Energy-saving control system of high-power motor

Abstract

The utility model discloses a high-power motor energy-saving control system, and belongs to the technical field of motor control systems. Comprising a fuse; a main circuit breaker; a first branch circuit breaker and a second branch circuit breaker; a main contactor; a frequency converter; a first thermal relay; a frequency conversion AC contactor; a current sensor; a second thermal relay; an underflow pump main motor; a rectifying circuit device; and an electric PLC device. The frequency converter and the electric PLC are used for changing the rotating speed of the underflow pump motor, so that the purposes of saving energy and reducing consumption are achieved, the configuration and starting program of an original control circuit are simplified, and the electric energy loss and the frequency of system fault maintenance are greatly reduced.

Description

Technical Field

[0001] This utility model relates to the field of motor control system technology, specifically to a high-power motor energy-saving control system. Background Technology

[0002] Thickeners in metal smelting plants are crucial pieces of equipment. The underflow pump motor control system within the thickener well uses a traditional relay-contactor system. This system combines buttons, contactors, and thermal relays to achieve its control functions. The circuitry contains a large number and variety of components, which, under full load startup, easily leads to significant energy waste, heat generation, and noise. Especially when the thickener's output is insufficient and supply and demand are unbalanced, the underflow pump operates under light or no load. Since the motors are directly controlled by three-phase AC power, they run at rated speed whenever the underflow pump starts, resulting in near-idle operation and causing the thickener to experience dry-running. Because this equipment uses a traditional relay-contactor system for direct control, and manual adjustment of the motor speed is impossible, the underflow pump flow rate cannot be controlled, leading to substantial energy waste during operation. Meanwhile, when the thickener produces too much liquid, its underflow pump will be under heavy load or overload. At this time, the motor will always be running under heavy load, which will damage the motor insulation performance, shorten the motor life, reduce the working efficiency of the equipment, and sometimes even cause various control circuit devices to fail due to motor failure, ultimately paralyzing the equipment, causing the equipment to stop midway or frequently malfunction.

[0003] In view of the above problems, it is necessary to design a high-power motor energy-saving control system device. This device, which controls the motor's operation, can not only solve the various energy loss problems that occur during the operation of the thickener well bottom flow pump, but also save a significant amount of energy and reduce the workload of operators. Simultaneously, it improves the automation level of the equipment control system, thereby increasing equipment efficiency and enterprise benefits. Summary of the Invention

[0004] The purpose of this utility model is to provide a high-power motor energy-saving control system, which uses a frequency converter and an electrical PLC to change the speed of its underflow pump motor, thereby achieving the purpose of energy saving and consumption reduction. It simplifies the configuration and startup procedure of the original control circuit, greatly reduces power loss and the frequency of system failure maintenance, and solves the problems mentioned in the background art.

[0005] The technical solution adopted in this utility model is as follows:

[0006] A high-power motor energy-saving control system includes:

[0007] Three-phase power input terminal, used to introduce 380V three-phase power;

[0008] Fuse 36, whose input terminal is connected to the three-phase power input terminal;

[0009] The main circuit breaker 37 has its input terminal connected to the output terminal of the fuse 36;

[0010] The input terminals of the first circuit breaker 38 and the second circuit breaker 41 are respectively connected to the output terminal of the main circuit breaker 37.

[0011] The main contactor 39 has its input terminal connected to the output terminal of the first circuit breaker 38;

[0012] The frequency converter 42 has its input terminal connected to the output terminal of the second circuit breaker 41;

[0013] The first thermal relay 40 has its input terminal connected to the output terminal of the main contactor 39;

[0014] The input terminal of the variable frequency AC contactor 43 is connected to the output terminal of the variable frequency drive 42;

[0015] Current sensor 44, whose input terminal is connected to the output terminal of frequency converter AC contactor 43;

[0016] The second thermal relay 45 has its input terminal connected to the output terminal of the current sensor 44.

[0017] The main motor 48 of the underflow pump has its terminals connected to the output terminals of the first thermal relay 40 and the second thermal relay 45.

[0018] The rectifier circuit device 46 has its input terminal connected to the wiring terminal of the current sensor 44;

[0019] The electrical PLC device 47 has its input terminal connected to the output terminal of the rectifier circuit device 46, and is used to receive and process current signals and feed data signals back to the frequency converter 42.

[0020] The main circuit of the control system includes a relay-contactor control system control circuit 34 and a frequency converter control system control circuit 35.

[0021] The control circuit 34 of the relay-contactor control system includes:

[0022] The relay-contactor control system operating circuit 26 includes:

[0023] The normally closed contact 1 of the first thermal relay is connected to the U-phase lead-out terminal of the live wire.

[0024] The stop button 2 of the relay-contactor control system circuit has its input terminal connected to the output terminal of the normally closed contact 1 of the first thermal relay;

[0025] The input terminal of the start button 3 of the relay-contactor control system circuit is connected to the output terminal of the stop button 2 of the relay-contactor control system circuit.

[0026] The normally closed contact A5 of the frequency converter AC contactor is connected to the output of the start button 3 of the relay-contaminator control system circuit.

[0027] The main contactor coil 6 has its input terminal connected to the output terminal of the normally closed contact A5 of the frequency converter AC contactor.

[0028] The normally open contact 4 of the main contactor is connected in parallel across the two ends of the start button 3 in the relay-contactor control system circuit;

[0029] The relay-contactor control system circuit operation indicator light 7 is connected in series with the normally open contact 4 of the main contactor;

[0030] The relay-contactor control system stop circuit 27 includes:

[0031] The stop indicator light 8 of the relay-contactor control system circuit has its input terminal connected to the U-phase lead-out terminal of the live wire.

[0032] The normally closed contact A9 of the main contactor is connected to the output of the stop indicator light 8 of the relay-contactor control system circuit.

[0033] The relay-contactor control system fault circuit 28 includes:

[0034] The fault indicator light 10 of the relay-contactor control system circuit has its input terminal connected to the live wire U-phase lead-out terminal;

[0035] The normally open contact 11 of the first thermal relay is connected to the output of the fault indicator light 10 of the relay-contactor control system circuit.

[0036] The power supply circuit 29 of the relay-contactor control system includes:

[0037] The power indicator light 12 of the relay-contactor control system circuit has its input terminal directly connected to the live wire U-phase lead-out terminal.

[0038] The inverter control system control circuit 35 includes:

[0039] The inverter control system operating circuit 30 includes:

[0040] The normally closed contact 13 of the second thermal relay is connected to the U-phase lead-out terminal of the live wire.

[0041] The input terminal of the stop button 14 of the inverter control system circuit is connected to the output terminal of the normally closed contact 13 of the second thermal relay.

[0042] The input terminal of the start button 15 of the inverter control system circuit is connected to the output terminal of the stop button 14 of the inverter control system circuit.

[0043] The normally closed contact B17 of the main contactor is connected to the output of the start button 15 of the inverter control system circuit.

[0044] The input terminal of the variable frequency AC contactor coil 18 is connected to the output terminal of the normally closed contact B17 of the main contactor.

[0045] The normally open contact 16 of the variable frequency AC contactor is connected in parallel across the two ends of the start button 15 of the variable frequency control system circuit.

[0046] The inverter control system circuit operation indicator light 19 is connected in series to the output terminal of the normally open contact 16 of the inverter AC contactor.

[0047] The inverter control system stop circuit 31 includes:

[0048] The inverter control system circuit stop indicator light 20 has its input terminal connected to the live wire U-phase lead-out terminal.

[0049] The normally closed contact B21 of the variable frequency AC contactor is connected to the output of the stop indicator light 20 of the variable frequency control system circuit.

[0050] The inverter control system fault circuit 32 includes:

[0051] The inverter control system circuit fault indicator light 22 has its input terminal connected to the live wire U-phase lead-out terminal.

[0052] The inverter's multi-function relay outputs a normally open contact 24, the input of which is connected to the output of the inverter's control system circuit fault indicator 22.

[0053] The normally open contact 23 of the frequency converter relay is connected in parallel with the normally open output contact 24 of the frequency converter multi-function relay;

[0054] The power supply circuit 33 of the frequency converter control system includes:

[0055] The power indicator light 25 of the inverter control system circuit has its input terminal directly connected to the live wire U-phase lead-out terminal.

[0056] The neutral line N-phase connection terminal is used to connect the output terminals of the relay-contactor control system operating circuit 26, relay-contactor control system stop circuit 27, relay-contactor control system fault circuit 28, relay-contactor control system power supply circuit 29, inverter control system operating circuit 30, inverter control system stop circuit 31, inverter control system fault circuit 32, and inverter control system power supply circuit 33 to the neutral line N-phase to form a closed loop.

[0057] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are:

[0058] This invention controls the motor's operation by combining relay-contactor control with frequency converter control. When the underflow pump motor is in normal operation, its current is constantly changing due to the continuously varying liquid output. Through online monitoring with an electrical PLC, the changes in the analog voltage output of the device can be observed, and the minimum and maximum values ​​reached during the change can be accurately obtained. Since the underflow pump motor's speed is controlled by a frequency converter, the operating frequency of the frequency converter can be automatically adjusted based on the numerical values, ultimately changing the motor's speed and controlling the underflow pump's liquid output to reduce the motor's energy consumption.

[0059] In summary, this utility model features a simple structure, convenient operation, and stable and efficient operation. It solves the various energy loss problems that occurred during the operation of the original thickening well bottom flow pump, and also improves the working efficiency of the equipment, creating profit and economic benefits for the enterprise. Statistical results show that the overall energy saving rate can reach more than 56% after the device is used. At the same time, because the inverter control system circuit of this device also has overvoltage, undervoltage, overcurrent, short circuit, locked rotor, and phase loss protection functions, the inverter and motor will not be burned out during operation. This solves the problems of frequent equipment failures, frequent maintenance by maintenance personnel, long maintenance time, and high maintenance labor intensity. Attached Figure Description

[0060] Figure 1 This is the electrical schematic diagram of the present utility model;

[0061] Figure 2 This is the control circuit diagram for this utility model;

[0062] In the diagram: 1-Normally closed contact of the first thermal relay; 2-Stop button of the relay-contactor control system circuit; 3-Start button of the relay-contactor control system circuit; 4-Normally open contact of the main contactor; 5-Normally closed contact A of the frequency converter AC contactor; 6-Main contactor coil; 7-Run indicator light of the relay-contactor control system circuit; 8-Stop indicator light of the relay-contactor control system circuit; 9-Normally closed contact A of the main contactor; 10-Fault indicator light of the relay-contactor control system circuit; 11-Normally open contact of the first thermal relay; 12-Power indicator light of the relay-contactor control system circuit; 13-Normally closed contact of the second thermal relay; 14-Stop button of the frequency converter control system circuit; 15-Start button of the frequency converter control system circuit; 16-Normally open contact of the frequency converter AC contactor; 17-Normally closed contact B of the main contactor; 18-Frequency converter AC contactor coil; 19-Run indicator light of the frequency converter control system circuit; 20-Stop indicator light of the frequency converter control system circuit; 21-Normally closed contact B of the frequency converter AC contactor; 22-Power indicator light of the frequency converter control system circuit. 23 - Circuit fault indicator; 24 - Variable frequency relay normally open contact; 25 - Variable frequency drive multi-function relay output normally open contact; 26 - Variable frequency drive control system circuit power indicator; 27 - Relay-contactor control system operating circuit; 28 - Relay-contactor control system stop circuit; 29 - Relay-contactor control system fault circuit; 30 - Relay-contactor control system power circuit; 31 - Variable frequency drive control system stop circuit; 32 - Variable frequency drive control system fault circuit. 33-Power supply circuit for frequency converter control system; 34-Control circuit for relay-contactor control system; 35-Control circuit for frequency converter control system; 36-Fuse; 37-Main circuit breaker; 38-First branch circuit breaker; 39-Main contactor; 40-First thermal relay; 41-Second branch circuit breaker; 42-Frequency converter; 43-Variable frequency AC contactor; 44-Current sensor; 45-Second thermal relay; 46-Rectifier circuit device; 47-Electrical PLC device; 48-Main motor of undercurrent pump; 49-Main circuit. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0064] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0065] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Example

[0066] like Figure 1 This embodiment provides a high-power motor energy-saving control system. The control system includes three-phase power input terminals (U, V, W). A 380V three-phase power supply (U, V, W phases) is introduced into the three-phase power input terminals. A fuse 36 is first installed on the main circuit 49 after the 380V three-phase power supply (U, V, W phases) to protect the line. The output of the fuse 36 is connected to the input of the main circuit breaker 37. The output of the main circuit breaker 37 is connected to the inputs of the first branch circuit breaker 38 and the second branch circuit breaker 41, respectively. Then, each output is connected to the input of the main contactor 39 and the input of the frequency converter 42, respectively. The output of the main contactor 39 is connected to the input of the first thermal relay 40. The output of the frequency converter 42 is connected to the input of the variable frequency AC contactor 43. The main wiring of the output of the variable frequency AC contactor 43 passes through a current sensor 44, then exits from the current sensor 44, and is then connected to the input of the second thermal relay 45. Finally, the output terminals of the first thermal relay 40 and the second thermal relay 45 are both connected to the terminals of the main motor 48 of the underflow pump. Three wires are led out from the terminals of the current sensor 44 and directly connected to the rectifier circuit 46, and then to the electrical PLC device 47. The electrical PLC device 47 then feeds back the data signal to the frequency converter 42.

[0067] like Figure 2 As shown, the main circuit of the control system consists of two parts, specifically including the relay-contactor control system control circuit 34 and the frequency converter control system control circuit 35.

[0068] The control circuit 34 of the relay-contactor control system is as follows:

[0069] A 220V power supply is introduced in phases U and N. The circuit is first led out from the live wire U phase, and then the circuit is divided into 4 paths (relay-contactor control system operation circuit 26, relay-contactor control system stop circuit 27, relay-contactor control system fault circuit 28, and relay-contactor control system power supply circuit 29): The first branch (relay-contactor control system operation circuit 26) is connected to a set of normally closed contacts 1 of the first thermal relay. Its output terminal is connected to the relay-contactor control system circuit stop button 2 and the relay-contactor control system circuit start button 3. Then, a set of normally closed contacts A5 of the frequency converter AC contactor and the main contactor coil 6 are connected in series. At the same time, a set of normally open contacts 4 of the main contactor are connected in parallel across the two ends of the relay-contactor control system circuit start button 3. Then, a set of relay-contactor control system circuit operation indicator lights 7 are connected in series from the other end of the normally open contacts 4.

[0070] The second branch (relay-contactor control system stop circuit 27) connects a set of relay-contactor control system circuit stop indicator lights 8 and the normally closed contact A9 of the main contactor.

[0071] The third branch (relay-contactor control system fault circuit 28) connects a set of relay-contactor control system circuit fault indicator lights 10 and a set of normally open contacts 11 of the first thermal relay.

[0072] The fourth branch (relay-contactor control system power supply circuit 29) is directly connected to a set of relay-contactor control system circuit power indicator lights 12.

[0073] The control circuit 35 of the inverter control system is as follows:

[0074] The circuit continues from the live U phase and then branches into four circuits (inverter control system operation circuit 30, inverter control system stop circuit 31, inverter control system fault circuit 32, and inverter control system power supply circuit 33): The inverter control system operation circuit 30 is connected to a set of normally closed contacts 13 of the second thermal relay. Its output is connected to the inverter control system circuit stop button 14 and the inverter control system circuit start button 15. Then, a set of normally closed contacts B17 of the main contactor and the inverter AC contactor coil 18 are connected in series. At the same time, a set of normally open contacts 16 of the inverter AC contactor are connected in parallel across the inverter control system circuit start button 15. Then, a set of inverter control system circuit operation indicator lights 19 are connected in series from the other end of the normally open contacts 16.

[0075] The inverter control system stop circuit 31 connects a set of inverter control system circuit stop indicator lights 20 and the normally closed contact B21 of the inverter AC contactor.

[0076] The inverter control system fault circuit 32 connects a set of inverter control system circuit fault indicator lights 22 and inverter multi-function relay output normally open contacts 24. At the same time, a set of inverter relay normally open contacts 23 are connected in parallel across the inverter multi-function relay output normally open contacts 24.

[0077] The power supply circuit 33 of the frequency converter control system is directly connected to a set of power indicator lights 25 of the frequency converter control system circuit.

[0078] Finally, the four outputs from the first part of the circuit (relay-contactor control system operating circuit, relay-contactor control system stop circuit, relay-contactor control system fault circuit, and relay-contactor control system power supply circuit) and the four outputs from the second part of the circuit (frequency converter control system operating circuit, frequency converter control system stop circuit, frequency converter control system fault circuit, and frequency converter control system power supply circuit) are all connected to the neutral line (N phase), thus forming a closed loop in the control circuit of the device.

[0079] In operation, this invention utilizes a current sensor to generate an induced voltage in the underflow pump motor. This voltage is then rectified by a rectifier circuit to produce a DC voltage. This DC voltage is converted into an analog voltage and read by an electrical PLC. The PLC then controls the inverter's operating frequency to automatically adjust the motor speed. Based on the motor speed, the pump's output is adjusted, ultimately reducing energy consumption and improving the efficiency of the underflow pump in thickening wells. Under normal conditions, the underflow pump motor is started and operated using an inverter control system circuit. As the pump operates in different states, its output changes. Based on these changes, a minimum value (X1) and a maximum value (X2) of the analog voltage are obtained. When the liquid production rate decreases to its minimum and the analog voltage reaches its minimum value X1, the electrical PLC outputs a signal Q1 to control the inverter's operating frequency. When the operating frequency increases to its maximum frequency F1, the motor speed rises rapidly, and the liquid production rate delivered by the underflow pump increases rapidly. At this time, the thickener accelerates its feed speed, thus avoiding motor idling and energy waste, achieving energy saving and consumption reduction. When the liquid production rate increases to its maximum and the analog voltage reaches its maximum value X2, the electrical PLC outputs another signal Q2 to control the inverter's operating frequency. When the operating frequency decreases to its minimum frequency F2, the motor speed drops rapidly, and the liquid production rate delivered by the underflow pump decreases rapidly. The corresponding energy consumption also decreases, thus avoiding excessive damage to the motor's insulation performance and improving equipment efficiency.

[0080] This invention's inverter system control method effectively replaces the relay-contactor system control method while retaining the latter. In other words, there are two control methods: one is a relay-contactor system control method, and the other is a inverter system control method. Each of these two control methods has a set of normally closed contactors connected in series in the control circuit, forming an interlock. Therefore, if one control method fails during equipment operation, the operator can simply press a button to switch to the other control method, allowing the equipment to operate continuously without interruption.

[0081] In summary, this utility model features a simple overall structure, convenient operation, and stable and efficient operation. It solves the various energy loss problems that occurred during the operation of the original thickener well bottom flow pump, and also improves the working efficiency of the equipment, creating profit and economic benefits for the enterprise. Statistical results show that the overall energy saving rate can reach more than 56% after the device is used. At the same time, because the inverter control system circuit of this device also has overvoltage, undervoltage, overcurrent, short circuit, locked rotor, and phase loss protection functions, the inverter and motor will not be burned out during operation. This solves the problems of frequent equipment failures, frequent maintenance by maintenance personnel, long maintenance time, and high maintenance labor intensity.

Claims

1. A high-power motor energy-saving control system, characterized in that, include: Three-phase power input terminal, used to introduce 380V three-phase power; The fuse (36) has its input terminal connected to the three-phase power input terminal; The main circuit breaker (37) has its input terminal connected to the output terminal of the fuse (36); The first circuit breaker (38) and the second circuit breaker (41) have their input terminals connected to the output terminals of the main circuit breaker (37), respectively. The main contactor (39) has its input terminal connected to the output terminal of the first circuit breaker (38); The frequency converter (42) has its input terminal connected to the output terminal of the second circuit breaker (41); The first thermal relay (40) has its input terminal connected to the output terminal of the main contactor (39); A variable frequency AC contactor (43) has its input terminal connected to the output terminal of a frequency converter (42); A current sensor (44) has its input terminal connected to the output terminal of a frequency converter AC contactor (43); The second thermal relay (45) has its input terminal connected to the output terminal of the current sensor (44); The main motor (48) of the underflow pump has its terminals connected to the output terminals of the first thermal relay (40) and the second thermal relay (45); A rectifier circuit device (46) has its input terminal connected to the wiring terminal of a current sensor (44); An electrical PLC device (47) has its input terminal connected to the output terminal of a rectifier circuit device (46) for receiving and processing current signals and feeding back data signals to the frequency converter (42).

2. The energy saving control system for high-power motor according to claim 1, characterized in that: The main circuit of the control system includes a relay-contactor control system control circuit (34) and a frequency converter control system control circuit (35).

3. The energy saving control system for high power motor as claimed in claim 2 wherein: The control circuit (34) of the relay-contactor control system includes: The relay-contactor control system operating circuit (26) includes: The normally closed contact (1) of the first thermal relay is connected to the U-phase lead-out terminal of the live wire; The relay-contactor control system circuit has a stop button (2), whose input terminal is connected to the output terminal of the normally closed contact (1) of the first thermal relay; The input terminal of the relay-contactor control system circuit start button (3) is connected to the output terminal of the relay-contactor control system circuit stop button (2); The normally closed contact A (5) of the variable frequency AC contactor is connected to the output of the start button (3) of the relay-contactor control system circuit. The main contactor coil (6) has its input terminal connected to the output terminal of the normally closed contact A (5) of the frequency converter AC contactor; The normally open contact (4) of the main contactor is connected in parallel across the two ends of the start button (3) of the relay-contactor control system circuit; The relay-contactor control system circuit operation indicator (7) is connected in series with the normally open contact (4) of the main contactor; The relay-contactor control system stop circuit (27) includes: The stop indicator light (8) of the relay-contactor control system circuit has its input terminal connected to the U-phase lead-out terminal of the live wire. The normally closed contact A (9) of the main contactor is connected to the output of the stop indicator (8) of the relay-contactor control system circuit. The relay-contactor control system fault circuit (28) includes: The relay-contactor control system circuit fault indicator (10) has its input terminal connected to the live wire U-phase lead-out terminal. The normally open contact (11) of the first thermal relay is connected to the output of the fault indicator (10) of the relay-contactor control system circuit. The power supply circuit (29) of the relay-contactor control system includes: The power indicator light (12) of the relay-contactor control system circuit has its input terminal directly connected to the live wire U-phase lead-out terminal.

4. The energy saving control system for high-power motor according to claim 3, characterized in that: The control circuit (35) of the frequency converter control system includes: The inverter control system operating circuit (30) includes: The normally closed contact (13) of the second thermal relay is connected to the U-phase lead-out terminal of the live wire. The inverter control system circuit stop button (14) has its input terminal connected to the output terminal of the normally closed contact (13) of the second thermal relay; The input terminal of the start button (15) of the inverter control system circuit is connected to the output terminal of the stop button (14) of the inverter control system circuit; The normally closed contact B (17) of the main contactor is connected to the output of the start button (15) of the inverter control system circuit. The input terminal of the variable frequency AC contactor coil (18) is connected to the output terminal of the normally closed contact B (17) of the main contactor; The normally open contact (16) of the variable frequency AC contactor is connected in parallel across the two ends of the start button (15) of the variable frequency control system circuit; The inverter control system circuit operation indicator (19) is connected in series to the output terminal of the normally open contact (16) of the inverter AC contactor; The inverter control system stop circuit (31) includes: The inverter control system circuit stop indicator light (20) has its input terminal connected to the live wire U-phase lead-out terminal; The normally closed contact B (21) of the variable frequency AC contactor is connected to the output of the stop indicator (20) of the variable frequency control system circuit. The inverter control system fault circuit (32) includes: The inverter control system circuit fault indicator (22) has its input terminal connected to the live wire U-phase lead-out terminal; The inverter multi-function relay outputs a normally open contact (24), the input of which is connected to the output of the inverter control system circuit fault indicator (22); The normally open contact (23) of the frequency converter relay is connected in parallel with the normally open output contact (24) of the frequency converter multi-function relay; The power supply circuit (33) of the frequency converter control system includes: The power indicator light (25) of the inverter control system circuit has its input terminal directly connected to the U-phase lead-out terminal of the live wire. The neutral line N-phase connection terminal is used to connect the output terminals of the relay-contactor control system operating circuit (26), relay-contactor control system stop circuit (27), relay-contactor control system fault circuit (28), relay-contactor control system power supply circuit (29), inverter control system operating circuit (30), inverter control system stop circuit (31), inverter control system fault circuit (32), and inverter control system power supply circuit (33) to the neutral line N-phase to form a closed loop.

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