A variable frequency motor rotating speed and direction measuring system and measuring method

Abstract

The application discloses a variable frequency motor rotating speed and direction measuring system and a measuring method. The measuring system comprises a driving power supply, a first sampling branch and a second sampling branch, the input ends of the first sampling branch and the second sampling branch are connected with a first phase power line and a second phase power line respectively, the first sampling branch and the second sampling branch comprise a current-voltage conversion unit, an amplification filtering unit and a square wave rectification unit connected in sequence respectively, the square wave rectification unit rectifies and outputs a unipolar pulse wave signal, a single-chip microcomputer collects a first pulse wave signal output by the first sampling branch and a second pulse wave signal output by the second sampling branch in a digital filtering mode by using an ADC mode, and obtains a first digital sequence and a second digital sequence, and the single-chip microcomputer obtains the rotating speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence. The application can directly use the electric signal of the driving power supply to measure the rotating speed and direction of the motor, and the environment is simple to construct and has good consistency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of variable frequency motor parameter measurement, in particular to a variable frequency motor rotating speed and direction measurement system and method. BACKGROUND

[0002] The variable frequency motor is a motor device commonly used in household appliances (for example, air conditioners, refrigerators, etc.), and its running speed and direction are the core embodiment of product function. Therefore, it is important to measure the rotating speed and direction of the variable frequency motor.

[0003] Conventionally, the rotating speed and direction of the variable frequency motor are measured mainly by subjective judgment and photoelectric speed measurement (for example, using a photoelectric speed measurement device to measure the exposed rotating shaft of the variable frequency motor), or by using a dedicated vibration sensor (for example, using a vibration sensor to detect the compressor shell to measure the rotating speed of the motor inside the compressor), etc. The measurement process is complex and involves hardware investment, which is costly and inconsistent in environmental construction, making measurement difficult. SUMMARY

[0004] To solve the above technical problems, the embodiments of the present application provide a variable frequency motor rotating speed and direction measurement system, which directly uses the electrical signal of the driving power supply to measure the rotating speed and direction of the motor, and has simple and consistent environmental construction, low cost and easy implementation, and meets the measurement needs of various variable frequency motors.

[0005] The embodiments of the present application are implemented by using the following technical solutions:

[0006] The present application provides a variable frequency motor rotating speed and direction measurement system, characterized by comprising:

[0007] A driving power supply provides a three-phase power supply for the variable frequency motor;

[0008] A first sampling branch and a second sampling branch, the input end of the first sampling branch is connected to the first phase power line of the variable frequency motor, the input end of the second sampling branch is connected to the second phase power line of the variable frequency motor, and the first sampling branch and the second sampling branch respectively comprise a current-voltage conversion unit, an amplification filter unit and a square wave rectification unit connected in sequence, wherein the square wave rectification unit rectifies a unipolar pulse wave signal;

[0009] A single-chip microcomputer collects the first pulse wave signal output by the first sampling branch and the second pulse wave signal output by the second sampling branch in a digital filtering manner by using ADC, to obtain a first digital sequence corresponding to the first pulse wave signal and a second digital sequence corresponding to the second pulse wave signal;

[0010] The single-chip microcomputer obtains the rotating speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence.

[0011] In the embodiment of the application, the current-voltage conversion unit is any one of a resistor, a current transformer or a Hall element.

[0012] In the embodiment of the application, the amplification filtering unit is a differential amplification filtering circuit, which is configured to amplify and filter the voltage signal output by the current-voltage conversion unit.

[0013] In the embodiment of the application, the single-chip microcomputer obtains the rotating speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence, specifically:

[0014] According to the first digital sequence and the second digital sequence, the frequency of the variable frequency motor is obtained.

[0015] According to the frequency, the rotating speed of the variable frequency motor is obtained.

[0016] According to the predetermined direction, the levels of the first group of collection points in the first digital sequence and the levels of the corresponding second group of collection points in the second digital sequence, the direction of the variable frequency motor is obtained.

[0017] In the embodiment of the application, the levels of the corresponding second group of collection points in the second digital sequence are determined as follows:

[0018] When the first group of collection points are falling edges or rising edges respectively, if the number of collection points with high levels at the second group of collection points is greater than the value M, it indicates that the levels at the second group of collection points are high.

[0019] When the first group of collection points are falling edges or rising edges respectively, if the number of collection points with low levels at the second group of collection points is greater than the value M, it indicates that the levels at the second group of collection points are low.

[0020] The value M is the integer part of the quotient of the total number of collection points and 2.

[0021] In the embodiment of the application, the measurement system further comprises:

[0022] The upper computer is in communication connection with the single-chip microcomputer, and is configured to receive the rotating speed and direction information output by the single-chip microcomputer.

[0023] The upper computer draws and displays the state curve of the running process of the variable frequency motor.

[0024] The variable frequency motor rotating speed and direction measurement system disclosed in the application has the following advantages and beneficial effects:

[0025] (1) directly sampling two-phase current of a driving power supply of the variable frequency motor to obtain a driving source of variable frequency speed regulation of the variable frequency motor, so that the most direct electrical signal data of variable frequency speed regulation of the variable frequency motor can be obtained, and reliable rotation speed and direction information can be obtained;

[0026] (2) the measurement system adopts a modular combination of a simple circuit, has good environmental construction consistency, is low in cost and easy to implement, and meets the measurement requirements of various variable frequency motors;

[0027] (3) the non-ideal waveform is pre-shaped by using an amplification filtering circuit and a square wave shaping circuit, then reliable data is obtained by digital filtering after single-chip microcomputer ADC sampling, the simple combination effect is multiplied, and the application capability of the measurement system is further improved;

[0028] (4) the measurement system can simultaneously realize speed measurement and direction measurement, and is convenient for comprehensively analyzing the variable frequency motor.

[0029] Embodiments of the present application also provide a variable frequency motor rotation speed and direction measurement method, which can measure the rotation speed and direction of the variable frequency motor by obtaining the direct driving current of the variable frequency motor, meet the measurement requirements of various variable frequency motors, and has simple and uniform environmental construction, is easy to implement and low in cost.

[0030] The present application provides a variable frequency motor rotation speed and direction measurement method, comprising the following steps:

[0031] obtaining a first voltage signal of a first-phase current and a second voltage signal of a second-phase current in the variable frequency motor;

[0032] amplifying and filtering the first voltage signal and the second voltage signal respectively;

[0033] shaping the amplified and filtered first voltage signal and second voltage signal respectively to obtain a first unipolar pulse wave signal corresponding to the first voltage signal and a second unipolar pulse wave signal corresponding to the second voltage signal;

[0034] collecting the first pulse wave signal and the second pulse wave signal by digital filtering in an ADC mode to obtain a first digital sequence corresponding to the first pulse wave signal and a second digital sequence corresponding to the second pulse wave signal;

[0035] obtaining the rotation speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence.

[0036] In the embodiments of the present application, the rotation speed and direction of the variable frequency motor are obtained according to the first digital sequence and the second digital sequence, specifically:

[0037] According to the first digital sequence and the second digital sequence, a frequency of the variable frequency motor is acquired;

[0038] According to the frequency, a rotating speed of the variable frequency motor is acquired;

[0039] According to the predetermined direction, the levels at the first groups of collection points in the first digital sequence and the levels at the corresponding second groups of collection points in the second digital sequence, a direction of the variable frequency motor is acquired.

[0040] In the embodiments of the present application,

[0041] The levels at the corresponding second groups of collection points in the second digital sequence are determined in the following manner:

[0042] When the first groups of collection points are falling edges or rising edges respectively, if the number of collection points with high levels at the second groups of collection points is greater than a value M, it indicates that the levels at the second groups of collection points are high levels;

[0043] When the first groups of collection points are falling edges or rising edges respectively, if the number of collection points with low levels at the second groups of collection points is greater than the value M, it indicates that the levels at the second groups of collection points are low levels;

[0044] The value M is an integer value of a quotient of a total number of collection points and 2.

[0045] In the embodiments of the present application, the measurement method further comprises:

[0046] The communication receives the rotating speed and direction information of the variable frequency motor;

[0047] The running process state curve of the variable frequency motor is drawn and displayed.

[0048] Other features and advantages of the present application will become more apparent after reading the detailed description of the application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0050] Figure 1 A principle block diagram of an embodiment of the variable frequency motor rotating speed and direction measurement system proposed in the present application;

[0051] Figure 2 A voltage waveform diagram acquired by a current collection unit in an embodiment of the variable frequency motor rotating speed and direction measurement system proposed in the present application;

[0052] Figure 3 The amplification filter unit obtains a certain phase voltage waveform chart in the embodiment of the variable frequency motor speed and direction measurement system of the present application;

[0053] Figure 4 The square wave trimming unit obtains a two-phase voltage waveform chart in the embodiment of the variable frequency motor speed and direction measurement system of the present application;

[0054] Figure 5 The flow chart of the embodiment of the variable frequency motor speed and direction measurement method of the present application;

[0055] Figure 6 The principle block diagram of another embodiment of the variable frequency motor speed and direction measurement system of the present application;

[0056] Figure 7 The partial operation process state curve drawn and displayed by the host computer in another embodiment of the variable frequency motor speed and direction measurement system of the present application.

[0057] Reference signs:

[0058] 10 - driving power supply; 20 - first sampling branch; 21 - first current-voltage conversion unit 21; 22 - first amplification filter unit; 23 - first square wave trimming unit; 30 - second sampling branch; 31 - second current-voltage conversion unit; 32 - second amplification filter unit; 33 - second square wave trimming unit; 40 - single-chip microcomputer; 50 - host computer. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the drawings and embodiments.

[0060] It should be noted that in the description of the present application, the terms of direction or position relationship indicated by the terms of "inner", "outer", "upper", "lower", "left", "right", "front", "back" and the like are based on the direction or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0061] In the description of the present application, it is necessary to point out that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In the description of the above embodiments, the specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0062] The terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "multiple" is two or more.

[0063] In order to construct a component environment unified system for measuring the speed and direction of a variable frequency motor, the present application relates to a variable frequency motor speed and direction measurement system.

[0064] Referring to Figure 1 The measurement system of the present application comprises a driving power supply 10, a first sampling branch 20, a second sampling branch 30 and a single-chip microcomputer 40.

[0065] Figure 5 The measurement system shown is based on Figure 1 The measurement method for measuring the speed and direction of a variable frequency motor is shown based on the measurement system, so that the measurement system can be combined Figure 1 and Figure 5 The present application is jointly described.

[0066] The driving power supply 10 can provide three-phase power supply for the variable frequency motor.

[0067] In the present application, the driving power supply 10 is a dedicated variable frequency power supply. The variable frequency power supply converts the alternating current in the commercial power supply into a pure sine wave through AC→DC→AC conversion, and the output frequency and voltage are adjustable within a certain range. The variable frequency power supply is very close to an ideal alternating current power supply. The characteristics of the ideal alternating current power supply are stable frequency, stable voltage, internal resistance equal to zero, and voltage waveform is a pure sine wave (without distortion).

[0068] A dedicated variable frequency power supply is used to power the variable frequency motor to ensure the accuracy of the power supply signal input.

[0069] The first sampling branch 20 and the second sampling branch 30 are two parallel sampling branches, which have the same structure and respectively comprise a current-voltage conversion unit, an amplification filter unit and a square wave rectification unit connected in sequence.

[0070] The first sampling branch 20 comprises a first current-voltage conversion unit 21, a first amplification filter unit 22 and a first square wave trimming unit 23 connected in sequence, and the input end of the first sampling branch 20 is the input end of the first current-voltage conversion unit 21.

[0071] The second sampling branch 30 comprises a second current-voltage conversion unit 31, a second amplification filter unit 32 and a second square wave trimming unit 33 connected in sequence, and the input end of the second sampling branch 30 is the input end of the second current-voltage conversion unit 31.

[0072] The input end of the first current-voltage conversion unit 21 is connected to the first phase power line (for example, the U phase) of the variable frequency motor, the output end is connected to the input end of the first amplification filter unit 22, the output end of the first amplification filter unit 22 is connected to the input end of the first square wave trimming unit 23, and the output end of the first square wave trimming unit 23 is connected to the single-chip microcomputer 40.

[0073] The input end of the second current-voltage conversion unit 31 is connected to the second phase power line (for example, the V phase) of the variable frequency motor, the output end is connected to the input end of the second amplification filter unit 32, the output end of the second amplification filter unit 32 is connected to the input end of the second square wave trimming unit 33, and the output end of the second square wave trimming unit 33 is connected to the single-chip microcomputer 40.

[0074] S1: Obtain a first voltage signal of a first phase current and a second voltage signal of a second phase current in the variable frequency motor.

[0075] The first current-voltage conversion unit 21 and the second current-voltage conversion unit 31 can adopt the same circuit structure, which is used to respectively convert the collected U phase / V phase phase current into the first voltage signal / second voltage signal.

[0076] In the present application, the first current-voltage conversion unit 21 and the second current-voltage conversion unit 31 with the same structure are selected.

[0077] As follows, the structure of the first current-voltage conversion unit 21 is taken as an example for description.

[0078] The first current-voltage conversion unit 21 can select any one of the existing multiple implementation forms, for example, a sampling resistor, a current transformer, a Hall element.

[0079] In the present application, the first current-voltage conversion unit 21 selects a general Hall sensor, which does not require high precision and high transformation ratio. For small current, the connected power line can be wound several more turns to improve the collection effect of the Hall sensor.

[0080] Referring to Figure 2Fig. 2 shows a voltage waveform of the first voltage signal corresponding to the phase current collected by the first current-voltage conversion unit 21.

[0081] From Figure 2 It can be seen that the Hall sensor obtains an AC weak signal, and a voltage signal of about tens of millivolts is obtained through the sampling resistor, and a serious interference signal is also obtained.

[0082] S2: respectively amplify and filter the first voltage signal and the second voltage signal.

[0083] The first amplification and filtering unit 22 and the second amplification and filtering unit 32 can adopt the same circuit structure, which is used to amplify and filter the converted first voltage signal and second voltage signal.

[0084] In this application, the first amplification and filtering unit 22 and the second amplification and filtering unit 32 with the same structure are selected.

[0085] As follows, the structure of the first amplification and filtering unit 22 is taken as an example for description.

[0086] The first amplification and filtering unit 22 can adopt the selected existing various implementation manners, such as a differential amplification and filtering circuit, a filtering and conditioning circuit, and a general filtering and amplification circuit, wherein the differential amplification and filtering circuit, the filtering and conditioning circuit, and the general filtering and amplification circuit can be built by using operational amplifiers, resistors, and capacitors, and the purpose is to amplify a weak signal and filter an interference signal.

[0087] In this application, the first amplification and filtering unit 22 adopts a differential amplification and filtering circuit, which is used to filter and reduce differential mode and common mode interference, and amplify a signal.

[0088] Referring to Figure 3 Fig. 4 shows a voltage waveform of the first voltage signal processed by the first amplification and filtering unit 22. Figure 2

[0089] From Figure 3 It can be seen that the signal processed by the first amplification and filtering unit 22 is relatively clean and the amplitude reaches an AC signal of, for example, 5V or less.

[0090] Of course, the amplitude size is related to the specific structure of the selected first amplification and filtering unit 22, which is not limited here.

[0091] S3: respectively modify the amplified and filtered first voltage signal and second voltage signal to obtain a single-polarity first pulse wave signal and a single-polarity second pulse wave signal.

[0092] ​To ensure that the current driving the variable frequency motor is within its operating range, an effective signal can be obtained, and thus the first voltage signal and the second voltage signal after amplification and filtering are respectively modified. Therefore, the first square wave modification unit 23 and the second square wave modification unit 33 are provided.

[0093] The first square wave modification unit 23 and the second square wave modification unit 33 can have the same circuit structure, which is used to square wave modify the amplified and filtered signals to obtain unipolar pulse wave signals, facilitating subsequent sampling by the single-chip microcomputer 40 in an ADC manner.

[0094] That is, the first square wave modification unit 23 and the second square wave modification unit 33 are respectively used to half-wave rectify the amplified and filtered first voltage signal and second voltage signal, and output pulse wave signals of positive half cycles or negative half cycles.

[0095] In the present application, the first square wave modification unit 23 and the second square wave modification unit 33 having the same structure are selected.

[0096] As follows, the structure of the first square wave modification unit 23 is taken as an example for description.

[0097] The first square wave modification unit 23 can be implemented in various ways, such as using a diode to build a half-wave rectification circuit, using an optical coupler isolator to build a half-wave rectification circuit, using a triode to build a half-wave rectification circuit, or using a hysteresis comparator, or using a voltage comparator to obtain the modified unipolar square wave signal.

[0098] The voltage amplitude of the output square wave signal should meet the high and low digital level definition of the subsequent single-chip microcomputer 40.

[0099] In the present application, the modified two-phase voltage waveform selects the pulse wave signal of the positive half cycle.

[0100] Referring to Figure 4 , which shows the two-phase voltage waveform output synchronously after processing by the first square wave modification unit 23 and the second square wave modification unit 33.

[0101] The pulse wave signal of the positive half cycle of the modified two-phase voltage waveform is respectively denoted as a first pulse wave signal and a second pulse wave signal, referring to Figure 4 .

[0102] In this way, the unipolar first pulse wave signal corresponding to the first voltage signal is obtained through the first sampling branch 20 as described above, and the unipolar second pulse wave signal corresponding to the second voltage signal is obtained through the second sampling branch 30 as described above.

[0103] S4: Collecting the first pulse wave signal and the second pulse wave signal respectively by using digital filtering in an ADC mode to obtain a first digital sequence and a second digital sequence.

[0104] Because the current sampling by using the Hall sensor has a very serious interference, even after being amplified and filtered by the amplification and filtering unit, there is still a large amount of interference, so the single-chip microcomputer 40 needs to use an effective sampling scheme to effectively and accurately collect the first pulse wave signal and the second pulse wave signal.

[0105] In the present application, the single-chip microcomputer 40 collects the first pulse wave signal and the second pulse wave signal by using digital filtering in an ADC mode.

[0106] The mode of digital filtering mainly uses the mode of taking the average value of multiple collected samples as the sampling value to filter the interference to a certain extent and improve the reliability of data collection, and also provides reliability for later data analysis.

[0107] In an embodiment, for the first pulse wave signal and the second pulse wave signal, the single-chip microcomputer 40 synchronously collects a plurality of times (for example, 10 times, 100 times) by using digital filtering in an ADC mode at a certain interval (for example, 9 μs) for the first pulse wave signal and the second pulse wave signal, respectively, as the sampling value of the current sampling, and the above process is continuously performed in a cycle.

[0108] In this way, the first digital sequence corresponding to the first pulse wave signal and the second digital sequence corresponding to the second pulse wave signal are obtained.

[0109] In an alternative embodiment, the sampling can also be performed in the following manner.

[0110] For the first pulse wave signal and the second pulse wave signal, the single-chip microcomputer 40 synchronously collects a plurality of times (for example, 10 times) by using digital filtering in an ADC mode at a first interval (for example, 9 μs) for the first pulse wave signal and the second pulse wave signal, respectively, as the sampling value of the current sampling, and the above sampling process is continuously performed in a cycle.

[0111] In this way, the first collection result corresponding to the first pulse wave signal and the second pulse wave signal is obtained.

[0112] And for the first collection result, the single-chip microcomputer 40 synchronously collects a plurality of times (for example, 15 times) by using digital filtering in an ADC mode at a second interval (for example, 9 μs, 10 μs) for the first collection result corresponding to the first pulse wave signal and the second pulse wave signal, respectively, as the sampling value of the current sampling, and the above process is continuously performed in a cycle.

[0113] In this way, the second collection result corresponding to the first collection result is obtained.

[0114] The second acquisition result corresponding to the first pulse wave signal is taken as a first digital sequence, and the second acquisition result corresponding to the second pulse wave signal is taken as a second digital sequence.

[0115] As described above, the voltage signals of the first pulse wave signal and the second pulse wave signal are accurately sampled by means of digital filtering, and ideal digital results, i.e., the first digital sequence and the second digital sequence, are obtained.

[0116] The numerical values of the first digital sequence and the second digital sequence can be stored in a digital array memory for calling.

[0117] S5: According to the first digital sequence and the second digital sequence, the speed and direction of the variable frequency motor are obtained.

[0118] The single-chip microcomputer 40 can calculate the speed and direction information of the variable frequency motor according to the obtained first digital sequence and second digital sequence. Details are described as follows.

[0119] The sampling module including the first sampling branch 20, the second sampling branch 30 and the single-chip microcomputer 40 is combined by using conventional circuits, and has good environmental consistency, simple wiring and easy implementation, and can meet the measurement requirements of various variable frequency motors; the digital filtering design in the single-chip microcomputer 40 can process the non-ideal waveform obtained by the simple hardware circuit into an ideal waveform, effectively achieving the purpose of effect multiplication.

[0120] In addition, the measurement system can simultaneously realize the speed and direction measurement requirements of the variable frequency motor. The specific speed and direction measurement process is described as follows.

[0121] As described above, the first digital sequence and the second digital sequence describe the relationship between the sampling time and the sampling voltage, so the frequency and phase difference of the variable frequency motor can be easily obtained.

[0122] Based on the relationship between the frequency and the speed, the speed of the variable frequency motor can be easily obtained according to the frequency of the variable frequency motor.

[0123] Considering that the phase difference may be disturbed, when measuring the direction, the level change between the multiple acquisition points in the first digital sequence (referred to as the first group of acquisition points) and the corresponding multiple acquisition points in the second digital sequence (referred to as the second group of acquisition points) is used to obtain the direction of the variable frequency motor.

[0124] The number of acquisition points in the first group of acquisition points is equal to the number of acquisition points in the second group of acquisition points, and each acquisition point in the first group of acquisition points corresponds in time to each acquisition point in the second group of acquisition points.

[0125] Since the direction is relative, the variable frequency motor can rotate clockwise / counterclockwise or forward / reverse, thus the motor direction can be determined in combination with the specified direction.

[0126] The specified direction can be: when the voltage signal collected at the first group of collection points is high at the rising edge and the voltage signal collected at the second group of collection points is low, the variable frequency motor is specified as forward; and when the voltage signal collected at the first group of collection points is high at the rising edge and the voltage signal collected at the second group of collection points is high, the variable frequency motor is specified as reverse.

[0127] For the purpose of convenient description, this case can be simply recorded as: A+B- is forward and A+B+ is reverse.

[0128] The direction can also be specified as follows: when the voltage signal collected at the first group of collection points is low at the falling edge and the voltage signal collected at the second group of collection points is high, the variable frequency motor is specified as forward; and when the voltage signal collected at the first group of collection points is low at the falling edge and the voltage signal collected at the second group of collection points is low, the variable frequency motor is specified as reverse.

[0129] Similarly, this case can be simply recorded as A-B+ is forward and A-B- is reverse.

[0130] In an embodiment, the direction determination of the variable frequency motor is described taking A+B- as forward and A+B+ as reverse as an example.

[0131] As described above, the obtained first digital sequence and second digital sequence are respectively the pulse wave signals filtered by the digital filter, thus the first group of collection points (the total number of collection points is N, and N>3) in the first digital sequence can be selected as the rising edge (i.e. high level) at different times, and the levels at the second group of collection points (the number is also N) in the second digital sequence are obtained.

[0132] If at the rising edge (high level L) of each collection point in the first group of collection points, the number of collection points in the second group of collection points corresponding to the high level is N1 (i.e. the high level collected by N1 points does not exist level change relative to the high level L), and the number of collection points in the second group of collection points corresponding to the low level is N2 (i.e. the low level collected by N2 points exists level change relative to the high level H).

[0133] Wherein, N1+N2=N, and M is the integer value of the quotient of N / 2.

[0134] When the rising edges of the voltage signals at the first group of sampling points are at different times, and the number N1 (i.e., the number of sampling points without level change) is greater than M, it is the case of A+B+, which is consistent with the level change trend in the specified reverse direction (i.e., A+B+), and thus, the direction of the variable frequency motor is the reverse direction.

[0135] When the rising edges of the voltage signals at the first group of sampling points are at different times, and the number N2 (i.e., the number of sampling points with level change) is greater than M, it is the case of A+B-, which is consistent with the level change trend in the specified forward direction (i.e., A+B-), and thus, the direction of the variable frequency motor is the forward direction.

[0136] The direction can also be specified as follows: when the voltage signals at the first group of sampling points are high at the rising edges, and the voltage signals at the second group of sampling points are low, the variable frequency motor is specified as the reverse direction; and when the voltage signals at the first group of sampling points are high at the rising edges, and the voltage signals at the second group of sampling points are high, the variable frequency motor is specified as the forward direction.

[0137] Similarly, this case can be simply noted as A+B+ for the forward direction and A+B- for the reverse direction.

[0138] The direction can also be specified as follows: when the voltage signals at the first group of sampling points are low at the falling edges, and the voltage signals at the second group of sampling points are high, the variable frequency motor is specified as the reverse direction; and when the voltage signals at the first group of sampling points are low at the falling edges, and the voltage signals at the second group of sampling points are low, the variable frequency motor is specified as the forward direction.

[0139] Similarly, this case can be simply noted as A-B- for the forward direction and A-B+ for the reverse direction.

[0140] In an embodiment, the direction determination formula of the variable frequency motor is described by taking A-B- for the forward direction and A-B+ for the reverse direction as an example.

[0141] As described above, the obtained first digital sequence and second digital sequence are the pulse wave signals filtered by the digital filter, and thus, the first group of sampling points (the total number of sampling points is N, and N>3) in the first digital sequence can be selected as the falling edges (i.e., low) at different times, and the levels at the second group of sampling points (the number is also N) in the second digital sequence are obtained.

[0142] If the number of the collection points in the second group of collection points whose corresponding levels are high at the falling edge (i.e., low level L) of each collection point in the first group of collection points is N1 (i.e., the high level of N1 points changes relative to the low level L), and the number of the collection points in the second group of collection points whose corresponding levels are low is N2 (i.e., the low level of N2 points does not change relative to the low level L).

[0143] wherein N1+N2=N, and M is the integer part of N / 2.

[0144] If each collection point in the first group of collection points is a falling edge (i.e., low level L) at different times, and the number N1 (i.e., the number of collection points with level change) is greater than M, it is the case of A-B+, which is consistent with the level change trend in the specified reverse direction (i.e., A-B+). Therefore, at this time, the direction of the variable frequency motor is the reverse direction.

[0145] If each collection point in the first group of collection points is a falling edge (i.e., low level L) at different times, and the number N2 (i.e., the number of collection points with no level change) is greater than M, it is the case of A-B-, which is consistent with the level change trend in the specified forward direction (i.e., A-B-). Therefore, at this time, the direction of the variable frequency motor is the forward direction.

[0146] It should be noted that the forward direction and the reverse direction of the variable frequency motor are relative.

[0147] If the number N1 / N2 is equal to M, the first group of collection points and the second group of collection points can be reselected for level judgment.

[0148] Using this statistical number to determine the direction can filter out interference to some extent and improve the direction-finding accuracy of the variable frequency motor.

[0149] The sampling module described above can be used for sampling both the variable frequency motor with exposed shaft (e.g., for a washing machine) and the variable frequency motor without exposed shaft (e.g., for a compressor), and only two driving power supply lines are needed, without the need for complex environmental construction. Compared with other sampling methods, it is simpler and more direct, and the data processing method is also easy to implement, avoiding the cumbersome problem of waveform processing and calculation in the later stage caused by sampling PMW driving voltage.

[0150] Referring to Figure 6 which shows another embodiment of the measurement system.

[0151] In addition to the driving power supply 10 and the sampling module as described above, the measurement system also includes an upper computer 50 for monitoring the running process state of the variable frequency motor.

[0152] The host computer 50 is in communication connection with the single-chip microcomputer 40, and receives the rotating speed and direction information of the variable frequency motor uploaded by the single-chip microcomputer 40.

[0153] By flexibly configuring the pole pair number and speed ratio of the variable frequency motor in the host computer 50, and combining the rotating speed and direction information of the variable frequency motor uploaded by the single-chip microcomputer 40, the running process state curve of the variable frequency motor is drawn and displayed, and the complete running measurement of the variable frequency motor is completed.

[0154] Referring to Figure 7 which shows the running process state curve drawn by the host computer 50 after analyzing the data.

[0155] In the running process state curve, the horizontal axis represents time (unit: s), and the vertical axis represents the rotating speed of the motor (unit: rpm).

[0156] Through the curve display on the host computer 50, the user can intuitively view the current running state of the variable frequency motor, and understand the running condition of the variable frequency motor.

[0157] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by the equivalent; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the present application.

Claims

1. A system for measuring the speed and direction of rotation of a variable frequency motor, comprising: The measurement system comprises: a dedicated variable frequency power supply providing three-phase power supply for a variable frequency motor; a first sampling branch and a second sampling branch, an input end of the first sampling branch being connected to a first phase power line of the variable frequency motor, an input end of the second sampling branch being connected to a second phase power line of the variable frequency motor, the first sampling branch and the second sampling branch each comprising a current-voltage conversion unit, an amplification filtering unit and a square wave rectification unit connected in sequence, wherein the square wave rectification unit rectifies an output pulse wave signal of single polarity; a single-chip microcomputer which collects a first pulse wave signal output by the first sampling branch and a second pulse wave signal output by the second sampling branch in an ADC manner by using digital filtering; for the first pulse wave signal and the second pulse wave signal, the single-chip microcomputer synchronously collects the first pulse wave signal and the second pulse wave signal in an ADC manner by using digital filtering for a plurality of times at a first interval of time in a cycle, and obtains a first collection result corresponding to the first pulse wave signal and the second pulse wave signal, respectively; for the first collection result, the single-chip microcomputer synchronously collects the first collection result corresponding to the first pulse wave signal and the second pulse wave signal in an ADC manner by using digital filtering for a plurality of times at a second interval of time in a cycle, and obtains a second collection result corresponding to the first collection result, respectively; the second collection result corresponding to the first pulse wave signal is taken as a first digital sequence, and the second collection result corresponding to the second pulse wave signal is taken as a second digital sequence; the single-chip microcomputer obtains the speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence.

2. The measurement system according to claim 1, wherein the current-voltage conversion unit is any one of a resistor, a current transformer or a Hall element.

3. The measurement system according to claim 1, wherein the amplification filtering unit is a differential amplification filtering circuit for amplifying and filtering a voltage signal output by the current-voltage conversion unit.

4. The measurement system of claim 1, wherein, the single-chip microcomputer obtains the speed and direction of the variable frequency motor according to the first digital sequence and the second digital sequence, specifically: obtaining the frequency of the variable frequency motor according to the first digital sequence and the second digital sequence; obtaining the speed of the variable frequency motor according to the frequency; obtaining the direction of the variable frequency motor according to a predetermined direction, the levels of a plurality of first group of collection points in the first digital sequence and the levels of a corresponding second group of collection points in the second digital sequence; wherein the plurality of first group of collection points are falling edges or rising edges, respectively.

5. The measurement system of claim 4, wherein, the levels of the corresponding second group of collection points in the second digital sequence are determined as follows: when the plurality of first group of collection points are falling edges or rising edges, respectively, if the number of collection points with high levels at the second group of collection points is greater than a value M, it indicates that the levels at the second group of collection points are high; when the plurality of first group of collection points are falling edges or rising edges, respectively, if the number of collection points with low levels at the second group of collection points is greater than the value M, it indicates that the levels at the second group of collection points are low; wherein the value M is an integer value obtained by dividing the total number of collection points by 2.

6. The measurement system of any one of claims 1 to 5, wherein, The measurement system further comprises: An upper computer is in communication connection with the single-chip microcomputer, and is used for receiving the rotating speed and direction information output by the single-chip microcomputer; The upper computer draws and displays the state curve of the running process of the variable frequency motor.

7. A method of measuring the speed and direction of rotation of a variable frequency motor, characterized by, The method comprises the following steps: A dedicated variable frequency power supply provides three-phase power supply for the variable frequency motor; A first voltage signal of a first phase current and a second voltage signal of a second phase current in the variable frequency motor are acquired; The first voltage signal and the second voltage signal are respectively amplified and filtered; The first voltage signal and the second voltage signal after amplification and filtering are respectively rectified to acquire a first pulse wave signal of single polarity corresponding to the first voltage signal and a second pulse wave signal of single polarity corresponding to the second voltage signal; For the first pulse wave signal and the second pulse wave signal, the single-chip microcomputer synchronously collects the first pulse wave signal and the second pulse wave signal in the ADC mode for a plurality of times at a first interval of a first period, and acquires a first collection result corresponding to the first pulse wave signal and the second pulse wave signal respectively; For the first collection result, the single-chip microcomputer synchronously collects the first collection result corresponding to the first pulse wave signal and the second pulse wave signal in the ADC mode for a plurality of times at a second interval of a second period, and acquires a second collection result corresponding to the first collection result; The second collection result corresponding to the first pulse wave signal is taken as a first digital sequence, and the second collection result corresponding to the second pulse wave signal is taken as a second digital sequence; The rotating speed and direction of the variable frequency motor are acquired according to the first digital sequence and the second digital sequence.

8. The measurement method according to claim 7, wherein The rotating speed and direction of the variable frequency motor are acquired according to the first digital sequence and the second digital sequence, specifically as follows: The frequency of the variable frequency motor is acquired according to the first digital sequence and the second digital sequence; The rotating speed of the variable frequency motor is acquired according to the frequency; The direction of the variable frequency motor is acquired according to the specified direction, the levels of a plurality of first collection points in the first digital sequence, and the levels of a plurality of second collection points in the second digital sequence; When the plurality of first collection points are falling edges or rising edges, if the number of collection points with high levels at the second collection points is greater than a value M, it indicates that the levels at the second collection points are high levels; 9. The measurement method according to claim 8, characterized in that, When the plurality of first collection points are falling edges or rising edges, if the number of collection points with low levels at the second collection points is greater than the value M, it indicates that the levels at the second collection points are low levels; The value M is an integer value obtained by dividing the total number of collection points by 2. The measurement method further comprises: The rotating speed and direction information of the variable frequency motor are received by communication; 10. The method of claim 7, wherein, The state curve of the running process of the variable frequency motor is drawn and displayed. ​ ​

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