Constant-voltage industrial control system of frequency converter

Abstract

A frequency converter constant voltage industrial control system comprises a main loop and a control loop, the main loop controls start and stop of a motor through a frequency converter, and the technical key points are that the control loop comprises an automatic frequency conversion PID operation circuit, a power frequency operation circuit and a change-over switch for circuit switching, a coil of the contactor is connected with an automatic frequency conversion PID operation gear of the change-over switch, the frequency converter is connected with the motor through a normally open contact of the contactor, and the normally open contact of the contactor is connected to a PID starting end of the frequency converter. In the power frequency operation circuit, a coil of a contactor is sequentially connected with a start button and a stop button in series and then connected with a power frequency operation gear of a change-over switch, a normally open contact of the contactor is connected beside the start button in parallel, and the normally open contact of the contactor is connected with a power source and a motor. A frequency converter adjusts the rotating speed of a motor through liquid pressure, and an automatic frequency conversion PID operation circuit and a manual power frequency operation circuit are arranged to work alternately so as to meet different control requirements of equipment.

Description

Technical Field:

[0001] The utility model relates to the field of industrial control, and particularly relates to a constant-pressure industrial control system for a frequency converter. Background Art:

[0002] In an industrial control system, for power equipment whose working objects are liquids such as oil extraction pumps and water pumps, the liquid pressures such as the outlet pressure, return water pressure, outlet oil pressure and return oil pressure of the liquid often affect the working effect and efficiency of the equipment, and even cause the equipment to fail to operate normally. Therefore, controlling the liquid pressure is extremely important. And the liquid pressure is often directly related to the running speed of the oil extraction pump or water pump. Therefore, how to control the corresponding liquid pressure is extremely important for the operation of such equipment. Moreover, the control requirements of existing control equipment are numerous, and a single control method often cannot meet the control requirements. It is necessary to ensure that the motor is in a normal working state in real time, which places high requirements on the frequency converter. If the frequency converter is always in a working state, it will inevitably affect its service life. If multiple frequency converters are set, it will inevitably increase the control cost. In addition, for most equipment, it needs to run for a long time, and some even run without interruption. And some equipment is often set in open and remote outdoor areas, such as oil pumping units. Letting the staff stay beside the equipment continuously to start and stop the equipment at any time will not only increase the labor intensity of the staff, but also inevitably result in untimely operation of the equipment. These will all affect the production progress of the equipment. At the same time, because accidents often occur at the equipment site and manual intervention is required to take corresponding measures and judge the running state and running mode of the equipment. Therefore, for such control equipment with complex working conditions, how to reasonably set the corresponding control system to ensure the normal operation of the equipment, reduce the control cost, control intensity and control difficulty is extremely important. Summary of the Invention:

[0003] The purpose of the utility model is to provide a constant-pressure industrial control system for a frequency converter. In the system, the frequency converter FC3 adjusts the speed of the motor M through the liquid pressure, and an automatic variable-frequency PID operation circuit and a manual power-frequency operation circuit are set to work alternately to meet different control requirements of the equipment.

[0004] The constant-pressure industrial control system for a frequency converter 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 the frequency converter FC3. The technical solution adopted is that the control circuit includes an automatic variable-frequency PID operation circuit, a power-frequency operation circuit and a change-over switch 3QK1 for circuit switching.

[0005] In the automatic variable-frequency PID operation circuit, the coil of contactor 3KM1 is connected to the automatic variable-frequency PID operation gear of change-over switch 3QK1. The frequency converter FC3 is connected to motor M through the normally open contact 3KM1-1 of contactor 3KM1, and the normally open contact 3KM1-2 of contactor 3KM1 is connected to the PID start terminal of frequency converter FC3.

[0006] In the power-frequency operation circuit, the coil of contactor 3KM1 is connected to the power-frequency operation gear of change-over switch 3QK1 after being serially connected with start button 3SB2 and stop button 3SB1 in sequence. A normally open contact 3KM2-2 of contactor 3KM2 is connected in parallel beside start button 3SB2, and the normally open contact 3KM2-1 of contactor 3KM2 is connected to the power supply and motor M.

[0007] In some preferred embodiments of the present utility model, a thermal relay 3FR1 is serially connected to the normally open contact 3KM2-1 of contactor 3KM2, and the normally closed contact 3FR1-1 of thermal relay 3FR1 is serially connected to the coil of contactor 3KM2.

[0008] In another preferred embodiment of the present utility model, the control circuit further includes a motor operation indication circuit. In the motor operation indication circuit, the normally open contact FC3 of frequency converter FC3 and the normally open contact 3KM2-4 of contactor 3KM2 are connected in parallel and then serially connected with motor operation indicator light 3HR2.

[0009] In another preferred embodiment of the present utility model, the control circuit further includes a motor fault indication circuit. The motor fault indication circuit includes the coil of relay 3KA1, motor fault indicator light 3HR1 and the normally open contact 3FR1-2 of the thermal relay. The coil of relay 3KA1 and motor fault indicator light 3HR1 are connected in parallel and then serially connected with the normally open contact 3FR1-2 of thermal relay 3FR1.

[0010] In another preferred embodiment of the present utility model, the motor fault indication circuit is connected to frequency converter FC3.

[0011] In another preferred embodiment of the present utility model, frequency converter FC3 is connected to the PLC controller.

[0012] In another preferred embodiment of the present utility model, a normally closed contact 3KM2-3 of contactor 3KM2 is serially connected beside the coil of contactor 3KM1.

[0013] In another preferred embodiment of the present utility model, a normally closed contact 3KM1-3 of contactor 3KM1 is serially connected beside the coil of contactor 3KM2.

[0014] The variable-frequency constant-pressure industrial control system of the present utility model has the following beneficial effects compared with the prior art:

[0015] 1), In the frequency converter FC3 of the present utility model, the speed of the motor M is adjusted by liquid pressure. Specifically, the operation of the motor M is controlled by setting an automatic variable frequency PID operation circuit. The frequency converter FC3 automatically adjusts the operating speed of the motor M through the given pressure setting. In this way, the operating speed of the motor M is automatically adjusted by the frequency converter through liquid pressure, achieving the purpose of constant pressure control. In this circuit, the coil of the contactor 3KM1 is connected to the automatic variable frequency PID operation gear of the change-over switch 3QK1. At the same time, the normally open contact 3KM1-1 of the frequency converter FC3 is connected to the motor M, and the normally open contact 3KM1-2 of the contactor 3KM1 is connected to the PID start terminal of the frequency converter FC3. When performing automatic variable frequency PID operation, the automatic gear of the change-over switch 3QK1 is turned on to start the frequency converter FC3. The frequency converter FC3 performs automatic adjustment through the given pressure setting. At the same time, the normally open contact 3KM1-1 of the contactor 3KM1 is closed, and the motor M starts to operate, thus realizing the automatic variable frequency PID start of the motor. At the same time, the frequency converter FC3 is connected to the PLC controller, and the operating state of the frequency converter FC3 and the operating state of the motor M are transmitted to the PLC controller.

[0016] 2), Through the set power frequency operation circuit of the present utility model, when the frequency converter fails or needs regular maintenance, the motor can be started by the power frequency operation circuit. Or when it is necessary to manually start the motor in case of an emergency on-site, the power frequency operation circuit can also replace the automatic operation circuit of the frequency converter. In this way, it can ensure that the motor M is in a normal operating state and avoid the motor M from stopping running and affecting the production progress and production efficiency. Description of the drawings:

[0017] Figure 1 is the control schematic diagram of the present utility model;

[0018] Figure 2 is the circuit schematic diagram of the main circuit in the present utility model;

[0019] Figure 3 is the circuit schematic diagram of the control circuit in the present utility model. Specific implementation manners:

[0020] The following specific examples illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0021] In the constant-voltage industrial control system of the frequency converter in this specific embodiment, refer to Figure 1 , which includes a main circuit and a control circuit. In the main circuit, the frequency converter FC3 controls the start and stop of the motor M. In the main circuit, the frequency converter FC3 is connected to a three-phase power supply through the circuit breaker 3QF1, and the normally open contact 3KM2-1 of the contactor 3KM2 is connected to the three-phase power supply through the circuit breaker 3QF2. The control circuit is connected to the three-phase power supply through 1QF2. The control circuit includes an automatic variable-frequency PID operation circuit, a power-frequency operation circuit, and a changeover switch 3QK1 for circuit switching. The frequency converter FC3 adjusts the speed of the motor M through the liquid pressure.

[0022] 2) In the automatic variable-frequency PID operation circuit, as Figure 1 and Figure 3 shown, the coil of the contactor 3KM1 is connected to the automatic variable-frequency PID operation gear of the changeover switch 3QK1. The frequency converter FC3 is connected to the motor M through the normally open contact 3KM1-1 of the contactor 3KM1. Combining Figure 2 , and the normally open contact 3KM1-2 of the contactor 3KM1 is connected to the PID start terminal of the frequency converter FC3. Refer to Figure 3 , when performing automatic variable-frequency PID operation, connect point ① and point ② of the changeover switch 3QK1. The coil of the contactor 3KM1 is energized, and the normally open contact 3KM1-2 of the contactor 3KM1 is closed. The frequency converter FC3 starts. The frequency converter FC3 automatically adjusts the running speed of the motor M through the given pressure setting. The given pressure is set through the control panel of the frequency converter. At the same time, the normally open contact 3KM1-1 of the contactor 3KM1 is closed, and the motor M starts to run, thus realizing the automatic variable-frequency PID start of the motor. At the same time, the frequency converter FC3 is connected to the PLC controller, and transmits the running state of the frequency converter FC3 and the running state of the motor M to the PLC controller.

[0023] In the power-frequency operation circuit, refer to Figure 3 , the coil of the contactor 3KM1 is connected to the power-frequency operation gear of the changeover switch 3QK1 in series with the start button 3SB2 and the stop button 3SB1 in sequence. The normally open contact 3KM2-2 of the contactor 3KM2 is connected in parallel beside the start button 3SB2. Combining Figure 2 , the normally open contact 3KM2-1 of the contactor 3KM2 is connected to the power supply and the motor M. Refer to Figure 3 , when performing power-frequency operation, connect point ⑤ and point ⑥ of the changeover switch 3QK1. Press the start button 3SB2, the coil of the contactor 3KM2 is energized, and its normally open contact 3KM2-2 is closed to keep the coil energized. Combining Figure 1 and Figure 2 , at the same time, the normally open contact 3KM2-1 of the contactor 3KM2 is closed, and the motor M is connected to the power supply for power-frequency start; refer to Figure 3, when the stop button 3SB1 is pressed, the coil of the contactor 3KM2 loses power, and its normally open contact 3KM2-2 disconnects. Combining Figure 1 and Figure 2 , at the same time, its normally open contact 3KM2-1 disconnects, and the motor M loses power and stops running.

[0024] In some embodiments, as Figure 1 and Figure 2 shown, a thermal relay 3FR1 is connected in series with the normally open contact 3KM2-1 of the contactor 3KM2. As Figure 1 and Figure 3 shown, the normally closed contact 3FR1-1 of the thermal relay 3FR1 is connected in series with the coil of the contactor 3KM2. When in the power-frequency operation state, when the motor M overheats, the normally closed contact 3FR1-1 of the thermal relay 3FR1 disconnects, the coil of the contactor 3KM2 loses power, its normally open contact 3KM2-1 disconnects, and the motor M loses power and stops running.

[0025] In some embodiments, the control circuit further includes a motor operation indication circuit. In the motor operation indication circuit, referring to Figure 1 and Figure 3 , the motor fault indication circuit is connected to the frequency converter FC3, so that the frequency converter FC3 can control the closing or opening of its normally open contact FC3-1. The normally open contact FC3 of the frequency converter FC3 is connected in parallel with the normally open contact 3KM2-4 of the contactor 3KM2 and then connected in series with the motor operation indicator light 3HR2. When the motor is in the variable-frequency PID operation state, the normally open contact FC3-1 of the frequency converter FC3 closes, and the motor operation indicator light 3HR2 lights up, indicating that the motor is in the running state; when the motor is in the power-frequency operation state, the normally open contact 3KM2-4 of the contactor 3KM2 closes, and the motor operation indicator light 3HR2 lights up, indicating that the motor is in the running state. When the motor stops the variable-frequency PID operation, the normally open contact FC3-1 of the frequency converter FC3 disconnects, and the motor operation indicator light 3HR2 goes out, indicating that the motor is in the stopped state; when the coil of the contactor 3KM2 loses power, its normally open contact 3KM2-4 disconnects, and the motor operation indicator light 3HR2 goes out, indicating that the motor is in the stopped state.

[0026] In some embodiments, referring to Figure 1 and Figure 3, the control loop further includes a motor fault indication circuit, which includes the coil of relay 3KA1, motor fault indicator light 3HR1, and normally open contact 3FR1-2 of the thermal relay. The coil of relay 3KA1 and motor fault indicator light 3HR1 are connected in parallel and then connected in series with the normally open contact 3FR1-2 of thermal relay 3FR1. When the motor M is running at industrial frequency and overheats, when the thermal relay 3FR1 works, its normally open contact 3FR1-2 closes, the coil of relay 3KA1 is energized, and a signal is sent to the PLC controller as the motor fault status signal. At the same time, the motor fault indicator light 3HR1 lights up, indicating that the motor is in a fault state; when the temperature of the motor M drops and it is in a normal industrial frequency operation state, the thermal relay 3FR1 stops working, its normally open contact 3FR1-2 is in an open state, the coil of relay 3KA1 is de-energized, and at the same time the motor fault indicator light 3HR1 goes out, indicating that the overheat fault of the motor is eliminated.

[0027] In some embodiments, the frequency converter FC3 is connected to the PLC controller. In this way, whether the motor is in the automatic variable frequency PID operation state or not, the PLC controller can know.

[0028] In some embodiments, a normally closed contact 3KM2-3 of contactor 3KM2 is connected in series beside the coil of contactor 3KM1. When the coil of contactor 3KM2 is energized, its normally closed contact 3KM2-3 opens, ensuring that the coil of contactor 3KM1 is in a de-energized state, so as to ensure that the motor cannot perform automatic variable frequency PID operation and can only perform industrial frequency operation; similarly, a normally closed contact 3KM1-3 of contactor 3KM1 is connected in series beside the coil of contactor 3KM2. When the coil of contactor 3KM1 is energized, its normally closed contact 3KM1-3 opens, ensuring that the coil of contactor 3KM2 is in a de-energized state, so as to ensure that the motor cannot perform industrial frequency operation and can only perform automatic variable frequency PID operation.

[0029] The above embodiments only illustratively explain the principle and its 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 frequency converter constant voltage industrial control system, comprising a main circuit and a control circuit, wherein the main circuit controls the start and stop of the motor M by the frequency converter FC3, characterized in that: The control loop includes an automatic frequency conversion PID operation circuit, an industrial frequency operation circuit and a conversion switch 3QK1 for circuit switching. In the automatic frequency conversion PID operation circuit, the coil of the contactor 3KM1 is connected to the automatic frequency conversion PID operation gear of the conversion switch 3QK1, the frequency converter FC3 is connected to the motor M through the normally open contact 3KM1-1 of the contactor 3KM1, and the normally open contact 3KM1-2 of the contactor 3KM1 is connected to the PID start end of the frequency converter FC3; In the industrial frequency operation circuit, the coil of the contactor 3KM1 is connected in series with the start button 3SB2 and the stop button 3SB1 in sequence, and then connected to the industrial frequency operation gear of the conversion switch 3QK1. The start button 3SB2 is connected in parallel with the normally open contact 3KM2-2 of the contactor 3KM2, and the normally open contact 3KM2-1 of the contactor 3KM2 is connected to the power supply and the motor M.

2. A frequency converter constant voltage industrial control system as claimed in claim 1, characterized in that: The normally open contact 3KM2-1 of the contactor 3KM2 is connected in series with the thermal relay 3FR1, and the normally closed contact 3FR1-1 of the thermal relay 3FR1 is connected in series with the coil of the contactor 3KM2.

3. A frequency converter constant voltage industrial control system as claimed in claim 1, characterized in that: The control circuit also includes a motor operation indication circuit, in which the normally open contact FC3 of the frequency converter FC3 and the normally open contact 3KM2-4 of the contactor 3KM2 are connected in parallel and then in series with the motor operation indicator light 3HR2.

4. A frequency converter constant voltage industrial control system as claimed in claim 2, characterized in that: The control circuit also includes a motor fault indication circuit, which includes a coil of a repeater 3KA1, a motor fault indicator light 3HR1 and a normally open contact 3FR1-2 of a thermal relay. The coil of the repeater 3KA1 is connected in parallel with the motor fault indicator light 3HR1 and then in series with the normally open contact 3FR1-2 of the thermal relay 3FR1.

5. A frequency converter constant voltage industrial control system as claimed in claim 4, characterized in that: The motor fault indication circuit is connected to the frequency converter FC3.

6. A frequency converter constant voltage industrial control system as claimed in claim 1, characterized in that: The frequency converter FC3 is connected to the PLC controller.

7. The inverter constant voltage industrial control system according to claim 1, characterized in that: A normally closed contact 3KM2 - 3 of the contactor 3KM2 is connected in series next to the coil of the contactor 3KM1 .

8. The inverter constant voltage industrial control system according to claim 1, characterized in that: The normally closed contact 3KM1 - 3 of the contactor 3KM1 is connected in series next to the coil of the contactor 3KM2 .

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