is connected in series with resistor R441 and then grounded, the eighth pin of optical partition 405 is connected in series with resistor R438 and then connected to power supply VCC, one end of resistor R439 is connected to power supply VCC, and the other end is connected to the sixth pin of optical partition 405, the capacitor C425 is connected in parallel between the eighth pin of optical partition 405 and the fifth pin of optical partition 405 and grounded, one end of capacitor C426 is connected to microprocessor 1 through Wip interface and the other end is grounded, the first pin of optical partition U405 and the fourth pin of optical partition U405 are suspended. When working, when V K6K5 When it is 0V or less than a certain voltage value (usually around 30V), the optocoupler is not conducting, Wip is high level, and when V K6K5 When the voltage is greater than a certain value (generally around 30V), the optocoupler is turned on and Wip is at a low level.

[0048] When working, in the U-phase optocoupler trigger circuit, when the network point Mu is at a low level, the input diodes of the optocouplers U7, U8 and U9 emit light, providing a trigger signal to the anti-parallel thyristors at the output ends of the optocouplers U7, U8 and U9. K2 >V K1 ), the current passes through the reverse diode D6, resistor R18, resistor R21, optocoupler U9, optocoupler U8, optocoupler U7, resistor R15, resistor R17 and then connects to the RC charging and discharging circuit of resistor R16 and capacitor C7. The reverse diode D5 is in the reverse cut-off state, and the voltage drop of optocouplers U7, U8 and U9 is only a few volts, which can be ignored. The gate voltage of thyristor SCR1 Where τ=(R 18 +R 21 +R 15 +R 17 )×C 17 , after a few microseconds, V G1K1 The voltage is greater than the gate trigger voltage of the thyristor SCR1, then the thyristor SCR1 starts to conduct. Once the thyristor SCR1 is turned on, the RC charge-discharge circuit composed of the resistor R16 and the capacitor C7 is in the discharge state, V G1K1 The voltage will not continue to rise; if the U phase voltage is in the negative half cycle (V K1 >V K2 ), the current passes through the reverse diode D5, resistor R17, resistor R15, optocoupler U7, optocoupler U8, optocoupler U9, resistor R21, resistor R18 and then connects to the RC charge and discharge circuit composed of resistor R19 and capacitor C9. The reverse diode D6 is in the reverse cut-off state. The voltage drop of optocouplers U7, U8 and U9 is only a few volts, which can be ignored. The gate voltage of thyristor SCR2 Where τ=(R 18 +R 21 +R 15 +R 17 )×C9, after a few microseconds, V G2K2 The voltage is greater than the gate trigger voltage of the thyristor SCR2, then the thyristor SCR2 starts to conduct. Once the thyristor SCR2 is turned on, the RC charge-discharge circuit composed of the resistor R19 and the capacitor C9 is in the discharge state, V G2K2 The voltage will not continue to rise.

[0049] When the microprocessor 1 sends the U-phase trigger signal Mu, if the U-phase thyristor SCR1 cannot be turned on in time or cannot be turned on, the thyristor trigger is abnormal. If the soft starter cannot report the thyristor trigger abnormality in time within 0 microseconds to 1000 microseconds, then V K2K1The voltage between is always relatively high (how high the voltage is depends on the phase voltage amplitude and the phase angle of the current phase voltage of the power grid corresponding to the moment when the CPU sends the trigger signal, and the voltage is highest at 90°), and the loop current I formed by the reverse diode D6, resistor R18, resistor R21, optocoupler U9, optocoupler U8, optocoupler U7, resistor R15, resistor R17, capacitor C7 and gate G1 of thyristor SCR1 LOOP ≈V K2K1 ÷(R 18 +R 21 +R 15 +R 17 ), usually, the sum of the resistance values ​​of the resistors R18, R21, R15 and R17 is about 100Ω to 500Ω, so I LOOP Approximately between 0.45A and 6.2A (according to the three-phase AC380V±15% grid voltage). If the current I LOOP Long-term passage through the optocoupler output terminal and the charging resistor will cause the corresponding U-phase optocoupler to fail or the charging resistor to burn out. Since the fault detection circuit 3 can timely report the abnormal triggering of the thyristor within 0 microseconds to 1000 microseconds, the microprocessor 1 stops sending trigger signals for all phases, so that no current passes through the U-phase optocoupler and the charging resistor, thereby preventing the failure of the U-phase optocoupler or the charging resistor. Since the working principle of the V-phase optocoupler trigger circuit and the W-phase optocoupler trigger circuit is exactly the same as that of the U-phase optocoupler trigger circuit, it will not be repeated here.

[0050] When the fault detection circuit 3 performs thyristor trigger detection, taking the U-phase detection circuit as an example, after the microprocessor 1 sends the U-phase trigger signal Wu, when the thyristor SCR1 or thyristor SCR2 of the U-phase optocoupler trigger circuit is turned on, V K2K1 The voltage between the two is 0V (ignore the voltage drop of the thyristor), and the corresponding U-phase detection circuit has no current input. The V of the output transistor of the optical isolation U403 of the U-phase detection circuit is CE When the U-phase optocoupler trigger circuit's thyristor SCR1 or thyristor SCR2 is not conducting, V K2K1The voltage between is not 0V, the corresponding U-phase detection circuit will have current input, the VCE of the output transistor of the optical isolation U403 of the U-phase detection circuit is turned on, and the output end of the U-phase detection circuit is low level. If the microprocessor 1 detects that the level of the output end of the U-phase detection circuit flips from a low level to a high level within a preset time of 0 microseconds to 1000 microseconds, it is considered that the thyristor corresponding to the U-phase is normally turned on. If the microprocessor 1 detects that the level of the output end of the U-phase detection circuit has not changed within a preset time of 0 microseconds to 1000 microseconds, it is considered that the thyristor SCR1 or thyristor SCR2 of the corresponding U-phase is not turned on or is not turned on in time, and the thyristor triggers abnormal protection, and the soft starter of the present invention will stop working due to fault protection to prevent the U-phase optical coupler or charging resistor from failing. Since the working principles of the V-phase detection circuit and the W-phase detection circuit are exactly the same as those of the U-phase detection circuit, they will not be repeated here. The present invention controls the thyristor conduction detection time of the microprocessor 1 to be between 0 microseconds and 1000 microseconds, thereby avoiding the failure of the optocoupler or the charging resistor due to too long a detection time, and avoiding the abnormal protection of the thyristor triggered due to too short a detection time.

[0051] like Fig.10 and 11 As shown, when the fault detection circuit 3 performs bypass switch closing detection, taking the U phase as an example, if the bypass switch of the thyristor drive circuit 2 is not closed, within the first 10 seconds after the bypass operation, within the angle of 0 to α (the range of α is 90°±10°) after the phase voltage of the U phase grid passes through the zero point, the trigger signal is continuously applied to the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2; and within the angle of α to π after the phase voltage of the U phase grid passes through the zero point, the trigger signal is stopped from being applied to the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2. If the bypass switch is not closed, when the phase voltage of the U phase crosses zero point within the angle of 0 to α, since the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2 always has a trigger signal, the thyristor SCR1 or the thyristor SCR2 will be turned on (ignoring the conduction delay), and the current zero-crossing signal U phase detection circuit output end is always high level. Since the motor stator is an inductive load, the current lags behind the voltage angle β (the range of β is 0° to 80°), so the U phase detection circuit output end is always high level within the angle of 0 to (α+β) (see Figure 6 Ui p signal); when the phase voltage of the U phase grid passes through zero point (α+β) to π angle, since there is no trigger signal at the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2, the thyristor SCR1 or the thyristor SCR2 will not be turned on, and the output end of the U phase detection circuit is low level (see Figure 6In the first 10 seconds after the bypass operation, if the microprocessor 1 detects that the number of falling edges at the output end of the U-phase detection circuit exceeds 250 to 500 within 10 seconds, it is determined that the bypass switch is faulty. Fig.10 T0 in it is the current zero-crossing negative pulse width during the first 10 seconds after the soft starter switches to bypass operation, when the trigger signal is not fully turned on and the bypass switch is not closed normally.

[0052] If the bypass switch is not closed, after the first 10s after the bypass operation, the trigger signal is always applied to the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2 within the angle range of 0 to π at the zero crossing point of the U phase, that is, the trigger signal of the gate G1 of the thyristor SCR1 or the gate G2 of the thyristor SCR2 always exists, so the anode and cathode of the thyristor SCR1 or the thyristor SCR2 are turned on due to the higher voltage within the time range of 0 to (π-T1×1 / 2) after the voltage crosses the zero point, and the output end of the U phase detection circuit is high level; Fig.11 T1 in the figure is the current zero-crossing negative pulse width when the trigger signal is fully turned on and the bypass switch is not closed normally within 10 seconds after the soft starter switches to bypass operation. In the short time T1×1 / 2 before and after the U phase voltage crosses the zero point, the thyristor is switching phases, V K2K1 The voltage is several tens of volts, the thyristor SCR1 or SCR2 cannot be turned on, and the current zero-crossing signal of the U-phase detection circuit is at a low level at the output end of the U-phase detection circuit. Figure 7 Uip waveform, in practical applications, since the motor stator is an inductive load, the current lags behind the voltage by a certain angle, which will make the width T1 of the low level at the output end of the U phase detection circuit smaller or even disappear. After 10s after the bypass operation, if the microprocessor 1 detects that the number of falling edges of the signal at the output end of the U phase detection circuit exceeds 250 to 500 within 300s, the bypass switch is judged to be faulty. Since the working principles of the V phase detection circuit and the W phase detection circuit are exactly the same as those of the U phase detection circuit, they will not be repeated here. In this technical solution, the falling edge and the rising edge, the high level and the low level, and the low level and the high level are considered to be equal solutions, because only a non-gate circuit is required to achieve it. In particular, the T0 and T1 are the widths of the non-conduction angle, and the time widths of the two are different. The former is longer and greater than 0ms, and the latter is shorter, with an approximate value of 0ms to 1ms and may be 0ms.

[0053] This embodiment uses a three-phase detection circuit for detection. The principle of the three-phase detection circuit is the same, and the specific circuit may be the same or slightly different. As a means of degradation, the fault detection circuit 3 may also be provided with only a single-phase or two-phase fault detection circuit, which also belongs to the protection scope of the present invention.

[0054] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A soft starter with thyristor triggered abnormal protection, characterized in that: The invention comprises a microprocessor (1), a thyristor drive circuit (2) and a fault detection circuit (3), wherein the input end of the thyristor drive circuit (2) is connected to the microprocessor (1) for receiving a trigger signal sent by the microprocessor (1), the output end of the thyristor drive circuit (2) is connected to a three-phase asynchronous motor 3M for driving the three-phase asynchronous motor 3M to start, and the input end and output end of the fault detection circuit (3) are respectively connected to the thyristor drive circuit (2) and the microprocessor (1) for detecting whether the thyristor component of the thyristor drive circuit (2) is turned on and feeding back to the microprocessor (1); The thyristor drive circuit (2) comprises an optocoupler component and a thyristor component, the input end of the optocoupler component is connected to the microprocessor (1), the output end of the optocoupler component is connected to the input end of the thyristor component, and the output end of the thyristor component is respectively connected to a fault detection circuit (3) and a three-phase asynchronous motor (3M) for detecting whether the thyristor component is turned on and soft-starting. After the microprocessor (1) sends a trigger signal to the thyristor component, if the microprocessor (1) detects that the thyristor component of the corresponding phase has been turned on within 0 microseconds to 1000 microseconds, it is considered that the thyristor triggering is normal, and the soft starter continues to work; If the microprocessor (1) detects that the thyristor component of the corresponding phase is not conducting within a time period of 0 microseconds to 1000 microseconds, it is considered that the thyristor component is triggered abnormally, and the soft starter will stop working due to fault protection; The fault detection circuit (3) is also used to detect whether a bypass switch of the soft starter has a fault; After bypass operation, when the number of falling edges or rising edges of the detection signal received by the microprocessor (1) from the fault detection circuit (3) within a preset bypass detection cycle exceeds a preset fault threshold, it is determined that the bypass switch is faulty.

2. The soft starter with thyristor triggered abnormal protection according to claim 1, characterized in that: The fault detection circuit (3) comprises a U-phase detection circuit, a V-phase detection circuit and a W-phase detection circuit, wherein the input end of the U-phase detection circuit is connected to the output end of the U-phase thyristor drive circuit of the thyristor drive circuit (2), the output end of the U-phase detection circuit is connected to the microprocessor (1), the input end of the V-phase detection circuit is connected to the output end of the V-phase thyristor drive circuit of the thyristor drive circuit (2), the output end of the V-phase detection circuit is connected to the microprocessor (1), the input end of the W-phase detection circuit is connected to the output end of the W-phase thyristor drive circuit of the thyristor drive circuit (2), and the output end of the W-phase detection circuit is connected to the microprocessor (1).

3. The soft starter with thyristor triggered abnormal protection according to claim 1 or 2, characterized in that: The thyristor drive circuit (2) comprises an optocoupler anode trigger circuit and a motor soft start circuit, the input end of the optocoupler anode trigger circuit is connected to the microprocessor (1), the output end of the optocoupler anode trigger circuit is connected to the input end of the motor soft start circuit to trigger the thyristor component of the motor soft start circuit, and the output end of the motor soft start circuit is respectively connected to the input end of the fault detection circuit (3) and the three-phase asynchronous motor 3M.

4. The soft starter with thyristor triggered abnormal protection according to claim 3 is characterized in that: The optical coupler anode trigger circuit comprises a U-phase optical coupler trigger circuit, a V-phase optical coupler trigger circuit and a W-phase optical coupler trigger circuit, each phase optical coupler trigger circuit comprises an optical coupler component formed by an optical coupler, the input end of each phase optical coupler trigger circuit is respectively connected to a microprocessor (1), and the output end of each phase optical coupler trigger circuit is connected to a motor soft start circuit; The motor soft start circuit comprises a U-phase thyristor drive circuit, a V-phase thyristor drive circuit and a W-phase thyristor drive circuit, each phase thyristor drive circuit comprises a thyristor assembly formed by thyristors, the input end of each phase thyristor drive circuit is connected to an optocoupler anode trigger circuit, and the output end of each phase thyristor drive circuit is respectively connected to a fault detection circuit (3) and a three-phase asynchronous motor 3M.

5. The soft starter with thyristor triggered abnormal protection according to claim 2, characterized in that: The U-phase detection circuit comprises a bridge DB400, a light barrier U403 and a U-phase rectifier circuit, the input end of the bridge DB400 is connected to the cathode K1 of the thyristor SCR1 of the U-phase thyristor drive circuit and the cathode K2 of the thyristor SCR2 of the U-phase thyristor drive circuit, the output end of the bridge DB400 is connected to the input end of the light barrier U403, the output end of the light barrier U403 is connected to the input end of the U-phase rectifier circuit, and the output end of the U-phase rectifier circuit is connected to the microprocessor (1) via a Uip interface; The structures of the V-phase detection circuit and the W-phase detection circuit are the same as that of the U-phase detection circuit.

6. The soft starter with thyristor triggered abnormal protection according to claim 5, characterized in that: The cathode K1 of the thyristor SCR1 is connected to the first pin of the bridge DB400, and resistors R421, R422 and R423 are connected in series between the cathode K1 of the thyristor SCR1 and the bridge DB400. The cathode K2 of the thyristor SCR2 is connected to the second pin of the bridge DB400. A capacitor C410 is connected in parallel between the first pin of the bridge DB400 and the second pin of the bridge DB400. The third pin of the bridge DB400 and the fourth pin of the bridge DB400 are connected to the second pin of the optical isolation U403 and the third pin of the optical isolation U403 respectively. A capacitor C409 is connected in series between the first pin of the bridge DB400 and the third pin of the bridge DB400. A capacitor C411 is connected in series between the first pin of the bridge DB400 and the fourth pin of the bridge DB400. The U phase integral The flow circuit includes a resistor R424, a resistor R425, a resistor R426, a resistor R427, a capacitor C413 and a capacitor C414, the fifth pin of the optical isolation U403 is grounded, the sixth pin of the optical isolation U403 is connected to one end of the resistor R426, the other end of the resistor R426 is connected to the microprocessor (1) through the Uip interface, the seventh pin of the optical isolation U403 is connected in series with the resistor R427 and then grounded, the eighth pin of the optical isolation U403 is connected in series with the resistor R424 and then connected to the power supply VCC end, one end of the resistor R425 is connected to the power supply VCC, and the other end is connected to the sixth pin of the optical isolation U403, the capacitor C413 is connected in parallel between the eighth pin of the optical isolation U403 and the fifth pin of the optical isolation U403 and is grounded, and the other end of the capacitor C414 is connected to the microprocessor (1) through the Uip interface and is grounded; The structures of the V-phase detection circuit and the W-phase detection circuit are the same as that of the U-phase detection circuit.

7. The soft starter with thyristor triggered abnormal protection according to claim 4, characterized in that: The U-phase optocoupler trigger circuit includes an optocoupler U7, an optocoupler U8, an optocoupler U9, a varistor RV7, a varistor RV8 and a varistor RV9, wherein the first pin of the optocoupler U7 is connected to the power supply, the second pin of the optocoupler U7 and the third pin of the optocoupler U7 are connected in parallel to the first pin of the optocoupler U8, the fourth pin of the optocoupler U7 is connected to the sixth pin of the optocoupler U8, the sixth pin of the optocoupler U7 is connected to one end of the resistor R15, the first pin of the optocoupler U8 is connected to the optocoupler U7, the second pin of the optocoupler U8 is connected to the The pin is connected in parallel with the third pin of the optocoupler U8 and then connected to the first pin of the optocoupler U9, the fourth pin of the optocoupler U8 is connected to the sixth pin of the optocoupler U9, the sixth pin of the optocoupler U8 is connected to the optocoupler U7, the first pin of the optocoupler U9 is connected to the optocoupler U8, the second pin of the optocoupler U9 and the third pin of the optocoupler U9 are connected in parallel and then connected to the microprocessor (1) through a resistor R20, the fourth pin of the optocoupler U9 is connected to one end of the resistor R21, the sixth pin of the optocoupler U9 is connected to the optocoupler U8, the varistor R The two ends of V7 are connected to the fourth pin of the optocoupler U7 and the sixth pin of the optocoupler U7 respectively, the two ends of the varistor RV8 are connected to the fourth pin of the optocoupler U8 and the sixth pin of the optocoupler U8 respectively, the two ends of the varistor RV9 are connected to the fourth pin of the optocoupler U9 and the sixth pin of the optocoupler U9 respectively, a capacitor C8 is connected in series between the first pin of the optocoupler U7 and the third pin of the optocoupler U9, the other end of the resistor R15 is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to the motor soft The starting circuit is connected to one end of a resistor R16, the other end of the resistor R16 is connected to a motor soft starting circuit, and a capacitor C7 and a reverse diode D5 are sequentially connected in parallel at both ends of the resistor R16, the other end of the resistor R21 is connected to one end of a resistor R18, the other end of the resistor R18 is respectively connected to the motor soft starting circuit and one end of a resistor R19, the other end of the resistor R19 is connected to the motor soft starting circuit, and a capacitor C9 and a reverse diode D6 are sequentially connected in parallel at both ends of the resistor R19; The structures of the V-phase optocoupler trigger circuit and the W-phase optocoupler trigger circuit are the same as the structure of the U-phase optocoupler trigger circuit.

8. The soft starter with thyristor triggered abnormal protection according to claim 4, characterized in that: The U-phase thyristor drive circuit comprises a thyristor SCR1, a thyristor SCR2 and a bypass switch S1. The thyristor SCR1 and the thyristor SCR2 are arranged in reverse parallel and are controlled by a trigger signal Mu of a microprocessor (1) to form a U-phase thyristor assembly. The bypass switch S1 is connected in parallel between the cathode K1 and the anode of the thyristor SCR1. The cathode K1 of the thyristor SCR1 serves as a network point and is connected to the U-phase input terminal of the three-phase asynchronous motor 3M. 1 and one end of the thyristor SCR2 connected in parallel and the gate electrode G1 of the thyristor SCR1 are respectively connected to the RC charging and discharging circuit composed of the capacitor C7 and the resistor R16 of the optocoupler anode trigger circuit, the cathode K2 of the thyristor SCR2 is a network point and is connected to the U-phase power grid, and the other end of the thyristor SCR1 and the thyristor SCR2 connected in parallel and the gate electrode G2 of the thyristor SCR2 are respectively connected to the RC charging and discharging circuit composed of the capacitor C9 and the resistor R19 of the optocoupler anode trigger circuit; The structures of the V-phase thyristor drive circuit and the W-phase thyristor drive circuit are the same as the structure of the U-phase thyristor drive circuit.

9. The soft starter with thyristor triggered abnormal protection according to claim 5, characterized in that: After the microprocessor (1) sends a U-phase trigger signal, if the microprocessor (1) detects that the output terminal of the U-phase detection circuit flips from a low level to a high level within a preset time, it is considered that the thyristor corresponding to the U-phase is normally turned on; if the microprocessor (1) detects that the level of the output terminal of the U-phase detection circuit has not changed within the preset time, it is considered that the thyristor SCR1 or thyristor SCR2 corresponding to the U-phase is not turned on or is not turned on in time; The principles of the V-phase detection circuit and the W-phase detection circuit are the same as the principle of the U-phase detection circuit.

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