Variable frequency speed regulation control system for oil field production circulating pump

Abstract

A frequency conversion speed regulation control system for an oil field production circulating pump comprises a main loop and a control loop, and is technically characterized in that the main loop comprises a frequency conversion main loop and a power frequency main loop, the input end of the frequency conversion main loop is connected with a power supply, and the output end of the frequency conversion main loop is connected with a motor M1 through a normally open contact of a contactor and is connected with the motor through a normally open contact of another contactor; one end of the power frequency main loop is connected with a power supply, and the other end is connected with the motor M1 through a normally open contact of the contactor and connected with the motor M2 through a normally open contact of the contactor. The control loop comprises a frequency conversion speed regulation control loop and a power frequency control loop which are connected in parallel, and the frequency conversion speed regulation control loop comprises a circulating pump frequency conversion start-stop circuit, a motor M1 frequency conversion speed regulation control loop and a motor M2 speed regulation control loop which are connected in parallel. The variable frequency speed regulation control loop of the motor M1 and the speed regulation control loop of the motor M2 are mutually connected in parallel and then are connected with the other change-over switch. The automatic starting device has the functions of manual starting and automatic starting, can meet various control modes of the oil pumping unit, and ensures that the oil pumping unit can operate safely and stably.

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 an oilfield production circulating pump. Background Art:

[0002] In an industrial control system, due to the development of the control system, single automatic control, manual control, variable frequency control and power frequency control can no longer meet the working requirements of equipment. Especially for the pumping units used in oilfield production, their working conditions are complex and they are located in open areas in the wild. If on-site control is adopted, the staff can start or cut off the operation of the pumping unit in time according to the on-site operation conditions of the equipment. Especially when an accident occurs on-site, it is necessary to cut off the operation of the pumping unit in time to ensure the safety of the equipment or personnel. In contrast, adopting automatic control can reduce the labor intensity of the staff, but the ability to respond to on-site emergencies is poor, and if the automatic control system itself fails, the operation state of the equipment cannot be accurately controlled. Simply adopting automatic control poses certain safety hazards to both the equipment and the personnel. Moreover, the on-site working environment of the pumping unit is complex and accidents occur frequently, often resulting in phenomena such as damage to the oil pump and failure of the frequency converter. No matter which situation occurs, it will make the oil well unable to carry out oil production operations normally. Since the oil production process is complex and the investment cost is huge, if the oil pump stops pumping, it will cause serious losses. And the existing control system structure of the oil pump is too simple, and if a failure occurs, it is impossible to let the staff know in time, which cannot ensure the normal operation of the oil pump. Therefore, how to design a reasonable control system according to the actual situation of the pumping unit to ensure the safe and stable operation of the pumping unit 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 an oilfield production circulating pump, which includes variable frequency speed regulation control and power frequency control, and at the same time has a manual start function and an automatic start function, can meet various control methods of the pumping unit, and ensure the safe and stable operation of the pumping unit.

[0004] The variable frequency speed regulation control system for an oilfield production circulating pump of the utility model includes a main circuit, a control circuit, a motor M1 and a motor M2. The adopted technical solution is as follows:

[0005] The main circuit includes a variable frequency main circuit and a power frequency main circuit. The input end of the variable frequency main circuit is connected to the power supply, and the output end is connected to the motor M1 through the normally open contact KM1-1 of the contactor KM1 and to the motor M2 through the normally open contact KM2-1 of the contactor KM2.

[0006] One end of the power frequency main circuit is connected to the power supply, and the other end is respectively connected to the motor M1 through the normally open contact KM3-1 of the contactor KM3 and to the motor M2 through the normally open contact KM4-1 of the contactor KM4.

[0007] The control loop includes a variable-frequency speed regulation control loop and a power-frequency control loop connected in parallel with each other. The circuit after the two are connected in parallel is connected to a change-over switch SA1.

[0008] The variable-frequency speed regulation control loop includes a circulating pump variable-frequency start-stop circuit, a motor M1 variable-frequency speed regulation control loop, and a motor M2 speed regulation control loop connected in parallel with each other. The motor M1 variable-frequency speed regulation control loop and the motor M2 speed regulation control loop are connected in parallel with each other and then connected to a change-over switch SA2.

[0009] In the circulating pump variable-frequency start-stop circuit, the coil of a relay KA1 is connected in series with a normally open contact KM1-2 of a contactor KM1, a start button SB2, and a stop button SB1. A normally open contact KA1-1 of the relay KA1 is connected in parallel beside the start button SB2, and a normally open contact KM2-2 of a contactor KM2 is connected in parallel beside the normally open contact KM1-2 of the contactor KM1.

[0010] In the motor M1 variable-frequency speed regulation control loop, the coil of the contactor KM1 is connected in series with a normally closed contact KM2-3 of the contactor KM2 and then connected to the motor M1 start terminal of the change-over switch SA2.

[0011] In the motor M2 variable-frequency speed regulation control loop, the coil of the contactor KM2 is connected in series with a normally closed contact KM1-3 of the contactor KM1 and then connected to the motor M2 start terminal of the change-over switch SA2.

[0012] The power-frequency control loop includes a motor M1 power-frequency control loop, a motor M2 power-frequency control loop, and a change-over switch SA3.

[0013] In the motor M1 power-frequency control loop, the coil of a contactor KM3 is connected in series with a start button SB4, a stop button SB3, and then connected to the motor M1 start terminal of the change-over switch SA3. A normally open contact KM3-2 of the contactor KM3 is connected in parallel beside the start button SB4.

[0014] In the motor M2 power-frequency control loop, the coil of a contactor KM4 is connected in series with a start button SB6, a stop button SB5, and then connected to the motor M2 start terminal of the change-over switch SA3. A normally open contact KM4-2 of the contactor KM4 is connected in parallel beside the start button SB6.

[0015] In a preferred embodiment of the present utility model, the variable-frequency speed regulation control loop further includes a variable-frequency fault circuit. In the variable-frequency fault circuit, there is a variable-frequency fault switch Q1 of a frequency converter. The variable-frequency fault switch Q1 is connected in series with the coil of a relay KA2. The coil of the relay KA2 is connected in parallel with a variable-frequency fault indicator light HL11, and after the two are connected in parallel, they are connected in series with the variable-frequency fault switch Q1 again.

[0016] In another preferred embodiment of the present utility model, a frequency conversion operation indicator light HL1 of a motor M1 is connected in parallel beside the coil of the contactor KM1, and the branch after their parallel connection is connected in series with the normally closed contact KM2-3 of the contactor KM2.

[0017] In another preferred embodiment of the present utility model, a frequency conversion operation indicator light HL2 of a motor M2 is connected in parallel beside the coil of the contactor KM2, and the branch after their parallel connection is connected in series with the normally closed contact KM1-3 of the contactor KM1.

[0018] In another preferred embodiment of the present utility model, a power frequency operation indicator light HL3 of a motor M1 is connected in parallel beside the coil of the contactor KM3, and the branch after their parallel connection is connected in series with the normally open contact KM3-2 of the contactor KM3 and the start button SB4.

[0019] In another preferred embodiment of the present utility model, a power frequency operation indicator light HL4 of a motor M2 is connected in parallel beside the coil of the contactor KM4, and the branch after their parallel connection is connected in series with the normally open contact KM4-2 of the contactor KM4 and the start button 6.

[0020] In another preferred embodiment of the present utility model, a thermal relay FR1 is connected in series with the normally open contact KM3-1 of the contactor KM3, and the coil of the contactor KM3 is connected in series with the normally closed contact FR1-1 of the thermal relay FR1.

[0021] In another preferred embodiment of the present utility model, a thermal relay FR2 is connected in series with the normally open contact KM4-1 of the contactor KM4, and the coil of the contactor KM4 is connected in series with the normally closed contact FR2-1 of the thermal relay FR2.

[0022] In another preferred embodiment of the present utility model, the variable frequency speed control loop further includes a fault circuit of the circulating pump of the motor M1. In the fault circuit of the circulating pump of the motor M1, a sound alarm HA1 is connected in series with the normally open contact FR1-2 of the thermal relay FR1.

[0023] In another preferred embodiment of the present utility model, the variable frequency speed control loop further includes a fault circuit of the circulating pump of the motor M2. In the fault circuit of the circulating pump of the motor M2, a sound alarm HA2 is connected in series with the normally open contact FR2-2 of the thermal relay FR2.

[0024] The variable frequency speed control system of the oilfield production circulating pump of the present utility model has the following beneficial effects compared with the prior art:

[0025] The utility model is provided with a variable-frequency speed regulation control loop and a power-frequency control loop, which can adopt different control modes according to the usage requirements of the pumping unit at different times. The variable-frequency speed regulation control can automatically adjust the speed of the oil pump by the frequency converter and realize the automatic start control of the oil pump, which is convenient for the operation of the staff; the power-frequency control can start or stop the oil pump by itself according to the actual situation on the site of the pumping unit, and its operation is more flexible and the adaptability is stronger. And when the frequency converter fails or needs maintenance, the power-frequency control of manual start can be adopted. At the same time, the motors in the utility model adopt a one-for-one standby control mode. When one of the oil pumps fails or needs maintenance and cannot work, the standby pump can be started, so as to ensure that the pumping unit can always operate safely and stably. Brief Description of the Drawings:

[0026] Figure 1 is the circuit schematic diagram of the main circuit in the utility model;

[0027] Figure 2 is the circuit schematic diagram of the control circuit in the utility model;

[0028] Figure 3 is the wiring diagram of the frequency converter. Specific Embodiments:

[0029] The following specific examples illustrate the embodiments of the utility model. Those skilled in the art can easily understand 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.

[0030] The variable-frequency speed regulation control system of the oilfield production circulating pump in this embodiment includes a main circuit, a control circuit, a motor M1 and a motor M2.

[0031] As Figure 1 shown, the main circuit includes a variable-frequency main circuit and a power-frequency main circuit. The input end of the variable-frequency main circuit is connected to the power supply, and the output end is connected to the motor M1 through the normally open contact KM1-1 of the contactor KM1 and to the motor M2 through the normally open contact KM2-1 of the contactor KM2; one end of the power-frequency main circuit is connected to the power supply, and the other end is respectively connected to the motor M1 through the normally open contact KM3-1 of the contactor KM3 and to the motor M2 through the normally open contact KM4-1 of the contactor KM4.

[0032] As Figure 2 shown, the control circuit includes a variable-frequency speed regulation control loop and a power-frequency control loop connected in parallel, and the circuit after the two are connected in parallel is connected to the change-over switch SA1.

[0033] As Figure 2 shown, the variable-frequency speed control loop includes a circulating pump variable-frequency start-stop circuit, a motor M1 variable-frequency speed control loop, and a motor M2 speed control loop that are connected in parallel with each other. The motor M1 variable-frequency speed control loop and the motor M2 variable-frequency speed control loop are connected in parallel with each other and then connected to a change-over switch SA2.

[0034] As Figure 2 shown, in the circulating pump variable-frequency start-stop circuit, the coil of a relay KA1 is connected in series with a normally open contact KM1-2 of a contactor KM1, a start button SB2, and a stop button SB1. A normally open contact KA1-1 of the relay KA1 is connected in parallel beside the start button SB2. As Figure 3 shown, the normally open contact KA1-2 of the relay KA1 is connected to the start terminal of an inverter FC; as Figure 2 shown, a normally open contact KM2-2 of a contactor KM2 is connected in parallel beside the normally open contact KM1-2 of the contactor KM1; when the start button SB2 is pressed, the coil of the relay KA1 is energized, and its normally open contact KA1-1 closes to keep the coil of the relay KA1 energized. Combining Figure 3 , its normally open contact KA1-2 closes, and the inverter FC is turned on.

[0035] As Figure 2 shown, in the motor M1 variable-frequency speed control loop, the coil of the contactor KM1 is connected in series with a normally closed contact KM2-3 of the contactor KM2 and then connected to the motor M1 start terminal of the change-over switch SA2. When the motor M1 needs to run in variable frequency, first connect point ① and point ② of the change-over switch SA1, and then connect point ① and point ② of the change-over switch SA2. The coil of the contactor KM1 is energized. As Figure 1 shown, its normally open contact KM1-1 closes, and the inverter FC is connected to the motor M1, so that the motor M1 starts in variable frequency; when the motor M1 needs to stop running, as Figure 2 shown, when the stop button SB1 is pressed, the coil of the relay KA1 loses power. Combining Figure 3 , its normally open contact KA1-2 opens, the inverter FC disconnects, and the motor M1 stops running;

[0036] As Figure 2 shown, in the motor M2 variable-frequency speed control loop, the coil of the contactor KM2 is connected in series with a normally closed contact KM1-3 of the contactor KM1 and then connected to the motor M2 start terminal of the change-over switch SA2; when the motor M2 needs to run in variable frequency, first connect point ① and point ② of the change-over switch SA1, and then connect point ③ and point ④ of the change-over switch SA2. The coil of the contactor KM2 is energized, and its normally open contact KM2-1 closes. Combining Figure 1, the frequency converter FC is connected to the motor M2, so that the motor M2 starts with frequency conversion; when the motor M2 needs to stop running, for example Figure 2 as shown, press the stop button SB1, the coil of the relay KA1 loses power, combined with Figure 3 , its normally open contact KA1-2 disconnects, the frequency converter FC disconnects, and the motor M2 stops running.

[0037] In the variable frequency speed control loop, when the coil of the contactor KM1 is powered on, its normally closed contact KM1-3 disconnects, ensuring that the coil of the contactor KM2 is de-energized, that is, ensuring that when the motor M1 is in variable frequency speed control operation, the motor M2 is in a stopped state; when the coil of the contactor KM2 is powered on, its normally closed contact KM2-3 disconnects, ensuring that the coil of the contactor KM1 is de-energized, that is, ensuring that when the motor M2 is in variable frequency speed control operation, the motor M1 is in a stopped state.

[0038] The industrial frequency control loop includes an industrial frequency control loop for the motor M1, an industrial frequency control loop for the motor M2, and a changeover switch SA3;

[0039] For example Figure 2 as shown, in the industrial frequency control loop of the motor M1, the coil of the contactor KM3 is connected in series with the start button SB4 and the stop button SB3 and then connected to the motor M1 start terminal of the changeover switch SA3. A normally open contact KM3-2 of the contactor KM3 is connected in parallel beside the start button SB4. When the motor M1 needs to run at industrial frequency, first connect the ③ point and the ④ point of the changeover switch SA1, then connect the ① point and the ② point of the changeover switch SA3, press the start button SB4, the coil of the contactor KM3 is powered on, and its normally open contact KM3-2 closes to keep the coil powered on. Combined with Figure 1 , at the same time its normally open contact KM3-1 closes, and the motor M1 is connected to run at industrial frequency; when the motor M1 needs to stop running at industrial frequency, for example Figure 2 as shown, press the stop button SB3, the coil of the contactor KM3 loses power, combined with Figure 1 , its normally open contact KM3-1 disconnects, and the motor M1 loses power and stops running.

[0040] For example Figure 2As shown, in the industrial frequency control circuit of the motor M2, the coil of the contactor KM4 is connected in series with the start button SB6 and the stop button SB5 and then connected to the start terminal of the motor M2 of the change-over switch SA3. A normally open contact KM4-2 of the contactor KM4 is connected in parallel beside the start button SB6. When the motor M2 needs to run at industrial frequency, first connect the points ③ and ④ of the change-over switch SA1, then connect the points ③ and ④ of the change-over switch SA3, and press the start button SB6. The coil of the contactor KM4 is energized, its normally open contact KM4-2 closes to keep the coil energized continuously, and at the same time its normally open contact KM4-1 closes, and the motor M2 is connected to run at industrial frequency; when the motor M2 needs to stop running, press the stop button SB5, the coil of the contactor KM4 loses power, combined with Figure 1 , its normally open contact KM4-1 disconnects, and the motor M2 loses power and stops running.

[0041] In some preferred embodiments, as Figure 2 shown, the variable frequency speed control circuit further includes a variable frequency fault circuit. A variable frequency fault switch Q1 of the frequency converter is provided in the variable frequency fault circuit. The variable frequency fault switch Q1 is connected in series with the coil of the relay KA2. The coil of the relay KA2 is connected in parallel with a variable frequency fault indicator light HL11, and after the two are connected in parallel, they are connected in series with the variable frequency fault switch Q1 again. When the frequency converter FC fails, its contact Q1 automatically closes, the coil of the relay KA2 is energized to send a signal to the remote control system, serving as a fault signal point of the frequency converter, and at the same time the variable frequency fault indicator light HL11 lights up to warn the staff.

[0042] In some preferred embodiments, as Figure 2 shown, a motor M1 variable frequency operation indicator light HL1 is connected in parallel beside the coil of the contactor KM1, and the branch after the two are connected in parallel is connected in series with the normally closed contact KM2-3 of the contactor KM2. When the motor M1 is in the variable frequency operation state, the motor M1 variable frequency operation indicator light HL1 lights up for the staff to view, so that the staff can understand the operation status of each motor.

[0043] In some preferred embodiments, as Figure 2 shown, a motor M2 variable frequency operation indicator light HL2 is connected in parallel beside the coil of the contactor KM2, and the branch after the two are connected in parallel is connected in series with the normally closed contact KM1-3 of the contactor KM1. When the motor M2 is in the variable frequency operation state, the motor M2 variable frequency operation indicator light HL2 lights up for the staff to view, so that the staff can understand the operation status of each motor.

[0044] In some preferred embodiments, as Figure 2As shown, an industrial frequency operation indicator light HL3 of the motor M1 is connected in parallel beside the coil of the contactor KM3, and the branch after their parallel connection is connected in series with the normally open contact KM3-2 of the contactor KM3 and the start button SB4. When the motor M1 is in the industrial frequency operation state, the industrial frequency operation indicator light HL3 of the motor M1 lights up for the staff to view, enabling the staff to understand the operation status of each motor.

[0045] In some preferred embodiments, as Figure 2 shown, an industrial frequency operation indicator light HL4 of the motor M2 is connected in parallel beside the coil of the contactor KM4, and the branch after their parallel connection is connected in series with the normally open contact KM4-2 of the contactor KM4 and the start button 6. When the motor M2 is in the industrial frequency operation state, the industrial frequency operation indicator light HL4 of the motor M2 lights up for the staff to view, enabling the staff to understand the operation status of each motor.

[0046] In some preferred embodiments, as Figure 1 shown, the normally open contact KM3-1 of the contactor KM3 is connected in series with a thermal relay FR1, as Figure 2 shown, the coil of the contactor KM3 is connected in series with the normally closed contact FR1-1 of the thermal relay FR1. When the motor M1 overheats, the thermal relay FR1 starts to work, its normally closed contact FR1-1 disconnects, the coil of the contactor KM3 loses power, combined with Figure 1 , its normally open contact KM3-1 disconnects, the motor M1 loses power and stops running, thus protecting the motor M1 from being damaged due to overheating.

[0047] In some preferred embodiments, as Figure 1 shown, the normally open contact KM4-1 of the contactor KM4 is connected in series with a thermal relay FR2, as Figure 2 shown, the coil of the contactor KM4 is connected in series with the normally closed contact FR2-1 of the thermal relay FR2. When the motor M2 overheats, the thermal relay FR2 starts to work, its normally closed contact FR2-1 disconnects, the coil of the contactor KM3 loses power, combined with Figure 1 , its normally open contact KM4-1 disconnects, the motor M2 loses power and stops running, thus protecting the motor M2 from being damaged due to overheating.

[0048] In some preferred embodiments, as Figure 2 shown, the variable frequency speed control loop further includes a motor M1 circulating pump fault circuit. In the motor M1 circulating pump fault circuit, a sound alarm HA1 is connected in series with the normally open contact FR1-2 of the thermal relay FR1. When the thermal relay FR1 starts to work, its normally open contact FR1-2 closes, and the sound alarm HA1 sounds to warn the staff that the motor M1 has a fault.

[0049] In some preferred embodiments, asFigure 2 As shown, the variable-frequency speed control loop further includes a motor M2 circulating pump fault circuit. In the motor M2 circulating pump fault circuit, a sound alarm HA2 is connected in series with a normally open contact FR2-2 of a thermal relay FR2. When the thermal relay FR2 starts to work, its normally open contact FR2-2 closes, and the sound alarm HA2 sounds to warn the staff that the motor M2 has a fault.

[0050] In some preferred embodiments, such as Figure 2 As shown, in the power-frequency control loop of the motor M1, a normally closed contact of the contactor KM4-3 is connected in series beside the coil of the contactor KM3. When the coil of the contactor KM4 is energized, its normally closed contact KM4-3 disconnects. In this way, it can be ensured that when the coil of the contactor KM4 is energized, the coil of the contactor KM3 is de-energized, that is, when the motor M2 operates at power frequency, it is ensured that the motor M1 is in a stopped state;

[0051] In some preferred embodiments, such as Figure 2 As shown, in the power-frequency control loop of the motor M2, a normally closed contact of the contactor KM3-3 is connected in series beside the coil of the contactor KM4. When the coil of the contactor KM3 is energized, its normally closed contact KM3-3 disconnects. In this way, it can be ensured that when the coil of the contactor KM3 is energized, the coil of the contactor KM4 is de-energized, that is, when the motor M1 operates at power frequency, it is ensured that the motor M2 is in a stopped state.

[0052] The above embodiments merely illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A variable frequency speed control system for oilfield production circulating pumps, comprising a main circuit, a control circuit, a motor M1 and a motor M2, characterized in that: The main circuit includes a frequency conversion main circuit and an industrial frequency main circuit. The input end of the frequency conversion main circuit is connected to the power supply, and the output end is connected to the motor M1 through the normally open contact KM1-1 of the contactor KM1, and connected to the motor M2 through the normally open contact KM2-1 of the contactor KM2; One end of the power frequency main circuit is connected to the power supply, and the other end is connected to the motor M1 through the normally open contact KM3-1 of the contactor KM3, and connected to the motor M2 through the normally open contact KM4-1 of the contactor KM4; The control circuit includes a variable frequency speed regulation control circuit and an industrial frequency control circuit connected in parallel, and the circuit after the two are connected in parallel is connected to a conversion switch SA1. The variable frequency speed control circuit includes a circulating pump variable frequency start-stop circuit, a motor M1 variable frequency speed control circuit and a motor M2 speed control circuit connected in parallel. The motor M1 variable frequency speed control circuit and the motor M2 speed control circuit are connected in parallel and then connected to a conversion switch SA2. In the circulating pump variable frequency start-stop circuit, the coil of the repeater KA1 is connected in series with the normally open contact KM1-2 of the contactor KM1, the start button SB2 and the stop button SB1, the normally open contact KA1-1 of the repeater KA1 is connected in parallel next to the start button SB2, the normally open contact KA1-2 of the repeater KA1 is arranged at the start end of the frequency converter FC, and the normally open contact KM2-2 of the contactor KM2 is connected in parallel next to the normally open contact KM1-2 of the contactor KM1; In the motor M1 variable frequency speed control circuit, the coil of the contactor KM1 is connected in series with the normally closed contact KM2-3 of the contactor KM2 and then connected to the motor M1 start end of the conversion switch SA2. In the variable frequency speed control circuit of the motor M2, the coil of the contactor KM2 is connected in series with the normally closed contact KM1-3 of the contactor KM1 and then connected to the start end of the motor M2 of the conversion switch SA2; The power frequency control circuit includes a power frequency control circuit of the motor M1, a power frequency control circuit of the motor M2 and a conversion switch SA3; In the power frequency control circuit of the motor M1, the coil of the contactor KM3 is connected in series with the start button SB4 and the stop button SB3, and then connected to the start end of the motor M1 of the conversion switch SA3. The start button SB4 is connected in parallel with the normally open contact KM3-2 of the contactor KM3. In the industrial frequency control circuit of the motor M2, the coil of the contactor KM4 is connected in series with the start button SB6 and the stop button SB5 and then connected to the start end of the motor M2 of the conversion switch SA3, and the normally open contact KM4-2 of the contactor KM4 is connected in parallel next to the start button SB6.

2. The variable frequency speed regulation control system for oil field production circulating pump according to claim 1, characterized in that: The variable frequency speed regulation control loop also includes a variable frequency fault circuit, in which a variable frequency fault switch Q1 of the frequency converter is provided. The variable frequency fault switch Q1 is connected in series with the coil of the repeater KA2, and the coil of the repeater KA2 is connected in parallel with the variable frequency fault indicator light HL11. The two are connected in parallel and then in series with the variable frequency fault switch Q1.

3. The variable frequency speed regulation control system for oil field production circulating pump according to claim 1, characterized in that: A variable frequency operation indicator light HL1 of the motor M1 is connected in parallel next to the coil of the contactor KM1, and the branch formed by the parallel connection of the two is connected in series with the normally closed contact KM2-3 of the contactor KM2.

4. The variable frequency speed regulation control system for oil field production circulating pump according to claim 1, characterized in that: The variable frequency operation indicator light HL2 of the motor M2 is connected in parallel next to the coil of the contactor KM2, and the branch formed by the parallel connection is connected in series with the normally closed contact KM1-3 of the contactor KM1.

5. The frequency conversion speed regulation control system for oil field production circulation pump according to claim 1, characterized in that: The power frequency operation indicator light HL3 of the motor M1 is connected in parallel next to the coil of the contactor KM3, and the branch formed by the parallel connection is connected in series with the normally open contact KM3-2 of the contactor KM3 and the start button SB4.

6. The variable frequency speed regulation control system for oil field production circulation pump according to claim 1, characterized in that: The power frequency operation indicator light HL4 of the motor M2 is connected in parallel next to the coil of the contactor KM4, and the branch formed by the parallel connection is connected in series with the normally open contact KM4-2 of the contactor KM4 and the start button 6.

7. The frequency conversion speed regulation control system for oilfield production circulation pump according to claim 6, characterized in that: The normally open contact KM3 - 1 of the contactor KM3 is connected in series with the thermal relay FR1 , and the coil of the contactor KM3 is connected in series with the normally closed contact FR1 - 1 of the thermal relay FR1 .

8. The variable frequency speed regulation control system for oilfield production circulating pumps according to claim 6, characterized in that: The normally open contact KM4 - 1 of the contactor KM4 is connected in series with the thermal relay FR2 , and the coil of the contactor KM4 is connected in series with the normally closed contact FR2 - 1 of the thermal relay FR2 .

9. The variable frequency speed regulation control system for oil field production circulating pump according to claim 1, characterized in that: The variable frequency speed regulation control loop also includes a motor M1 circulating pump fault circuit, in which the sound alarm HA1 is connected in series to the normally open contact FR1-2 of the thermal relay FR1.

10. The variable frequency speed regulation control system for oil field production circulation pump according to claim 1, characterized in that: The variable frequency speed regulation control loop also includes a motor M2 circulating pump fault circuit, in which the sound alarm HA2 is connected in series with a normally open contact FR2-2 of a thermal relay FR2.

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