Dynamic balance online detection method of fan

Abstract

A dynamic balance online detection method for a fan is characterized by comprising the steps of detecting A-phase current, B-phase current and C-phase current of a motor of the fan, judging whether the A-phase current crosses zero or not, when the A-phase current crosses zero, calculating the difference between the instantaneous absolute value of the B-phase current and the instantaneous absolute value of the C-phase current, if the difference values are equal, indicating that the dynamic balance of the fan is normal, and if not, indicating that the dynamic balance of the fan is normal. If the difference values are not equal, dynamic balance of the fan is abnormal. The method has the beneficial effects that when the A-phase current of the motor crosses zero, interference generated by power supply voltage fluctuation can be eliminated by comparing instantaneous values of the B-phase current and the C-phase current of the motor, and whether the dynamic balance of the fan is normal or not can be accurately judged; according to the method, the structure of the detection device is simple, and the cost can be reduced; in addition, a pressure sensor is not adopted, the current transformer is adopted, installation and debugging are convenient, and the service life of the current transformer is far longer than that of the pressure sensor.

Description

Technical Field

[0001] The invention relates to an online dynamic balance detection method for a fan. Background Art

[0002] The structure of the direct-drive fan includes a motor and fan blades. The fan blades are installed on a shaft sleeve, and the shaft sleeve is connected to the main shaft of the motor. It has high transmission efficiency.

[0003] When the fan is running, the dust in the air will adhere to the fan blades unevenly. As the running time increases, the dust attached to the fan blades gradually destroys the dynamic balance of the fan, causing the vibration of the motor bearing to gradually increase. Once the vibration reaches the maximum value allowed by the fan, the fan must be shut down for maintenance. The fan vibration can be detected regularly using a handheld vibration measuring instrument. The handheld vibration measuring instrument cannot reflect the vibration of the fan in time. In addition, when the fan is installed at a high position, manual detection is very inconvenient. The fan vibration can also be detected by installing a vibration measuring instrument on the fan for online detection, but the price of the vibration measuring instrument is high, which increases the cost of using the fan. In addition, there are many precautions for installing the sensor of the vibration measuring instrument, which makes it inconvenient to debug the vibration measuring instrument. Summary of the invention

[0004] In view of the above problems, the present invention proposes an online detection method for dynamic balance of a fan. The method has high detection reliability, simple structure, low manufacturing cost and is easy to install and debug.

[0005] The technical solution of the present invention is an online detection method for the dynamic balance of a fan, which is characterized in that the A-phase current, B-phase current and C-phase current of the fan motor are detected to determine whether the A-phase current passes through zero. When the A-phase current passes through zero, the difference between the instantaneous absolute value of the B-phase current and the instantaneous absolute value of the C-phase current is calculated. If the difference is equal, it indicates that the dynamic balance of the fan is normal. If the difference is not equal, it indicates that the dynamic balance of the fan is abnormal.

[0006] The device for implementing the above method includes a first current transformer for detecting the A-phase current IA, a first full-wave rectifier for rectifying the output signal of the first current transformer, a second current transformer for detecting the B-phase current IB, a second full-wave rectifier for rectifying the output signal of the second current transformer, a third current transformer for detecting the C-phase current IC, and a third full-wave rectifier for rectifying the output signal of the third current transformer; The output signal Ia of the first full-wave rectifier is connected to the first input terminal of the 3-to-1 analog switch, the output signal Ib of the second full-wave rectifier is connected to the second input terminal of the 3-to-1 analog switch, and the output signal Ic of the third full-wave rectifier is connected to the third input terminal of the 3-to-1 analog switch; The output end of the 3-to-1 analog switch is connected to the input end of the A / D converter, and the output end of the A / D converter is connected to the input port of the microcontroller; The first output port of the single chip microcomputer is connected to the control port of a 3-to-1 analog switch; The second output port of the single chip microcomputer outputs a signal indicating whether the dynamic balance of the fan is normal; There is a program inside the microcontroller, and its execution steps are: 1. The first output port outputs a control signal to sequentially conduct the first input terminal, the second input terminal, the third input terminal and the output terminal of the 3-to-1 analog switch; during each conduction period, the A / D converter converts the analog signal of the corresponding input terminal into a digital signal and stores it respectively; after the sequential conduction is completed, go to step 2; 2. Read the Ia digital signal. If Ia is not zero, go to the first step. If Ia is zero, read the Ib digital signal and the Ic digital signal, and find the difference between Ib and Ic. If the absolute value of the difference is less than or equal to the set value, the second output port will output 1, indicating that the dynamic balance is normal, and go to step 1; If the absolute value of the difference is greater than the set value, the second output port will output 0, indicating that the dynamic balance is abnormal and the program execution ends.

[0007] Its working principle is that when the dynamic balance of the fan is normal, the amplitudes of the three-phase currents of the motor are equal. When the A-phase current of the motor passes through zero, the instantaneous absolute values ​​of the B-phase current and the C-phase current of the motor are equal, that is, the sum of the instantaneous values ​​of the B-phase current and the C-phase current of the motor is zero; when the dynamic balance of the fan is destroyed, the vibration of the motor bearing increases, the bearing wears, the rotor and the stator are not concentric, the air gap between the rotor and the stator changes periodically or randomly, and the amplitude of the three-phase current of the motor fluctuates. When the A-phase current of the motor passes through zero, the instantaneous absolute values ​​of the B-phase current and the C-phase current of the motor are not equal, that is, when the B-phase current is greater than the reference value, the C-phase current is less than the reference value, and vice versa; when the A-phase current of the motor passes through zero, the instantaneous values ​​of the B-phase current and the C-phase current of the motor are compared to determine whether the dynamic balance of the fan is normal.

[0008] Its beneficial effect is that when the A-phase current of the motor passes through zero, by comparing the instantaneous values ​​of the B-phase current and the C-phase current of the motor, the interference caused by the power supply voltage fluctuation can be eliminated, and it can accurately judge whether the dynamic balance of the fan is normal; this method can simplify the structure of the detection device, which is conducive to reducing costs; in addition, instead of using a pressure sensor, a current transformer is used, which is easy to install and debug, and the service life of the current transformer is much longer than that of the pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a circuit principle block diagram of the present invention.

[0010] Figure 2 for Figure 1 Waveform diagram of relevant points in .

[0011] Figure 3 for Figure 2 Magnified view of section C.

[0012] Figure 4 This is a schematic diagram of the fan structure. DETAILED DESCRIPTION

[0013] The fan comprises a fan blade 1, a shaft sleeve 2, a main shaft 3 and a motor 4. The fan blade is connected to the flange of the shaft sleeve, and the shaft sleeve is connected to the main shaft of the motor.

[0014] The online detection method for the dynamic balance of the fan is to detect the A-phase current, B-phase current and C-phase current of the fan motor, and determine whether the A-phase current passes through zero. When the A-phase current passes through zero, calculate the difference between the instantaneous absolute value of the B-phase current and the instantaneous absolute value of the C-phase current. If the difference is equal, it means that the dynamic balance of the fan is normal. If the difference is not equal, it means that the dynamic balance of the fan is abnormal.

[0015] The device for implementing the above method is as follows Figure 1 As shown, it includes a first current transformer for detecting the A-phase current IA, a first full-wave rectifier for rectifying the output signal of the first current transformer, a second current transformer for detecting the B-phase current IB, a second full-wave rectifier for rectifying the output signal of the second current transformer, a third current transformer for detecting the C-phase current IC, and a third full-wave rectifier for rectifying the output signal of the third current transformer; The output signal Ia of the first full-wave rectifier is connected to the first input terminal of the 3-to-1 analog switch, the output signal Ib of the second full-wave rectifier is connected to the second input terminal of the 3-to-1 analog switch, and the output signal Ic of the third full-wave rectifier is connected to the third input terminal of the 3-to-1 analog switch; The output end of the 3-to-1 analog switch is connected to the input end of the A / D converter, and the output end of the A / D converter is connected to the input port of the microcontroller; The first output port of the single chip microcomputer is connected to the control port of a 3-to-1 analog switch; The second output port of the single chip microcomputer outputs a signal indicating whether the dynamic balance of the fan is normal; There is a program inside the microcontroller, and its execution steps are: 1. The first output port outputs a control signal to sequentially conduct the first input terminal, the second input terminal, the third input terminal and the output terminal of the 3-to-1 analog switch; during each conduction period, the A / D converter converts the analog signal of the corresponding input terminal into a digital signal and stores it respectively; after the sequential conduction is completed, go to step 2; 2. Read the Ia digital signal. If Ia is not zero, go to the first step. If Ia is zero, read the Ib digital signal and the Ic digital signal, and find the difference between Ib and Ic. If the absolute value of the difference is less than or equal to the set value, the second output port will output 1, indicating that the dynamic balance is normal, and go to step 1; If the absolute value of the difference is greater than the set value, the second output port will output 0, indicating that the dynamic balance is abnormal and the program execution ends.

[0016] The output signal of the microcontroller can be used to display the dynamic balance status of the fan and to control the motor.

[0017] The single chip microcomputer model is 89C51, and the 3-to-1 analog switch model is CD4051, which has 8 input terminals, but only 3 are used.

[0018] The detection principle is: When the dynamic balance of the fan is normal, when the A-phase current of the motor passes through zero, the instantaneous values ​​of the B-phase current and the C-phase current of the motor are equal in magnitude and opposite in polarity, and their waveforms are as follows: Figure 2 As shown in a, the waveform after rectification is as follows Figure 2 As shown in b, that is, when Ia is zero, the instantaneous absolute value of Ib is equal to the instantaneous absolute value of Ic.

[0019] After the dynamic balance of the fan is destroyed, the vibration of the motor bearing increases, the bearing wears, the rotor and stator are not concentric, the magnetic field air gap between the rotor and the stator changes periodically or randomly, and the current of each phase of the motor fluctuates, such as Figure 2 c, when Ia is zero, the instantaneous absolute value of Ib is not equal to the instantaneous absolute value of Ic. If Ib increases while Ic decreases, or Ib decreases while Ic increases, the increase is equal to the decrease (e.g. Figure 3 as shown).

[0020] When the A-phase current passes through zero, the instantaneous absolute values ​​of the B-phase current and the C-phase current are compared to determine whether the dynamic balance of the fan is normal; in addition, the interference caused by the fluctuation of the power supply voltage is eliminated, and the judgment is accurate.

[0021] This method uses a current transformer as a sensor. The vibration of the fan has no effect on the service life of the current transformer. However, the sensor of the existing detection device is a pressure sensor. The vibration of the fan will cause fatigue of the pressure sensor and its service life is short. The detection device of this method is installed on the control box of the motor, which is easy to install and debug.

Claims

1. The online detection method for dynamic balance of a fan is characterized by: Detect the A-phase current, B-phase current and C-phase current of the fan motor, and determine whether the A-phase current passes through zero. When the A-phase current passes through zero, calculate the difference between the instantaneous absolute value of the B-phase current and the instantaneous absolute value of the C-phase current. If the difference is equal, it means that the fan dynamic balance is normal. If the difference is not equal, it means that the fan dynamic balance is abnormal.

2. The method for online dynamic balance detection of a fan according to claim 1 is characterized in that: The device for implementing the above method includes a first current transformer for detecting the A-phase current IA, a first full-wave rectifier for rectifying the output signal of the first current transformer, a second current transformer for detecting the B-phase current IB, a second full-wave rectifier for rectifying the output signal of the second current transformer, a third current transformer for detecting the C-phase current IC, and a third full-wave rectifier for rectifying the output signal of the third current transformer; The output signal Ia of the first full-wave rectifier is connected to the first input terminal of the 3-to-1 analog switch, the output signal Ib of the second full-wave rectifier is connected to the second input terminal of the 3-to-1 analog switch, and the output signal Ic of the third full-wave rectifier is connected to the third input terminal of the 3-to-1 analog switch; The output end of the 3-to-1 analog switch is connected to the input end of the A / D converter, and the output end of the A / D converter is connected to the input port of the microcontroller; The first output port of the single chip microcomputer is connected to the control port of a 3-to-1 analog switch; The second output port of the single chip microcomputer outputs a signal indicating whether the dynamic balance of the fan is normal; There is a program inside the microcontroller, and its execution steps are:

1. The first output port outputs a control signal to sequentially conduct the first input terminal, the second input terminal, the third input terminal and the output terminal of the 3-to-1 analog switch; during each conduction period, the A / D converter converts the analog signal of the corresponding input terminal into a digital signal and stores it respectively; after the sequential conduction is completed, go to step 2; 2. Read the Ia digital signal. If Ia is not zero, go to the first step. If Ia is zero, read the Ib digital signal and the Ic digital signal, and find the difference between Ib and Ic. If the absolute value of the difference is less than or equal to the set value, the second output port will output 1, indicating that the dynamic balance is normal, and go to step 1; If the absolute value of the difference is greater than the set value, the second output port will output 0, indicating that the dynamic balance is abnormal and the program execution ends.

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