A system and method for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of winding motor

Abstract

The present invention discloses a system and method for implementing contactless cascade control and fault monitoring of multi-stage rotor series resistances in a winding motor. The system comprises multiple contactless controllers, each of which is provided with U, V, and W three-phase conduction signal output terminals, a cascade signal input terminal, and a rotor series resistance control signal input terminal for the current stage. From top to bottom, the cascade signal of the previous-stage contactless controller and the rotor series resistance control signal of the previous stage are connected in parallel and then connected in series with the cascade signal input terminal of the next-stage contactless controller. The cascade signal input terminal of the top-stage contactless controller is connected in series with the brake signal. The present invention not only implements cascade control between multi-stage rotor series resistances, thus saving energy, extending service life, and improving operating efficiency, but also monitors whether the thyristors used for contactless control are faulty, which is of great value in improving the safety and stability of motor operation.

Description

Technical Field

[0001] The present invention relates to a system and method for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of a winding motor, belonging to the technical field of winding motor control. Background Art

[0002] Rotor series resistance, commonly referred to as "switching resistance," regulates the speed of a wound motor by varying the resistance of its rotor circuit. Because starting with a rotor series resistance limits starting current and increases starting torque, it's often used in machines with difficult starting conditions, including heavy-loaded and frequently started industrial machinery (such as cranes and elevators).

[0003] In order to obtain a relatively large acceleration torque during the entire starting process and make the starting process smooth, the starting resistor is usually divided into several sections and must be removed step by step during the starting process.

[0004] At present, there are two main ways to achieve rotor series resistance control, one is electromagnetic AC contactor control, and the other is contactless contactor control. Electromagnetic AC contactor control has many defects, such as: 1) there is power loss during use, and the coil generates noise when running, especially when there is dirt on the armature; 2) when the load current is large, it is easy to burn the contacts so that the contacts cannot be released in time; 3) when the main electronic contacts are released under load, it is easy to generate arc sparks, causing the contacts to burn, resulting in poor contact, and in severe cases, it can cause power phase loss and burn the motor coil; 4) in applications with frequent switching, it is easy to be damaged; 5) the service life is short, the control coil consumes a lot of energy, which is more obvious when the power is high; therefore, with the development of power electronics technology, contactless contactors using thyristors as switches have replaced electromagnetic contactors.

[0005] Although the contactless contactor control method has the advantages of no sparks, no contact sticking, long life and low cost, when it is applied to the multi-stage series resistance control of the rotor, if there is no serious short circuit, it is difficult to identify from the appearance whether the thyristor that realizes the contactless control is faulty. If one of the several thyristors that realize the contactless control fails, it will cause the three-phase rotor resistance of the wound motor to be different, which will affect the motor output. However, this effect will only be more obvious when the motor load is close to the rated load, which increases the difficulty of fault detection of the contactless control and poses a safety hazard and accident risk.

[0006] In addition, the multiple contactless contactors currently used for controlling the multi-stage series resistance of the winding motor rotor are independently controlled, and there is no correlation control between them. As a result, when the upper-stage resistance cutting is working, the lower-stage resistance cutting is still working redundantly, resulting in redundant resistance cutting work, generating unnecessary energy consumption and affecting work efficiency, and also affecting the service life of the contactless contactor. Summary of the Invention

[0007] In response to the above-mentioned problems and needs in the prior art, the purpose of the present invention is to provide a system and method for realizing contactless cascade control and fault monitoring of the multi-stage rotor string resistance of the winding motor, so as to realize contactless control of the multi-stage rotor string resistance of the winding motor, and at the same time realize cascade control between multiple stages and monitoring of contactless control faults at each stage, so that the multi-stage rotor string resistance of the winding motor can be accurately and intelligently controlled, thereby achieving the purpose of saving energy, extending life, improving work efficiency and the safety and stability of motor operation.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0009] A system for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of a winding motor, wherein the three-phase rotor resistance of the winding motor is provided with N sections, and a contactless controller is provided between each adjacent section, and each contactless controller is provided with U, V, and W three-phase conduction signal output terminals, a cascade signal input terminal, and a rotor series resistance control signal input terminal of the current stage; wherein: the cascade signal input terminal of the uppermost contactless controller is connected in series with the braking signal, the rotor series resistance control signal of the uppermost contactless controller and the braking signal are connected in parallel and then connected in series with the cascade signal input terminal of the next uppermost contactless controller, the cascade signal of the next uppermost contactless controller and the rotor series resistance control signal are connected in parallel and then connected in series with the cascade signal input terminal of the contactless controller of the next lower stage; and so on, from top to bottom, the cascade signal of the contactless controller of the previous stage and the rotor series resistance control signal of the previous stage are connected in parallel and then connected in series with the cascade signal input terminal of the contactless controller of the next lower stage; and N is a natural number ≥2.

[0010] In a preferred embodiment, N is a natural number between 3 and 7.

[0011] In one implementation scheme, each contactless controller includes an input-output control circuit, a cascade detection circuit, a rotor frequency detection circuit, a thyristor switching circuit, and a thyristor drive module. The signal input end of the cascade detection circuit is connected to the parallel signal of the braking signal and the control signal of the previous-stage rotor series resistance, the signal output end of the cascade detection circuit is connected to the cascade signal input end of the input-output control circuit, and the input-output control circuit is further provided with an input end connected to the control signal of the rotor series resistance of the current stage, the signal input end of the rotor frequency detection circuit is connected to the rotor frequency signal, the signal output end of the rotor frequency detection circuit is connected to the rotor frequency signal input end of the input-output control circuit, the signal output end of the input-output control circuit is connected to the signal input end of the thyristor switching circuit, the signal output end of the thyristor switching circuit is connected to the signal input end of the thyristor drive module, and the signal output end of the thyristor drive module is connected to the rotor resistor.

[0012] In one implementation scheme, the input-output control circuit is a digital logic circuit consisting of two NOT gates, a three-input NAND gate, a two-input OR gate, and an XOR gate, wherein: the input cascade signal and the input rotor frequency signal are respectively processed by a NOT gate and then, together with the input current-stage rotor string resistance control signal, are logically processed by a three-input NAND gate, and then a switching signal is output to the thyristor switching circuit; and the input current-stage rotor string resistance control signal and the input rotor frequency signal are logically processed by an XOR gate, together with the input cascade signal, and then, after being logically processed by a two-input OR gate, a switching signal is output to the thyristor fault indicator light.

[0013] In one implementation scheme, the cascade detection circuit is composed of a rectifier circuit, a step-down circuit, a voltage stabilization protection circuit, a filter circuit, a discharge protection circuit, a photoelectric isolation circuit and a signal shaping and amplifying circuit.

[0014] In one implementation scheme, the rotor frequency detection circuit converts the rotor frequency pulse signal into a level signal, which is a high level when there is a rotor frequency and a low level when there is no rotor frequency.

[0015] In one implementation scheme, the thyristor switching circuit is composed of a switching circuit to convert the DC5V output into a DC24V switching output signal to drive the thyristor driving module to operate.

[0016] In one implementation scheme, the thyristor drive module is provided with a thyristor conduction signal output copper busbar connected to the rotor resistor.

[0017] In a preferred solution, the thyristor drive module is integrated by two MTC-100A thyristor modules.

[0018] A method for realizing contactless cascade control and fault monitoring of a multi-stage rotor series resistor of a wound motor comprises the following steps:

[0019] S1) Each contactless controller determines whether the current stage is allowed to operate or prohibited to operate based on the brake signal detected by each controller and the control signal of the previous stage rotor series resistor; if the brake signal is detected to be on and the control signal of the previous stage rotor series resistor is off, the current stage is determined to be allowed to operate; otherwise, the current stage is determined to be prohibited to operate;

[0020] S2) If it is determined that the current stage is currently allowed to operate, and the rotor string resistance control signal of the current stage is on, and a rotor frequency signal is detected at the same time, it is determined that the thyristor used for the contactless control of the current stage has an open circuit fault; if it is determined that the current stage is currently allowed to operate, and the rotor string resistance control signal of the current stage is off, and no rotor frequency signal is detected at the same time, it is determined that the thyristor used for the contactless control of the current stage has a short circuit fault;

[0021] S3) If it is determined that the current stage is prohibited from operating, the thyristor fault detection is not performed.

[0022] A further implementation plan is that the contactless controller of this level will output a turn-on signal to the rotor resistor to cut off the resistance of this level only when the current level is allowed to operate, the rotor series resistance control signal of this level is on, and it is determined that the thyristor used for the contactless control of this level has no fault.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention creatively uses the braking signal and the control signal of the previous-stage rotor string resistor as the judgment premise for allowing or prohibiting operation at the current stage. This not only realizes cascade control between the multi-stage rotor string resistors, enabling precise and intelligent control of the multi-stage rotor string resistors of the winding motor, but also significantly reduces the excess energy consumption caused by redundant and ineffective work and the impact on work efficiency and service life, thus saving energy, extending service life, and improving work efficiency. In addition, the present invention can monitor whether the thyristor used for contactless control is faulty based on the braking signal, the control signal of the previous-stage rotor string resistor, the control signal of the current-stage rotor string resistor, and the presence of the rotor frequency. This allows for timely and accurate detection of contactless control faults and prompts maintenance personnel to promptly address them. This is of great value in improving the safety and stability of motor operation and can be used to upgrade and transform the electronic control systems of existing crane equipment in the metallurgical industry, thereby maximizing and ensuring the control performance and safety of traditional lifting motors. Therefore, compared with the existing technology, the present invention represents a significant improvement and has strong industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1Schematic diagram of the electrical structure of a system for implementing contactless cascade control and fault monitoring of a multi-stage rotor series resistor of a winding motor, provided by an embodiment of the present invention;

[0026] Figure 2 This is a circuit principle block diagram of the contactless controller described in an embodiment of the present invention;

[0027] Figure 3 is a specific circuit diagram of the input and output control circuit described in an embodiment of the present invention;

[0028] Figure 4 is a specific circuit diagram of the cascade detection circuit described in an embodiment of the present invention;

[0029] Figure 5 is a specific circuit diagram of the rotor frequency detection circuit described in an embodiment of the present invention;

[0030] Figure 6 is a specific circuit diagram of the thyristor switch circuit described in an embodiment of the present invention;

[0031] Figure 7 1 is a schematic diagram of the three-dimensional structure of the contactless controller described in an embodiment of the present invention;

[0032] Figure 8 yes Figure 7 The diagram shown is a schematic diagram of the internal structure of the contactless controller after removing the metal box.

[0033] The numbers in the figure are as follows: 01, winding motor; 02, rotor resistance; 03, contactless controller; 031, input and output control circuit; 031-1, NOT gate; 031-2, three-input NAND gate; 031-3, XOR gate; 031-4, two-input OR gate; 032, cascade detection circuit; 032-1, rectifier circuit; 032-2, step-down circuit; 032-3, voltage stabilization protection circuit; 032-4, filter circuit; 032-5, Discharge protection circuit; 032-6, optoelectronic isolation circuit; 032-7, signal shaping and amplification circuit; 033, rotor frequency detection circuit; 034, thyristor switching circuit; 035, thyristor drive module; 035-1, signal input terminal; 036, metal housing; 037, integrated circuit board; 038, heat sink; 039, cooling fan; 0310, drive signal terminal; 04, rotor resistor; 05, thyristor conduction signal output copper busbar. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Example

[0036] See also Figure 1As shown: This embodiment provides a system for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of winding motor, wherein the three-phase rotor resistance 02 of the winding motor 01 is provided with N segments ( Figure 1 Taking 4 segments as an example, but not limited to this design, N is a natural number ≥ 2, preferably a natural number of 3 to 7), and a contactless controller 03 is provided between each adjacent segment (such as Figure 1 K40, K41 and K42 in each contactless controller 03 are provided with U, V, W three-phase conduction signal output terminals (such as Figure 1 U, V, W terminals in the cascade signal input terminal (such as Figure 1 RE terminal in the figure) and the rotor string resistance control signal input terminal of this stage (such as Figure 1 The top level contactless controller (such as Figure 1 The cascade signal input terminal (RE terminal) of K40 in Figure 1 K71 in the series), the top level contactless controller (such as Figure 1 The rotor string resistance control signal of this stage (such as K40 in Figure 1 K040 in) and brake signal (such as Figure 1 K71 in the Figure 1 The cascade signal input terminal (RE terminal) of K41 in the second stage is connected in series, and the contactless controller (such as Figure 1 The cascade signal of K41 in (parallel signal of K71 and K040) and the secondary upper rotor series resistance control signal (such as Figure 1 K041 in the Figure 1 and so on, from top to bottom, the cascade signal of the previous level contactless controller and the previous level rotor series resistance control signal are connected in parallel and then connected in series to the cascade signal input terminal of the next level contactless controller.

[0037] Please combine Figure 1 As shown, the method for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of a winding motor according to the present invention comprises the following steps:

[0038] S1) Each contactless controller (such as Figure 1 K40, K41 and K42 in FIG respectively detect the braking signal (such as Figure 1 K71 in the front stage) and the control signal of the rotor string resistance (such as Figure 1In the example, the control signal of the rotor string resistor of the preceding stage of K42 refers to K040 and K041, the control signal of the rotor string resistor of the preceding stage of K41 refers to K040, and the top stage K40 has no preceding stage), and determines whether the current stage is allowed to run or prohibited to run; if it is detected that the brake signal is on and the control signal of the rotor string resistor of the preceding stage is off, then the current stage is judged to be allowed to run, otherwise it is judged to be prohibited to run; for example: Figure 1 The permissible operating condition of K40 is that K71 is on (connected), the permissible operating condition of K41 is that K71 is on (connected) and the control signal K040 of the preceding rotor series resistor is off (disconnected), and the permissible operating condition of K42 is that K71 is on (connected) and the control signals K040 and K041 of the preceding rotor series resistor are both off (disconnected);

[0039] S2) If it is determined that the current stage is allowed to run, and the rotor series resistance control signal of the current stage (such as: Figure 1 When the rotor string resistance control signal of K40 at this stage is K040, the rotor string resistance control signal of K41 at this stage is K041, and the rotor string resistance control signal of K42 at this stage is K042) is on and a rotor frequency signal is detected at the same time (e.g., the detected rotor frequency signal is high), it is determined that the thyristor used for contactless control at this stage has an open circuit fault; if it is determined that the current stage is allowed to run, and the rotor string resistance control signal of this stage is off, and no rotor frequency signal is detected at the same time (e.g., the detected rotor frequency signal is low), it is determined that the thyristor used for contactless control at this stage has a short circuit fault;

[0040] S3) If it is determined that the current stage is prohibited from operating, the thyristor fault detection is not performed.

[0041] A further implementation plan is that the contactless controller of this level will output a turn-on signal to the rotor resistor to cut off the resistance of this level only when the current level is allowed to operate, the rotor series resistance control signal of this level is on, and it is determined that the thyristor used for the contactless control of this level has no fault.

[0042] From the above, it can be seen that the present invention creatively adopts the braking signal and the control signal of the previous-stage rotor string resistance as the judgment premise for allowing or prohibiting operation at this stage, which not only realizes the cascade control between the multi-stage rotor string resistance, but also enables the multi-stage rotor string resistance of the winding motor to be accurately and intelligently controlled, and can greatly reduce the excess energy consumption caused by redundant and invalid work and the impact on work efficiency and service life, and has the beneficial effects of saving energy consumption, extending service life and improving work efficiency, etc., and can also monitor whether there is a fault in the thyristor used for contactless control based on the braking signal and the control signal of the previous-stage rotor string resistance and the control signal of the rotor string resistance at this stage and the rotor frequency, and can timely and accurately detect the contactless control fault and prompt the maintenance personnel to deal with it in time, which is of great value to improving the safety and stability of the motor operation.

[0043] Figure 2 This is a circuit diagram of a contactless controller provided by an embodiment of the present invention. Figure 2 As shown in the figure, the contactless controller 03 includes an input-output control circuit 031, a cascade detection circuit 032, a rotor frequency detection circuit 033, a thyristor switch circuit 034 and a thyristor drive module 035. The signal input end of the cascade detection circuit 032 is connected to the parallel signal of the braking signal and the control signal of the previous stage rotor series resistance, and the signal output end of the cascade detection circuit 032 is connected to the cascade signal input end of the input-output control circuit 031. In addition, the input-output control circuit 031 is also provided with a signal input end connected to the current stage rotor series resistance control signal. The signal input end of the rotor frequency detection circuit 033 is connected to the rotor frequency signal, the signal output end of the rotor frequency detection circuit 033 is connected to the rotor frequency signal input end of the input-output control circuit 031, the signal output end of the input-output control circuit 031 is connected to the signal input end of the thyristor switching circuit 034, the signal output end of the thyristor switching circuit 034 is connected to the signal input end of the thyristor driving module 035, and the signal output end of the thyristor driving module 035 is connected to the rotor resistor 04.

[0044] Figure 3 This is a specific circuit diagram of the input and output control circuit 031 provided in an embodiment of the present invention, which is composed of Figure 3 As shown in the figure, the input-output control circuit 031 is a digital logic circuit composed of two NOT gates 031-1, a three-input NAND gate 031-2, an XOR gate 031-3 and a two-input OR gate 031-4, wherein: the input cascade signal (such as Figure 3 AC_LIMIT1 signal on the left side of the figure) and the input rotor frequency signal (such as Figure 3 The MOT_IN1 signal on the left side of the middle) is processed by a NOT gate 031-1 and then combined with the input current level rotor string resistance control signal (such as Figure 3 The CONTROL signal on the left side of the middle) is processed by the three-input NAND gate 031-2 logic and outputs the switching signal to the thyristor switch circuit (such as Figure 3 RUN_OUT1 signal on the right side of the middle); and the input current level rotor string resistance control signal (such as Figure 3 The CONTROL signal on the left side of the middle) and the input rotor frequency signal (such as Figure 3 The MOT_IN1 signal on the left side of the middle) is processed by the XOR gate 031-3 and then combined with the input cascade signal (such as Figure 3 The AC_LIMIT1 signal on the left side of the middle) is then processed by the two-input OR gate 031-4 logic and then sent to the thyristor fault indicator (such as Figure 3The FAULT_LED on the right side of the display outputs a switching signal.

[0045] Figure 4 is a specific circuit diagram of the cascade detection circuit 032 provided in an embodiment of the present invention, Figure 4 As shown in the figure, the cascade detection circuit 032 is composed of a rectifier circuit 032-1, a step-down circuit 032-2, a voltage stabilization protection circuit 032-3, a filter circuit 032-4, a discharge protection circuit 032-5, a photoelectric isolation circuit 032-6 and a signal shaping amplifier circuit 032-7. The parallel signal of the braking signal and the control signal of the previous stage rotor series resistor is Figure 4 The RE input on the left, the processed cascade signal is Figure 4 AC_LIMIT1 on the right is sent to the input and output control circuit 031 (please combine Figure 3 shown).

[0046] The rotor frequency detection circuit 033 converts the rotor frequency pulse signal into a level signal, which is a high level when there is a rotor frequency and a low level when there is no rotor frequency; this detection circuit is an existing technology and can be specifically used Figure 5 The specific circuit structure shown in the figure, the rotor frequency signal is Figure 5 The FB1 and FB2 inputs on the left side of the circuit are rectified, stepped down, filtered, optically isolated and shaped and amplified before being sent to the input and output control circuit 031 by MOT_IN1 on the right side (please refer to the Figure 3 shown).

[0047] The thyristor switch circuit 034 is composed of a switch circuit, which converts the DC5V output into a DC24V switch output signal to drive the thyristor drive module 035 to operate; this circuit is an existing technology and can be specifically used Figure 6 The specific circuit structure shown.

[0048] Please combine again Figure 7 and Figure 8 As shown, the contactless controller 03 of the present invention further includes a metal box 036, in which the input / output control circuit 031, the cascade detection circuit 032, the rotor frequency detection circuit 033, the thyristor switch circuit 034 and the thyristor drive module 035 are all integrated and installed. In addition, the input / output control circuit 031, the cascade detection circuit 032, the rotor frequency detection circuit 033 and the thyristor switch circuit 034 are all integrated on an integrated circuit board 037, and the thyristor drive module 035 is provided with a thyristor conduction signal output copper bus 05 connected to the rotor resistor 04 (not shown in the figure).

[0049] The thyristor driving module 035 can be integrated by two MTC-100A thyristor modules.

[0050] In addition, the contactless controller 03 of the present invention further includes a heat sink 038 and a cooling fan 039 to achieve a better heat dissipation effect, thereby extending the service life of the contactless controller; a drive signal terminal 0310 is also provided on the integrated circuit board 037, which is signal-connected to the signal input terminal 035-1 of the thyristor drive module 035.

[0051] The working principle of the contactless controller of the present invention is as follows:

[0052] When the brake signal is on (i.e., it is detected that there is power) and the control signal of the previous stage rotor series resistor is off (i.e., it is detected that there is no power), the cascade detection circuit 032 outputs a signal to allow operation (low level), otherwise it outputs a signal to prohibit operation (high level);

[0053] When the input and output control circuit 031 collects the output of the cascade detection circuit 032 as the operation permission signal (low level), and the input rotor string resistance control signal (such as Figure 3 When the CONTROL signal on the left side is on (i.e., power is detected), the output to the thyristor switch circuit 034 enters the operating state, otherwise the output enters the standby state;

[0054] When the input and output control circuit 031 collects the output of the cascade detection circuit 032 as the operation permission signal (low level), and the input rotor string resistance control signal (such as Figure 3 When the CONTROL signal on the left side of the middle is on (i.e., there is power), and the input rotor frequency signal is high, the input and output control circuit 031 determines that the thyristor is open circuit fault, and sends a Figure 3 Thyristor fault indicator light (such as Figure 3 The FAULT_LED on the right side of the middle outputs an open signal, which lights up the fault indicator and shuts down the machine for protection.

[0055] When the input and output control circuit 031 collects the output of the cascade detection circuit 032 as the operation permission signal (low level), and the input rotor string resistance control signal (such as Figure 3 When the CONTROL signal on the left side of the circuit is off (i.e. no power is detected), and the rotor frequency signal input is not (low level), the input and output control circuit 031 determines that the thyristor is short-circuited and sends a Figure 3 Thyristor fault indicator light (such as Figure 3 The FAULT_LED on the right side of the middle outputs an open signal to light up the fault indicator light;

[0056] When the input / output control circuit 031 collects the operation prohibition signal (high level) output by the cascade detection circuit 032, the thyristor fault monitoring is not performed;

[0057] Only when the thyristor switch circuit 034 collects the operation permission signal (low level), and the input rotor string resistance control signal of this stage is on (that is, power is detected), and at the same time no thyristor fault is detected, the thyristor switch circuit 034 outputs a conduction signal to the thyristor drive module 035 to cut the resistance of the rotor of this stage.

[0058] Finally, it is necessary to point out here that the above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered within the scope of protection of the present invention.

Claims

1. A system for implementing contactless cascade control and fault monitoring of multi-stage rotor series resistance of a wound-rotor motor, wherein each of the three-phase rotor resistances of the wound-rotor motor has N segments, and a contactless controller is provided between each adjacent segment; characterized in that: Each contactless controller is provided with U, V, W three-phase conduction signal output terminals and cascade signal input terminals and current-stage rotor series resistance control signal input terminals; wherein: the cascade signal input terminal of the uppermost contactless controller is connected in series with the braking signal, the current-stage rotor series resistance control signal of the uppermost contactless controller is connected in parallel with the braking signal and then connected in series with the cascade signal input terminal of the next upper-stage contactless controller, the cascade signal of the next upper-stage contactless controller and the next upper-stage rotor series resistance control signal are connected in parallel and then connected in series with the cascade signal input terminal of the next-stage contactless controller; and so on, from top to bottom, the cascade signal of the previous-stage contactless controller and the previous-stage rotor series resistance control signal are connected in parallel and then connected in series with the cascade signal input terminal of the next-stage contactless controller; and N is a natural number ≥2, and each contactless controller includes an input-output control circuit, a cascade detection circuit , rotor frequency detection circuit, thyristor switching circuit and thyristor driving module, the signal input end of the cascade detection circuit is connected to the parallel signal of the braking signal and the control signal of the previous stage rotor series resistance, the signal output end of the cascade detection circuit is connected to the cascade signal input end of the input-output control circuit, the input-output control circuit is also provided with an input end connected to the control signal of the rotor series resistance of this stage, the signal input end of the rotor frequency detection circuit is connected to the rotor frequency signal, the signal output end of the rotor frequency detection circuit is connected to the rotor frequency signal input end of the input-output control circuit, the signal output end of the input-output control circuit is connected to the signal input end of the thyristor switching circuit, the signal output end of the thyristor switching circuit is connected to the signal input end of the thyristor driving module, and the signal output end of the thyristor driving module is connected to the rotor resistor.

2. The system according to claim 1, wherein: The input-output control circuit is a digital logic circuit consisting of two NOT gates, a three-input NAND gate, a two-input OR gate, and an XOR gate, wherein: the input cascade signal and the input rotor frequency signal are respectively processed by a NOT gate, and then together with the input current-stage rotor string resistance control signal, are logically processed by a three-input NAND gate, and then a switching signal is output to the thyristor switching circuit; and the input current-stage rotor string resistance control signal and the input rotor frequency signal are logically processed by an XOR gate, and then together with the input cascade signal, are logically processed by a two-input OR gate, and then a switching signal is output to the thyristor fault indicator light.

3. The system according to claim 1, wherein: The cascade detection circuit is composed of a rectifier circuit, a voltage step-down circuit, a voltage stabilization protection circuit, a filter circuit, a discharge protection circuit, a photoelectric isolation circuit and a signal shaping and amplifying circuit.

4. The system according to claim 1, wherein: The rotor frequency detection circuit converts the rotor frequency pulse signal into a level signal, which is a high level when there is a rotor frequency and a low level when there is no rotor frequency.

5. The system according to claim 1, wherein: The thyristor switching circuit is composed of a switching circuit to convert the DC5V output into a DC24V switching output signal to drive the thyristor drive module to operate.

6. The system according to claim 1, wherein: The thyristor drive module is provided with a thyristor conduction signal output copper bar connected to the rotor resistor.

7. The system according to claim 1, wherein: The thyristor drive module is obtained by integrating two MTC-100A thyristor modules.

8. A method for realizing contactless cascade control and fault monitoring of multi-stage rotor series resistance of a winding motor, characterized by: The method comprises the following steps: S1) Each contactless controller determines whether the current stage is allowed to operate or prohibited to operate based on the brake signal detected by each controller and the control signal of the previous stage rotor series resistor; if the brake signal is detected to be on and the control signal of the previous stage rotor series resistor is off, the current stage is determined to be allowed to operate; otherwise, the current stage is determined to be prohibited to operate; S2) If it is determined that the current stage is currently allowed to operate, and the rotor string resistance control signal of the current stage is on, and a rotor frequency signal is detected at the same time, it is determined that the thyristor used for the contactless control of the current stage has an open circuit fault; if it is determined that the current stage is currently allowed to operate, and the rotor string resistance control signal of the current stage is off, and no rotor frequency signal is detected at the same time, it is determined that the thyristor used for the contactless control of the current stage has a short circuit fault; S3) If it is determined that the current stage is prohibited from operating, the thyristor fault detection is not performed.

9. The method according to claim 8, characterized in that: Only when this stage is currently allowed to operate, and the rotor series resistance control signal of this stage is on, and it is judged that the thyristor used for the contactless control of this stage has no fault, will the contactless controller of this stage output a turn-on signal to the rotor resistor to cut off the resistance of this stage.

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