Device and method for calculating output power of three-phase asynchronous motor based on speed and current

Abstract

The present invention relates to a device and method for calculating the output power of a three-phase asynchronous motor based on rotation speed and current, and is characterized by at least comprising: a three-phase power supply (1), a three-phase asynchronous motor (2), a current sensor (3), a rotation angle / rotation speed sensor (4), a data processing unit (5), a solution point unknown data prediction algorithm (6), and a pre-measured two-dimensional array of motor data (7); the three-phase power supply (1) and the three-phase asynchronous motor (2) are connected in a star or triangle connection, and a non-contact current sensor sleeve is connected to the connection circuit between the three-phase power supply (1) and the three-phase asynchronous motor (2). The device and method for calculating the output power of a three-phase asynchronous motor based on rotation speed and current can calculate the load state and working state of the motor, and then judge the working state and load state of the switch machine, guide maintenance work, make maintenance and repair work timely and effective, reduce or avoid ineffective maintenance, and improve maintenance efficiency.

Description

Technical Field

[0001] The present invention relates to a monitoring technology for the working state of a three-phase asynchronous motor, in particular to a device and a method for calculating the output power of the three-phase asynchronous motor according to the rotation speed and the current. Background Art

[0002] Railway turnouts are used outdoors. Due to changes in the environment or their own structural parameters, the driving force required for their switching will change. The turnout switch machine is usually the driving device for turnout switching, that is, the load of the turnout switch machine will change significantly during use. This load change may cause turnout switching failures, thereby affecting the operation of the train.

[0003] In order to truly understand the load of the turnout machine (that is, the turnout switching resistance), a force sensor can be installed on the load transfer path. However, due to reliability and safety issues, there are currently no practical force sensors for electric turnout machines. Electro-hydraulic turnout machines can calculate the output force of the hydraulic cylinder by measuring the system pressure.

[0004] Since the power of the switch machine comes from the motor, the output power of the motor can reflect the load condition of the switch machine. At present, the monitoring of motor power has been widely used. Most of the existing signal monitoring systems have the function of switch machine power monitoring, which can draw the power change curve during the operation of the switch machine. However, most of the current signal monitoring systems collect the voltage and current values ​​of the corresponding switch machine at the distribution board (distribution cabinet). If the power supply and working circuit of the switch machine after this test port are regarded as a single-port network, the apparent power input of the single-port network is usually calculated. Due to the existence of line resistance and reactive devices, the power calculated by the single-port network cannot truly reflect the input power of the motor, let alone the output power of the motor.

[0005] In the actual switch machine circuit, since the switch machine is installed in different positions, the line resistance is also different, and the actual voltage drop at the motor end is also significantly different from the power output end. In other words, the actual working voltage of the switch machine motor is different, and its actual working state is also different. In this way, it is difficult to determine other parameters according to a certain working voltage and a certain parameter.

[0006] When the motor load changes, the power factor and motor efficiency of its operating point change accordingly. Therefore, the relationship between the motor output power and the motor voltage and current changes with the operating point. Even if the motor terminal voltage and coil current are measured, it is difficult to determine the motor output power because the power factor and motor efficiency are unknown. Even if the power factor is calculated by technical means, the motor efficiency is still unknown. In addition, due to safety factors, the motor terminal voltage cannot be connected to the circuit for measurement and can only be measured using non-contact methods. However, non-contact voltage measurement methods are currently difficult to implement.

[0007] In summary, it is difficult to calculate the output power of the three-phase asynchronous motor of the switch machine by measuring the voltage and line current at the distribution board (distribution cabinet), or even directly measuring the voltage and coil current at the motor end, or the data reliability is low. If this data is used to guide maintenance work, it may increase the maintenance and repair work, resulting in ineffective maintenance or even waste.

[0008] Since the working state (output power) of the motor will change with the load under certain power supply conditions, the motor output power can reflect the load state of the motor, and then reflect the load of the switch machine. It can be seen that the load condition of the switch machine (including the internal resistance of the switch machine) can be monitored by monitoring the motor output power. The motor output power can be calculated by measuring the motor torque and motor speed. For the finalized equipment, the torque measurement may be difficult, but the speed of the transmission system can be conveniently achieved using non-contact methods. When the motor speed cannot be measured directly, the motor speed can be calculated by measuring other rotating parts and the reduction ratio. Therefore, the method of calculating the motor output power by the motor speed is of practical significance and can easily achieve the measurement of the motor output power. Summary of the invention

[0009] The present invention provides a device and method for calculating the output power of a three-phase asynchronous motor based on the rotational speed and current, so as to accurately understand the load state and working state of the motor, and then judge the working state and load state of the switch machine, guide the maintenance work, make the maintenance and repair work timely and effective, reduce or avoid ineffective maintenance, and improve maintenance efficiency.

[0010] The technical solution of the present invention is: a device for calculating the output power of a three-phase asynchronous motor based on the rotation speed and current, which is characterized by: at least comprising: a three-phase power supply, a three-phase asynchronous motor, a current sensor, a rotation angle / rotation speed sensor, a data processing unit, a prediction algorithm for unknown data at a solution point, and a two-dimensional array of motor data measured in advance; the three-phase power supply and the three-phase asynchronous motor are connected in a star or triangle connection, and a non-contact current sensor is connected to the connection loop between the three-phase power supply and the three-phase asynchronous motor; the rotation angle / rotation speed sensor is connected to the motor output shaft or a rotating part having a proportional relationship with the motor output shaft rotation speed to detect the motor output shaft rotation angle / speed, the output ends of the current sensor and the angle / speed sensor are electrically connected to the input end of the data processing unit; the current detection value and the angle / speed detection value are input into the data processing unit, and the unknown data prediction algorithm of the solution point in the data processing unit is combined with the two-dimensional array of motor data to perform calculations to solve the unknown data such as the torque, voltage, power factor, etc. that need to be solved; then, the motor output power is calculated from the speed and torque values, the motor input power is calculated from the current, voltage and power factor values, and the motor instantaneous efficiency is calculated from the input power and output power; these calculated data can basically reflect the motor state corresponding to the solution point.

[0011] The connection between the rotation angle / rotation speed sensor and the motor output shaft or other parts having a proportional relationship with the rotation speed of the motor output shaft is a photoelectric or magnetoelectric non-contact connection.

[0012] Each two-dimensional array in the motor data two-dimensional array is instantaneous data such as speed, torque, current, power factor, etc. measured under a constant voltage. The motor data two-dimensional array has k two-dimensional arrays, and the constant voltage corresponding to each two-dimensional array is arranged in order from small to large to form a one-dimensional array v[k]={v1, v2, ..., vk}. The speed, torque, current, power factor and voltage value measured under each voltage value constitute a two-dimensional array, recorded as avm[5][j]={{n1, t1, i1, θ1, vm},{n2, t2, i2, θ2, vm},……, {nj, tj, ij, θj, vm}}; nj represents the speed value, tj represents the torque value, ij represents the current value, θj represents the power factor, vm represents the voltage value, nj, tj, ij, θj, vm constitute a row of data. Each row of data must have at least three columns of speed n, torque t, and current i to calculate the motor output power. Corresponding data columns are required when calculating other motor parameters. According to the motor working state parameters that need to be mastered, the content of the data column in each row of the motor data two-dimensional array is determined.

[0013] In the one-dimensional array v[k], v1≤vmin, vk≥vmax, vmin is the minimum voltage value in the motor working environment, and vmax is the maximum voltage value in the motor working environment.

[0014] The method for calculating the output power of a three-phase asynchronous motor based on the speed and current includes at least the following steps:

[0015] Data preprocessing, the speed value and current value of each row in the k two-dimensional array are used as the coordinates of the point, and each point is plotted in the rectangular coordinate system formed by the speed coordinate axis and the current coordinate axis, which is called the known point, and the point is plotted with the measured speed and current values ​​as the coordinates, which is called the solution point.

[0016] Calculate the unknown data of the solution point, calculate the unknown data of the solution point or draw a circle with the solution point as the center and the set initial value as the radius, so that the circle contains at least d known points. If there are less than d points, gradually increase the radius until d known points are included. From the data rows corresponding to each known point included in the drawn circle, unknown values ​​such as torque, power factor, voltage, etc. are extracted, and their average value is calculated as the various values ​​corresponding to the solution point position.

[0017] Calculate the unknown data of the solution point or find the two known points closest and second closest to the solution point, establish a proportional relationship between the current value or speed value of the solution point and the two known points, extract the torque, voltage, power factor and other values ​​from the data rows corresponding to the two known points, perform proportional interpolation according to the established proportional relationship, and obtain the torque, voltage, power factor and other values ​​corresponding to the solution point.

[0018] Calculate the working state parameters such as motor power corresponding to the solution point, and after solving the torque, voltage, power factor and other values ​​corresponding to the solution point, obtain the motor output power from the speed and torque values, obtain the motor input power from the current, voltage and power factor values, and obtain the motor instantaneous efficiency from the input power and output power.

[0019] The advantages of the present invention are that the rotation speed and current of the three-phase asynchronous motor can be detected by a non-contact method, and combined with the pre-measured working state data (torque, power factor, etc.) of the motor under different voltages, the torque, power factor and other values ​​of the motor at the corresponding detection time can be predicted, and the output power, instantaneous efficiency and other data reflecting the working state of the motor can be calculated using the measured data and the predicted data. Since both the rotation speed and current can be detected by a non-contact method, the method has no effect on the safety of the motor and the switch machine, and can safely and conveniently predict other parameters and working states of the motor for guiding maintenance work, so that maintenance and repair work can be timely and fast, reduce ineffective maintenance, and improve maintenance efficiency.

[0020] The present invention will be further described below in conjunction with the accompanying drawings of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a schematic diagram of the structure of embodiment 1 of the present invention, in which a rotation angle / rotation speed sensor is used to directly detect the motor rotation speed.

[0022] Figure 2 It is a structural schematic diagram of embodiment 2 of the present invention, in which an angle / speed sensor is used to detect the speed of a gear shaft or gear in a reducer that is proportional to the speed of a motor shaft, and the speed of the motor shaft needs to be calculated.

[0023] In the figure, 1. three-phase power supply, 2. three-phase asynchronous motor, 3. current sensor, 4. angle / speed sensor, 5. data processing unit; 6. prediction algorithm for unknown data at solution point; 7. two-dimensional array of motor data; 8. reducer. DETAILED DESCRIPTION

[0024] Example 1

[0025] like Figure 1 As shown, the present invention relates to a device for calculating the output power of a three-phase asynchronous motor according to the rotation speed and current, which is characterized by at least comprising: a three-phase power supply 1, a three-phase asynchronous motor 2, a current sensor 3, a rotation angle / rotation speed sensor 4, a data processing unit 5, a solution point unknown data prediction algorithm 6, and a pre-measured motor data two-dimensional array 7; the three-phase power supply 1 and the three-phase asynchronous motor 2 are connected in a star or triangle connection, and the non-contact current sensor sleeve is connected to the connection loop between the three-phase power supply 1 and the three-phase asynchronous motor 2; the rotation angle / rotation speed sensor 4 is connected to the motor output shaft by a magnetoelectric or photoelectric device to detect the motor output shaft rotation angle / rotation speed, and detect the motor output The output shaft angle / speed, the output ends of the current sensor 3 and the angle / speed sensor 4 are electrically connected to the input end of the data processing unit 5; the current detection value and the angle / speed detection value are input to the data processing unit 5, and the unknown data prediction algorithm 6 of the solution point in the data processing unit 5 is combined with the two-dimensional array 7 of motor data to perform calculations to solve the required torque, voltage, power factor and other unknown data, and then the motor output power is calculated from the speed and torque values, the motor input power is calculated from the current, voltage and power factor values, and the motor instantaneous efficiency is calculated from the input power and output power, and these calculated data are used to reflect the motor state corresponding to the solution point.

[0026] The data processing unit 5 may include a memory for storing the two-dimensional array 7 of motor data, or may be externally connected to a memory for storing the two-dimensional array 7 of motor data, and reads data in the memory through a data channel.

[0027] The rotation angle / speed sensor 4 is connected to the motor output shaft by means of magnetoelectric or photoelectric devices. Parts that generate or change the magnetic field, change light reflection, or emit light are installed on the motor output shaft. Detection devices are installed at appropriate positions. The detection devices and the parts on the motor output shaft are coupled through magnetic fields or light and are not directly connected.

[0028] The motor data two-dimensional array 7 has k two-dimensional arrays, each of which is instantaneous data such as speed, torque, current, power factor, etc. measured under a constant voltage. The constant voltage corresponding to each two-dimensional array is arranged in order from small to large to form a one-dimensional array v[k]={v1, v2, ..., vk}, and the speed, torque, current, power factor and voltage value measured under each voltage value constitute a two-dimensional array. At least three columns of speed n, torque t, and current i are required in the two-dimensional array to calculate the motor output power. The two-dimensional array with the least number of columns is recorded as avm[3][j]={{n1, t1, i1},{n2, t2, i2}, ..., {nj, tj, ij}}; nj represents the speed value, tj represents the torque value, ij represents the current value, vm represents the voltage value, and nj, tj, ij constitute a row of data. When calculating other parameters of the motor, the two-dimensional array needs to have corresponding data columns, that is, according to the motor working state parameters that need to be mastered, the content of the data column in each row of the motor data two-dimensional array 7 is determined. If the motor input power needs to be calculated, two columns of data, voltage and power factor, need to be added to each row of the two-dimensional array. The expanded two-dimensional array is recorded as avm[5][j]={{n1, t1, i1, θ1, vm},{n2, t2, i2, θ2, vm},...,{nj, tj, ij, θj, vm}}; θj represents the power factor, vm represents the voltage value, and nj, tj, ij, θj, vm constitute a row of data.

[0029] In the one-dimensional array v[k], v1≤vmin, vk≥vmax, vmin is the minimum voltage value in the motor working environment, and vmax is the maximum voltage value in the motor working environment.

[0030] The solution point unknown data prediction algorithm at least includes the following steps:

[0031] Data preprocessing, the speed value and current value of each row in the k two-dimensional array are used as the coordinates of the point, and each point is plotted in the rectangular coordinate system formed by the speed coordinate axis and the current coordinate axis, which is called the known point, and the point is plotted with the measured speed and current values ​​as the coordinates, which is called the solution point.

[0032] Calculate the unknown data of the solution point or draw a circle with the solution point as the center and the set initial value as the radius, so that the circle contains at least d known points. If there are less than d points, gradually increase the radius until d known points are included. From the data rows corresponding to each known point included in the drawn circle, extract the unknown values ​​such as torque, power factor, voltage, etc., and calculate their average value as the various values ​​corresponding to the solution point position.

[0033] Calculate the unknown data of the solution point or find the two known points closest and second closest to the solution point, establish a proportional relationship between the current value or speed value of the solution point and the two known points, extract the torque, voltage, power factor and other values ​​from the data rows corresponding to the two known points, perform proportional interpolation according to the established proportional relationship, and obtain the torque, voltage, power factor and other values ​​corresponding to the solution point.

[0034] Example 2

[0035] like Figure 2 As shown, the rotation angle / speed sensor 4 is photoelectrically or electromagnetically connected to a gear shaft in the reducer 8 connected to the output shaft of the three-phase asynchronous motor 2, and the speed of the motor shaft is calculated according to the proportional relationship. Except that the motor shaft speed is measured by an indirect method, the rest is the same as Example 1 and will not be described in detail.

Claims

1. A method for calculating the output power of a three-phase asynchronous motor based on speed and current, characterized in that: include: A three-phase power supply (1), a three-phase asynchronous motor (2), a current sensor (3), a rotation angle / speed sensor (4), a data processing unit (5), a solution point unknown data prediction algorithm (6), and a pre-measured two-dimensional array of motor data (7); the three-phase power supply (1) and the three-phase asynchronous motor (2) are connected in a star or triangle connection, and a non-contact current sensor sleeve is connected to the connection circuit between the three-phase power supply (1) and the three-phase asynchronous motor (2); the rotation angle / speed sensor (4) is connected to the motor output shaft or a rotating part in a power transmission path that has a proportional relationship with the motor output shaft speed to detect the motor output shaft rotation angle / speed, and the output ends of the current sensor (3) and the rotation angle / speed sensor (4) are electrically connected to the input end of the data processing unit (5); the electric The current detection value and the rotation angle / speed detection value are input to the data processing unit (5), and the unknown data prediction algorithm (6) of the solution point in the data processing unit (5) is combined with the motor data two-dimensional array (7) to perform calculations to solve the unknown data of torque, voltage and power factor to be solved; then, the motor output power is obtained from the speed and torque values, the motor input power is obtained from the current, voltage and power factor values, and the motor instantaneous efficiency is obtained from the input power and output power; these calculated data can reflect the motor state corresponding to the solution point; the rotation angle / speed sensor (4) is connected to the motor output shaft or a rotating part that has a proportional relationship with the motor output shaft speed, and is a part installed on the measured part to generate or change the magnetic field or change the light reflection or emit light , a detection device is installed at an appropriate position, and the detection device and the parts on the motor output shaft are not directly connected through magnetic field or optical coupling; the data processing unit (5) includes a memory for storing the two-dimensional array (7) of motor data, or an external memory for storing the two-dimensional array (7) of motor data, and reads the data in the memory through a data channel; the two-dimensional array of motor data is k two-dimensional arrays, wherein each two-dimensional array is composed of instantaneous data rows of speed, torque, current, and power factor measured under a constant voltage, and each two-dimensional array contains at least three types of data: speed, torque, and current. The k voltage values ​​are arranged in order from small to large to form a one-dimensional array v[k]={v1, v2, ..., vk}, which contains speed, torque, The two-dimensional array of three types of current data is recorded as avm[3][j]={{n1, t1, i1},{n2, t2, i2},...,{nj, tj, ij}}; nj represents the speed value, tj represents the torque value, ij represents the current value, vm represents the test voltage value, nj, tj, ij constitute a row of data, n, t, i have three columns of data, and each row of data can be expanded to more columns as needed, using more parameters to describe the working state of the motor, and adding power factor and voltage parameters; in the one-dimensional array v[k], v1≤vmin, vk≥vmax, vmin is the minimum voltage value in the motor working environment, and vmax is the maximum voltage value in the motor working environment; the method described comprises at least the following steps: Data preprocessing, taking the speed value and current value of each row in the k two-dimensional array as the coordinates of the point, plotting each point in the rectangular coordinate system formed by the speed coordinate axis and the current coordinate axis, called the known point, and plotting the point with the measured speed and current value as the coordinate, called the solution point; Calculate the unknown data of the solution point, based on the known speed and current data of the solution point, combined with the known two-dimensional array of motor data, apply the unknown data prediction algorithm of the solution point to calculate the unknown data compared with the solution point and the two-dimensional array; Calculate the required motor working state parameters, perform calculations based on the measured and calculated data as needed, obtain the motor output power from the speed and torque values, obtain the motor input power from the current, voltage and power factor values, and obtain the motor instantaneous efficiency from the input power and output power.

2. The method for calculating the output power of a three-phase asynchronous motor according to the rotation speed and current according to claim 1 is characterized in that: To calculate the unknown data of the solution point, a circle is drawn with the solution point as the center and the set initial value as the radius, so that the circle contains at least d known points. If there are less than d known points, the radius is gradually increased until d known points are included. The unknown values ​​of torque, power factor, and voltage are taken from the data rows corresponding to each known point included in the drawn circle, and their average values ​​are calculated as the values ​​corresponding to the solution point position.

3. The method for calculating the output power of a three-phase asynchronous motor according to the rotation speed and current according to claim 1 is characterized in that: The method of calculating the unknown data of the solution point is to find the two known points closest and second closest to the solution point, establish a proportional relationship between the current value or speed value of the solution point and the two known points, extract the torque, voltage, and power factor values ​​from the data rows corresponding to the two known points, perform proportional interpolation according to the established proportional relationship, and obtain the torque, voltage, and power factor values ​​corresponding to the solution point.

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