Double clutch test device and method for measuring mechanical loss of variable frequency motor

Abstract

The application discloses a double-machine clutching type testing device and method for mechanical loss measurement of a variable-frequency motor, which comprises two identical variable-frequency motors, a rotating speed measurement unit, a power measurement unit and a driving control unit, wherein any one of the variable-frequency motors is used as a driving motor, and the other one is a load motor and is always powered off during the whole testing process; the driving motor is separated from or connected with the load motor through a shaft coupling to realize no-load or load; when the driving motor is connected with the load motor, the input active power of the driving motor under different rotating speeds is measured through the rotating speed measurement unit and the power measurement unit; when the driving motor is separated from the load motor, the input active power of the driving motor under different rotating speeds is measured; and the change of the input active power measurement value of the driving motor under the same rotating speed and no-load operation is the mechanical loss of the corresponding rotating speed. The application has the advantages of relatively simple measurement process and experimental data processing process, high measurement efficiency and high measurement precision.

Description

Technical Field

[0001] This invention mainly relates to the field of motor testing technology, specifically to a dual-clutch testing device and method for measuring the mechanical losses of variable frequency motors. Background Technology

[0002] Due to the rapid development of human industry, the uncontrolled emission of industrial pollutants, and the overexploitation of resources and energy in the past few decades, the global resource and energy shortage crisis and environmental pollution problems are becoming increasingly severe. Statistics show that industrial electricity consumption accounts for more than 70% of the world's total electricity consumption. The electrical energy required for industrial production is mainly consumed by electric motors. Electric motors, as power sources, indirectly drive actuators through transmission systems or directly drive them without transmission systems. Variable frequency speed control motors (VFDs) utilize electromagnetic induction or the principle of frequency conversion speed regulation to achieve stepless speed regulation. Because their structure eliminates intermediate transmission links such as belts, gears, and chains, they achieve direct drive and possess significant technological advantages such as compact structure, small size, high power density, high transmission efficiency, high energy efficiency, wide speed range, low vibration and noise, low failure rate, and the ability to achieve precise online or remote control. They are increasingly widely used in aerospace, high-speed precision machine tools, high-speed fans and compressors, and new energy electric vehicles. Due to their high efficiency, energy saving, and environmental friendliness, variable frequency motors are currently a key focus in motor research, development, design, production, application, and development. They will have significant strategic importance in alleviating the current resource and energy shortage crisis and environmental pollution problems.

[0003] Mechanical loss, a major type of loss in variable frequency motors, is the power consumed by the motor's rotation to overcome rotor friction. It significantly impacts the motor's energy consumption, efficiency, mechanical characteristics, and overall performance. Traditional measurement methods, due to various limitations, are not yet adequate for measuring the mechanical losses of variable frequency motors, and their impact on the development of variable frequency motor technology cannot be ignored, necessitating the research and exploration of new methods.

[0004] The traditional no-load constant-speed transformer method is a common method for measuring the mechanical losses of ordinary 50Hz industrial frequency induction motors. The specific implementation process is as follows: 1. Connect a voltage regulator between the motor under test and a 50Hz three-phase sinusoidal AC power supply. The output voltage of the voltage regulator is adjustable within a certain range. 2. Start the motor under test directly under no-load at its rated voltage (380V) and rated frequency (50Hz), allowing it to run sufficiently until the mechanical losses stabilize. 3. After the mechanical losses stabilize, measure the input voltage, input current, and input active power of the motor under test under different supply voltage conditions. The input voltage of the motor under test is changed by adjusting the output voltage of the voltage regulator, gradually decreasing the input voltage from 1.25 times the rated voltage until the input current of the motor under test reaches its minimum or begins to show an unstable rebound. However, during the voltage adjustment and no-load test, the supply frequency of the motor under test remains at 50Hz to ensure that the speed or mechanical losses of the motor under test remain constant throughout the test. Take 7-9 measuring points, and measure the three-phase input voltage, three-phase input current, and input active power of the stator winding of the motor under test at each point. To reduce random errors in the measurement process, take the average of multiple measurements at each measuring point. 4. Measure the stator winding resistance of the motor under test after stopping the machine. After completing the measurement in step 3, stop the operation of the motor under test, and immediately measure the stator winding resistance of the motor under test after stopping the machine to minimize the influence of temperature on the measurement results. 5. Based on the measurement results of steps 3 and 4, indirectly obtain the measured values ​​of copper loss and the measured values ​​of loss after deducting copper loss at each measuring point through calculation. Based on the measured values ​​of the three-phase input current of the stator winding of the motor under test and the measured values ​​of the stator winding resistance when the machine is stopped, indirectly obtain the measured values ​​of copper loss at each measuring point through the copper loss formula. Subtract the corresponding measured value of copper loss from the measured input active power at each measuring point to obtain the measured value of loss after deducting copper loss at each measuring point. 6. Plot the input active power curve and the loss curve after deducting copper loss of the motor under test under no-load operation on graph paper. The horizontal axis represents the change in input voltage, and the vertical axis represents the change in input active power and losses after deducting copper losses (including mechanical and iron losses). Using graph paper, plot the curves of the no-load input active power and losses after deducting copper losses as a function of input voltage on the same coordinate system. 7. Based on the two curves plotted in step 6, obtain the test result of the mechanical losses of the tested motor by extending the two curves to obtain their intersection point. The two curves intersect on the vertical axis (at which point the input voltage of the tested motor is zero), and the vertical coordinate value of the intersection point is the test result of the mechanical losses of the tested motor.

[0005] The no-load constant speed transformer method can eliminate electromagnetic losses and separate mechanical losses in terms of measurement principle, resulting in high reliability of measurement results. However, this method is not suitable for measuring the mechanical losses of variable frequency motors because:

[0006] 1. The method principle is inapplicable. The no-load constant speed variable voltage method requires the tested motor to run at a constant speed while simultaneously changing the input voltage of the tested motor to perform multi-point and multi-physical quantity measurements. The purpose is to obtain the curves of the no-load input active power and losses after deducting copper losses as a function of the input voltage, and to obtain the test results of the mechanical losses of the tested motor by extending the intersection of the two curves. Compared with ordinary 50Hz power frequency motors, variable frequency motors use inverters for drive control speed regulation. However, regardless of the control speed regulation range, once the power supply frequency or speed is determined, the inverter output voltage or the motor input voltage cannot be changed. In the constant torque control speed regulation range at and below the rated speed, the inverter output voltage is proportional to the power supply frequency. While the frequency and voltage are changed simultaneously, once the power supply frequency of the inverter or the speed of the motor are determined, the inverter output voltage or the motor input voltage is uniquely determined. In the constant power field weakening control speed regulation range above the rated speed, the inverter output voltage has reached its maximum value and remains constant, always equal to the rated voltage of the motor. For the reasons mentioned above, the measurement principle of the no-load constant speed transformer method is not suitable for measuring the mechanical losses of variable frequency motors.

[0007] 2. The measurement process and data processing are cumbersome, resulting in low measurement efficiency. At the same rotational speed, numerous measurement points and quantities are required, typically 7-9 points for measuring three-phase input voltage, three-phase input current, and input active power. Furthermore, a series of post-processing steps are necessary for the raw experimental data, including: calculating copper losses at each measurement point, calculating losses after deducting copper losses, plotting the curves of the tested motor's no-load input active power and losses after deducting copper losses as a function of input voltage, and extending the two curves to find their intersection. In short, the measurement process and data processing are relatively cumbersome, leading to low measurement efficiency.

[0008] 3. Obtaining the test results of the mechanical losses of the tested motor by plotting and extending the curves to find the intersection point affects the measurement accuracy. The test results of the mechanical losses of the tested motor are obtained by plotting the curves of the no-load input active power and the loss after deducting copper losses as a function of input voltage, and then extending the two curves to find the intersection point. Theoretically, this method can separate mechanical losses, but in practice, it introduces certain errors. This is because: firstly, there is no experimental data to support the extended portions of the two curves; secondly, the variation law of the extended portions of the two curves is theoretically unclear. These two uncertainties will affect the specific location of the intersection point of the two curves, causing the actual intersection point to not coincide with or deviate from the theoretical intersection point (at the theoretical intersection point, the input voltage and input current of the tested motor are zero, which can completely eliminate electromagnetic losses and achieve separation of mechanical losses). Summary of the Invention

[0009] The technical problem to be solved by the present invention is: in view of the problems existing in the prior art, the present invention provides a dual-clutch test device and method for measuring the mechanical loss of variable frequency motors with a relatively simple measurement process and experimental data processing process and high measurement efficiency.

[0010] A dual-clutch testing device for measuring the mechanical loss of a variable frequency motor includes two identical variable frequency motors, a speed measurement unit, a power measurement unit, and a drive control unit. One variable frequency motor is a drive motor, and the other is a load motor. The drive motor is separated from or connected to the load motor via a coupling to achieve mechanical engagement / disengagement of the drive motor and the load motor or to enable the drive motor to operate under no-load conditions. The load motor is always in a de-energized state.

[0011] When the drive motor is connected to the load motor via a coupling, the speed of the drive motor is measured by the speed measurement unit, and the load input active power of the drive motor at the corresponding speed is measured by the power measurement unit.

[0012] When the drive motor is disconnected from the load motor through the coupling, the speed of the drive motor is measured by the speed measurement unit, and the no-load input active power of the drive motor at the corresponding speed is measured by the power measurement unit.

[0013] The drive control unit is connected to the drive motor and is used to drive the drive motor and control its speed by frequency conversion, so that the drive motor can change its speed arbitrarily within its speed range for testing.

[0014] The drive control unit is connected to the speed measurement unit and the power measurement unit respectively, and is used to obtain the mechanical loss of the variable frequency motor based on the active power input under load and the active power input under no-load.

[0015] Preferably, the drive motor is always connected to the coupling during the testing process to eliminate the influence of coupling windage loss on the measurement results.

[0016] Preferably, the speed measurement unit includes a speed sensor and a signal conditioning box. The speed sensor is used to measure the speed signal of the drive motor, and the signal conditioning box is used to amplify and filter the speed signal.

[0017] Preferably, the power measurement unit includes a current sensor, a voltage sensor, and a power measurement analyzer. The current sensor is used to measure the input current of the drive motor; the voltage sensor is used to measure the input voltage of the drive motor; and the power measurement analyzer is connected to the current sensor and the voltage sensor respectively, and is used to obtain the input active power of the drive motor based on the measured input voltage, input current, and power factor of the drive motor.

[0018] This invention also discloses a test method based on the dual-clutch test device for measuring the mechanical losses of variable frequency motors as described above, comprising the following steps:

[0019] The drive motor is connected to the load motor via a coupling, and the load input active power of the drive motor is measured when the load motor is running at different speeds.

[0020] The drive motor is disconnected from the load motor by a coupling, and the no-load input active power of the drive motor is measured when it is running at different speeds.

[0021] The difference between the load input active power and the no-load input active power measured under the same speed conditions is the test result of the mechanical loss of the drive motor at the corresponding speed.

[0022] Preferably, the specific process for measuring the active power input to the load is as follows:

[0023] The drive motor is connected to or coupled in series with a non-powered load motor via a coupling, so that the drive motor is under load.

[0024] The drive motor is started by reducing the load voltage and frequency through the inverter, and the speed of the drive motor is increased to the target measured speed by adjusting the power supply frequency of the inverter.

[0025] The drive motor is fully loaded and operated at the target measured speed until the mechanical loss stabilizes. After the mechanical loss stabilizes, the speed of the drive motor and the corresponding load input active power are measured by the speed measurement unit and the power measurement unit, respectively. The target measured speed is changed and this step is repeated to obtain the load input active power at different speeds.

[0026] Preferably, the specific process for measuring the no-load input active power is as follows:

[0027] The unpowered load motor is not connected to, separated from, or disconnected from the coupling, so that the drive motor is in an unloaded state.

[0028] The drive motor is started under no-load voltage and frequency reduction soft start through the inverter, and the speed of the drive motor is increased to the target measured speed by adjusting the power supply frequency of the inverter.

[0029] The drive motor is fully idled at the target measurement speed until the mechanical loss stabilizes. After the mechanical loss stabilizes, the idle speed of the drive motor and the corresponding no-load input active power are measured by the speed measurement unit and the power measurement unit, respectively. The target measurement speed is changed, and this step is repeated to obtain the no-load input active power at different speeds.

[0030] During the test, the drive motor was controlled by constant torque in the speed regulation range at and below the rated speed, and by constant power field weakening control in the speed regulation range above the rated speed.

[0031] By measuring the three-phase input current of the drive motor when it is running at the same speed under no-load or load and the phase resistance of the stator winding when it is stopped, the effects of changes in current and copper loss of the drive motor before and after loading are eliminated through calculation.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] This invention only requires measuring the change in active power input between the drive motor and the unpowered load motor via mechanical clutch or when the drive motor is running at the same speed under no-load conditions. It does not require changing the input voltage of the test motor at the same speed to perform multi-point and multi-physical quantity measurements, nor does it require a series of post-processing steps on the measured raw experimental data. It has the advantages of small error introduced by the method principle, relatively simple measurement process and experimental data processing, and high measurement efficiency.

[0034] This invention requires only two identical variable frequency motors as test motors, either of which can be used as a drive motor or a load motor. The drive motor is always connected to the coupling during the test to eliminate the influence of coupling windage loss on the measurement results. However, the load motor is always de-energized during the test, ensuring that when the drive motor is connected to the de-energized load motor through the coupling or coupled in series for load operation testing, the load is always the mechanical loss of the drive motor itself. Attached Figure Description

[0035] Figure 1 This is a flowchart of the testing method of the present invention in an embodiment.

[0036] Figure 2 This is a schematic diagram of the test device of the present invention in an embodiment.

[0037] Figure 3 This is an example diagram of a specific application of the testing method of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 2As shown in the embodiment of the present invention, a dual-clutch testing device for measuring the mechanical loss of a variable frequency motor includes two identical variable frequency motors, a speed measurement unit, a power measurement unit, and a drive control unit. One variable frequency motor is a drive motor, and the other is a load motor. The drive motor is separated from or connected to the load motor via a coupling to achieve mechanical engagement / disengagement of the drive motor and the load motor, or to enable or disable the drive motor. The load motor is in a de-energized state. When the drive motor is connected to the load motor via the coupling, the speed of the drive motor is measured by the speed measurement unit, and the power measurement unit is used to measure the speed of the load motor. The measurement unit measures the load input active power of the drive motor at the corresponding speed. When the drive motor is disconnected from the load motor via a coupling, the speed measurement unit measures the speed of the drive motor, and the power measurement unit measures the no-load input active power of the drive motor at the corresponding speed. The drive control unit is responsible for driving and frequency conversion speed regulation of the drive motor, allowing the drive motor to change its speed arbitrarily within its speed regulation range for testing. The difference between the load input active power and the no-load input active power measured under the same speed conditions is the mechanical loss test result of the frequency converter or the tested motor at the corresponding speed.

[0040] In practical applications, two identical variable frequency motors are randomly selected as the test motors. Either one can be used as the drive motor or the load motor. The two motors are mechanically engaged and disengaged via a coupling, allowing the drive motor to be either unloaded or loaded. However, regardless of whether the drive motor is unloaded or loaded, the load motor is always de-energized. The mechanical losses of the test motor are measured by measuring the change in active power input to the drive motor under no-load and load operation at any given speed.

[0041] The input active power of the drive motor during no-load operation includes copper loss, iron loss, and mechanical loss components. Since the drive motor and the load motor are identical, when the drive motor is connected to the unpowered load motor via a coupling or series coupling for load operation testing, the load applied is always the drive motor's own mechanical loss. Mechanical loss typically accounts for only a few percentage points of the rated power of the tested motor, resulting in a small load. Furthermore, because the drive motor's speed is the same during no-load and load operation tests, the changes in speed, mechanical loss, current, and copper loss before and after loading are minimal and can be approximated as unchanged, while iron loss remains unchanged. Therefore, this invention loads the mechanical loss of the tested motor, and the measured and separated components are almost entirely the mechanical loss of the tested motor.

[0042] like Figure 2As shown, the drive motor and load motor are bolted to a cast iron plate with T-slots and mechanically engaged / disengaged via a coupling. When the coupling is connected only to the drive motor and not to the load motor, the drive motor is disconnected or separated from the load motor, and is in an unloaded state. When the drive motor is connected or coupled to the load motor via the coupling, it is under load. The input terminals of the drive motor are connected to the output terminals R, S, and T of the inverter via cables, while the input terminals U, V, and W of the inverter are connected to the output terminals of a 50Hz three-phase sinusoidal AC power supply via cables. The rated power, rated voltage, rated current, rated speed, and maximum speed of the drive motor should match those of the frequency converter. A power measurement unit is used to measure the change in input active power of the drive motor under no-load operation at any given speed, and a speed measurement unit is used to measure the corresponding speed.

[0043] Specifically, the power measurement unit consists of current sensors, a power measurement and analysis instrument (integrating signal conditioning, acquisition, analysis, and display functions), and a computer. The current sensors are used to measure the input current of the drive motor. Three wires connecting the drive motor input terminal to the inverter output terminal pass through the central holes of the three current sensors, as shown below. Figure 2 As shown, the output signals of the three current sensors are connected to the corresponding current input terminals of the power measurement and analysis instrument via signal transmission lines. The drive motor input voltage (inverter output voltage) is directly connected to the corresponding voltage input terminals of the power measurement and analysis instrument via three wires.

[0044] The speed measurement unit consists of a speed sensor, a signal conditioning box, and a computer. The signal measured by the speed sensor is amplified and filtered by the signal conditioning box, then acquired by the signal conditioning box's acquisition card, and finally directly imported into the computer for analysis via a data transmission line. Voltage, current, and power signals measured by the power measurement and analysis instrument can also be imported into the computer for analysis via the data transmission line.

[0045] This invention only requires measuring the change in active power input between the drive motor and the unpowered load motor via mechanical clutch or when the drive motor is running at the same speed under no-load conditions. It does not require changing the input voltage of the test motor at the same speed to perform multi-point and multi-physical quantity measurements, nor does it require a series of post-processing steps on the measured raw experimental data. It has the advantages of small error introduced by the method principle, relatively simple measurement process and experimental data processing, and high measurement efficiency.

[0046] This invention requires only two identical variable frequency motors as test motors, either of which can be used as a drive motor or a load motor. The drive motor is always connected to the coupling during the test to eliminate the influence of coupling windage loss on the measurement results. However, the load motor is always de-energized during the test, ensuring that when the drive motor is connected to the de-energized load motor through the coupling or coupled in series for load operation testing, the load is always the mechanical loss of the drive motor itself.

[0047] like Figure 1 As shown, this embodiment of the invention also discloses a test method based on the dual-clutch test device for measuring the mechanical losses of a variable frequency motor as described above, including the following steps:

[0048] The drive motor is connected to the load motor via a coupling, and the active power of the drive motor at different speeds is measured under load.

[0049] The drive motor is disconnected from the load motor by a coupling, and the no-load active power of the drive motor is measured at different speeds.

[0050] The difference between the load input active power and the no-load input active power measured under the same speed conditions is the mechanical loss test result of the variable frequency motor at the corresponding speed.

[0051] The present invention utilizes the principle that the losses of a dual-motor mechanical clutch drive motor remain approximately constant during operation at the same speed. It applies the mechanical losses of the tested motor, and the measured losses are almost entirely those of the tested motor, ensuring the accuracy of the measurement results. The method of this invention is innovative in principle, introduces minimal error, and yields highly reliable measurement results. Existing no-load constant-speed variable voltage measurement methods require the tested motor to run at the same speed while simultaneously varying its input voltage for multi-point, multi-physical quantity measurements. The aim is to obtain curves showing the changes in the tested motor's no-load input active power and losses (excluding copper losses) as a function of the input voltage. The test results for the tested motor's mechanical losses are obtained by extending the intersection of these two curves. However, this method is not applicable to the measurement of mechanical losses in variable frequency motors where the speed is fixed and the input voltage cannot be changed. The measurement principle of the same dual-machine mechanical clutch drive motor with approximately constant loss during operation at the same speed is as follows: Two identical variable frequency motors are randomly selected as test motors, either of which can be used as a drive motor or a load motor. The drive motor is always connected to the coupling to eliminate the influence of wind friction loss of the coupling, but the load motor is always in a de-energized state. The two motors are mechanically clutched through the coupling to realize the no-load or load of the drive motor. The mechanical loss of the test motor is measured by measuring the change of active power input when the drive motor is running at the same speed under no-load.

[0052] The input active power of the drive motor during no-load operation (disconnected from the unpowered load motor) includes mechanical losses, iron losses, and copper losses. The drive motor is connected to or coupled in series with a load motor that is identical to the drive motor, and drives the unpowered load motor to run at the same speed as the drive motor during no-load operation, applying load by utilizing the drive motor's own mechanical losses. The degree to which the load affects the drive motor's mechanical losses, iron losses, and copper losses directly determines the measurement accuracy.

[0053] The impact of loading on the speed and mechanical loss of the drive motor is very small and can be approximated as unchanged. The reasons are as follows: 1. Since the drive motor and the load motor are the same motors, the speed of the drive motor during no-load operation test is also the same. When the drive motor is loaded, it is its own mechanical loss that is loaded. The mechanical loss usually only accounts for a few percentage points of the rated power of the drive motor. The load is small and has almost no impact on the speed of the drive motor; 2. The difference in the rotor rotation friction characteristics of the same motors is almost negligible.

[0054] Loading has no impact on the iron loss of the drive motor because: 1. Since the active power input of the drive motor is measured at the same speed before and after loading, and the inverter's power supply frequency remains the same, the alternating frequency of the magnetic field does not change before and after loading; 2. Regardless of the speed control zone, once the drive motor speed or inverter power supply frequency is determined, the magnetic flux or magnetic flux density is also uniquely determined, regardless of the load. The drive motor uses constant torque control speed regulation at and below its rated speed, and the magnetic flux remains constant. Above the rated speed, constant power field weakening control speed regulation is implemented, and the magnetic flux is inversely proportional to the speed. Once the speed is determined, the magnetic flux is also determined.

[0055] Although the input current of the drive motor changes before and after loading, the changes in current and copper losses are also small due to the small applied load, and can be approximated as unchanged. Nevertheless, the effects of the changes in current and copper losses of the drive motor before and after loading can be eliminated by measuring the three-phase input current of the drive motor running at the same speed under no-load or load conditions and the stator winding phase resistance when stopped, and then by the following calculations.

[0056] Specifically, the input active power measured before the drive motor is loaded is P. 1， The measured three-phase input currents are I 11 I 12 and I 13 The measured rotational speed is n1; the input active power of the drive motor under the same rotational speed condition after loading is P2, and the measured three-phase input currents are I... 21 I 22 and I 23 The stator winding phase resistances measured when the drive motor is stopped are R1, R2, and R3, respectively. The corrected mechanical loss measurement results are as follows: Similarly, the measurement results of mechanical loss at any measured rotational speed can be corrected.

[0057] This invention measures the mechanical loss of the test motor by measuring the change in active power input when the drive motor is engaged with a non-energized load motor or when the drive motor is running at the same speed under no-load conditions. It does not require multiple measurement points and multiple physical quantities by changing the input voltage of the test motor at the same speed, nor does it require a series of post-processing steps on the raw experimental data (including copper loss calculation at each measurement point, loss calculation after deducting copper loss, and eliminating electromagnetic loss and separating mechanical loss test results by plotting and extending to obtain intersection points). The measurement process and experimental data processing are relatively simple and the measurement efficiency is high.

[0058] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0059] (1) Select any two identical variable frequency motors as the test motors. Either one can be used as a drive motor or a load motor (never powered on). The two motors are mechanically engaged or disengaged through a coupling. The drive motor is either disengaged (the drive motor is disconnected from the unpowered load motor through the coupling) or engaged (the drive motor is connected to the unpowered load motor through the coupling or coupled in series) to achieve no-load or load conditions. However, regardless of no-load or load conditions, the drive motor is always connected to the coupling to eliminate the influence of coupling windage loss on the measurement results.

[0060] (2) Set the parameters of the drive motor, control mode, starting frequency and speed-up method.

[0061] 2.1 Connect the output terminals of the 50Hz three-phase sinusoidal AC power supply to the power input terminals U, V and W of the inverter using power cables, and connect the power output terminals R, S and T of the inverter to the input terminals of the stator windings of the drive motor.

[0062] 2.2 Closure Figure 2 The inverter power switch S1 shown puts the inverter into a powered state, preparing in advance for the setting of drive motor parameters, control mode, starting frequency and speed-up method.

[0063] 2.3. Set the drive motor parameters via the inverter control panel. The parameters that need to be set for the drive motor include its basic parameters (resistance, inductance, number of poles, type), rated parameters (rated power, rated voltage, rated current, rated speed), and maximum operating frequency. Locate the motor parameter setting module in the inverter control software using the navigation keys on the inverter control panel. Once located, it will be displayed on the control panel screen. Then, use the navigation keys to find the corresponding code for the motor parameter to be set and press Enter to confirm. Finally, use the increment and shift keys on the control panel to set the drive motor parameter values, and press Enter to confirm after setting.

[0064] 2.4. Set the control mode of the drive motor through the inverter control panel. Use a method similar to setting the motor parameters to set the control mode of the drive motor. Since the control mode used for the drive motor in the speed regulation range at and below the rated speed is different from that in the speed regulation range above the rated speed, they should be set separately. When setting, constant torque control should be selected in the speed regulation range at and below the rated speed, while constant power field weakening control should be selected in the speed regulation range above the rated speed.

[0065] 2.5. Set the starting frequency and acceleration method of the drive motor through the inverter control panel. Use a method similar to setting the motor parameters to set the starting frequency and acceleration method. To reduce system impact, decrease starting current, and prevent excessive starting current that could cause the inverter to trip automatically due to overcurrent protection, leading to starting failure, while ensuring sufficient starting torque, the drive motor does not use direct starting (starting at rated voltage and frequency), but rather a reduced-voltage, reduced-frequency soft start. Typically, the starting frequency of a soft start is relatively low (ranging from a few hertz, tens of hertz to several tens of hertz), and the starting voltage is also relatively low (much lower than the rated voltage of 380V). The selection and setting of the soft start frequency should be determined based on the specific application of the motor under test. Different applications of the motor under test have different requirements for the acceleration method; the specific acceleration method selected depends on the specific circumstances. Commonly available acceleration methods include linear, broken line, S-curve, and parabolic curves.

[0066] (3) Measurement of active power input and corresponding speed when the drive motor is separated from or disconnected from the unpowered load motor at different speeds during no-load operation.

[0067] 3.1 The unpowered load motor is not connected to, separated from, or disconnected from the coupling, leaving the drive motor in an unloaded state.

[0068] 3.2 The drive motor is started by no-load voltage reduction and frequency reduction soft start through the inverter, and the speed is increased to the target measured speed by adjusting the power supply frequency of the inverter.

[0069] 3.3. Run the drive motor at the target measured speed for a sufficient period of time until the mechanical loss stabilizes. Once the mechanical loss has stabilized, then proceed with the following steps: Figure 2 The power meter and speed sensor shown measure the active power and corresponding speed of the drive motor during no-load operation, respectively.

[0070] 3.4. Change the target measurement speed and repeat step 3.3 to obtain the test results of the input active power of the drive motor at different idle speeds and the corresponding speeds. The measurement results are detailed in Table 1.

[0071] Table 1. Measurement results of the input active power of the drive motor at different speeds during idle operation and the corresponding speeds.

[0072] Measure the rotational speed n (r / min) <![CDATA[n1]]> <![CDATA[n2]]> <![CDATA[n3]]> … <![CDATA[n i ]]> <![CDATA[Measuring active power P no-load (W)]]> <![CDATA[P no-load1 ]]> <![CDATA[P no-load2 ]]> <![CDATA[P no-load3 ]]> … <![CDATA[P no-loadi ]]>

[0073] In Table 1, i represents the number of measurement points, i = 1, 2, 3, ..., n. To accurately reflect the variation of mechanical losses of the tested motor with rotational speed, the number of measurement points should be determined based on the rated operating speed and maximum operating speed of the tested motor.

[0074] (4) Measurement of input active power and corresponding speed when the drive motor is connected to or coupled in series with a non-energized load motor via a coupling and operates at different speeds.

[0075] 4.1 After the no-load test of the drive motor is completed, stop the drive motor by pressing the Stop button on the inverter control panel.

[0076] 4.2 The drive motor is connected to a non-powered load motor or coupled in series through a coupling, so that the drive motor is under load.

[0077] 4.3 The drive motor is started by reducing the load voltage and frequency through the inverter. The speed is increased to the target measured speed by adjusting the power supply frequency of the inverter.

[0078] 4.4. Run the drive motor at the target measured speed under full load until the mechanical loss stabilizes. After the mechanical loss stabilizes, proceed with... Figure 2 The power meter and speed sensor shown measure the active power input and corresponding speed of the drive motor under load, respectively.

[0079] 4.5. Change the target measurement speed and repeat step 4.4 to obtain the test results of the input active power and corresponding speed of the drive motor under different load speeds. See Table 2 for the measurement results.

[0080] Table 2. Measurement results of input active power and corresponding speed of the drive motor under different load speeds.

[0081] Measure the rotational speed n (r / min) <![CDATA[n1]]> <![CDATA[n2]]> <![CDATA[n3]]> … <![CDATA[n j ]]> <![CDATA[Measuring active power P load (W)]]> <![CDATA[P load1 ]]> <![CDATA[P load2 ]]> <![CDATA[P load3 ]]> … <![CDATA[P loadj ]]>

[0082] In Table 2: j represents the number of measuring points, j = 1, 2, 3, ..., n. Regardless of how the number of measuring points and the measurement data change in Tables 1 and 2, when i = j, n must be present. i =n j This ensures that the measurement of the input active power of the drive motor under no-load operation is carried out under the same speed conditions.

[0083] (5) The difference between the measured active power values ​​of the drive motor when it is running at the same speed under no-load is the test result of the mechanical loss of the test motor at the corresponding speed, as detailed in Table 3. The test curve of the mechanical loss of the test motor as a function of speed or the mechanical loss test curve can be generated by the measurement results of each speed.

[0084] Table 3. Test results of mechanical loss of the tested motor

[0085]

[0086]

[0087] As shown in this disclosure and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. The terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "comprising" or "including" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects. The terms "connected" or "linked" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect.

[0088] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A dual-clutch testing device for measuring the mechanical losses of variable frequency motors, characterized in that, It includes two identical variable frequency motors, a speed measurement unit, a power measurement unit, and a drive control unit. One variable frequency motor is a drive motor, and the other is a load motor. The drive motor is separated from or connected to the load motor through a coupling to achieve mechanical engagement or disengagement of the drive motor and the load motor, or to enable the drive motor to be unloaded. The load motor is always in a de-energized state. When the drive motor is connected to the load motor via a coupling, the speed of the drive motor is measured by the speed measurement unit, and the load input active power of the drive motor at the corresponding speed is measured by the power measurement unit. When the drive motor is disconnected from the load motor through the coupling, the speed of the drive motor is measured by the speed measurement unit, and the no-load input active power of the drive motor at the corresponding speed is measured by the power measurement unit. The drive control unit is connected to the drive motor and is used to drive the drive motor and control its speed by frequency conversion, so that the drive motor can change its speed arbitrarily within its speed range for testing. The drive control unit is connected to the speed measurement unit and the power measurement unit respectively, and is used to obtain the mechanical loss of the variable frequency motor based on the active power input under load and the active power input under no-load. The load motor is always in a de-energized state. The difference between the load input active power and the no-load input active power measured under the same speed conditions is the mechanical loss test result of the variable frequency motor at the corresponding speed.

2. The dual-clutch testing device for measuring the mechanical loss of a variable frequency motor according to claim 1, characterized in that, The drive motor is always connected to the coupling during the test to eliminate the influence of coupling windage loss on the measurement results.

3. The dual-clutch testing device for measuring the mechanical loss of a variable frequency motor according to claim 1 or 2, characterized in that, The speed measurement unit includes a speed sensor and a signal conditioning box. The speed sensor is used to measure the speed signal of the drive motor, and the signal conditioning box is used to amplify and filter the speed signal.

4. The dual-clutch testing device for measuring the mechanical loss of a variable frequency motor according to claim 1 or 2, characterized in that, The power measurement unit includes a current sensor, a voltage sensor, and a power measurement analyzer. The current sensor is used to measure the input current of the drive motor; the voltage sensor is used to measure the input voltage of the drive motor; and the power measurement analyzer is connected to the current sensor and the voltage sensor respectively, and is used to obtain the input active power of the drive motor based on the measured input voltage, input current, and power factor of the drive motor.

5. A test method for a dual-clutch test device for measuring the mechanical losses of a variable frequency motor, based on any one of claims 1-4, characterized in that, Including the following steps: The drive motor is connected to the load motor via a coupling, and the load input active power of the drive motor is measured when the load motor is running at different speeds. The drive motor is disconnected from the load motor by a coupling, and the no-load input active power of the drive motor is measured when it is running at different speeds. The load motor is always in a de-energized state. The difference between the load input active power and the no-load input active power measured under the same speed conditions is the test result of the mechanical loss of the drive motor at the corresponding speed.

6. The test method according to claim 5, characterized in that, The specific process for measuring the active power input to the load is as follows: The drive motor is connected to or coupled in series with a non-powered load motor via a coupling, so that the drive motor is under load. The drive motor is started by reducing the load voltage and frequency through the inverter, and the speed of the drive motor is increased to the target measured speed by adjusting the power supply frequency of the inverter. The drive motor is fully loaded and operated at the target measured speed until the mechanical loss stabilizes. After the mechanical loss stabilizes, the speed of the drive motor and the corresponding load input active power are measured by the speed measurement unit and the power measurement unit, respectively. The target measured speed is changed and this step is repeated to obtain the load input active power at different speeds.

7. The test method according to claim 5, characterized in that, The specific process for measuring the no-load input active power is as follows: The unpowered load motor is not connected to, separated from, or disconnected from the coupling, so that the drive motor is in an unloaded state. The drive motor is started under no-load voltage and frequency reduction soft start through the inverter, and the speed of the drive motor is increased to the target measured speed by adjusting the power supply frequency of the inverter. The drive motor is fully idled at the target measurement speed until the mechanical loss stabilizes. After the mechanical loss stabilizes, the idle speed of the drive motor and the corresponding no-load input active power are measured by the speed measurement unit and the power measurement unit, respectively. The target measurement speed is changed, and this step is repeated to obtain the no-load input active power at different speeds.

8. The test method according to claim 5, 6, or 7, characterized in that, During the test, the drive motor was controlled by constant torque in the speed regulation range at and below the rated speed, and by constant power field weakening control in the speed regulation range above the rated speed.

9. The test method according to claim 5, 6, or 7, characterized in that, By measuring the three-phase input current of the drive motor when it is running at the same speed under no-load or load and the phase resistance of the stator winding when it is stopped, the effects of changes in current and copper loss of the drive motor before and after loading are eliminated through calculation.

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