A cutting frequency converter

Abstract

The utility model belongs to coal mine mining equipment control technical field and discloses a kind of cutting frequency changer, including rectifier unit and inverter unit, the input end of rectifier unit is connected with input electric reactor through cutting frequency changer input contactor, the output end of rectifier unit is connected with the input end of inverter unit through first positive-negative laminated busbar, the output end of inverter unit is connected with cutting motor through cutting frequency changer output frequency changer.The technical scheme of the utility model can improve the overall performance and operation efficiency of coal mining machine.

Description

Technical Field

[0001] This utility model belongs to the field of coal mine mining equipment control technology, and in particular relates to a cutting frequency converter. Background Technology

[0002] Currently, the traction motors of electric coal mining machines use low-voltage variable frequency drives, while the cutting motors use power frequency starting. Power frequency starting has many disadvantages, specifically: During power frequency starting, the starting current can reach 5-8 times the rated current, causing a sudden surge in current to the power grid, leading to a significant drop in grid voltage. This can also trigger the protection trip of the upstream mobile transformer, affecting the normal operation of the coal mining machine and other equipment on the same circuit. Simultaneously, the excessive starting current intensifies the instantaneous temperature rise of the motor windings, accelerating the aging of insulation materials and reducing motor lifespan. Furthermore, power frequency starting causes mechanical shock, generating excessively high starting torque, which can easily damage gears and reduce their lifespan. When the cutting drum encounters hard rock or coal seams, intense friction causes severe drum wear, reducing drum lifespan and generating large sparks, posing safety hazards. When the cutting drum operates in softer coal seams, excessively high speeds generate severe coal dust, affecting the health of workers, impacting coal product quality, and posing significant safety risks. Moreover, power frequency starting also results in higher energy consumption, reducing enterprise profits.

[0003] In summary, the existing motor frequency starting technology has many drawbacks and can no longer meet the requirements of efficient, safe and economical operation of electric coal mining machines. It is necessary to upgrade the cutting motor with frequency conversion drive to improve the overall performance and operating efficiency of electric coal mining machines. Utility Model Content

[0004] The purpose of this invention is to provide a cut-off frequency converter to solve the problems existing in the prior art.

[0005] To achieve the above objectives, this utility model provides a cutting frequency converter, including a rectifier unit and an inverter unit. The input terminal of the rectifier unit is connected to an input reactor through a cutting frequency converter input contactor. The output terminal of the rectifier unit is connected to the input terminal of the inverter unit through a first positive and negative stacked busbar. The output terminal of the inverter unit is connected to a cutting motor through the cutting frequency converter output frequency converter.

[0006] Optionally, it also includes an external capacitor bank, wherein the external capacitor bank consists of two DC filter capacitors connected in parallel to a second positive and negative stacked busbar, and the second positive and negative stacked busbar of the external capacitor bank is connected to the first positive and negative stacked busbar.

[0007] Optionally, the DC filter capacitor is a high-density thin-film filter capacitor.

[0008] Optionally, the input reactor is connected to the cutting motor via a cutting power frequency contactor.

[0009] Optionally, the cutting power frequency contactor, the cutting frequency converter input contactor, and the cutting frequency converter output frequency converter are all three-phase vacuum contactors.

[0010] The technical effects of this utility model are as follows:

[0011] This utility model employs a variable frequency drive (VFD) cutting motor, which offers the following advantages: The motor has a low starting current, resulting in minimal impact on the power grid. A stable power grid is essential for the normal operation of the equipment. Due to the low starting current, the motor windings do not overheat instantly, extending the motor's lifespan. Simultaneously, the VFD-driven motor gradually increases speed from low to the set speed, preventing impact on the gears and extending their lifespan. When cutting hard rock or coal seams, the VFD reduces speed, extending the cutting drum's lifespan and reducing safety hazards caused by sparks. When cutting soft coal seams without requiring high torque, the VFD reduces speed to decrease coal dust at the working face, protecting worker health and reducing safety hazards associated with coal dust. When cutting coal seams of suitable hardness, the VFD increases speed for rapid cutting, increasing production capacity. Furthermore, the VFD-driven linkage between the traction motor and the cutting motor enables dynamic speed regulation, maximizing production efficiency while saving energy, thus improving the overall performance and operational benefits of the electric coal mining machine. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0014] Figure 1 This is a schematic diagram of the redundancy control principle of the cut-off frequency converter in the embodiment of this utility model;

[0015] Figure 2 This is a schematic diagram of the cutting frequency converter in the embodiment of this utility model;

[0016] Figure 3 This is a schematic diagram of the cut-off frequency converter structure in an embodiment of this utility model. Detailed Implementation

[0017] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features and implementations of the present invention.

[0018] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Various improvements and variations can be made to the specific embodiments described in this utility model without departing from the scope or spirit of this utility model, which will be obvious to those skilled in the art. Other embodiments derived from this utility model description will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 - Figure 3 As shown, this embodiment provides a cutting frequency converter, including a rectifier unit and an inverter unit. The input terminal of the rectifier unit is connected to an input reactor through a cutting frequency converter input contactor. The output terminal of the rectifier unit is connected to the input terminal of the inverter unit through a first positive and negative stacked busbar. The output terminal of the inverter unit is connected to a cutting motor through the cutting frequency converter output frequency converter.

[0023] Figure 1 This is a schematic diagram of the redundant control principle of the cutting frequency converter in this embodiment. In this diagram, KM1 is the left cutting power frequency contactor, KM2 is the left cutting frequency converter input contactor, BP1 is the left cutting frequency converter, KM3 is the left cutting frequency converter output frequency converter, M1 is the left cutting motor, KM4 is the right cutting power frequency contactor, KM5 is the right cutting frequency converter input contactor, BP2 is the right cutting frequency converter, KM6 is the left cutting frequency converter output frequency converter, and M2 is the right cutting motor.

[0024] KM describes a three-phase vacuum contactor used to control the on / off state of the main circuit; M describes a cutting motor used to drive the left and right cutting drums, which cut the coal seam to achieve coal mining; BP describes an 1140V medium-voltage cutting three-level frequency converter.

[0025] The redundancy control principle of the cut-off frequency converter is as follows (taking the left-cut frequency converter as an example):

[0026] During normal operation, KM1 is disconnected, while KM2 and KM3 are engaged, and the left cutting inverter drives the cutting motor. If the cutting inverter malfunctions, KM2 and KM3 disconnect, KM1 engages, and the cutting motor starts at the mains frequency. This redundancy design prevents production disruptions due to cutting inverter failure; the cutting inverter can be replaced during inspection.

[0027] The coal mining machine cutting frequency converter provided in this embodiment has a redundant design, which allows for free switching between power frequency and frequency conversion. When the cutting frequency converter fails and cannot drive the cutting motor, the power frequency direct start is adopted by switching contactors. The power frequency and frequency conversion are switched through three contactors. Power frequency and frequency conversion can only work independently. When working at power frequency, no current or voltage circuit will be generated in the frequency conversion circuit. Similarly, when working at frequency conversion, no current or voltage circuit will be generated in the power frequency circuit.

[0028] Figure 2 This is a schematic diagram of the cut-off frequency converter in this embodiment. BUS and BUS- are positive and negative stacked busbars, and EC1 and EC2 are external capacitor banks DC filter capacitors, which are high-density thin-film filter capacitors.

[0029] The coal mining machine cutting frequency converter in this embodiment is a two-quadrant three-level frequency converter, including but not limited to two-level, three-level and other multi-level frequency converters. The frequency converter itself has lower power consumption. The heat sink of the cutting frequency converter uses aluminum with sintered heat pipes, which increases the thermal conductivity of the heat sink by 5-8 times, which is beneficial for heat dissipation.

[0030] Figure 3This is a schematic diagram of a cutting frequency converter. The input reactor is a voltage filter reactor installed at the input terminal of the cutting frequency converter to effectively suppress instantaneous voltage from the power grid and protect the converter from damage caused by power grid surges. The external capacitor bank is a DC filter capacitor assembly used to filter noise signals in the power grid, ensuring the stability of current and voltage. The cutting frequency converter is a two-quadrant, three-level 1140V frequency converter used for variable frequency speed control of the coal mining machine's cutting motor. Its heat sink uses an aluminum plate with sintered heat pipes to improve heat dissipation efficiency. The external capacitor bank is a specially designed structure to reduce the weight of the cutting frequency converter itself. The power devices of the frequency converter, such as IGBTs, are designed for high power. Depending on the power of the coal mining machine's cutting motor, various frequency converter specifications and models can be combined by changing the capacitance value of the external capacitor bank. The frequency converter's own BUS+ and BUS- are connected to the external capacitor bank's BUS+ and BUS, respectively. With the external capacitor bank, the cutting frequency converter itself is smaller in size and lighter in weight, making it easier to transport, maintain or replace the cutting frequency converter, especially in the narrow space of underground coal mines.

[0031] The cutting frequency converter in this embodiment adopts a split design, and can be combined with external capacitors to form frequency converters of various power specifications. According to the power of the cutting motor, a suitable DC capacitor is selected to make reasonable use of the space of the electrical control box. The cutting frequency converter in this embodiment is small in size and light in weight, and is easy to transport, maintain and replace, which is especially important for its application in the narrow space of underground coal mines.

[0032] The DC capacitors of the external capacitor bank are high-density film capacitors, which have high ripple current and self-healing function. The external capacitor bank adopts a multilayer busbar design, which has low temperature rise and extremely low stray inductance, protecting the IGBT.

[0033] The above description is merely a preferred embodiment of this application, but the scope of protection of this application 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 application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A cut-off frequency converter, characterized in that, It includes a rectifier unit and an inverter unit. The input terminal of the rectifier unit is connected to the input reactor through the input contactor of the cutting frequency converter. The output terminal of the rectifier unit is connected to the input terminal of the inverter unit through the first positive and negative stacked busbar. The output terminal of the inverter unit is connected to the cutting motor through the output frequency converter of the cutting frequency converter.

2. The cut-off frequency converter according to claim 1, characterized in that, It also includes an external capacitor bank, which consists of two DC filter capacitors connected in parallel to a second positive and negative stacked busbar. The second positive and negative stacked busbar of the external capacitor bank is connected to the first positive and negative stacked busbar.

3. The cut-off frequency converter according to claim 2, characterized in that, The DC filter capacitor is a high-density thin-film filter capacitor.

4. The cut-off frequency converter according to claim 1, characterized in that, The input reactor is connected to the cutting motor via a cutting power frequency contactor.

5. The cut-off frequency converter according to claim 1, characterized in that, The cutting power frequency contactor, the cutting frequency converter input contactor, and the cutting frequency converter output frequency converter all adopt three-phase vacuum contactors.

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