Rotating speed tracking hardware detection circuit

Abstract

The utility model relates to a rotating speed tracking hardware detection circuit, which comprises a high-precision frequency detection circuit, an anti-interference frequency detection circuit and a DSP control chip, and is characterized in that the high-precision frequency detection circuit comprises a voltage detection circuit which is used for detecting the size relation of any two-phase voltage in a motor, calculating to obtain a motor frequency value and sending the motor frequency value to the DSP control chip; the anti-interference frequency detection circuit comprises a current detection circuit and is used for monitoring the current of the motor in real time, inputting the current value into the DSP control chip to calculate the frequency, calculating the rotating speed torque S by combining the frequency with the current of the motor, and comparing the rotating speed torque S with the current V / F parameter to obtain a final frequency value; and the DSP control chip judges the difference between two frequency values obtained by the high-precision frequency detection circuit and the anti-interference frequency detection circuit, and selects a more suitable frequency value for output according to the difference. The problems of accuracy and stability of motor rotating speed tracking in an electromagnetic interference environment can be well solved, and the current frequency of the motor can be accurately displayed.

Description

Technical Field

[0001] The utility model relates to the technical field of motor speed tracking, in particular to a speed tracking hardware detection circuit. Background Art

[0002] In the field of industrial control, frequency converter is a very important power control device, which is widely used in various mechanical equipment. Frequency converter can control the speed of the motor by changing the power frequency, so as to achieve energy saving and speed regulation. However, in field use, frequency converter is often affected by electromagnetic interference, which leads to performance degradation, false alarm fault, abnormal frequency display and other problems.

[0003] At present, most inverters use separate software tracking or hardware tracking to detect the motor speed. This can meet basic needs in normal use, but when the motor power increases and the electromagnetic interference on site is strong, the use of software tracking or hardware tracking alone will cause the inverter to frequently report false faults or abnormal frequency display. The data obtained by using software speed tracking alone often lacks accuracy, while the data obtained by using hardware tracking alone is easily affected by interference factors such as load changes and power supply fluctuations and lacks stability.

[0004] Therefore, there is an urgent need to provide a speed tracking hardware detection circuit to solve the above problems. Utility Model Content

[0005] The purpose of the utility model is to overcome the deficiencies and defects of the prior art and provide a speed tracking hardware detection circuit, which can effectively improve the accuracy and stability of motor speed detection of the inverter in an electromagnetic interference environment and accurately display the current frequency of the motor.

[0006] The purpose of this utility model is achieved through the following technical solutions:

[0007] A speed tracking hardware detection circuit comprises a high-precision frequency detection circuit, an anti-interference frequency detection circuit and a DSP control chip. The high-precision frequency detection circuit comprises a voltage detection circuit. The current detection circuit is used to detect the magnitude relationship between any two-phase voltages in a motor, calculate the motor frequency value, and send the frequency value to the DSP control chip; the anti-interference frequency detection circuit comprises a current detection circuit. The current detection circuit is used to monitor the current of the motor in real time, input the current value into the DSP control chip to calculate the frequency, and then calculate the speed torque S by combining the frequency with the motor current, and then compare the speed torque S with the current V / F parameter to obtain the final frequency value; the DSP control chip determines the difference between the two frequency values ​​obtained by the high-precision frequency detection circuit and the anti-interference frequency detection circuit, and selects a more suitable frequency value to output according to the difference.

[0008] As a preferred technical solution of the utility model, the voltage detection circuit includes an operational amplifier, a voltage follower, a window comparator and a photoelectric coupler PC9. The operational amplifier is used to compare the voltages of the U phase and the V phase, isolate and buffer the signal through the voltage follower, output the level through the window comparator, and finally transmit the signal to the DSP control chip through the photoelectric coupler PC9.

[0009] As a preferred technical solution of the utility model, the operational amplifier is LM258DR.

[0010] As a preferred technical solution of the utility model, the model of the photoelectric coupler is PC817C.

[0011] As a preferred technical solution of the utility model, the current detection circuit detects the motor current and outputs it to the DSP control chip. The DSP control chip determines the current size including 0<i≤0.5, 0.5<i<rated, i≥rated, 0<i≤0.5 corresponds to output 0Hz, i≥rated corresponds to output 50Hz, and 0.5<i<rated corresponds to output a frequency calculated according to the motor deceleration time and current size.

[0012] As a preferred technical solution of the utility model, the DSP control chip also includes a keyboard communication circuit, and the keyboard communication circuit is electrically connected to the keyboard.

[0013] Compared with the prior art, the utility model has the following beneficial effects:

[0014] The utility model realizes motor speed tracking by using two testing methods, namely, high-precision frequency detection circuit in hardware and anti-interference frequency detection circuit in software, and outputs the motor frequency detected by the appropriate detection method according to the actual situation. It can well solve the accuracy and stability problems of motor speed tracking in electromagnetic interference environment. It enables the frequency converter to work in places with strong interference, reduces the number of motor failures caused by interference, and prolongs the working life of the motor. At the same time, it can adjust the motor speed according to actual needs and reduce the power consumption of the motor, thereby achieving the purpose of energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the principle diagram of the voltage detection circuit of the utility model.

[0016] Figure 2 This is a flowchart of the DSP control chip of the utility model calculating the frequency according to the motor current. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with embodiments and drawings, but the implementation manner of the present invention is not limited thereto.

[0018] The specific implementation process of the utility model is as follows:

[0019] like Figure 1 to Figure 2 As shown, a speed tracking hardware detection circuit includes a high-precision frequency detection circuit, an anti-interference frequency detection circuit and a DSP control chip. The high-precision frequency detection circuit includes a voltage detection circuit. The current detection circuit is used to detect the magnitude relationship between any two-phase voltages in the motor, calculate the motor frequency value, and send the frequency value to the DSP control chip; the anti-interference frequency detection circuit includes a current detection circuit. The current detection circuit is used to monitor the current i of the motor in real time, and input the current value i into the DSP control chip to calculate the frequency, and then calculate the speed torque S by combining the frequency with the motor current i, and then compare the speed torque S with the current V / F parameter to obtain the final frequency value; the DSP control chip determines the difference between the two frequency values ​​obtained by the high-precision frequency detection circuit and the anti-interference frequency detection circuit, and selects a more suitable frequency value to output according to the difference.

[0020] Specifically, the high-precision frequency detection circuit detects the magnitude of any two-phase voltage in the motor through the voltage detection circuit, and then calculates the motor frequency according to the magnitude of the two-phase voltage, thereby obtaining the motor speed. The anti-interference frequency detection circuit detects the magnitude of the motor current i through the current detection circuit, and then transmits it to the DSP control chip to calculate the motor frequency, thereby obtaining the motor speed. The frequency data obtained by the high-precision frequency detection circuit has high accuracy, but weak anti-interference ability. The frequency data obtained by the anti-interference frequency detection circuit has poor accuracy, but strong anti-interference ability. Through the high-precision frequency detection circuit and the anti-interference frequency detection circuit, the DSP control chip can obtain two frequency values. When the two frequency values ​​are not much different, the DSP control chip preferentially outputs the frequency obtained by the speed tracking of the high-precision frequency detection circuit, providing a faster and more stable frequency output; when the difference between the two is large, the DSP control chip will preferentially display the frequency matching the V / F parameter according to the calculation, which can better reflect the actual operation of the motor and avoid speed errors caused by factors such as load changes. The utility model realizes motor speed tracking through two detection methods, hardware and software, and outputs the motor frequency detected by the appropriate detection method according to the actual situation. It can well solve the accuracy and stability problems of motor speed tracking under electromagnetic interference environment. The inverter can operate in places with strong interference, reduce the number of motor failures caused by interference, and extend the working life of the motor. At the same time, the motor speed can be adjusted according to actual needs to reduce the power consumption of the motor, thereby achieving the purpose of energy saving and emission reduction.

[0021] In the embodiments of the present invention, referring to Figure 1 The voltage detection circuit includes operational amplifiers U3A and U3B, a voltage follower, a window comparator and a photocoupler PC9. The operational amplifiers U3A and U3B are used to compare the voltages of the U phase and the V phase, isolate and buffer the signal through the voltage follower, output the level through the window comparator, and finally transmit the signal to the DSP control chip through the photocoupler PC9. Specifically, the utility model inputs any two-phase AC power in the motor into the voltage detection circuit, and the two are sinusoidal waves with a phase difference of 120°. The two-phase AC power input by the utility model is the U phase and the V phase. When the U phase voltage is greater than the V phase, the pin 7 of the operational amplifier U3B outputs a high level VHU+, which is 13V. At this time, the operational amplifier U3B is used as a window comparator, and the operational amplifier U3A is used as a voltage follower to output the output voltage of the pin 7 of the operational amplifier U3B, that is, the pin 1 of the operational amplifier U3A also outputs a high level of 13V. At this time, the photocoupler PC9 is not turned on because both pins 1 and 2 are high levels of 13V, and the voltage difference does not reach 0.7V, that is, the speed tracking signal FCH is a high level of 5V. When the U phase voltage is less than the V phase, the pin 1 of the operational amplifier U3A and the pin 7 of the operational amplifier U3B output a low level VHU-, which is -5V. The voltage difference between pins 1 and 2 of the photocoupler PC9 is (VHU+)-(VHU-)=13-(-5)=18V, the photocoupler PC9 is turned on, and the FCH signal is pulled down to 0V. Therefore, the FCH signal will form a square wave with a certain frequency. By detecting whether the voltage of phase U is greater than that of phase V or the voltage of phase V is greater than that of phase U, and comparing the voltage signals of phase U and phase V, a square wave signal representing the motor speed is generated and transmitted to the DSP control chip for processing, thereby realizing tracking and control of the motor speed through hardware detection.

[0022] Speed ​​tracking is based on the two-phase feedback of the motor for frequency detection. The input voltage of the motor is 380V. Affected by the start-up and running state of the motor, the input voltage will fluctuate to a certain extent. Therefore, the maximum value of the input voltage is 380*(1+10%)=418V. When the motor stops running, the input line will have a surge impact of about 5%. The highest voltage between the U and V phases is 418*(1+5%)=439V. After rectification, this voltage is converted into a DC voltage of about 439*1.414=620V. Use BAV99 clamping diode D40 to limit the input voltage. Clamping diode D40 can clamp the input voltage at ±0.7V. The maximum input voltage of clamping diode D40 is 70V, the maximum current is 200mA, and the working current is 1mA. In order to match the input resistance of the circuit, a 200K ohm, 2010 package resistor is selected in series. At this time, the maximum current flowing through the circuit is about 1.03mA. The power of the resistor is calculated by the formula P = I2 * U, which is 0.2W, and the power of the 2010 package is 0.5W. Capacitor C75 and resistor R87 form a charge and discharge loop, which enables the clamping diode D40 to respond quickly to changes in the motor frequency and protect the components in the circuit from voltage fluctuations.

[0023] In the embodiment of the utility model, the operational amplifier is LM258DR. Specifically, the operational amplifier U3B and the resistor R96 form a comparator. When the voltage of the operational amplifier pin 5 is higher than the voltage of the pin 6, the operational amplifier pin 7 outputs a high level VHU+, which is 13V, and vice versa, it outputs a low level VHU-, which is -5V, thus forming a square wave of the feedback motor frequency. The power supply voltage of LM258DR can be between -16 and 16V, so the power supply voltages of -5V and 13V are consistent. The capacitance of the power supply filter capacitor C74 is selected to be 100nF, and the resistors R85 and R92 are used as input impedances to improve the stability of the operational amplifier, and the resistance value is selected to be 10k.

[0024] In the embodiment of the utility model, the model of the photocoupler PC9 is PC817C. Specifically, the operational amplifier U3A is used as the input voltage of the output pin 3 of the voltage follower, and the photocoupler PC9 is used as an isolation switch to separate the circuit strong current from the weak current, and the frequency of the motor is fed back in real time through the frequency of the switch. The maximum operating current of the PC817C photocoupler PC9 is 50mA, the maximum input voltage is 80V, the input voltage of the photocoupler PC9 is (VHU+)-(VHU-)=13-(-5)=18V, the operating current I=U / R=18 / 5100=3.5mA, the output current I=U / R=5 / 5100=1mA, C55 is a filter capacitor, and the capacitance value is selected as 100nF.

[0025] In the embodiment of the utility model, the motor speed tracking is realized by software by analyzing the stop time of the motor, combining the output current of the motor, and then analyzing the change of the current signal through the DSP control chip to judge the motor speed and load condition, thereby realizing the tracking control of the motor speed. Figure 2 Specifically, the current detection circuit can detect the motor current i in real time, and convert the current value i into a digital signal and input it into the DSP control chip. The DSP control chip determines the magnitude of the current to determine a frequency. When 0<i≤0.5, the corresponding output is 0Hz; when i≥rated, the corresponding output is 50Hz; when 0.5<i<rated, the corresponding output is the frequency calculated according to the motor deceleration time and the magnitude of the current i; then the determined frequency and the motor current i are used to calculate the torque S, and then the obtained torque S is compared and matched with the V / F parameter. The V / F parameter is the ratio of voltage to frequency, which can be calculated based on the voltage and current of the motor. If it matches, the frequency value is output. If it does not match, the frequency is +0.1Hz or -0.1Hz, and then compared. Finally, the corresponding frequency value is obtained and output. At this time, the output frequency value is not much different from the actual frequency of the motor.

[0026] In an embodiment of the utility model, the DSP control chip further includes a keyboard communication circuit, which is electrically connected to a keyboard, and a user can input instructions or parameters through the keyboard to communicate with the DSP control chip. The user can set the target speed of the motor, adjust the motor control parameters, etc. through the keyboard, thereby realizing remote control and adjustment of the motor.

[0027] The above-mentioned embodiments only express the implementation methods of the utility model, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the utility model. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, and these all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A speed tracking hardware detection circuit, It is characterized in that It includes a high-precision frequency detection circuit, an anti-interference frequency detection circuit and a DSP control chip. The high-precision frequency detection circuit includes a voltage detection circuit. The current detection circuit is used to detect the magnitude relationship between any two-phase voltages in the motor, calculate the motor frequency value, and send the frequency value to the DSP control chip; the anti-interference frequency detection circuit includes a current detection circuit. The current detection circuit is used to monitor the current of the motor in real time, and input the current value into the DSP control chip to calculate the frequency, and then calculate the speed torque S by combining the frequency with the motor current, and then compare the speed torque S with the current V / F parameter to obtain the final frequency value; The DSP control chip determines the difference between the two frequency values ​​obtained by the high-precision frequency detection circuit and the anti-interference frequency detection circuit, and selects a more suitable frequency value to output according to the difference.

2. A speed tracking hardware detection circuit according to claim 1, It is characterized in that The voltage detection circuit includes an operational amplifier, a voltage follower, a window comparator and a photoelectric coupler PC. The operational amplifier is used to compare the voltages of the U phase and the V phase, isolate and buffer the signal through the voltage follower, output the level through the window comparator, and finally transmit the signal to the DSP control chip through the photoelectric coupler.

3. A speed tracking hardware detection circuit according to claim 2, It is characterized in that The operational amplifier is LM258DR.

4. A speed tracking hardware detection circuit according to claim 2, It is characterized in that The model of the photoelectric coupler is PC817C.

5. A speed tracking hardware detection circuit according to claim 1, It is characterized in that The current detection circuit detects the motor current and outputs it to the DSP control chip. The DSP control chip determines the current size including 0<i≤0.5, 0.5<i<rated, i≥rated, 0<i≤0.5 corresponds to output 0Hz, i≥rated corresponds to output 50Hz, 0.5<i<rated corresponds to output the frequency calculated according to the motor deceleration time and current size.

6. A speed tracking hardware detection circuit according to claim 1, It is characterized in that The DSP control chip also includes a keyboard communication circuit, and the keyboard communication circuit is electrically connected to the keyboard.

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