Single-phase brushless motor control mechanism without attracting iron powder and control method

Abstract

The invention discloses a single-phase brushless motor control mechanism without attracting iron powder and a control method, and the mechanism comprises a motor body, a stepless speed change fan, a Hall sensor, a circuit board, a power circuit, a control circuit, a current-limiting protection circuit, a drive circuit, and a serial port. A period is reserved in the operation process of the motor to discharge metal dust, so that the problem of iron powder adsorption in an industrial environment is solved, and the motor has the advantages of high efficiency, durability, low maintenance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of single-phase motors, and in particular to the technical field of a single-phase brushless motor control mechanism and a control method that does not absorb iron powder. Background Art

[0002] Existing motors, whether three-phase or single-phase, are widely used in all walks of life, among which single-phase motors are particularly widely used in industrial motors. Industrial motors are key equipment widely used in modern industry, and they play a vital role in driving machinery, transmitting power and controlling systems. A large amount of dust is generated in the industrial environment, among which the iron powder that can be adsorbed by magnetic materials has the greatest impact on the motor. The iron powder enters the motor with the air and is easily attached to the motor windings. When the motor is running, some of the iron powder will be thrown out, but most of the iron powder will still be attached to the motor windings due to the effect of electromagnetic attraction. After a long period of accumulation, it is easy to damage the internal insulation of the motor, resulting in a winding short circuit and burning of the motor. The reasons why the motor produces iron powder adsorption are: 1. Wear inside the motor: When the industrial motor rotates at high speed and runs for a long time, the internal metal parts (such as bearings, gears and rotors) will rub against each other, producing tiny metal particles. These particles are mainly composed of iron and other metals, commonly known as iron powder; 2. Magnetic field effect: The electromagnetic field generated by the motor when it is working is the main power source to drive the rotor to rotate. However, these electromagnetic fields not only act on the inside of the motor, but also spread to the surrounding environment. These magnetic fields will attract iron powder in the surrounding environment, especially in an environment with a lot of iron materials. More obvious; 3. Environmental pollution: There are a large number of tiny particles, including iron powder, in the industrial production environment. These particles are transmitted through air, lubricating oil or other media It enters the motor and accumulates in key parts, causing the motor to absorb iron powder. The absorption of iron powder has many negative effects on the normal operation of industrial motors: 1. Performance degradation: Iron powder accumulates between the rotor and stator of the motor, which increases friction resistance and reduces the operating efficiency of the motor. This friction not only consumes more energy, but also may cause the motor to heat up, further affecting the performance of the motor; 2. Increased wear: Iron powder will accelerate the wear of metal parts inside the motor and shorten the service life of the motor. Especially for high-speed motors, increased wear will cause the motor to need to be repaired and replaced more frequently, increasing maintenance costs; 3. Increased failure rate: Iron powder may block the cooling channel inside the motor, causing the motor to be unable to effectively dissipate heat. , increasing the risk of motor overheating and burning. In addition, iron powder may damage the insulation layer of the motor, causing electrical faults such as short circuits; 4. Weakened lubrication effect: Iron powder enters the lubricating oil system, which will contaminate the lubricating oil and reduce its lubrication effect. The contaminated lubricating oil not only cannot effectively reduce friction, but may also increase component wear, further affecting the operation of the motor. The above multiple impacts have caused industrial motors to have to consider this issue. The common solution on the market is to install a filter device at the air inlet or lubricating oil system of the motor, which can partially filter out the iron powder, but the filter device needs to be replaced and maintained regularly, otherwise it will fail, and the problem of iron powder adsorption cannot be avoided for a long time. Therefore, it is necessary to study a single-phase brushless motor that does not absorb iron powder and the electronic equipment to control it. Summary of the invention

[0003] The purpose of the present invention is to solve the problems in the prior art and to propose a single-phase brushless motor control mechanism and control method that does not absorb iron powder. The drive waveform can be chopped in the full-open mode, so that the motor can leave a cycle during operation to discharge metal dust, thereby solving the problem of iron powder adsorption in industrial environments and making the motor have the advantages of high efficiency, durability and low maintenance.

[0004] To achieve the above-mentioned purpose, the present invention proposes a control mechanism for a single-phase brushless motor that does not absorb iron powder, comprising a motor body, a stepless speed-changing fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port, wherein a Hall sensor is arranged in the motor body, and the Hall sensor is connected to the serial port of the circuit board, and a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port are arranged on the circuit board, the power supply circuit is connected to the current limiting protection circuit, the current limiting protection circuit is connected to the control circuit, the control circuit is connected to the drive circuit, the drive circuit comprises an H-bridge circuit and a drive unit, and a plurality of serial ports respectively connected to the power supply circuit, the control circuit, the current limiting protection circuit and the drive circuit are evenly arranged on the circuit board, the Hall sensor is connected to the control circuit through the serial port, and a stepless speed-changing fan is arranged on the outside of the motor body, and the stepless speed-changing fan is connected to the drive circuit through the serial port.

[0005] Preferably, a plurality of temperature sensors are arranged in the motor body, a plurality of cooling fins are evenly arranged around the outer side surface of the motor body, a liquid cooling pipe is inserted in the cooling fins, the liquid cooling pipe is a heat-conducting hose, both ends of the liquid cooling pipe extend to the outside of the cooling fins, and both ends of the liquid cooling pipe are respectively connected to a micro-stepless speed water pump, the micro-stepless speed water pump is immersed in an external cooling liquid tank, and the external cooling liquid tank is detachably arranged outside the motor body, and the temperature sensor is connected to the micro-stepless speed water pump.

[0006] Preferably, there are a plurality of Hall sensors, and the Hall sensors are evenly arranged around the rotor in the motor body. A limited position mounting groove is arranged inside the motor body corresponding to the position of the Hall sensor.

[0007] Preferably, the power supply circuit includes a main power supply circuit and an auxiliary power supply circuit, the main power supply circuit is connected to the current limiting protection circuit, the auxiliary power supply circuit is directly connected to the control circuit, the output voltage and current of the auxiliary power supply circuit are less than the voltage and current of the main power supply circuit, the output voltage of the auxiliary power supply circuit is 12V, and the output current of the auxiliary power supply circuit is 1A.

[0008] Preferably, the current limiting protection circuit comprises a constant current module, a filter circuit and a current limiting protector, the filter circuit is connected to the constant current module, and the constant current module is connected to the current limiting protector.

[0009] Preferably, the control circuit comprises a single-chip microcomputer with a built-in control program and an auxiliary power supply module, the single-chip microcomputer and the auxiliary power supply module are connected, and a button battery is detachably installed in the auxiliary power supply module.

[0010] Preferably, the driving unit comprises a microchip with a built-in control program, and the microchip is connected to the H-bridge circuit.

[0011] Preferably, the H-bridge circuit includes a control switch Q1, a control switch Q2, a control switch Q3, a control switch Q4, an inductor L and a resistor R, the control switch Q1 and the control switch Q2 are arranged in parallel, one end of the control switch Q1 is connected to one end of the inductor L, one end of the control switch Q2 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are arranged in parallel, one end of the control switch Q3 is connected to one end of the inductor L, one end of the control switch Q4 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected in parallel to the resistor R, and one end of the resistor R is grounded.

[0012] Preferably, the outer side of the stepless speed variable fan is covered with a protective mesh cover, which includes an isolation inner mesh cover and a magnetic outer mesh cover, the isolation inner mesh cover is an insulating plastic mesh cover, the magnetic outer mesh cover is an electromagnet mesh cover, the magnetic outer mesh cover is detachably arranged on the outside of the isolation inner mesh cover, and the mesh diameter of the magnetic outer mesh cover is larger than the mesh diameter of the isolation inner mesh cover.

[0013] To achieve the above object, the present invention proposes a single-phase brushless motor control method that does not absorb iron powder, which comprises the following steps in sequence: Step 1: Start the motor body, the Hall sensor senses the rotor position of the motor body in real time, and the Hall sensor transmits the sensed rotor position information to the control circuit; Step 2: After calculation and analysis, the control circuit transmits the position information to the drive circuit. The drive circuit controls the drive unit to push the start duty cycle according to the position information calculated and analyzed by the control circuit. The drive unit determines whether the full-open speed has been reached. If the full-open speed has not been reached, the duty cycle continues to be pushed. Otherwise, it enters the full-open mode. The entire commutation cycle of the full-open mode follows the frequency of the Hall signal, and the square wave duty cycle is adjusted according to the power size. Step three, chop the waveform of the full-open mode. When the rotor rotates to the position between the two poles of the rotor position signal waveform read by the Hall sensor and the waveform after chopped in the full-open mode, the voltage is chopped to form an instantaneous change in current, so that the magnetic field is weakened to the point where it does not absorb iron powder. Then the strong wind pushed out by the continuously variable speed fan at a high speed blows the iron powder out of the motor body, and each cycle continues to reciprocate.

[0014] Beneficial effects of the present invention: The present invention combines a motor body, a continuously variable speed fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port together, and after experimental optimization, the entire commutation cycle follows the frequency of the Hall signal, wherein the square wave duty cycle is adjusted according to the power size, and there is only one opening and closing when fully open, which greatly reduces the switching frequency. When the full-open mode is used for driving, the program will use chopping, and the period of no work is used to offset the inherent magnetic field of the permanent magnet, so that there is a period of time in each cycle when the iron powder can be blown out by the fan connected to the motor shaft, so as to achieve the function of not absorbing iron powder. The drive waveform can be chopped in the full-open mode, so that the motor can leave a cycle to discharge metal dust during operation, thereby solving the problem of iron powder adsorption in industrial environments and making the motor have the advantages of high efficiency, durability and low maintenance.

[0015] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a control mechanism of a single-phase brushless motor that does not absorb iron powder according to the present invention; Figure 2 It is a chopping waveform diagram of a single-phase brushless motor control method without attracting iron powder according to the present invention; Figure 3 The present invention is a schematic diagram of an H-bridge circuit structure of a control mechanism of a single-phase brushless motor that does not absorb iron powder. DETAILED DESCRIPTION

[0017] Example 1: See Figure 1 , Figure 2 and Figure 3The present invention discloses a control mechanism for a single-phase brushless motor that does not absorb iron powder, comprising a motor body, a stepless speed-changing fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The motor body is provided with a Hall sensor, and the Hall sensor is connected to the serial port of the circuit board. The circuit board is provided with a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The power supply circuit is connected to the current limiting protection circuit, the current limiting protection circuit is connected to the control circuit, the control circuit is connected to the drive circuit, the drive circuit comprises an H-bridge circuit and a drive unit, and the circuit board is provided with a Hall sensor. A plurality of serial ports respectively connected to the power supply circuit, the control circuit, the current limiting protection circuit and the drive circuit are uniformly provided, the Hall sensor is connected to the control circuit through the serial port, a stepless speed-changing fan is provided on the outside of the motor body, the stepless speed-changing fan is connected to the drive circuit through the serial port, the H-bridge circuit includes a control switch Q1, a control switch Q2, a control switch Q3, a control switch Q4, an inductor L and a resistor R, the control switch Q1 and the control switch Q2 are arranged in parallel, one end of the control switch Q1 is connected to one end of the inductor L, one end of the control switch Q2 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected to each other, and the control switch Q4 is connected to the control switch Q5. The control switch Q4 is arranged in parallel, one end of the control switch Q3 is connected to one end of the inductor L, one end of the control switch Q4 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected in parallel to the resistor R, one end of the resistor R is grounded, there are multiple Hall sensors, the Hall sensors are evenly arranged around the rotor in the motor body, and a limited position mounting groove is arranged inside the motor body corresponding to the position of the Hall sensor, the current limiting protection circuit includes a constant current module, a filter circuit and a current limiting protector, the filter circuit is connected to the constant current module, the constant current module is connected to the current limiting protector, and the The control circuit includes a single-chip microcomputer with a built-in control program and an auxiliary power supply module, the single-chip microcomputer is connected to the auxiliary power supply module, a button battery is detachably installed in the auxiliary power supply module, the drive unit includes a microchip with a built-in control program, the microchip is connected to the H-bridge circuit, the outer side of the stepless speed variable fan is covered with a protective mesh cover, the protective mesh cover includes an isolation inner mesh cover and a magnetic outer mesh cover, the isolation inner mesh cover is an insulating plastic mesh cover, the magnetic outer mesh cover is an electromagnet mesh cover, the magnetic outer mesh cover is detachably arranged on the outside of the isolation inner mesh cover, and the mesh diameter of the magnetic outer mesh cover is larger than the mesh diameter of the isolation inner mesh cover.

[0018] Example 2: See Figure 1 , Figure 2 and Figure 3The present invention discloses a control mechanism for a single-phase brushless motor that does not absorb iron powder, comprising a motor body, a stepless speed-changing fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The motor body is provided with a Hall sensor, and the Hall sensor is connected to the serial port of the circuit board. The circuit board is provided with a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The power supply circuit is connected to the current limiting protection circuit, and the current limiting protection circuit is connected to the control circuit, and the control circuit is connected to the drive circuit. The drive circuit comprises an H-bridge circuit and a drive unit. The circuit board is evenly provided with a plurality of components that are respectively connected to the power supply circuit, the control circuit and the drive unit. A serial port connected to a control circuit, a current limiting protection circuit, and a drive circuit, the Hall sensor is connected to the control circuit through the serial port, a stepless speed fan is arranged on the outside of the motor body, and the stepless speed fan is connected to the drive circuit through the serial port, the H-bridge circuit includes a control switch Q1, a control switch Q2, a control switch Q3, a control switch Q4, an inductor L and a resistor R, the control switch Q1 and the control switch Q2 are arranged in parallel, one end of the control switch Q1 is connected to one end of the inductor L, one end of the control switch Q2 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are arranged in parallel, one end of the control switch Q3 is connected to one end of the inductor L The control switch Q3 and the control switch Q4 are connected in parallel, one end of the control switch Q4 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected in parallel to the resistor R, one end of the resistor R is grounded, there are multiple Hall sensors, the Hall sensors are evenly arranged around the rotor in the motor body, and a limited position installation groove is arranged inside the motor body corresponding to the position of the Hall sensor. The current limiting protection circuit includes a constant current module, a filter circuit and a current limiting protector, the filter circuit is connected to the constant current module, the constant current module is connected to the current limiting protector, the control circuit includes a single-chip microcomputer with a built-in control program and an auxiliary power supply module, the single-chip microcomputer is connected to the auxiliary power supply module, and the auxiliary A button battery is detachably installed in the power supply module, the drive unit includes a microchip with a built-in control program, the microchip is connected to the H-bridge circuit, a plurality of temperature sensors are arranged in the motor body, a plurality of cooling fins are evenly arranged on the outer side of the motor body, a liquid cooling duct is inserted in the cooling fins, the liquid cooling duct is a heat-conducting hose, both ends of the liquid cooling duct extend to the outside of the cooling fins, a micro-stepless speed water pump is respectively connected to both ends of the liquid cooling duct, the micro-stepless speed water pump is immersed in an external cooling liquid tank, the external cooling liquid tank is detachably arranged outside the motor body, and the temperature sensor is connected to the micro-stepless speed water pump.

[0019] Example 3: See Figure 1 , Figure 2 and Figure 3The present invention discloses a control mechanism for a single-phase brushless motor that does not absorb iron powder, comprising a motor body, a stepless speed-changing fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The motor body is provided with a Hall sensor, the Hall sensor is connected to the serial port of the circuit board, the circuit board is provided with a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port, the power supply circuit is connected to the current limiting protection circuit, the current limiting protection circuit is connected to the control circuit, the control circuit is connected to the drive circuit, the drive circuit comprises an H-bridge circuit and a drive unit, and the circuit board is provided with a Hall sensor. A plurality of serial ports respectively connected to the power supply circuit, the control circuit, the current limiting protection circuit and the drive circuit are evenly arranged. The Hall sensor is connected to the control circuit through the serial port. A continuously variable speed fan is arranged on the outside of the motor body. The continuously variable speed fan is connected to the drive circuit through the serial port. The H-bridge circuit includes a control switch Q1, a control switch Q2, a control switch Q3, a control switch Q4, an inductor L and a resistor R. The control switch Q1 and the control switch Q2 are arranged in parallel. One end of the control switch Q1 is connected to one end of the inductor L, one end of the control switch Q2 is connected to the other end of the inductor L, and the control switch Q3 is connected to the inductor L. The control switch Q3 is connected in parallel with the control switch Q4, one end of the control switch Q3 is connected to one end of the inductor L, one end of the control switch Q4 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected in parallel with the resistor R, one end of the resistor R is grounded, there are multiple Hall sensors, the Hall sensors are evenly arranged around the rotor in the motor body, and a limited position mounting groove is arranged inside the motor body corresponding to the position of the Hall sensor, the current limiting protection circuit includes a constant current module, a filter circuit and a current limiting protector, the filter circuit is connected to the constant current module, and the constant current module is connected to the current limiting protector The control circuit includes a single-chip microcomputer with a built-in control program and an auxiliary power supply module, the single-chip microcomputer is connected to the auxiliary power supply module, a button battery is detachably installed in the auxiliary power supply module, the drive unit includes a microchip with a built-in control program, the microchip is connected to the H-bridge circuit, the power supply circuit includes a main power supply circuit and an auxiliary power supply circuit, the main power supply circuit is connected to the current limiting protection circuit, the auxiliary power supply circuit is directly connected to the control circuit, the output voltage and current of the auxiliary power supply circuit are less than the voltage and current of the main power supply circuit, the output voltage of the auxiliary power supply circuit is 12V, and the output current of the auxiliary power supply circuit is 1A.

[0020] The present invention proposes a single-phase brushless motor control method that does not absorb iron powder, which comprises the following steps in sequence: Step 1: Start the motor body, the Hall sensor senses the rotor position of the motor body in real time, and the Hall sensor transmits the sensed rotor position information to the control circuit; Step 2: After calculation and analysis, the control circuit transmits the position information to the drive circuit. The drive circuit controls the drive unit to push the start duty cycle according to the position information calculated and analyzed by the control circuit. The drive unit determines whether the full-open speed has been reached. If the full-open speed has not been reached, the duty cycle continues to be pushed. Otherwise, it enters the full-open mode. The entire commutation cycle of the full-open mode follows the frequency of the Hall signal, and the square wave duty cycle is adjusted according to the power size. Step three, chop the waveform of the full-open mode. When the rotor rotates to the position between the two poles of the rotor position signal waveform read by the Hall sensor and the waveform after chopped in the full-open mode, the voltage is chopped to form an instantaneous change in current, so that the magnetic field is weakened to the point where it does not absorb iron powder. Then the strong wind pushed out by the continuously variable speed fan at a high speed blows the iron powder out of the motor body, and each cycle continues to reciprocate.

[0021] The present invention combines a motor body, a continuously variable speed fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port together. After experimental optimization, the entire commutation cycle follows the frequency of the Hall signal, wherein the square wave duty cycle is adjusted according to the power size, and there is only one opening and closing when fully open, which greatly reduces the switching frequency. When the full-open mode is used for driving, the program will use chopping, and the period of no work is used to offset the inherent magnetic field of the permanent magnet, so that there is a period of time in each cycle when iron powder can be blown out by the fan connected to the motor shaft, so as to achieve the function of not absorbing iron powder. The drive waveform can be chopped in the full-open mode, so that the motor can leave a cycle to discharge metal dust during operation, thereby solving the problem of iron powder adsorption in industrial environments and making the motor have the advantages of high efficiency, durability and low maintenance.

[0022] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. A control mechanism for a single-phase brushless motor that does not absorb iron powder, characterized in that: The invention comprises a motor body, a continuously variable speed fan, a Hall sensor, a circuit board, a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. A Hall sensor is arranged in the motor body, and the Hall sensor is connected to the serial port of the circuit board. The circuit board is provided with a power supply circuit, a control circuit, a current limiting protection circuit, a drive circuit and a serial port. The power supply circuit is connected to the current limiting protection circuit, and the current limiting protection circuit is connected to the control circuit, and the control circuit is connected to the drive circuit. The drive circuit comprises an H-bridge circuit and a drive unit. Several serial ports respectively connected to the power supply circuit, the control circuit, the current limiting protection circuit and the drive circuit are evenly arranged on the circuit board. The Hall sensor is connected to the control circuit through the serial port. A continuously variable speed fan is arranged on the outside of the motor body, and the continuously variable speed fan is connected to the drive circuit through the serial port.

2. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: A plurality of temperature sensors are arranged in the motor body, a plurality of heat dissipation fins are evenly arranged around the outer side surface of the motor body, a liquid cooling pipe is inserted in the heat dissipation fin, the liquid cooling pipe is a heat-conducting hose, both ends of the liquid cooling pipe extend to the outside of the heat dissipation fins, and both ends of the liquid cooling pipe are connected to a micro-stepless speed water pump respectively, the micro-stepless speed water pump is immersed in an external cooling liquid tank, and the external cooling liquid tank is detachably arranged outside the motor body, and the temperature sensor is connected to the micro-stepless speed water pump.

3. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: There are a plurality of Hall sensors, and the Hall sensors are evenly arranged around the rotor in the motor body. A limited position installation groove is arranged inside the motor body corresponding to the position of the Hall sensor.

4. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The power supply circuit includes a main power supply circuit and an auxiliary power supply circuit. The main power supply circuit is connected to a current limiting protection circuit, and the auxiliary power supply circuit is directly connected to a control circuit. The output voltage and current of the auxiliary power supply circuit are less than the voltage and current of the main power supply circuit. The output voltage of the auxiliary power supply circuit is 12V, and the output current of the auxiliary power supply circuit is 1A.

5. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The current limiting protection circuit comprises a constant current module, a filter circuit and a current limiting protector. The filter circuit is connected to the constant current module, and the constant current module is connected to the current limiting protector.

6. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The control circuit comprises a single-chip microcomputer with a built-in control program and an auxiliary power supply module. The single-chip microcomputer and the auxiliary power supply module are connected to each other, and a button battery is detachably installed in the auxiliary power supply module.

7. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The driving unit includes a microchip with a built-in control program, and the microchip is connected to an H-bridge circuit.

8. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The H-bridge circuit includes a control switch Q1, a control switch Q2, a control switch Q3, a control switch Q4, an inductor L and a resistor R. The control switch Q1 and the control switch Q2 are arranged in parallel, one end of the control switch Q1 is connected to one end of the inductor L, one end of the control switch Q2 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are arranged in parallel, one end of the control switch Q3 is connected to one end of the inductor L, one end of the control switch Q4 is connected to the other end of the inductor L, the control switch Q3 and the control switch Q4 are connected in parallel to the resistor R, and one end of the resistor R is grounded.

9. The control mechanism of a single-phase brushless motor without attracting iron powder as claimed in claim 1, characterized in that: The outer side of the stepless speed variable fan is covered with a protective mesh cover, which includes an isolation inner mesh cover and a magnetic outer mesh cover. The isolation inner mesh cover is an insulating plastic mesh cover, and the magnetic outer mesh cover is an electromagnet mesh cover. The magnetic outer mesh cover is detachably arranged on the outside of the isolation inner mesh cover, and the mesh diameter of the magnetic outer mesh cover is larger than the mesh diameter of the isolation inner mesh cover.

10. A single-phase brushless motor control method that does not absorb iron powder, characterized in that: The following steps are included in sequence: Step 1: Start the motor body, the Hall sensor senses the rotor position of the motor body in real time, and the Hall sensor transmits the sensed rotor position information to the control circuit; Step 2: After calculation and analysis, the control circuit transmits the position information to the drive circuit. The drive circuit controls the drive unit to push the start duty cycle according to the position information calculated and analyzed by the control circuit. The drive unit determines whether the full-open speed has been reached. If the full-open speed has not been reached, the duty cycle continues to be pushed. Otherwise, it enters the full-open mode. The entire commutation cycle of the full-open mode follows the frequency of the Hall signal, and the square wave duty cycle is adjusted according to the power size. Step three, chop the waveform of the full-open mode. When the rotor rotates to the position between the two poles of the rotor position signal waveform read by the Hall sensor and the waveform after chopped in the full-open mode, the voltage is chopped to form an instantaneous change in current, so that the magnetic field is weakened to the point where it does not absorb iron powder. Then the strong wind pushed out by the continuously variable speed fan at a high speed blows the iron powder out of the motor body, and each cycle continues to reciprocate.

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