Motor soft starting device suitable for pump load

Abstract

The utility model relates to the field of automatic control, and particularly discloses a motor soft starting device suitable for pump loads, which comprises a main circuit breaker module, a three-phase antiparallel thyristor module, a current detection module, a bypass contactor module, a thermal overload relay module and a user interface module. The main circuit breaker module is used for controlling start and stop of a motor and generating a control signal according to a preset start parameter; the three-phase antiparallel thyristor module is used for smoothly adjusting voltage applied to a motor stator winding; the bypass contactor module comprises one or more contacts to ensure that current passes through the thyristor assembly in the soft starter; the current detection module monitors the working current of the motor in real time and feeds back the detected current value to the main circuit breaker module; the thermal overload relay module is used for preventing the motor from being damaged due to long-time overload operation; the user interface module is used for setting soft start parameters and displaying the running state of the motor.

Description

Technical Field

[0001] This application relates to the field of automatic control, and more particularly to a motor soft starter suitable for pump loads. Background Technology

[0002] Soft starters for pump-type loads have significant application value in modern industry. Traditional motor starting methods, such as direct starting and reduced-voltage starting, while simple, have obvious drawbacks, such as large current surges during startup and severe damage to the power grid and mechanical equipment. These problems are particularly prominent with pump-type loads because they generate a huge water hammer effect during startup, leading to damage to pipelines and equipment. To solve these problems, soft starters have emerged. Soft starters gradually increase the motor's input voltage, allowing the motor to smoothly accelerate from zero current to its rated speed, thus avoiding current and mechanical shocks during startup. Furthermore, soft starters also have a soft-stop function, which gradually reduces the motor speed when stopping, minimizing the water hammer effect and extending the equipment's lifespan.

[0003] With the development of automation technology, the operation of fuel pump set motors is no longer limited to traditional on-site manual control. Currently, many applications require both local and remote control modes. In local mode, operators can directly control the motor from the environment where the fuel pump set is located via physical buttons or panels; this method is suitable for situations requiring immediate response. Remote control, on the other hand, involves issuing commands through a central control system and utilizing network communication technology to remotely operate the pump set motor. This is particularly important for large gas stations or oil depots, as it allows for monitoring and management of multiple refueling points from a secure control center, improving operational efficiency while reducing labor costs. During refueling operations, the fuel pump set motor needs to start and stop according to actual task requirements to meet the refueling flow demands of the upper-level system. The start and stop control of the fuel pump set motor must accommodate both local and remote control modes. Throughout the start, progress, and end of a refueling task, the current information of the pump set motor needs to be monitored in real time for various protection operations such as overcurrent protection, current imbalance protection, and stall protection.

[0004] Currently, common starting methods for pump-type load motors include direct power frequency starting or star-delta starting, as well as using a frequency converter (VDC). Direct power frequency starting, also known as full-voltage starting, applies the upstream grid voltage to the pump motor at the moment of connection. This method results in a large instantaneous inrush current, reaching 5 to 7 times the rated current, placing high demands on the main components of the electrical circuit and the upstream grid capacity, making capacity expansion unavoidable. Star-delta starting, used for three-phase asynchronous motors initially connected in a delta configuration, is switched to delta connection to reduce starting current. However, inrush current still occurs during startup and star-delta switching, and the starting current is not adjustable. Frequency converter control enables stepless speed regulation. For applications without frequency conversion speed regulation requirements, a soft starter can be used, avoiding harmonics generated by the frequency converter and reducing operating costs.

[0005] In the control process of the fuel pump unit motor, real-time monitoring of the pump unit motor current information is crucial. A current sensor monitors the motor current in real time and compares it with a set value. Once the current exceeds the safety threshold, the system immediately triggers the overcurrent protection mechanism, cutting off the power supply to prevent damage to the motor due to excessive current. Furthermore, motor stall protection is also essential. When the motor is overloaded or stalls, the system detects an abnormal increase in motor current. If the current fails to return to normal within a set time, the system automatically cuts off the power supply to prevent the motor from burning out.

[0006] To ensure the safe and reliable operation of the fuel pump unit motor, factors such as starting current, starting smoothness, and impact on the power grid must be comprehensively considered when selecting the starting method. Direct power frequency starting is simple and economical, but it has a significant impact on the power grid; star-delta starting can effectively reduce the starting current, but there is still an impact during switching; while inverter starting provides greater flexibility and safety, and is especially suitable for applications requiring speed regulation and energy saving.

[0007] Although the technology is quite mature, some challenges remain. Therefore, future research could focus on developing a soft-start device for motors suitable for pump loads to meet the increasingly complex operational needs of power system control. Utility Model Content

[0008] The purpose of this invention is to provide a motor soft starter suitable for pump loads. This soft starter for pump loads solves the problems of soft starting and soft stopping, effectively reducing starting current and power distribution capacity. See the description below for details:

[0009] This utility model embodiment provides a motor soft starter suitable for pump loads, mainly comprising:

[0010] The system includes a main circuit breaker module, a three-phase parallel thyristor module, and a bypass contactor module; wherein the main circuit breaker module is connected to both the three-phase parallel thyristor module and the bypass contactor module; and the three-phase parallel thyristor module is connected to a motor.

[0011] The main circuit breaker module is used for on / off control of the main circuit;

[0012] The three anti-parallel thyristor modules are used to boost or buck the voltage of the main circuit to obtain the operating voltage of the motor.

[0013] The bypass contactor module is used to allow current to flow through the thyristor assembly in the three-opposite-parallel thyristor module when closed.

[0014] Furthermore, the main circuit breaker module includes a first circuit breaker, a second circuit breaker, and a third circuit breaker;

[0015] The three-phase parallel thyristor module includes at least a first thyristor group, a second thyristor group, and a third thyristor group.

[0016] The first terminal of the first circuit breaker is connected to the three-phase input power supply;

[0017] The second terminal of the first circuit breaker is connected to the first thyristor group;

[0018] The first terminal of the second circuit breaker is connected to the three-phase input power supply.

[0019] The second terminal of the second circuit breaker is connected to the second thyristor group;

[0020] The first terminal of the third circuit breaker is connected to the three-phase input power supply.

[0021] The second terminal of the third circuit breaker is connected to the third thyristor group;

[0022] Furthermore, the first thyristor group includes a first thyristor and a second thyristor; the second thyristor group includes a third thyristor and a fourth thyristor; and the third thyristor group includes a fifth thyristor and a sixth thyristor.

[0023] The bypass contactor module includes at least a first contactor, a second contactor, and a third contactor.

[0024] The first terminal of the first contactor is connected to the first terminal of the third thyristor group;

[0025] The second terminal of the first contactor is connected to the second terminal of the third thyristor group;

[0026] The first end of the second contactor is connected to the first end of the second thyristor group;

[0027] The second terminal of the second contactor is connected to the second terminal of the second thyristor group;

[0028] The first end of the third contactor is connected to the first end of the first thyristor group;

[0029] The second terminal of the third contactor is connected to the second terminal of the first thyristor group;

[0030] The main circuit breaker module is an NDM3AR series electronic circuit breaker.

[0031] The device further includes a current detection module, which is used to detect the current flowing through the conductor and convert the detected current signal into an electrical signal.

[0032] The device also includes a thermal overload relay module, which is connected to the motor and is used to cut off the power supply when the current exceeds a preset safety threshold.

[0033] The device also includes a user interface module, which is used to display the motor's starting parameters and operating status.

[0034] Optionally, the user interface is a touchscreen or a button-based interface.

[0035] Compared with existing motor starting devices, the advantages of the motor soft starter device for pump loads provided by this utility model are:

[0036] 1. Effectively reduces inrush current during startup, eliminating the need for increased investment in components and upstream power grid;

[0037] 2. A soft-stop algorithm suitable for pump loads avoids the damage to pipelines and pump bodies caused by water hammer effect due to direct shutdown;

[0038] 3. Design control loops and panel devices to facilitate operators in controlling the motor start and stop, setting local / remote control modes, and accurately indicating the equipment's working status. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the motor soft starter device applicable to pump loads in this application;

[0040] Figure 2 This is a schematic diagram of the main circuit of the motor soft starter in this application;

[0041] Figure 3 This is a schematic diagram of the system architecture of the motor soft starter in this application;

[0042] Figure 4 This is a schematic diagram of the three-phase thyristor voltage regulation triggering sequence in this application;

[0043] Figure 5 This is a flowchart of the soft parking procedure in this application;

[0044] Figure 6 This is a schematic diagram of the control circuit of the motor soft starter in this application; Detailed Implementation

[0045] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings:

[0046] like Figure 1 As shown, the motor soft starter device for pump loads in this embodiment includes a main circuit breaker module 101, a three-phase parallel thyristor module 102, a current detection module, a bypass contactor module 103, a thermal overload relay module, and a user interface module.

[0047] The main circuit breaker module includes at least three circuit breakers: a first circuit breaker, a second circuit breaker, and a third circuit breaker, used for power-on control of the main circuit. The first contactor's first terminal is connected to the first terminal of the third thyristor group, and its second terminal is connected to the second terminal of the third thyristor group. The second contactor's first terminal is connected to the first terminal of the second thyristor group, and its second terminal is connected to the second terminal of the second thyristor group. The third contactor's first terminal is connected to the first terminal of the first thyristor group, and its second terminal is connected to the second terminal of the first thyristor group.

[0048] like Figure 2 As shown, optionally, the first, second, and third circuit breakers are Liangxin NDM3AR series electronic circuit breakers, which can prevent the entire system from shutting down due to local faults in other parts of the system, and realize the on-off control of the main circuit through their auxiliary contacts. The auxiliary contacts of the first, second, and third circuit breakers are connected to the panel switching devices to realize remote control of the soft starter.

[0049] The three-phase parallel thyristor module includes at least three groups of thyristors: a first thyristor group, a second thyristor group, and a third thyristor group, used to receive control signals from the circuit breaker module. The first, second, and third thyristor groups are respectively composed of a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, and a sixth thyristor. These groups are responsible for regulating the voltage applied to the motor stator windings. By adjusting the conduction angle of each thyristor, the voltage gradually increases during motor startup, eventually reaching full voltage, ensuring a soft-start without impact. The conduction angles of the first, second, third, fourth, fifth, and sixth thyristors are controlled by electronic circuitry.

[0050] During startup, the electronic circuit controls the conduction angle of the thyristor, which gradually increases the terminal voltage of the motor until it reaches full voltage, enabling the motor to achieve a soft start without impact. After startup, the bypass contactor closes, short-circuiting the thyristor, and the motor receives full voltage, allowing it to continue operating normally.

[0051] During shutdown, the turn-off speed of the thyristors is controlled to gradually reduce the motor's terminal voltage from full voltage to zero, achieving soft stopping. The connection structure of the main circuit breaker, three-way anti-parallel thyristors, bypass contactor, and motor terminals is as follows: Figure 3 As shown; for the current to form a loop, it must be initiated by two-phase thyristors. With the phase sequence positive, taking a firing angle of 0 degrees as an example, each phase's voltage zero-crossing triggers two-phase thyristors. The firing sequence is AB, CA, BC, AB, CA, BC, as shown. Figure 4 As shown;

[0052] The bypass contactor module includes three contactors: a first contactor, a second contactor, and a third contactor. These three contactors ensure current flows through the thyristor assembly and provide a short-circuit path after motor startup. The first terminal of the first contactor is connected to the first terminal of the third thyristor assembly, and its second terminal is connected to the second terminal of the third thyristor assembly. The first terminal of the second contactor is connected to the first terminal of the second thyristor assembly, and its second terminal is connected to the second terminal of the second thyristor assembly. The first terminal of the third contactor is connected to the first terminal of the first thyristor assembly, and its second terminal is connected to the second terminal of the first thyristor assembly.

[0053] When the motor enters the pre-stop state, the starting contactor is engaged, and the current power factor angle is used as the initial trigger angle. This triggers the thyristor valve group, and then the grid-connected contactor is disconnected. Following a predetermined pattern, the trigger angle gradually increases from the initial trigger angle to the maximum trigger angle. During this process, the current detection module continuously monitors the increment of the motor's freewheeling angle. If the increment exceeds a set threshold, it begins calculating the trigger angle increment required to compensate for the stator voltage, providing a new trigger angle to eliminate current oscillations. When the trigger angle reaches the set maximum value, the starting contactor is disconnected, and the motor enters the stop state. The program flow is as follows: Figure 5 As shown.

[0054] The current detection module is connected to the circuit breaker module, which can monitor the motor current in real time, adjust the conduction angle of the thyristor according to the detected data, and transmit the detection signal to the thermal overload relay module.

[0055] The first terminal of the thermal overload relay module is connected to the current detection module, and the second terminal is connected to the first terminal of the thyristor group. The thermal overload relay module provides overload protection to prevent the motor from cutting off the power supply when it reaches the preset overload threshold due to prolonged high current operation. At the same time, it adopts a contactless reset mechanism or a stepper motor reset method based on the controller to speed up the reset speed of the relay.

[0056] The pump load characteristics applicable to this utility model are as follows: the load torque is quadratically related to the speed, equivalent to a parabola, and its shaft power P is cubically related to the speed. In the initial startup phase, the motor of the pump load has a slow speed and low torque, equivalent to a light load start. Towards the end of the startup phase, as the motor speed increases, the load torque also increases, equivalent to a heavy load start. However, at this point, the stator voltage has increased, the voltage slip has decreased, and the starting torque is sufficient to drive the load.

[0057] The electrical principle of the soft starter for motors used in pump loads described in this utility model is as follows:

[0058] After the three-phase AC 380V power supply is input, it passes through the Z01 filter and the QF01 main circuit breaker, and is connected to the L1, L2, and L3 terminals of the soft starter and the miniature circuit breaker QF02, respectively. QF02 is then connected to the T01 AC transformer to provide control power to the core of the soft starter.

[0059] In addition, SB01, SB02, SB03, and SB04 are configured to control the power-on of the soft starter, pump start-up, pump stop-up, and control mode switching, respectively. HL01, HL02, and HL03 are configured to indicate the fault, running, and power-on status of the soft starter, respectively. FR01 is configured as a thermal overload relay to provide overload protection after the soft starter switches to bypass mode. For detailed electrical connections, see [link to details]. Figure 6 As shown;

[0060] The user interface module uses a high-definition LED or LCD display to ensure clear and intuitive display content, facilitating user viewing and operation. The display should support both Chinese and English to accommodate different language environments. The user interface module should provide menu-driven operation, allowing users to access corresponding parameter setting interfaces by selecting different menu items. For example, pressing the "P" key in standby mode enters parameter editing mode, while the "U" or "D" keys are used to select and modify parameter values. Finally, pressing the "P" key saves the parameters. The parameter interface should contain multiple parameter groups, with each parameter placed within its specific submenu for easy searching and modification. The user interface module should display corresponding fault codes and distinguish between resettable and non-resettable faults to facilitate timely user intervention.

[0061] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0062] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A soft starter for a motor suitable for pump-type loads, characterized in that, The device includes: a main circuit breaker module, a three-phase parallel thyristor module, and a bypass contactor module; the main circuit breaker module is connected to the three-phase parallel thyristor module and the bypass contactor module respectively; the three-phase parallel thyristor module is connected to a motor; The main circuit breaker module is used for on / off control of the main circuit; The three anti-parallel thyristor modules are used to boost or buck the voltage of the main circuit to obtain the operating voltage of the motor. The bypass contactor module is used to allow current to flow through the thyristor assembly in the three-opposite-parallel thyristor module when closed.

2. The motor soft starter device suitable for pump loads according to claim 1, characterized in that, The main circuit breaker module includes a first circuit breaker, a second circuit breaker, and a third circuit breaker.

3. A motor soft starter device suitable for pump loads according to claim 2, characterized in that, The three-phase parallel thyristor module includes at least a first thyristor group, a second thyristor group, and a third thyristor group; The first terminal of the first circuit breaker is connected to the three-phase input power supply; The second terminal of the first circuit breaker is connected to the first thyristor group; The first terminal of the second circuit breaker is connected to the three-phase input power supply; The second terminal of the second circuit breaker is connected to the second thyristor group; The first terminal of the third circuit breaker is connected to the three-phase input power supply. The second end of the third circuit breaker is connected to the third thyristor group.

4. A motor soft starter device suitable for pump loads according to claim 3, characterized in that, The first thyristor group includes a first thyristor and a second thyristor; The second thyristor group includes a third thyristor and a fourth thyristor; The third thyristor group includes a fifth thyristor and a sixth thyristor.

5. A motor soft starter device suitable for pump loads according to claim 4, characterized in that, The bypass contactor module includes at least a first contactor, a second contactor, and a third contactor; The first terminal of the first contactor is connected to the first terminal of the third thyristor group; The second end of the first contactor is connected to the second end of the third thyristor group; The first end of the second contactor is connected to the first end of the second thyristor group; The second terminal of the second contactor is connected to the second terminal of the second thyristor group; The first end of the third contactor is connected to the first end of the first thyristor group; The second end of the third contactor is connected to the second end of the first thyristor group.

6. A soft starter for a motor suitable for pump loads according to claim 1, characterized in that, The main circuit breaker module is an NDM3AR series electronic circuit breaker.

7. A motor soft starter device suitable for pump loads according to claim 1, characterized in that, The device also includes a current detection module, which is used to detect the current in the motor and convert the detected current signal into an electrical signal.

8. A soft starter for a motor suitable for pump loads according to claim 1, characterized in that, The device also includes a thermal overload relay module, which is connected to the motor and is used to cut off the power supply when the current exceeds a preset safety threshold.

9. A soft starter for a motor suitable for pump loads according to claim 1, characterized in that, The device also includes a user interface module, which is used to display the motor's starting parameters and operating status.

10. A motor soft starter device suitable for pump loads according to claim 9, characterized in that, The user interface is a touchscreen or a button-based interface.

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