Variable frequency speed regulation control system of oil well pump

Abstract

A frequency conversion speed regulation control system of an oil well pump comprises a main loop and a control loop, and is technically characterized in that the control loop comprises a frequency conversion operation circuit and a power frequency operation circuit, in the frequency conversion operation circuit, a coil of a repeater and a coil of a contactor are connected in parallel, then are connected with a PLC starting switch in series and then are connected with an automatic frequency conversion gear of a change-over switch; a normally open contact of the repeater is connected with a starting end of the frequency converter; the start button is connected with a coil of the repeater in series, the start button is connected with the manual frequency conversion gear, and a coil of the contactor is connected with the coil of the repeater and the start button in series through a normally open contact of the repeater; in the power frequency operation circuit, a start button is connected in parallel with a normally open contact of a contactor, then connected in series with a coil of a repeater and then connected with a manual frequency conversion gear, and the normally open contact of the contactor is respectively connected with a power supply and a motor. The rotating speed of the oil well pump is adjusted through the frequency converter to meet the operation requirement of the oil well pump, and the standby power frequency operation circuit is arranged to ensure that the oil well pump is in a normal operation state.

Description

Technical Field

[0001] The utility model relates to the field of industrial control, and particularly relates to a variable frequency speed regulation control system for a sucker rod pump. Background Art

[0002] In oilfield oil production operations, oil production plants mostly use pumping units as oil wells for oil production operations. Due to the complexity of oil production work, there are many parameters that affect the operation of the pumping unit, such as the rotational speed of the sucker rod pump, the pressure, temperature, voltage, and current at various locations during operation. Among them, the rotational speed is undoubtedly an important factor affecting the operation of the pumping unit. Therefore, how to set the speed of the sucker rod pump according to the actual oil production situation on site is particularly important. Moreover, the on-site working environment of the pumping unit is complex and accidents occur frequently. There are often phenomena such as damage to the sucker rod pump and failure of the frequency converter. No matter which situation occurs, it will make the oil production well unable to carry out normal oil production operations. Due to the complexity of the oil production process and the huge investment cost, if the oil production well stops pumping, it will cause serious losses. The existing control system structure of the sucker rod pump is too simple, and if a failure occurs, it cannot enable the staff to understand in time, which cannot ensure the normal operation of the sucker rod pump. If only a control system is set on site, the staff needs to stay beside the pumping unit in real time, increasing the labor intensity and difficulty of the staff; if a remote automatic control mode is set, although it can reduce the labor intensity and difficulty of the staff, the ability to respond to sudden accidents on site of the pumping unit is poor, and if the remote monitoring system itself fails, the operation state of the pumping unit cannot be accurately controlled. Simply adopting remote automation control has certain safety hazards for both the pumping unit and the personnel. Therefore, how to design a reasonable variable frequency control system for the sucker rod pump is extremely crucial. Summary of the Invention

[0003] The purpose of the utility model is to provide a variable frequency speed regulation control system for a sucker rod pump, which adjusts the rotational speed of the sucker rod pump through a frequency converter to meet the operation requirements of the sucker rod pump, and sets a standby power frequency operation circuit to ensure the normal operation state of the sucker rod pump.

[0004] The variable frequency speed regulation control system for the sucker rod pump of the utility model includes a main circuit and a control circuit. The main circuit controls the start and stop of the motor M by a frequency converter. The technical solution adopted to achieve the above purpose is that the control circuit includes a variable frequency speed regulation circuit, a power frequency operation circuit, and a change-over switch 1SA1 for circuit switching. The variable frequency speed regulation circuit includes a variable frequency automatic operation circuit and a variable frequency manual operation circuit.

[0005] In the variable frequency automatic operation circuit, the coil of the relay 1KA1 and the coil of the contactor 1KM1 are connected in parallel and then connected in series with the PLC start switch. The PLC start switch is connected to the automatic variable frequency gear of the change-over switch 1SA1. The normally open contact 1KA1-1 of the relay 1KA1 is connected to the start terminal of the frequency converter.

[0006] In the variable-frequency manual operation circuit, the start button 1SB2 is connected in parallel with the normally open contact 1KA2-2 of the relay 1KA2 and then connected in series with the coil of the relay 1KA2. The input end where the start button 1SB2 is connected in parallel with the normally open contact 1KA2-2 of the relay 1KA2 is connected in series with the stop button 1SB1 and then connected to the manual variable-frequency gear of the change-over switch 1SA1. The coil of the contactor 1KM1 is connected in series with the coil of the relay 1KA2 and the start button 1SB2 through the normally open contact 1KA2-4 of the relay 1KA2. The normally open contact 1KA2-1 of the relay 1KA2 is connected to the start end of the frequency converter. The normally open contact 1KA1-1 of the relay 1KA1 is connected in parallel with the frequency converter and the normally open contact 1KA2-1 of the relay 1KA2;

[0007] In the power-frequency operation circuit, the start button 1SB4 is connected in parallel with the normally open contact 1KM2 of the contactor 1KM2 and then connected in series with the coil of the relay 1KM2. The input end where the start button 1SB4 is connected in parallel with the normally open contact 1KM2-2 of the contactor 1KM2 is connected in series with the stop button 1SB4 and then connected to the manual variable-frequency gear of the change-over switch 1SA1. The normally open contact 1KM2-1 of the contactor 1KM2 is respectively connected to the power supply and the motor M.

[0008] In some preferred embodiments of the present invention, the control circuit further includes a variable-frequency automatic operation indication circuit. In the variable-frequency automatic operation indication circuit, there are a normally open contact 1KA1-3 of the relay 1KA1 and a variable-frequency automatic operation indicator light 1HO connected in series with each other.

[0009] In another preferred embodiment of the present invention, the control circuit further includes a variable-frequency manual operation indication circuit. In the variable-frequency manual operation indication circuit, there are a normally open contact 1KA2-3 of the relay 1KA2 and a variable-frequency manual operation indicator light 1HR connected in series with each other.

[0010] In another preferred embodiment of the present invention, the control circuit further includes a power-frequency operation indication circuit. In the power-frequency operation indication circuit, there are a normally open contact 1KM2-3 of the contactor 1KAM2 and a power-frequency operation indicator light 1HW connected in series with each other.

[0011] In another preferred embodiment of the present invention, the control circuit further includes a motor stop indication circuit.

[0012] The coil of the relay 1KA11 is connected in parallel beside the coil of the relay 1KA1. The coil of the relay 1KA22 is connected in parallel beside the coil of the relay 1KA2. The coil of the relay 1KA4 is connected in parallel beside the coil of the contactor 1KM2.

[0013] In the motor stop indication circuit, there are normally closed contacts 1KA11-1 of relay 1KA11, normally closed contacts 1KA22-1 of relay 1KA22, normally closed contacts 1KA4-1 of relay 1KA4 and motor stop indicator light 1HG connected in series with each other.

[0014] In another preferred embodiment of the present utility model, the control loop further includes a frequency converter fault indication circuit. In the frequency converter fault indication circuit, there are a coil of relay 1KA3 and a frequency converter fault indicator light 1HY connected in parallel with each other. After being connected in parallel with each other, they are then connected to the fault terminal of the frequency converter.

[0015] In another preferred embodiment of the present utility model, a normally open contact 1KM2-1 of contactor 1KM2 is connected in series with a thermal relay 1FR, and a normally closed contact 1FR-1 of thermal relay 1FR is connected in series at the input end after the coils of contactor 1KM2 and relay 1KA4 are connected in parallel.

[0016] In another preferred embodiment of the present utility model, a circuit breaker 1QF1 is provided at the input end of the frequency converter, a fuse 1QF2 is provided at the input end of the normally open contact 1KM2-1 of contactor 1KM2, and a circuit breaker 5QF is provided at the input end of the control loop.

[0017] In another preferred embodiment of the present utility model, a normally closed contact 1KM2-4 of contactor 1KM2 is connected in series beside the coil of contactor 1KM1, and a normally closed contact 1KM1-2 of contactor 1KM1 is connected in series beside the coil of contactor 1KM2.

[0018] In another preferred embodiment of the present utility model, a normally closed contact 1KM2-4 of contactor 1KM2 is connected in series beside the coil of contactor 1KM1, and a normally closed contact 1KM1-2 of contactor 1KM1 is connected in series beside the coil of contactor 1KM2.

[0019] In another preferred embodiment of the present utility model, a fault reset button 1SB5 is provided beside the frequency converter. The fault reset button 1SB5 is respectively connected in parallel with a normally open contact 1KA1-1 of relay 1KA1 and a normally open contact 1KA2-1 of relay 1KA2-1.

[0020] The variable frequency speed regulation control system of the oil extraction pump of the present utility model has the following beneficial effects compared with the prior art:

[0021] The utility model is provided with a variable-frequency speed regulation circuit, which adjusts the speed of the oil extraction pump through a frequency converter to meet the operation requirements of the oil extraction pump. Further, the variable-frequency speed regulation circuit is set as a variable-frequency automatic operation circuit and a variable-frequency manual operation circuit. Through the variable-frequency automatic operation circuit, the oil extraction pump can be remotely controlled to operate automatically, which is convenient to operate, time-saving and labor-saving, and can reduce the labor intensity and difficulty of the staff. Through the variable-frequency manual operation circuit, the oil extraction pump can be manually controlled according to the sudden situation on the spot of the pumping unit to ensure the safety and stability of the operation of the pumping unit.

[0022] In order to further meet the operation requirements of on-site equipment under different working conditions, the utility model further sets a power-frequency operation circuit. When the frequency converter fails or needs maintenance, the power-frequency operation circuit can replace the variable-frequency speed regulation circuit to ensure that the oil extraction pump is in a normal operation state. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the control schematic diagram of the utility model;

[0024] Figure 2 is the circuit schematic diagram of the main circuit in the utility model;

[0025] Figure 3 is the circuit schematic diagram of the control circuit in the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following specific examples illustrate the embodiments of the utility model. Those skilled in the art can easily understand the other advantages and effects of the utility model from the content disclosed in this specification. The utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0027] The variable-frequency speed regulation control system of the oil extraction pump in this specific embodiment refers to Figure 1 , and includes a main circuit and a control circuit. The main circuit controls the start and stop of the motor M through a frequency converter. The control circuit includes a variable-frequency speed regulation circuit, a power-frequency operation circuit and a changeover switch 1SA1 for circuit switching. The variable-frequency speed regulation circuit includes a variable-frequency automatic operation circuit and a variable-frequency manual operation circuit.

[0028] Refer to Figure 1 and Figure 3, in the variable-frequency automatic operation circuit, the coil of relay 1KA1 and the coil of contactor 1KM1 are connected in parallel and then connected in series with the PLC start switch. The PLC start switch is connected to the automatic variable-frequency gear of change-over switch 1SA1. The normally open contact 1KA1-1 of relay 1KA1 is connected to the start terminal of the frequency converter. Refer to Figure 1 and Figure 3 , when variable-frequency automatic operation is required, as Figure 1 and Figure 3 shown, points ① and ② in change-over switch 1SA1 are connected, thus switching change-over switch 1SA1 to the variable-frequency automatic operation gear. A start command is issued through the PLC remote control system, the PLC start switch closes, the coil of relay 1KA1 is powered on. Combining Figure 1 and Figure 2 , its normally open contact 1KA1-1 closes, the frequency converter is turned on. At the same time, the normally open contact 1KA1-2 of relay 1KA1 closes, the coil of contactor 1KM1 is powered on, and its normally open contact 1KM1-1 closes, connecting the frequency converter to motor M to start the operation of motor M; when the PLC remote control system issues a stop operation command, the PLC start switch disconnects, the coil of relay 1KA1 loses power, its normally open contact 1KA1-1 disconnects, the frequency converter disconnects. At the same time, the normally open contact 1KA1-2 of relay 1KA1 disconnects, the coil of contactor 1KM1 loses power, its normally open contact 1KM1-1 disconnects, disconnecting the connection between the frequency converter and motor M, and motor M stops running.

[0029] Refer to Figure 1 and Figure 3 , in the variable-frequency manual operation circuit, start button 1SB2 is connected in parallel with the normally open contact 1KA2-2 of relay 1KA2 and then connected in series with the coil of relay 1KA2. The input end where start button 1SB2 is connected in parallel with the normally open contact 1KA2-2 of relay 1KA2 is connected in series with stop button 1SB1 and then connected to the manual variable-frequency gear of change-over switch 1SA1. The coil of contactor 1KM1 is connected in series with the coil of relay 1KA2 and start button 1SB2 through the normally open contact 1KA2-4 of relay 1KA2. Refer to Figure 1 and Figure 2 , the normally open contact 1KA2-1 of relay 1KA2 is connected to the start terminal of the frequency converter. The normally open contact 1KA1-1 of relay 1KA1 is connected in parallel with the normally open contact 1KA2-1 of the frequency converter and relay 1KA2. When variable-frequency manual operation is required, points ③ and ④ in change-over switch 1SA1 are connected, thus switching change-over switch 1SA1 to the variable-frequency manual operation gear. Press start button 1SB2, the coil of relay 1KA2 is powered on, and its normally closed contact 1KA2-2 closes to keep the coil of relay 1KA2 powered on to achieve self-locking. Refer to Figure 1 and Figure 2, the normally open contact 1KA2-1 of the relay 1KA2 closes, the frequency converter is turned on, refer to Figure 1 and Figure 3 , the normally open contact 1KA2-4 of the relay 1KA2 closes, the coil of the contactor 1KM1 is energized, combined with Figure 1 and Figure 2 , its normally open contact 1KM1-1 closes, the frequency converter turns on the motor M, and the motor M starts; when the stop button 1SB1 is pressed, the coil of the relay 1KA2 loses power, its normally open contact 1KA2-1 de-energizes, the frequency converter disconnects, and at the same time its normally open contact 1KA2-4 disconnects, the coil of the contactor 1KM1 loses power, its normally open contact 1KM1-1 disconnects, the frequency converter disconnects the connection with the motor M, and the motor M stops running.

[0030] Refer to Figure 1 and Figure 3 , in the power frequency operation circuit, the start button 1SB4 is connected in parallel with the normally open contact 1KM2 of the contactor 1KM2 and then connected in series with the coil of the relay 1KM2, and the input end of the start button 1SB4 connected in parallel with the normally open contact 1KM2-2 of the contactor 1KM2 is connected in series with the stop button 1SB4 and then connected to the manual frequency conversion gear of the change-over switch 1SA1. The normally open contact 1KM2-1 of the contactor 1KM2 is respectively connected to the power supply and the motor M. When power frequency operation is required, the points ⑤ and ⑥ in the change-over switch 1SA1 are connected, so as to switch the change-over switch 1SA1 to the power frequency operation gear. When the start button 1SB4 is pressed, the coil of the contactor 1KM2 is energized, its normally open contact 1KM2-2 closes, so that the coil of the contactor 1KM2 continues to be energized to form self-locking. At the same time, the normally open contact 1KM2-1 of the contactor 1KM2 closes, the motor M is connected to the power supply, and the motor M runs; when the stop button 1SB3 is pressed, the coil of the contactor 1KM2 loses power, its normally open contacts 1KM2-1 and 1KM2-2 disconnect, the motor M is disconnected from the power supply, and the motor M stops running.

[0031] In some preferred embodiments, refer to Figure 3 , the control circuit further includes a frequency conversion automatic operation indication circuit. In the frequency conversion automatic operation indication circuit, there are a normally open contact 1KA1-3 of the relay 1KA1 and a frequency conversion automatic operation indicator light 1HO connected in series. When in the frequency conversion automatic operation state, the normally open contact 1KA1-3 of the relay 1KA1 closes, and the frequency conversion automatic operation indicator light 1HO is turned on and lights up.

[0032] In some preferred embodiments, refer to Figure 3, the control loop further includes a variable-frequency manual operation indication circuit, in which a normally open contact 1KA2-3 of a relay 1KA2 and a variable-frequency manual operation indicator light 1HR are connected in series. When in the variable-frequency manual operation state, the normally open contact 1KA2-3 of the relay 1KA2 closes, and the variable-frequency automatic operation indicator light 1HR is turned on and lights up.

[0033] In some preferred embodiments, referring to Figure 3 , the control loop further includes a power-frequency operation indication circuit, in which a normally open contact 1KM2-3 of a contactor 1KAM2 and a power-frequency operation indicator light 1HW are connected in series. When in the power-frequency operation state, the normally open contact 1KM2-3 of the relay 1KM2 closes, and the power-frequency operation indicator light 1HW is turned on and lights up.

[0034] In some preferred embodiments, the control loop further includes a motor stop indication circuit, referring to Figure 1 and Figure 3 ,

[0035] A coil of a relay 1KA11 is connected in parallel beside the coil of the relay 1KA1.

[0036] A coil of a relay 1KA22 is connected in parallel beside the coil of the relay 1KA2.

[0037] A coil of a relay 1KA4 is connected in parallel beside the coil of the contactor 1KM2.

[0038] The motor stop indication circuit is provided with a normally closed contact 1KA11-1 of the relay 1KA11, a normally closed contact 1KA22-1 of the relay 1KA22, a normally closed contact 1KA4-1 of the relay 1KA4 and a motor stop indicator light 1HG connected in series. When the coil of the relay 1KA1 loses power, the coil of the relay 1KA11 connected in parallel with it also loses power at the same time; when the coil of the relay 1KA2 loses power, the coil of the relay 1KA22 connected in parallel with it also loses power at the same time; when the coil of the contactor 1KM2 loses power, the coil of the relay 1KA4 connected in parallel with it also loses power at the same time. At this time, the normally closed contacts 1KA11-1 of the relay 1KA11, 1KA22-1 of the relay 1KA22, and 1KA4-1 of the relay 1KA4 are all in the closed state, and the motor stop indicator light 1HG is turned on, thereby indicating that the motor M is in the stopped state.

[0039] In some preferred embodiments, referring to Figure 1 and Figure 3, the control loop further includes a frequency converter fault indication circuit. In the frequency converter fault indication circuit, a coil of a relay 1KA3 and a frequency converter fault indicator light 1HY are connected in parallel with each other. After being connected in parallel with each other, they are then connected to the fault terminal of the frequency converter. When the frequency converter fails, the coil of the relay 1KA3 is energized, sending a signal to the remote control system as the status signal of the frequency converter fault. At the same time, the frequency converter fault indicator light 1HY lights up, indicating that the frequency converter is in a fault state.

[0040] In some preferred embodiments, referring to Figure 1 , Figure 2 and Figure 3 , a normally open contact 1KM2-1 of the contactor 1KM2 is connected in series with a thermal relay 1FR, and a normally closed contact 1FR-1 of the thermal relay 1FR is connected in series at the input end of the parallel connection of the coil of the contactor 1KM2 and the coil of the relay 1KA4. When in the power frequency operation state, if the motor M overheats, the normally closed contact 1FR-1 of the thermal relay 1FR will open, the coil of the contactor 1KM2 will lose power, its normally open contact 1KM2-1 will open, and the motor M will stop running, so that the thermal relay 1FR provides overheat protection for the motor M.

[0041] In some preferred embodiments, referring to Figure 1 , Figure 2 and Figure 3 , a circuit breaker 1QF1 is provided at the input end of the frequency converter for connecting the frequency converter and the power supply. A fuse 1QF2 is provided at the input end of the normally open contact 1KM2-1 of the contactor 1KM2 for connecting the motor M and the power supply. A circuit breaker 5QF is provided at the input end of the control loop for connecting the control loop.

[0042] In some preferred embodiments, referring to Figure 1 and Figure 3 , a normally closed contact 1KM2-4 of the contactor 1KM2 is connected in series beside the coil of the contactor 1KM1, and a normally closed contact 1KM1-2 of the contactor 1KM1 is connected in series beside the coil of the contactor 1KM2. When the coil of the contactor 1KM2 is energized, its normally closed contact 1KM2-4 opens, ensuring that the coil of the contactor 1KM1 is in a de-energized state, that is, ensuring that the motor M cannot be in the frequency conversion operation state (i.e., the frequency conversion automatic operation state and the frequency conversion manual operation state), and can only be in the power frequency operation state; when the coil of the contactor 1KM1 is energized, its normally closed contact 1KM1-2 opens, ensuring that the contactor 1KM2 is in a de-energized state, that is, ensuring that the motor cannot be in the power frequency operation and can only be in the frequency conversion operation state. The interlock between the contactor 1KM1 and the contactor 1KM2 ensures that the motor M can only operate in a single frequency conversion operation or power frequency operation.

[0043] The above embodiments are only illustrative of the principles and effects of the present utility model and are not intended to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A variable frequency speed control system for a wellbore pump, comprising a main circuit and a control circuit, wherein the main circuit controls the start and stop of the motor M by a frequency converter, and is characterized in that: The control circuit includes a variable frequency speed regulation circuit, an industrial frequency operation circuit and a conversion switch 1SA1 for circuit switching. The variable frequency speed regulation circuit includes a variable frequency automatic operation circuit and a variable frequency manual operation circuit. In the variable frequency automatic operation circuit, the coil of the repeater 1KA1 and the coil of the contactor 1KM1 are connected in parallel and then connected in series with the PLC start switch. The PLC start switch is connected to the automatic frequency conversion gear of the conversion switch 1SA1, and the normally open contact 1KA1-1 of the repeater 1KA1 is connected to the start end of the frequency converter; In the variable frequency manual operation circuit, the start button 1SB2 is connected in parallel with the normally open contact 1KA2-2 of the repeater 1KA2 and then connected in series with the coil of the repeater 1KA2, and the input end of the start button 1SB2 connected in parallel with the normally open contact 1KA2-2 of the repeater 1KA2 is connected in series with the stop button 1SB1 and then connected to the manual variable frequency gear of the conversion switch 1SA1, the coil of the contactor 1KM1 is connected in series with the coil of the repeater 1KA2 and the start button 1SB2 through the normally open contact 1KA2-4 of the repeater 1KA2, the normally open contact 1KA2-1 of the repeater 1KA2 is connected to the start end of the frequency converter, the normally open contact 1KA1-1 of the repeater 1KA1 is connected to the frequency converter and the normally open contact 1KA2-1 of the repeater 1KA2 is connected in parallel with each other; In the industrial frequency operation circuit, the start button 1SB4 is connected in parallel with the normally open contact 1KM2 of the contactor 1KM2 and then in series with the coil of the repeater 1KM2. The input end of the start button 1SB4 connected in parallel with the normally open contact 1KM2-2 of the contactor 1KM2 is connected in series with the stop button 1SB4 and then connected to the manual frequency conversion gear of the conversion switch 1SA1. The normally open contact 1KM2-1 of the contactor 1KM2 is respectively connected to the power supply and the motor M.

2. A variable frequency speed control system for an oil well pump as claimed in claim 1, characterized in that: The control circuit also includes a variable frequency automatic operation indication circuit, in which a normally open contact 1KA1-3 of a repeater 1KA1 and a variable frequency automatic operation indicator light 1HO are provided.

3. A variable frequency speed control system for a wellbore pump as claimed in claim 1, characterized in that: The control circuit also includes a variable frequency manual operation indication circuit, in which a normally open contact 1KA2-3 of a repeater 1KA2 and a variable frequency manual operation indicator light 1HR are provided.

4. A variable frequency speed control system for a wellbore pump as claimed in claim 1, characterized in that: The control circuit also includes a power frequency operation indication circuit, in which a normally open contact 1KM2-3 of a contactor 1KAM2 and a power frequency operation indicator light 1HW are provided, which are connected in series.

5. The oil well pump variable frequency speed regulation control system according to claim 1, characterized in that: The control circuit also includes a motor stop indication circuit, The coil of the repeater 1KA1 is connected in parallel with the coil of the repeater 1KA11, the coil of the repeater 1KA2 is connected in parallel with the coil of the repeater 1KA22, and the coil of the contactor 1KM2 is connected in parallel with the coil of the repeater 1KA4. The motor stop indication circuit is provided with a normally closed contact 1KA11-1 of a repeater 1KA11, a normally closed contact 1KA22-1 of a repeater 1KA22, a normally closed contact 1KA4-1 of a repeater 1KA4 and a motor stop indication lamp 1HG which are connected in series.

6. A variable frequency speed control system for a wellbore pump as claimed in claim 1, characterized in that: The control loop also includes a frequency converter fault indication circuit, in which a coil of a repeater 1KA3 and a frequency converter fault indicator light 1HY are connected in parallel to each other, and the two are connected in parallel to the fault end of the frequency converter.

7. A variable frequency speed control system for a wellbore pump as claimed in claim 6, characterized in that: The normally open contact 1KM2-1 of the contactor 1KM2 is connected in series with a thermal relay 1FR, and the input end after the coil of the contactor 1KM2 is connected in parallel with the coil of the repeater 1KA4 is connected in series with the normally closed contact 1FR-1 of the thermal relay 1FR.

8. A variable frequency speed control system for a wellbore pump as claimed in claim 1, characterized in that: The input end of the frequency converter is provided with a circuit breaker 1QF1, the input end of the normally open contact 1KM2-1 of the contactor 1KM2 is provided with a fuse 1QF2, and the input end of the control loop is provided with a circuit breaker 5QF.

9. A variable frequency speed control system for a wellbore pump as claimed in claim 1, characterized in that: A normally closed contact 1KM2 - 4 of the contactor 1KM2 is connected in series next to the coil of the contactor 1KM1 , and a normally closed contact 1KM1 - 2 of the contactor 1KM1 is connected in series next to the coil of the contactor 1KM2 .

10. The oil well pump variable frequency speed regulation control system according to claim 1, characterized in that: A fault reset button 1SB5 is provided next to the frequency converter, and the fault reset button 1SB5 is respectively connected in parallel with the normally open contact 1KA1-1 of the repeater 1KA1 and the normally open contact 1KA2-1 of the repeater 1KA2-1.

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