Full-automatic efficiency testing device and method for variable frequency motor

Abstract

The invention discloses a full-automatic efficiency testing device and method for a variable frequency motor. A main control part in the device comprises a human-computer interface, and a data acquisition module, an efficiency calculation module and a communication module which are connected with the human-computer interface; the data acquisition module is connected with the test bench and acquires the rotating speed and the torque of the motor; the efficiency calculation module is connected with the data acquisition module and calculates the power and efficiency of the motor; the communication module performs signal interaction with external equipment; and the human-computer interface is used for displaying and setting parameters. The load motor and the tested motor are independently controlled through the load frequency converter and the tested frequency converter respectively, the step length and range of a load torque factor and a motor rotating speed factor are flexibly adjusted, and various test requirements are met. The test method allows a user to set the duration of the test points as required, realizes automatic traversal of the test points, and significantly improves efficiency and precision.

Description

Technical Field

[0001] The invention belongs to the field of motor detection, and in particular relates to a fully automatic efficiency testing device and method for a variable frequency motor. Background Art

[0002] In modern industry, variable frequency motors are widely used in water pumps, fans, air conditioners, elevators and other equipment due to their advantages of energy saving and flexible speed regulation. However, their operating efficiency is affected by many factors such as load changes, voltage fluctuations and speed changes. Accurate detection and evaluation of the efficiency of variable frequency motor systems is of great significance for improving equipment performance, extending motor service life and reducing maintenance costs.

[0003] In the prior art, the fully automatic efficiency test method of the variable frequency motor has certain limitations. It includes a method for testing the efficiency of the variable frequency motor through a DC motor load. This method uses a DC motor as a load or generator, and uses a power analyzer, a resistance tester, a temperature sensor and other devices to collect data such as voltage, current and speed, and the PLC control unit processes and calculates the motor efficiency. However, this solution has the following problems: the adjustment of the DC motor load characteristics is relatively cumbersome, and the measurement accuracy of torque and power is limited, which affects the adaptability to different types of motors. In addition, the test device integrates a large number of hardware and control units, and the operation and maintenance process is relatively complicated. The use of a hydraulic lifting platform in the system further increases the test complexity and overall cost.

[0004] There is also an efficiency estimation method based on the variable frequency working condition of a three-phase asynchronous motor in the prior art. This method obtains parameters such as the rated power of the motor, the measured speed and the operating frequency of the inverter, and constructs the mathematical relationship between the motor output power and frequency, the power adjustment coefficient and the pole number adjustment coefficient based on the constant torque speed regulation principle of the inverter to calculate the motor output power. Combined with the input power and efficiency verification of the inverter, the motor efficiency is finally obtained. However, the shortcoming of this method is that under complex working conditions, the calculation method that relies on a small amount of field parameters and nameplate data is difficult to achieve real-time and high-precision efficiency evaluation. The test process still requires manual intervention for data collection and verification, which cannot fully meet the needs of modern industry for full automation. Summary of the invention

[0005] In view of this, the present invention provides a fully automatic efficiency test device for a variable frequency motor, comprising a main control unit and a variable frequency power supply unit, a tested motor unit, a load motor unit and a test bench, all of which are connected to the main control unit, wherein: The main control unit includes a human-machine interface and a data acquisition module, an efficiency calculation module and a communication module all connected to the human-machine interface; the data acquisition module is connected to the test bench to collect the speed and torque of the motor; the efficiency calculation module is connected to the data acquisition module to calculate the power and efficiency of the motor; the communication module performs signal interaction with external devices; the human-machine interface performs display and parameter setting; The variable frequency power supply unit includes a three-phase AC power supply and a single-phase AC power supply, the three-phase AC power supply is connected to the tested motor unit and the load motor unit through a three-phase cable, and the single-phase AC power supply is connected to the main control unit; The tested motor unit includes a tested inverter and a tested motor, wherein the input end of the tested inverter is electrically connected to a three-phase AC power supply, and the output end is electrically connected to the input end of the tested motor; The load motor unit includes a load frequency converter and a load motor, wherein the input end of the load frequency converter is electrically connected to the three-phase AC power supply, and the output end is electrically connected to the input end of the load motor; The test bench comprises a motor fixture, a speed torque detection module and an electrical signal detection module, wherein the speed torque detection module and the electrical signal detection module perform data acquisition and signal detection on the tested motor and the load motor.

[0006] Preferably, an electrical signal detection module is arranged between the tested inverter and the tested motor to collect in real time the voltage, current and frequency output from the tested inverter to the tested motor; the tested inverter receives the control signal from the main control unit, adjusts the output frequency point by point according to a fixed step size, and controls the speed of the tested motor.

[0007] Preferably, an electrical signal detection module is provided at the connection between the load frequency converter and the load motor to measure the voltage, current and power of the load motor; the load frequency converter applies a progressive load torque to the test motor with a fixed step size, and the speed sensor on the load motor side is used to detect the real-time speed of the motor and convert it into an electrical signal for transmission to the main control unit.

[0008] Preferably, the speed and torque detection module includes a torque sensor and a speed sensor. The test motor, the torque sensor and the load motor are mechanically connected through a coupling. The coupling transmits the speed and torque. The torque sensor detects the real-time torque of the test motor and converts it into an electrical signal for transmission to the main control unit.

[0009] Based on the above purpose, a fully automatic efficiency test method of a variable frequency motor is provided, using the fully automatic efficiency test device of the variable frequency motor, comprising the following steps: S1, system initialization: the speed and torque detection module is calibrated and the test parameters are set, including the speed range, torque range, number of speed test points, number of torque test points and test time of the test points; S2, system efficiency test: including S21, setting test points, after completing the test of all test points; S22, collecting operation data; S23, calculating system efficiency; S3, output the corresponding results: efficiency values ​​of all test points, corresponding torque values ​​and speed values.

[0010] Preferably, setting the test parameters in S1 specifically includes: Speed ​​range[ n 0,n max ]: Determine the speed range according to the rated operating parameters of the motor, where n 0 Usually set to the minimum speed allowed by the motor. n max Set it to the rated speed of the motor or close to its maximum allowable value; Torque range[ T 0 ,T max ]: Define the torque range according to application requirements and motor rated torque, T 0 is set to the torque when the motor is unloaded, T max Set to the motor rated torque or maximum allowable torque; Speed ​​test points N :Based on the discretization principle of series and step size division algorithm, the range is divided into N Speed ​​points, speed division formula: (1) in, Defined as the step size of the rotation speed; Torque test points M :Based on the discretization principle of series and step size division algorithm, the range is divided into M Torque points, torque division formula: (2) in, Defined as the step size of the torque; Test point test duration t :Determine the duration of each speed and torque test point. This duration must be greater than the response time of the motor system to ensure that the motor is in a stable operation process when data is collected after the speed and torque are adjusted.

[0011] Preferably, the step S21 of setting the test point includes the main control system sending a control data packet to the tested inverter through the communication module to control the tested motor to reach a specified speed. n The main control system sends a control data packet to the load inverter through the communication module to set the load motor to reach the specified load torque. T .

[0012] Preferably, the step S21 sets test points, and completing the test on all test points specifically includes: M × N Within the test point range, the initial motor speed is given for the first time n 0 and initial torque T 0 to determine the initial test point, and then implement the traversal process according to the law of torque first and speed later: first maintain the speed n 0 remains unchanged, and the torque is adjusted in uniform steps from T 0 increments to T max , then increase the speed once , the torque is adjusted in uniform steps from T max Decrease to T 0, and then increase the speed again , repeat the above process until completion ( n max , T max ) point test, ending the traversal test process.

[0013] Preferably, the step S22 collects operating data, specifically including when the motor stably operates at a set speed and torque, each sensor in the data acquisition module of the main control unit reads the operating data, including the motor speed n , motor torque T , and the inverter operating parameters, where the inverter operating parameters include the output frequency f , Motor voltage U , Motor current I and power factor , forming a data group; to ensure that the motor has enough time to enter a stable operating state, each test point maintains the test time t The data sampling frequency is one group every t / 100, so 100 groups of data are sampled at each test point.

[0014] Preferably, the step S23 of calculating system efficiency specifically includes: According to the read motor operation data and inverter operation data, calculate the variable frequency motor system efficiency η, which is defined as the motor output power P out With input power P in The ratio of (3) Among them, the motor output power P out Through the motor torqueT and speed n The calculations show that: (4) Motor input power P in The motor input voltage U and current I and power factor The calculation results are: (5) During the test t The efficiency of the continuously collected data sets is calculated by using equations (3)-(5), and multiple sets of efficiency values ​​are processed by first-order low-pass filtering to make the efficiency values ​​more stable: (6) In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, the value range is 0< α <1; Set the filter coefficient according to the sampling frequency and dynamic response requirements.

[0015] Compared with the prior art, the present invention is a fully automatic efficiency test device for variable frequency motors and a detection method thereof. The device controls the load motor and the tested motor independently through the load frequency converter and the tested frequency converter, supports flexible adjustment of the step size and range of the load torque factor and the motor speed factor, and adapts to various test requirements. The test method allows the user to set the test point duration as required, realizes automatic traversal of the test points, and significantly improves efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural block diagram of a fully automatic efficiency testing device for a variable frequency motor according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the specific structure of the fully automatic efficiency testing device of the variable frequency motor according to an embodiment of the present invention; Figure 3 This is a flow chart of a fully automatic efficiency testing method for a variable frequency motor according to an embodiment of the present invention; Figure 4 Schematic diagram of the S21 traversal test process of the fully automatic efficiency test method for a variable frequency motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] See the block diagram of the embodiment Figure 1 and Figure 2, including a main control unit 50 and a variable frequency power supply unit 10, a tested motor unit 20, a load motor unit 30 and a test bench 40, all of which are connected to the main control unit 50, wherein: The main control unit 50 includes a human-machine interface 54 and a data acquisition module 51, an efficiency calculation module 52 and a communication module 53, all of which are connected to the human-machine interface 54; the data acquisition module 51 is connected to the test bench 40 to collect the speed and torque of the motor; the efficiency calculation module 52 is connected to the data acquisition module 51 to calculate the power and efficiency of the motor; the communication module 53 exchanges signals with external devices; the human-machine interface 54 performs display and parameter settings; specifically, the communication module 53 interacts with external devices through an Ethernet interface and a serial port to implement user interface operation and monitoring. The user can set the motor speed, load torque range and test duration on the human-machine interface 54, and the device automatically adjusts the inverter output according to the set operating point, collects data in real time, and feeds back the test results and efficiency values ​​to the host computer, and the user can view the test results in real time.

[0019] The variable frequency power supply unit 10 includes a three-phase AC power supply and a single-phase AC power supply. The three-phase AC power supply is connected to the tested motor unit 20 and the load motor unit 30 through a three-phase cable, and the single-phase AC power supply is connected to the main control unit 50. The tested motor part 20 includes a tested inverter 21 and a tested motor 22. The input end of the tested inverter 21 is electrically connected to the three-phase AC power supply, and the output end is electrically connected to the input end of the tested motor 22. An electrical signal detection module 42 is arranged between the tested inverter 21 and the tested motor 22 to collect the voltage, current and frequency output from the tested inverter 21 to the tested motor 22 in real time. The tested inverter 21 receives the control signal of the main control part 50, adjusts the output frequency point by point according to a fixed step size, and controls the speed of the tested motor 22.

[0020] The load motor unit 30 includes a load inverter 31 and a load motor 32. The input end of the load inverter 31 is electrically connected to the three-phase AC power supply, and the output end is electrically connected to the input end of the load motor 32. An electrical signal detection module 42 is provided at the connection between the load inverter 31 and the load motor 32 to measure the voltage, current and power of the load motor 32. The load inverter 31 applies a progressive load torque to the test motor 22 with a fixed step size. The speed sensor on the side of the load motor 32 is used to detect the real-time speed of the motor and convert it into an electrical signal for transmission to the main control unit 50.

[0021] The test bench 40 includes a motor fixture, a speed torque detection module 41 and an electrical signal detection module 42, wherein the speed torque detection module 41 and the electrical signal detection module 42 perform data acquisition and signal detection on the test motor 22 and the load motor 32. The speed torque detection module 41 includes a torque sensor and a speed sensor. The test motor 22, the torque sensor and the load motor 32 are mechanically connected through a coupling, and the coupling transmits the speed and torque. The torque sensor detects the real-time torque of the test motor 22 and converts it into an electrical signal to transmit to the main control unit 50.

[0022] Based on the above purpose, a fully automatic efficiency test method for a variable frequency motor is provided, using the fully automatic efficiency test device for the variable frequency motor, comprising the following steps: S1, system initialization: the speed and torque detection module is calibrated and the test parameters are set, including the speed range, torque range, number of speed test points, number of torque test points and test time of the test points; S2, system efficiency test: including S21, setting test points, after completing the test of all test points; S22, collecting operation data; S23, calculating system efficiency; S3, output the corresponding results: efficiency values ​​of all test points, corresponding torque values ​​and speed values.

[0023] The test parameters set in S1 include: Speed ​​range[ n 0,n max ]: Determine the speed range according to the rated operating parameters of the motor, where n 0 Usually set to the minimum speed allowed by the motor. n max Set it to the rated speed of the motor or close to its maximum allowable value; Torque range[ T 0 ,T max ]: Define the torque range according to application requirements and motor rated torque, T 0 is set to the torque when the motor is unloaded, T max Set to the motor rated torque or maximum allowable torque; Speed ​​test points N :Based on the discretization principle of series and step size division algorithm, the range is divided into N Speed ​​points, speed division formula: (1) in, Defined as the step size of the rotation speed; Torque test points M:Based on the discretization principle of series and step size division algorithm, the range is divided into M Torque points, torque division formula: (2) in, Defined as the step size of the torque; Test point test duration t :Determine the duration of each speed and torque test point. This duration must be greater than the response time of the motor system to ensure that the motor is in a stable operation process when data is collected after the speed and torque are adjusted.

[0024] S21 sets the test point, which includes sending a control data packet from the main control system to the tested inverter through the communication module to control the tested motor to reach the specified speed. n The main control system sends a control data packet to the load inverter through the communication module to set the load motor to reach the specified load torque. T .

[0025] In the set M × N Within the test point range, the initial motor speed is given for the first time n 0 and initial torque T 0 to determine the initial test point, and then implement the traversal process according to the law of torque first and speed later: first maintain the speed n 0 remains unchanged, and the torque is adjusted in uniform steps from T 0 increments to T max , then increase the speed once , the torque is adjusted in uniform steps from T max Decrease to T 0, and then increase the speed again , repeat the above process until completion ( n max , T max ) point test, ending the traversal test process. Figure 4 , which is a schematic diagram of the traversal test process.

[0026] S22 collects operating data, specifically, when the motor stably runs at a set speed and torque, each sensor in the data acquisition module of the main control unit 50 reads the operating data, including the motor speed n , motor torque T , and the inverter operating parameters, where the inverter operating parameters include the output frequency f , Motor voltage U , Motor current Iand power factor , forming a data group; to ensure that the motor has enough time to enter a stable operating state, each test point maintains the test time t , the preferred test duration is set to 5s; to ensure t A sufficient number of data groups can be collected within 10 seconds. The preferred data sampling frequency is 50 ms / group, so 100 groups of data can be sampled at each test point.

[0027] S23 calculates system efficiency specifically including: According to the read motor operation data and inverter operation data, calculate the variable frequency motor system efficiency η, which is defined as the motor output power P out With input power P in The ratio of (3) Among them, the motor output power P out Through the motor torque T and speed n The calculations show that: (4) Motor input power P in The motor input voltage U and current I and power factor The calculation results are: (5) During the test t The efficiency of the continuously collected data sets is calculated by using equations (3)-(5), and multiple sets of efficiency values ​​are processed by first-order low-pass filtering to make the efficiency values ​​more stable: (6) In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, the value range is 0< α <1; Set the filter coefficient according to the sampling frequency and dynamic response requirements, usually α = 0.1~0.2.

[0028] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fully automatic efficiency test device for variable frequency motors, characterized in that: It includes a main control unit and a variable frequency power supply unit, a tested motor unit, a load motor unit and a test bench, all of which are connected to the main control unit, wherein: The main control unit includes a human-machine interface and a data acquisition module, an efficiency calculation module and a communication module all connected to the human-machine interface; the data acquisition module is connected to the test bench to collect the speed and torque of the motor; the efficiency calculation module is connected to the data acquisition module to calculate the power and efficiency of the motor; the communication module performs signal interaction with external devices; the human-machine interface performs display and parameter setting; The variable frequency power supply unit includes a three-phase AC power supply and a single-phase AC power supply, the three-phase AC power supply is connected to the tested motor unit and the load motor unit through a three-phase cable, and the single-phase AC power supply is connected to the main control unit; The tested motor unit includes a tested inverter and a tested motor, wherein the input end of the tested inverter is electrically connected to a three-phase AC power supply, and the output end is electrically connected to the input end of the tested motor; The load motor unit includes a load frequency converter and a load motor, wherein the input end of the load frequency converter is electrically connected to a three-phase AC power supply, and the output end is electrically connected to the input end of the load motor; The test bench comprises a motor fixture, a speed torque detection module and an electrical signal detection module, wherein the speed torque detection module and the electrical signal detection module perform data acquisition and signal detection on the tested motor and the load motor.

2. The device according to claim 1, characterized in that An electrical signal detection module is arranged between the tested inverter and the tested motor to collect the voltage, current and frequency output from the tested inverter to the tested motor in real time; the tested inverter receives the control signal of the main control unit, adjusts the output frequency point by point according to a fixed step size, and controls the speed of the tested motor.

3. The device according to claim 1, characterized in that An electrical signal detection module is provided at the connection between the load frequency converter and the load motor to measure the voltage, current and power of the load motor; the load frequency converter applies a progressive load torque to the tested motor with a fixed step size, and the speed sensor on the load motor side is used to detect the real-time rotation speed of the motor and convert it into an electrical signal for transmission to the main control unit.

4. The device according to claim 1, characterized in that The speed and torque detection module includes a torque sensor and a speed sensor. The test motor, the torque sensor and the load motor are mechanically connected through a coupling. The coupling transmits the speed and torque. The torque sensor detects the real-time torque of the test motor and converts it into an electrical signal for transmission to the main control unit.

5. A fully automatic efficiency test method for a variable frequency motor, characterized in that: The fully automatic efficiency testing device for a variable frequency motor according to any one of claims 1 to 4 comprises the following steps: S1, system initialization: the speed and torque detection module is calibrated and the test parameters are set, including the speed range, torque range, number of speed test points, number of torque test points and test time of the test points; S2, system efficiency test: including S21, setting test points, after completing the test of all test points; S22, collecting operation data; S23, calculating system efficiency; S3, output the corresponding results: efficiency values ​​of all test points, corresponding torque values ​​and speed values.

6. The method according to claim 5, characterized in that The test parameters set in S1 specifically include: Speed ​​range[ n 0,n max ]: Determine the speed range according to the rated operating parameters of the motor, where n 0 Usually set to the minimum speed allowed by the motor. n max Set it to the rated speed of the motor or close to its maximum allowable value; Torque range[ T 0 ,T max ]: Define the torque range according to application requirements and motor rated torque, T 0 is set to the torque when the motor is unloaded, T max Set to the motor rated torque or maximum allowable torque; Speed ​​test points N :Based on the discretization principle of series and step size division algorithm, the range is divided into N Speed ​​points, speed division formula: (1) in, Defined as the step size of the rotation speed; Torque test points M :Based on the discretization principle of series and step size division algorithm, the range is divided into M Torque points, torque division formula: （2） in, Defined as the step size of the torque; Test point test duration t :Determine the duration of each speed and torque test point. This duration must be greater than the response time of the motor system to ensure that the motor is in a stable operation process when data is collected after the speed and torque are adjusted.

7. The method according to claim 5, characterized in that The S21 test point setting includes the main control system sending a control data packet to the tested inverter through the communication module to control the tested motor to reach a specified speed. n The main control system sends a control data packet to the load inverter through the communication module to set the load motor to reach the specified load torque. T .

8. The method according to claim 6, characterized in that The step S21 sets the test points, and the test of all the test points specifically includes: M × N Within the test point range, the initial motor speed is given for the first time n 0 and initial torque T 0 to determine the initial test point, and then implement the traversal process according to the law of torque first and speed later: first maintain the speed n 0 remains unchanged, and the torque is adjusted in uniform steps from T 0 increments to T max , then increase the speed once , the torque is adjusted in uniform steps from T max Decrease to T 0, and then increase the speed again , repeat the above process until completion ( n max , T max ) point test, ending the traversal test process.

9. The method according to claim 5, characterized in that The S22 collects operating data, specifically including when the motor stably runs at a set speed and torque, each sensor in the data acquisition module of the main control unit reads the operating data, including the motor speed n , motor torque T , and the inverter operating parameters, where the inverter operating parameters include the output frequency f , Motor voltage U , Motor current I and power factor , forming a data group; to ensure that the motor has enough time to enter a stable operating state, each test point maintains the test time t The data sampling frequency is one group every t / 100, so 100 groups of data are sampled at each test point.

10. The method according to claim 5, characterized in that The S23 calculation system efficiency specifically includes: According to the read motor operation data and inverter operation data, calculate the variable frequency motor system efficiency η, which is defined as the motor output power P out With input power P in The ratio of （3） Among them, the motor output power P out Through the motor torque T and speed n The calculations show that: （4） Motor input power P in The motor input voltage U and current I and power factor The calculation results are: （5） During the test t The efficiency of the continuously collected data sets is calculated by using equations (3)-(5), and multiple sets of efficiency values ​​are processed by first-order low-pass filtering to make the efficiency values ​​more stable: （6） In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, the value range is 0< α <1; Set the filter coefficient according to the sampling frequency and dynamic response requirements.

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