A warning system for a coal mill

Abstract

The application provides a warning system for a coal mill, which comprises a sensing loop, a first contactor, a second contactor, an amplification module and a rectification module; the sensing loop is arranged between two phases of a three-phase power supply; the first contactor is used for controlling the on-off connection of a coal mill motor and the three-phase power supply; the input side of the amplification module is coupled with the coal mill motor, so as to amplify the working current of the coal mill motor and form a state signal for driving the second contactor; the second contactor is used for switching the running state of the first contactor according to the state signal; the input side of the rectification module is coupled with the sensing loop, and the output side of the rectification module is used for outputting a direct current voltage to the amplification module. The application controls the running state of the first contactor by arranging the second contactor, and amplifies the fluctuation generated when the coal mill motor runs as the starting condition of the second contactor by the amplification module, so that the coal mill motor stops running after the centrifugal disc is blocked.

Description

Technical Field

[0001] This invention belongs to the field of coal mill monitoring technology, and particularly relates to an early warning system for coal mills. Background Technology

[0002] A coal mill is a device that grinds large pieces of coal into powder using rolling steel balls, and then feeds the powdered coal into the boiler furnace through the output holes of a centrifugal disc using protective gas. During operation, some organic matter and impurities that are difficult to grind finely or break down will float around the small holes of the centrifugal disc due to the suction force of the negative pressure in the pipeline. Over time, these particles gradually accumulate and block the output holes of the centrifugal disc, thus reducing the amount of pulverized coal output from the mill and affecting the power generation of the turbine units in thermal power plants. When the centrifugal disc in the coal mill is blocked, the mill's energy consumption increases, and its rotational speed also increases, accelerating the grinding speed of the coal lumps. With the output holes of the centrifugal disc blocked, the gradual increase in pulverized coal production will increase the gas pressure inside the mill, potentially causing backflow of pulverized coal, which poses a significant safety hazard to the entire coal mill pulverizing system. Summary of the Invention

[0003] To address the problem described in the background art where the blockage of the centrifugal disc inside the coal mill may cause backflow of pulverized coal, the present invention proposes the following technical solution:

[0004] An early warning system for a coal mill includes: an induction circuit, a first contactor, a second contactor, an amplification module, and a rectifier module; the induction circuit is located between two phases of a three-phase power supply; the first contactor controls the connection between the coal mill motor and the three-phase power supply; the input side of the amplification module is coupled to the coal mill motor to amplify the operating current of the coal mill motor and form a status signal for driving the second contactor; the second contactor switches the operating state of the first contactor according to the status signal; the input side of the rectifier module is coupled to the induction circuit, and the output side of the rectifier module outputs a DC voltage to the amplification module.

[0005] The first contactor includes a first coil, a first normally closed contact, and a plurality of first normally open contacts; the first coil is located within the induction circuit; the first normally open contacts are all located between the three-phase power supply and the coal mill motor, and the first normally closed contact is connected in parallel with the first coil.

[0006] Furthermore, the induction circuit is provided with a first start switch, a second start switch, and a third start switch; the first start switch is located between the three-phase power supply and the first normally open contact; the second start switch is connected in parallel with the first coil and the first normally closed contact respectively; the third start switch is connected in parallel with the second normally open contact; when the first start switch and the second start switch are closed simultaneously, the first coil is energized, thereby causing the first normally open contact to close and the first normally closed contact to open, and the coal mill motor starts to run.

[0007] Furthermore, the second contactor includes a second coil, a second normally closed contact, and a second normally open contact; the second coil is connected to the output side of the amplification module; the second normally open contact is grounded through an alarm; the second normally closed contact is connected in parallel with the second coil to block the second coil from being energized; when the centrifugal disc is blocked, the amplification module receives the operating current of the coal mill motor, amplifies it, and drives the second coil to become energized, thereby causing the alarm to sound and the coal mill motor to be de-energized.

[0008] Further, the amplification module includes: a primary coil, a secondary coil, a detector circuit, and a proportional amplifier; the primary coil is located between the three-phase power supply and the coal mill motor; the secondary coil is used to sense the operating voltage of the primary coil and output the induced voltage to the detector circuit; the detector circuit is used to output a DC voltage to the proportional amplifier; the input terminal of the proportional amplifier is connected to the detector circuit through an adjustable resistor; the output terminal of the proportional amplifier is connected to the second coil; the proportional amplifier amplifies the DC voltage and generates the status signal; when the status signal reaches a threshold, the proportional amplifier outputs the status signal to the second coil and drives the second coil to become inductive.

[0009] Furthermore, the detection circuit includes: a rectifier diode and a voltage regulator capacitor connected in series; the conducting side of the rectifier diode is connected to one end of the secondary coil, and the cutting-off side of the rectifier diode is connected to one end of the voltage regulator capacitor; the other end of the voltage regulator capacitor is grounded, and the voltage regulator capacitor is connected in parallel with the regulating resistor.

[0010] Furthermore, a transformer is provided on the induction circuit, and the transformer is coupled to the input side of the rectifier module through a coil.

[0011] Furthermore, the amplification module also includes a relay, which is connected to the output side of the proportional amplifier. The normally open contact of the relay is located between the third start switch and the second coil, and the series circuit formed by the second coil and the normally closed contact of the relay is connected in parallel with the second normally closed contact.

[0012] Beneficial effects: The present invention controls the operating state of the first contactor by setting a second contactor, and amplifies the fluctuations generated during the operation of the coal mill motor by an amplification module as the starting condition of the second contactor, thereby causing the coal mill motor to stop running after the centrifugal disc is blocked. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of an early warning system for a coal mill according to an embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0015] It should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent.

[0016] Figure 1 This is a schematic diagram of an early warning system for a coal mill according to an embodiment of the present invention.

[0017] Reference Figure 1 According to an embodiment of the present invention, an early warning system for a coal mill includes: an induction circuit, a first contactor, a second contactor, an amplifier module, and a rectifier module. The induction circuit is located between two phases of a three-phase power supply and is coupled to the input side of the rectifier module. The first contactor controls the connection between the coal mill motor and the three-phase power supply, and the second contactor switches the operating state of the first contactor. The input side of the amplifier module is coupled to the coal mill motor, and the output side of the amplifier module is connected to the second contactor. The output side of the rectifier module is connected to the amplifier module, thereby providing a stable power supply to the amplifier module.

[0018] When the centrifugal disc inside the coal mill is blocked, the operating current of the coal mill motor will fluctuate. The amplification module senses the operating current of the coal mill motor and amplifies it to form a status signal. When the fluctuation of the coal mill operating current reaches a certain level, the amplification module sends a status signal to the second contactor, thereby driving the second contactor to run and switching the operating state of the first contactor, thus stopping the coal mill motor.

[0019] Specifically, the amplification module includes a primary coil, a secondary coil, a detector circuit, and a proportional amplifier. The primary coil is located between the coal mill motor and the three-phase power supply. The two ends of the secondary coil are connected to the detector circuit. The detector circuit receives the induced voltage from the secondary coil and rectifies it to form a DC voltage, which is then input into the proportional amplifier. The input side of the proportional amplifier is connected to the detector circuit via an adjustable resistor, and the output side is connected to the second coil. When the magnitude of the DC voltage output by the detector circuit exceeds a threshold set by the proportional amplifier, the amplifier outputs a status signal to the second coil, thereby energizing the second coil and switching the operating state of the first contactor.

[0020] Furthermore, the amplification module also includes a relay. The first contactor includes a first coil, a first normally closed contact, and a first normally open contact. The second contactor includes a second coil, a second normally closed contact, and a second normally open contact. The first coil is located in the induction circuit, the first normally open contact is located between the three-phase power supply and the coal mill motor, and the first normally closed contact is connected in parallel with the first coil. The second coil is located between the output terminal of the amplification module and the output terminal of the rectifier module. One end of the second normally open contact is connected to the output terminal of the rectifier module, and the other end is grounded through an alarm. The relay is located at the output terminal of the proportional amplifier. The circuit formed by connecting one of the relay's normally open contacts in series with the second coil is connected in parallel with the second normally closed contact, and the circuit formed by connecting the other normally open contact of the relay in series with the first normally closed contact is connected in parallel with the first coil.

[0021] When the second coil is energized, the second normally open contact and the normally open contact of the relay close simultaneously, thereby de-energizing the first coil and cutting off power to the coal mill motor. At the same time, when the second normally open contact closes, the alarm is energized and sounds an alarm, thus reminding workers to clean the centrifuge disc. In this embodiment, the alarm is a buzzer. In other embodiments, the alarm can also be a device with a strong alerting function, such as a warning light.

[0022] Furthermore, the induction circuit is also equipped with a first start switch, a second start switch, and a third start switch. The first start switch is located between the three-phase power supply and the first coil; the second start switch is connected in series with the first coil; and the third start switch is connected in series with the second coil. Both the first and second start switches are used to manually control the induction state of the first coil, and the third start switch is used to manually control the induction state of the second coil.

[0023] When the centrifugal discs inside the coal mill are not blocked, the coal mill motor operates normally. The second normally closed contact closes, and the normally open contact of the relay opens, thus de-energizing the second coil and keeping the alarm silent. When the centrifugal discs inside the coal mill are blocked, the output of the proportional amplifier controls the relay, causing the normally open contact of the relay to close. This energizes the second coil, causing the second normally open contact to close and the second normally closed contact to open, thereby driving the alarm to sound. Simultaneously, the first coil experiences a short circuit and loses power because one of the first normally open contacts and the normally open contact of the relay closes simultaneously. This causes the first normally open contact between the three-phase power supply and the coal mill motor to open, stopping the coal mill motor.

[0024] Specifically, a transformer is also provided in the induction circuit, and the transformer is coupled to the input side of the rectifier module through a coil. In this embodiment, the rectifier module is a rectifier bridge circuit. The AC voltage induced in the induction circuit is rectified by the rectifier module and converted into DC voltage, which is then output to the amplifier module to power its operation.

[0025] In this embodiment, the detection circuit consists of a rectifier diode and a Zener capacitor connected in series. The conducting side of the rectifier diode is connected to the secondary coil, and the cutting side of the rectifier diode is connected to one end of the Zener capacitor. The other end of the Zener capacitor is grounded, and the Zener capacitor is connected in parallel with the regulating resistor. When the induced voltage is in the positive half-cycle, the secondary coil charges the Zener capacitor, and the input voltage of the proportional amplifier is less than or equal to the induced voltage of the secondary coil. When the induced voltage is in the negative half-cycle, the Zener capacitor discharges into the proportional amplifier, and the input voltage of the proportional amplifier is equal to the voltage of the Zener capacitor, thereby converting the alternating current induced in the secondary coil into direct current.

[0026] In summary, the present invention controls the operating state of the first contactor by setting a second contactor, and amplifies the fluctuations generated during the operation of the coal mill motor by an amplification module as the starting condition for the second contactor, thereby causing the coal mill motor to stop operating after the centrifugal disc is blocked.

[0027] The foregoing has described specific embodiments of the invention. Other embodiments are within the scope of the appended claims.

[0028] The terms “exemplary,” “example,” etc., used throughout this specification mean “serving as an example, instance, or illustration” and do not imply “preferred” or “advantageous” than other embodiments. Detailed descriptions are included for the purpose of providing an understanding of the described techniques. However, these techniques can be practiced without these detailed descriptions. In some instances, well-known structures and apparatuses are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0029] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0030] The foregoing description of this specification is provided to enable any person skilled in the art to implement or use the content of this specification. Various modifications to the content of this specification will be apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of protection of this specification. Therefore, this specification is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.

Claims

1. An early warning system for a coal mill, characterized in that, The early warning system includes: an induction circuit, a first contactor, a second contactor, an amplification module, and a rectifier module; the induction circuit is located between two phases of the three-phase power supply; the first contactor is used to control the connection between the coal mill motor and the three-phase power supply; the first contactor includes a first coil, a first normally closed contact, and multiple first normally open contacts; the first coil is located within the induction circuit; the first normally open contacts are all located between the three-phase power supply and the coal mill motor, and the first normally closed contacts are connected in parallel with the first coil to control the connection between the coal mill motor and the three-phase power supply; the input side of the amplification module is coupled to the coal mill motor to amplify the operating current of the coal mill motor and form a status signal for driving the second contactor; The second contactor is used to switch the operating state of the first contactor according to the status signal; the second contactor includes a second coil, a second normally closed contact, and a second normally open contact; the second coil is connected to the output side of the amplification module; the second normally open contact is grounded through an alarm; the second normally closed contact is connected in parallel with the second coil to block the second coil from being energized; when the centrifugal disc is blocked, the amplification module receives the operating current of the coal mill motor, amplifies it, and drives the second coil to be energized, thereby causing the alarm to sound and the coal mill motor to be de-energized; The input side of the rectifier module is coupled to the induction circuit, and the output side of the rectifier module is used to output DC voltage to the amplification module. The induction circuit is provided with a first start switch, a second start switch, and a third start switch. The first start switch is located between the three-phase power supply and the first normally open contact. The second start switch is connected in parallel with the first coil and the first normally closed contact. The third start switch is connected in parallel with the second normally open contact. When the first start switch and the second start switch are closed simultaneously, the first coil is energized, thereby causing the first normally open contact to close and the first normally closed contact to open, and the coal mill motor starts to run.

2. The early warning system for a coal mill according to claim 1, characterized in that, The amplification module includes a primary coil, a secondary coil, a detector circuit, and a proportional amplifier. The primary coil is located between the three-phase power supply and the coal mill motor. The secondary coil senses the operating voltage of the primary coil and outputs an induced voltage to the detector circuit. The detector circuit outputs a DC voltage to the proportional amplifier. The input terminal of the proportional amplifier is connected to the detector circuit via an adjustable resistor. The output terminal of the proportional amplifier is connected to the second coil. The proportional amplifier amplifies the DC voltage and generates the status signal. When the status signal reaches a threshold, the proportional amplifier outputs the status signal to the second coil and drives the second coil to become inductive.

3. The early warning system for a coal mill according to claim 2, characterized in that, The detection circuit includes: a rectifier diode and a voltage regulator capacitor connected in series; the conducting side of the rectifier diode is connected to one end of the secondary coil, and the cutting side of the rectifier diode is connected to one end of the voltage regulator capacitor; the other end of the voltage regulator capacitor is grounded, and the voltage regulator capacitor is connected in parallel with the regulating resistor.

4. The early warning system for a coal mill according to claim 2, characterized in that, The induction circuit is equipped with a transformer, which is coupled to the input side of the rectifier module through a coil.

5. The early warning system for a coal mill according to claim 4, characterized in that, The amplification module also includes a relay, which is connected to the output side of the proportional amplifier. The normally open contact of the relay is located between the third start switch and the second coil, and the series circuit formed by the second coil and the normally closed contact of the relay is connected in parallel with the second normally closed contact.

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