Motor overload protection method and device, electronic equipment and storage medium

Abstract

The invention relates to a motor overload protection method and device, electronic equipment and a storage medium, and the method comprises the steps: obtaining a current current value and a current rotating speed value of a motor, calculating the initial delay execution time of a motor protection action based on the current current value, the current rotating speed value and a motor thermal time coefficient, and carrying out the motor overload protection according to the initial delay execution time; executing a motor protection action; according to the method, the motor thermal time constants are determined through the motor historical temperature data, the motor historical current data and the motor historical rotating speed data, and due to the fact that the motor historical temperature data, the motor historical current data and the motor historical rotating speed data of different motors are different, the calculated motor thermal time constants are different; therefore, the technical problem that the delay execution time of the motor protection action calculated through the fixed motor thermal time constant is inaccurate and the motor protection effect is affected is solved, the thermal capacity of the synchronous motor can be correctly simulated, and the protection effect of the synchronous motor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor overload protection, and in particular to a motor overload protection method, device, electronic equipment and storage medium. Background Art

[0002] The low-voltage motor protector is suitable for three-phase motor applications with an AC voltage of 380V, a frequency of 50Hz, and a current of less than 800A. It can provide protection for motor overload, short circuit, phase loss and other faults. At the same time, it has the functions of monitoring parameters, motion control and communication, and can replace thermal relays, ammeters, voltmeters, transmitters and other equipment. The low-voltage motor protector consists of a three-phase current input circuit, a voltage transformer, a detection circuit, an amplification circuit, a delay circuit, an adjustment circuit, an execution relay and a microcontroller. When the low-voltage motor protector detects that the motor current or voltage is overloaded, or the motor voltage is phase-loss, etc., the microprocessor calculates the output protection action time to activate the execution relay. After the execution relay is activated, the contactor can be powered off to protect the motor.

[0003] The digital inverse time protection action curves currently used in motor protectors are all first-order heat conduction equations established through approximation or simplification of a lumped parameter thermal network composed of heat sources representing motor losses. This method only considers the influence of motor current and motor working time on motor temperature, and the motor thermal time constant, as an important parameter in the first-order heat conduction equation, is fixed, resulting in inaccurate calculated protection action time, affecting the protection effect on the motor. In addition, the first-order heat conduction equation based on a fixed thermal time constant cannot correctly simulate the thermal capacity of the synchronous motor, especially when accelerating from a stopped state to a high-speed state or when the synchronous motor is in a deceleration state, it cannot effectively protect the synchronous motor.

[0004] Therefore, it is necessary to improve the existing motor overload protection method. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present application provides a motor overload protection method, device, electronic device and storage medium to solve the above-mentioned technical problems.

[0006] The present invention provides a motor overload protection method, which includes: obtaining a current current value and a current speed value of a motor; calculating an initial delay execution time of a motor protection action based on the current current value, the current speed value and a motor thermal time coefficient; the motor thermal time coefficient is determined by historical motor temperature data, historical motor current data and historical motor speed data; the motor protection action is used to protect the motor from overload; and executing the motor protection action according to the initial delay execution time.

[0007] In one embodiment of the present invention, based on the current current value, the current speed value and the motor thermal time coefficient, the process of calculating the initial delayed execution time of the motor protection action includes: converting the current current value into a current per unit value, and converting the current speed value into a speed per unit value; using the motor thermal time coefficient as the adjustment coefficient in the preset time fitting curve, using the current per unit value as the input current value in the preset time fitting curve, and using the speed per unit value as the input speed value in the preset time fitting curve to calculate the initial delayed execution time of the motor protection action.

[0008] In one embodiment of the present invention, the process of determining the thermal time coefficient of the motor through the motor historical temperature data, the motor historical current data and the motor historical speed data includes: obtaining a preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed; the motor historical temperature data includes the detected temperature values ​​of the motor stator winding at different historical moments; the motor historical current data includes the detected current values ​​of the motor at different historical moments; the motor historical speed data includes the detected speed values ​​of the motor at different historical moments; the motor historical current data and the motor historical speed data are input into the preset relationship function to obtain the calculated temperature rise values ​​of the motor stator winding at different unit times; the preset relationship function is converted into a regression equation, and based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value, the polynomial coefficients in the regression equation are solved, and the solved polynomial coefficients are used as the thermal time coefficient of the motor.

[0009] In one embodiment of the present invention, based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value, the process of solving the polynomial coefficients in the regression equation includes: calculating the difference between the detected temperature values ​​at adjacent moments as the actual temperature rise value of the motor stator winding at different unit times; based on the actual temperature rise value, the calculated temperature rise value, the detected current value and the detected speed value, calculating the polynomial coefficients.

[0010] In one embodiment of the present invention, before obtaining the preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed, the method includes: establishing a heat conduction equation of the motor; the variables in the heat conduction equation include the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor; solving the heat conduction equation to obtain the preset relationship function between the motor stator winding temperature rise and the motor current and the motor speed.

[0011] In one embodiment of the present invention, the process of executing the motor protection action according to the initial delayed execution time includes: obtaining the sampled current value and the sampled speed value of the motor within the initial delayed execution time; determining the updated delayed execution time of the motor protection action based on the comparison results of the sampled current value and the current current value, and the comparison results of the sampled speed value and the current speed value; and executing the motor protection action according to the updated delayed execution time.

[0012] In one embodiment of the present invention, according to the comparison result of the sampled current value and the current current value, and the comparison result of the sampled speed value and the current speed value, the process of determining the update delay execution time of the motor protection action includes: if the sampled current value is consistent with the current current value, and the sampled speed value is consistent with the current speed value, the initial delay execution time is used as the update delay execution time; if the sampled current value is inconsistent with the current current value, and the sampled speed value is consistent with the current speed value, the update delay execution time is calculated according to the sampled current value, the current speed value and the motor thermal time coefficient; if the sampled current value is consistent with the current current value, and the sampled speed value is inconsistent with the current speed value, the update delay execution time is calculated according to the current current value, the sampled speed value and the motor thermal time coefficient; if the sampled current value is inconsistent with the current current value, and the sampled speed value is inconsistent with the current speed value, the update delay execution time is calculated according to the sampled current value, the sampled speed value and the motor thermal time coefficient.

[0013] According to one aspect of an embodiment of the present invention, a motor overload protection device is provided, comprising: a current acquisition module, used to acquire a current current value and a current speed value of a motor; a time calculation module, used to calculate an initial delay execution time of a motor protection action based on the current current value, the current speed value and a thermal time coefficient of the motor; the thermal time coefficient of the motor is determined by historical temperature data of the motor, historical current data of the motor and historical speed data of the motor; the motor protection action is used to protect the motor from overload; and an overload protection module, used to execute the motor protection action according to the initial delay execution time.

[0014] According to one aspect of an embodiment of the present invention, there is provided an electronic device, comprising: one or more processors; a storage device for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the electronic device implements the motor overload protection method as described above.

[0015] According to one aspect of an embodiment of the present application, a computer storage medium is provided, including: computer-readable instructions are stored thereon, and when the computer-readable instructions are executed by a processor of a computer, the computer executes the motor overload protection method described above.

[0016] Beneficial effects of the present invention: The present invention obtains the current current value and the current speed value of the motor, calculates the initial delayed execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient, and executes the motor protection action according to the initial delayed execution time. In the above process, the motor thermal time constant is determined by the motor historical temperature data, the motor historical current data and the motor historical speed data. Due to the differences in the motor historical temperature data, the motor historical current data and the motor historical speed data of different motors, the calculated motor thermal time constants are different, thereby avoiding the technical problem that the delayed execution time of the motor protection action calculated by the fixed motor thermal time constant is inaccurate, which affects the motor protection effect; in addition, the thermal conduction equation of the motor is a second-order conduction equation established based on the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor, which can correctly simulate the thermal capacity of the synchronous motor and improve the protection effect of the synchronous motor.

[0017] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0019] Figure 1 is a schematic diagram of an exemplary system architecture shown in an exemplary embodiment of the present application;

[0020] Figure 2 is a flow chart of a motor overload protection method shown in an exemplary embodiment of the present application;

[0021] Figure 3 is a schematic diagram of a second-order heat conduction model of a motor shown in an exemplary embodiment of the present application;

[0022] Figure 4is a block diagram of a motor overload protection device shown in an exemplary embodiment of the present application;

[0023] Figure 5 A schematic diagram of the structure of a computer system suitable for implementing an electronic device of an embodiment of the present application is shown. DETAILED DESCRIPTION

[0024] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0025] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0026] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0027] Figure 1 It is a schematic diagram of an exemplary system architecture shown in an exemplary embodiment of the present application.

[0028] Reference Figure 1As shown, the system architecture may include an acquisition device 101 and a computer device 102. The computer device 102 may be at least one of a desktop graphics processing unit (GPU) computer, a GPU computing cluster, a neural network computer, etc. Relevant technicians may use the computer device 102 to obtain the current current value and the current speed value of the motor, and calculate the initial delay execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient, and execute the motor protection action according to the initial delay execution time. The acquisition device 101 is used to collect the current current value and the current speed value of the motor. In this embodiment, the acquisition device 101 uses sensors and other devices to collect the current current value and the current speed value of the motor, and provides them to the computer device 102 for processing.

[0029] Indicatively, after obtaining the current current value and current speed value of the motor in the acquisition device 101, the computer device 102 calculates the initial delay execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient, and executes the motor protection action according to the initial delay execution time. In the above process, the motor thermal time constant is determined by the motor historical temperature data, the motor historical current data and the motor historical speed data. Due to the differences in the motor historical temperature data, the motor historical current data and the motor historical speed data of different motors, the calculated motor thermal time constant Different, thereby avoiding the technical problem that the delayed execution time of the motor protection action calculated by a fixed motor thermal time constant is inaccurate, which affects the protection effect of the motor; in addition, the thermal conduction equation of the motor is a second-order conduction equation based on the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor. It can correctly simulate the thermal capacity of the synchronous motor and improve the protection effect of the synchronous motor.

[0030] It should be noted that the motor overload protection method provided in the embodiment of the present application is generally executed by the computer device 102 , and accordingly, the motor overload protection device is generally disposed in the computer device 102 .

[0031] The implementation details of the technical solution of the embodiment of the present application are described in detail below:

[0032] Figure 2 is a flow chart of a motor overload protection method shown in an exemplary embodiment of the present application. The motor overload protection method can be executed by a computing and processing device. The computing and processing device can be Figure 1 The computer device 102 shown in FIG. Figure 2As shown, the motor overload protection method at least includes steps S210 to S230, which are described in detail as follows:

[0033] In step S210, the current current value and the current speed value of the motor are obtained. In one embodiment of the present application, the current current value of the motor can be detected by a current sensor, or calculated by parameters such as the power, voltage, and power factor of the motor, and the current speed value of the motor can be detected by a speed sensor, or calculated by the power supply frequency of the motor and the number of pole pairs of the motor's rotating magnetic field.

[0034] In step S220, based on the current current value, the current speed value and the motor thermal time coefficient, the initial delayed execution time of the motor protection action is calculated. In the present embodiment, the motor protection action is used to protect the motor from overload, and the motor protection action includes controlling the motor to stop running, controlling the motor power supply to trip and other actions. The motor thermal time coefficient is determined by the motor historical temperature data, the motor historical current data and the motor historical speed data, which improves the accuracy of the motor thermal time coefficient calculation and avoids using a fixed motor thermal time constant to calculate the delayed execution time of the motor protection action. Based on the current current value, the current speed value and the motor thermal time coefficient, the process of calculating the initial delayed execution time of the motor protection action includes: converting the current current value into a current per unit value, and converting the current speed value into a speed per unit value; using the motor thermal time coefficient as the adjustment coefficient in the preset time fitting curve, using the current per unit value as the input current value in the preset time fitting curve, and using the speed per unit value as the input speed value in the preset time fitting curve, calculating the initial delayed execution time of the motor protection action, on the basis of improving the accuracy of the motor thermal time coefficient, improving the accuracy of the initial delayed execution time, thereby improving the protection effect on the motor.

[0035] In step S230, the motor protection action is executed according to the initial delayed execution time. In this embodiment, the process of executing the motor protection action according to the initial delayed execution time includes: obtaining the sampled current value and the sampled speed value of the motor within the initial delayed execution time; determining the updated delayed execution time of the motor protection action according to the comparison result of the sampled current value and the current current value, and the comparison result of the sampled speed value and the current speed value; executing the motor protection action according to the updated delayed execution time, after determining the initial delayed execution time, if the sampled current value within the initial delayed execution time changes relative to the current current value or the sampled speed value changes relative to the current current value, then the initial delayed execution time is updated, and the motor protection action is executed according to the updated delayed execution time, so that the delayed execution time of the motor protection action can be determined according to the real-time operation of the motor, which improves the accuracy and flexibility of determining the delayed execution time of the motor protection action.

[0036] In one embodiment of the present application, based on the current current value, the current speed value and the motor thermal time coefficient, the process of calculating the initial delayed execution time of the motor protection action includes:

[0037] The current current value is converted into a current per unit value, and the current speed value is converted into a speed per unit value.

[0038] In this embodiment, the expression of the per unit current value is as follows:

[0039] I pu =I / I r Formula (1)

[0040] Among them, I pu Indicates the current per unit value, I indicates the current current value, I r Indicates the rated current value of the motor.

[0041] The expression of the speed per unit value is as follows:

[0042] n pu =n / n r Formula (2)

[0043] Among them, n pu Indicates the speed per unit value, n indicates the current speed value, n r Indicates the rated speed of the motor.

[0044] The initial delayed execution time of the motor protection action is calculated by using the motor thermal time coefficient as the adjustment coefficient in the preset time fitting curve, the current per unit value as the input current value in the preset time fitting curve, and the speed per unit value as the input speed value in the preset time fitting curve.

[0045] In this embodiment, the expression of the preset time fitting curve is as follows:

[0046] t y =θ max / (x 00 +x 01 I pu +x 10 n pu +x 20 I pu 2 +x 02 n pu 2 ) Formula (3)

[0047] Among them, t y represents the initial delay execution time, θ max Indicates the motor insulation level corresponding to the winding temperature rise, I pu Indicates the per unit current value, npu Indicates the speed per unit value, x 00 、x 01 、x 10 、x 20 and x 02 The motor thermal time coefficient is composed of x 00 As the adjustment coefficient of the constant term in the preset time fitting curve, x 01 As the adjustment coefficient of the first-order term of the current per unit value in the preset time fitting curve, x 10 As the adjustment coefficient of the first-order term of the speed per unit value in the preset time fitting curve, x 20 As the adjustment coefficient of the quadratic term of the current per unit value in the preset time fitting curve, x 02 As the adjustment coefficient of the quadratic term of the speed per unit value in the preset time fitting curve.

[0048] In one embodiment of the present application, the process of determining the thermal time coefficient of the motor by using the historical temperature data, the historical current data and the historical speed data of the motor includes:

[0049] Obtain a preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed. In this embodiment, the historical temperature data of the motor includes the detected temperature values ​​of the motor stator winding at different historical moments, and the detected temperature values ​​are collected by devices such as temperature sensors. The historical current data of the motor includes the detected current values ​​of the motor at different historical moments, and the detected current values ​​are collected by devices such as current sensors. The historical speed data of the motor includes the detected speed values ​​of the motor at different historical moments, and the detected speed values ​​are collected by devices such as speed sensors.

[0050] In this embodiment, the expression of the preset relationship function is as follows:

[0051] θ k = x′ 00 Δt+x′ 01 I pu (k)Δt+x′ 10 n pu (k)Δt+x′ 20 I pu (k) 2 Δt+x′ 02 n pu (k) 2 Δt Formula (4)

[0052] Among them, θ k represents the temperature rise value of the motor stator winding at the kth unit time. The temperature rise value of the kth unit time is the difference between the temperature value of the motor stator winding at the kth moment and the temperature value of the motor stator winding at the k-1th moment. Δt represents the duration of the unit time. I pu(k) represents the per unit current value at the kth moment, n pu (k) represents the speed per unit value at the kth moment, x′ 00 Represents the adjustment coefficient of the constant term in the preset relationship function, x′ 01 represents the adjustment coefficient of the first-order term of the current per unit value at the kth moment in the preset relationship function, x′ 10 represents the adjustment coefficient of the first-order term of the k-th moment speed per unit value in the preset relationship function, x′ 20 represents the adjustment coefficient of the quadratic term of the current per unit value at the kth moment in the preset relationship function, x′ 02 It represents the adjustment coefficient of the quadratic term of the speed per unit value at the kth moment in the preset relationship function, where k is a positive integer.

[0053] The motor historical current data and the motor historical speed data are input into a preset relationship function to obtain the calculated temperature rise values ​​of the motor stator winding at different unit times. In this embodiment, the adjustment coefficient in the preset relationship function is determined by at least two of the motor rated speed, the motor rated current, the thermal resistance between the motor stator winding and the motor stator core, the thermal resistance between the motor stator core and the environment, the motor stator core hysteresis loss coefficient, the motor stator core eddy current loss coefficient, the motor stator core magnetic flux peak value, the Steinmetz constant, the motor current speed, the motor pole pair number, the motor stator core mass, the motor stator winding thermal capacity and the motor stator core thermal capacity. Since the calculation of the adjustment coefficient in the preset relationship function fully considers parameters such as the motor stator iron loss and the motor stator heating, the accuracy of the adjustment coefficient in the preset relationship function is improved, thereby improving the accuracy of the calculated temperature rise values ​​of the motor stator winding at different unit times.

[0054] The preset relationship function is converted into a regression equation, and the polynomial coefficients in the regression equation are solved based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value, and the solved polynomial coefficients are used as the motor thermal time coefficients. In this embodiment, the regression equation is a binary regression equation, and the expression of the binary regression equation is as follows:

[0055]

[0056] Among them, θ k represents the temperature rise of the motor stator winding in the kth unit time, λ represents the order of the current motor current, γ represents the order of the current motor speed, and x γλ represents the polynomial coefficient in the regression equation, ε k It represents the error between the actual temperature rise value of the motor stator winding at the kth unit time and the calculated temperature rise value of the motor stator winding at the kth unit time, and q represents the maximum value of the sum of λ and γ.

[0057] In this embodiment, the binary regression equation is written in matrix form as follows:

[0058] θ=XT Inp +ε Formula (6)

[0059] Among them, θ represents the temperature rise value matrix of the motor stator winding k unit time, x represents the polynomial coefficient matrix in the regression equation, T Inp It represents the matrix of different order terms of the current motor current and the current motor speed in the regression equation within k unit time, and ε represents the error matrix between the actual temperature rise value and the calculated temperature rise value of the motor stator winding within k unit time.

[0060] In this embodiment, the least square method is used to solve formula (6) to obtain the expression of the polynomial coefficients:

[0061] X=(T Inp T T Inp ) -1 T Inp T (θ-ε) Formula (7)

[0062] Where X represents the polynomial coefficient matrix in the regression equation, T Inp represents the matrix of different order terms of the current motor current and the current motor speed in the regression equation within k unit time, θ represents the temperature rise value matrix of the motor stator winding within k unit time, and ε represents the error matrix between the actual temperature rise value and the calculated temperature rise value of the motor stator winding within k unit time.

[0063] In this embodiment, when q=2, X=[x 00 , x 01 , x 10 , x 20 , x 02 ] T , x 00 represents the constant term coefficient in the regression equation, x 01 represents the coefficient of the first-order term of the current per unit value in the regression equation, x 10 represents the coefficient of the first-order term of the speed per unit value in the regression equation, x 20 represents the coefficient of the quadratic term of the current per unit value in the regression equation, x 02 It represents the coefficient of the quadratic term in the regression equation with the speed per unit value as the coefficient.

[0064] In this embodiment, ε=[ε 1 , ε 2 , …, ε k ] T , ε 1Indicates the error between the actual temperature rise value and the calculated temperature rise value of the motor stator winding in the first unit time, ε 2 Indicates the error between the actual temperature rise value and the calculated temperature rise value of the motor stator winding in the second unit time, ε k It represents the error between the actual temperature rise value and the calculated temperature rise value of the motor stator winding in the kth unit time.

[0065] In this embodiment, θ=[θ 1 ,θ 2 ,…,θ k ] T ,θ 1 Indicates the temperature rise of the motor stator winding in the first unit time, θ 2 Indicates the temperature rise of the motor stator winding in the second unit time, θ k It represents the temperature rise value of the motor stator winding in the kth unit time.

[0066] In this embodiment, I pu (1) represents the current per unit value at the first moment, I pu (2) represents the current per unit value at the second moment, I pu (k) represents the per unit current value at the kth moment, n pu (1) represents the speed per unit value at the first moment, n pu (2) represents the speed per unit value at the second moment, n pu (k) represents the speed per unit value at the kth moment.

[0067] In one embodiment of the present application, based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value, the process of solving the polynomial coefficients in the regression equation includes:

[0068] The difference of the detected temperature values ​​at adjacent moments is calculated as the actual temperature rise value of the motor stator winding at different unit times. In this embodiment, the unit time is set according to the actual situation, for example, the unit time is set to 1s, or the unit time is set to a sampling period, etc.

[0069] Based on the actual temperature rise value, the calculated temperature rise value, the detected current value and the detected speed value, the polynomial coefficients are calculated. In this embodiment, the actual temperature rise value, the calculated temperature rise value, the detected current value and the detected speed value are input into formula (7) to calculate the polynomial coefficients.

[0070] In one embodiment of the present application, before obtaining a preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed, the motor overload protection method includes:

[0071] A heat conduction equation of the motor is established. In this embodiment, the variables in the heat conduction equation include the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor.

[0072] Figure 3 is a schematic diagram of a second-order heat conduction model of a motor shown in an exemplary embodiment of the present application, such as Figure 3 As shown in FIG. 1 , the second-order heat conduction model of the motor is established by considering only the heating of the motor stator during the operation of the motor and according to the lumped parameter method and the law of conservation of energy. When only the heating of the motor stator is considered, the variables in the second-order heat conduction model of the motor include the stator winding temperature U 2 、Motor stator winding heat capacity C 2 , thermal resistance R between the motor stator winding and the motor stator core 2 , Motor stator winding copper loss P cu , Motor stator core temperature U 1 、Motor stator core heat capacity C 1 , thermal resistance R between the motor stator core and the environment 1 、Motor stator core iron loss P fe And the overall motor temperature U.

[0073] In this embodiment, based on the second-order heat conduction model of the motor, the expression of the heat conduction equation is as follows:

[0074]

[0075] Among them, U 2 Indicates the motor stator winding temperature, C 2 Represents the heat capacity of the motor stator winding, R 2 Represents the thermal resistance between the motor stator winding and the motor stator core, P cu Indicates the copper loss of the motor stator winding, U 1 Indicates the motor stator core temperature, C 1 Represents the heat capacity of the motor stator core, R 1 Represents the thermal resistance between the motor stator core and the environment, P fe It represents the iron loss of the motor stator core, and U is the overall temperature of the motor.

[0076] The heat conduction equation is solved to obtain a preset relationship function between the temperature rise of the motor stator winding and the motor current and motor speed. In this embodiment, the heat conduction equation is solved to obtain the following expression:

[0077]

[0078] Among them, U 2 Indicates the motor stator winding temperature, C 2 Represents the heat capacity of the motor stator winding, R 2 Represents the thermal resistance between the motor stator winding and the motor stator core, P cu Indicates the copper loss of the motor stator winding, U 1 Indicates the motor stator core temperature, C 1 Represents the heat capacity of the motor stator core, R 1 Represents the thermal resistance between the motor stator core and the environment, P fe represents the iron loss of the motor stator core, U is the overall temperature of the motor, and t represents the motor running time.

[0079] In this embodiment, when harmonic current is not considered, the calculation formula of the motor stator winding copper loss is as follows:

[0080] P cu =I 2 R formula (10)

[0081] Among them, P cu represents the copper loss of the motor stator winding, I represents the current current value, which is the effective value of the motor phase current, and R represents the resistance of each phase winding of the motor stator. According to the Steinmentz equation, the formula for calculating the iron loss of the motor stator core is as follows:

[0082]

[0083] Among them, P fe Indicates the iron loss of the motor stator core, k h Indicates the hysteresis loss coefficient of the motor stator core, k e It represents the eddy current loss coefficient of the motor stator core, B represents the peak magnetic flux density of the motor stator core, β represents the Steinmetz constant, n represents the current speed value, p represents the number of motor pole pairs, and m represents the mass of the motor stator core.

[0084] In this embodiment, the motor insulation level refers to the maximum temperature that the motor stator winding can withstand during operation. In order to prevent the motor insulation material from being broken down or aged, thereby affecting the motor's service life, the key to thermal protection is to control the motor stator winding temperature rise not to exceed the insulation level.

[0085] In this embodiment, formula (9), formula (10) and formula (11) are combined to obtain the following expression:

[0086]

[0087] Among them, U 2 (t) represents the motor stator winding temperature related to the motor running time t, R 1Represents the thermal resistance between the motor stator core and the environment, k 1 Indicates the current motor speed coefficient, n indicates the current speed value, k 2 Indicates the motor speed rating factor, n r Indicates the rated speed of the motor, τ 2 Represents the second time adjustment coefficient, R 2 It represents the thermal resistance between the motor stator winding and the motor stator core, I represents the current current value, R represents the resistance value of each phase winding of the motor stator, τ 1 represents the first time adjustment coefficient, and U(t) represents the overall temperature of the motor related to the motor running time t.

[0088] In this embodiment, k 1 The expression is as follows:

[0089] k 1 =mk h B β pπ / 30 Formula (13)

[0090] Among them, k 1 It represents the coefficient of the current motor speed value, m represents the mass of the motor stator core, kh represents the hysteresis loss coefficient of the motor stator core, B represents the peak magnetic flux density of the motor stator core, β represents the Steinmetz constant, and p represents the number of motor pole pairs.

[0091] In this embodiment, k 2 The expression is as follows:

[0092] k 2 =mk e B 2 p 2 π 2 / 900 Formula (14)

[0093] Among them, k 2 represents the motor speed rating coefficient, m represents the motor stator core mass, k e represents the eddy current loss coefficient of the motor stator core, B represents the peak magnetic flux density of the motor stator core, and p represents the number of motor pole pairs.

[0094] In this embodiment, τ 1 The expression is as follows:

[0095] τ 1 =C 2 R 2 Formula (15)

[0096] Among them, τ 1 Indicates the first time adjustment coefficient, C 2 Represents the heat capacity of the motor stator winding, R 2Represents the thermal resistance between the motor stator winding and the motor stator core.

[0097] In this embodiment, τ 2 The expression is as follows:

[0098]

[0099] Among them, τ 2 Indicates the second time adjustment coefficient, C 1 Represents the heat capacity of the motor stator core, R 1 Represents the thermal resistance between the motor stator core and the environment, R 2 Represents the thermal resistance between the motor stator winding and the motor stator core.

[0100] In this embodiment, formula (12) reflects the preset relationship function between the motor stator winding temperature and the motor current and motor speed, reflecting the main part of the motor stator winding heat accumulation during the motor operation, and the motor stator winding temperature is exponentially related to the motor current and motor speed. When the motor is running at the rated state, the motor stator winding heat generation and heat dissipation are balanced, and the temperature reaches a stable value. At this time, t = 0, I = I r , n=n r , U(0)=U r , formula (12) can be rewritten as:

[0101]

[0102] Among them, U 2 (t) represents the motor stator winding temperature related to the motor running time t, R 1 Represents the thermal resistance between the motor stator core and the environment, k 1 Indicates the motor speed coefficient, n r Indicates the rated speed of the motor, n pu Indicates the motor speed per unit value, k 2 Indicates the motor speed rating factor, τ 2 Represents the second time adjustment coefficient, R 2 Represents the thermal resistance between the motor stator winding and the motor stator core, I r Indicates the rated current of the motor, R indicates the resistance of each phase winding of the motor stator, I pu Represents the per-unit value of the motor current, τ 1 Indicates the first time adjustment coefficient.

[0103] In this embodiment, Taylor expansion is performed on the exponential term in formula (17), and only the first two terms of the expanded polynomial are taken to obtain the following expression:

[0104] U 2 (t) = R1 k 1 n r (n pu +1)t+R 1 k 2 n r 2 (n pu 2 +1)t+(R 1 +R 2 )I r 2 R(I pu 2 +1)t Formula (18)

[0105] Among them, U 2 (t) represents the motor stator winding temperature related to the motor running time t, R 1 Represents the thermal resistance between the motor stator core and the environment, k 1 Indicates the motor speed coefficient, n r Indicates the rated speed of the motor, n pu Indicates the motor speed per unit value, k 2 Indicates the motor speed rating factor, R 2 Represents the thermal resistance between the motor stator winding and the motor stator core, I r Indicates the rated current of the motor, R indicates the resistance of each phase winding of the motor stator, I pu Indicates the per unit value of the motor current.

[0106] In this embodiment, formula (18) is discretized to obtain the following expression:

[0107]

[0108] Among them, U 2 (k) represents the motor stator winding temperature at the kth moment, U 2 (k-1) represents the motor stator winding temperature at the k-1th moment, R 1 Represents the thermal resistance between the motor stator core and the environment, k 1 Indicates the motor speed coefficient, n r Indicates the rated speed of the motor, n pu represents the per unit value of motor speed, Δt represents the duration of unit time, k 2 Indicates the motor speed rating factor, I r Indicates the rated current of the motor, R indicates the resistance of each phase winding of the motor stator, I pu Indicates the per unit value of the motor current.

[0109] In this embodiment, formula (19) is an inverse time protection algorithm, and the temperature rise is calculated once in each unit time (sampling period) Δt. When the temperature rise is greater than the action threshold U at a certain moment, 2max When the overload protection action is executed, the protection action is executed, but there are still many factors that are not considered in formula (19), such as the temperature difference between the motor stator and the motor rotor, the temperature difference between the motor rotor and the environment, etc. If the protection action execution time is calculated directly using formula (19), the calculation result is too conservative, resulting in the overload protection action being executed in advance, and the motor's overload operation capability is not fully utilized. Therefore, formula (19) is approximately expressed as:

[0110]

[0111] Among them, U 2 (k) represents the motor stator winding temperature at the kth moment, U 2 (k-1) represents the motor stator winding temperature at the k-1th moment, Δt represents the unit time, I pu (k) represents the per unit current value at the kth moment, n pu (k) represents the speed per unit value at the kth moment, x′ 00 Represents the adjustment coefficient of the constant term in the preset relationship function, x′ 01 represents the adjustment coefficient of the first-order term of the current per unit value at the kth moment in the preset relationship function, x′ 10 represents the adjustment coefficient of the first-order term of the k-th moment speed per unit value in the preset relationship function, x′ 20 represents the adjustment coefficient of the quadratic term of the current per unit value at the kth moment in the preset relationship function, x′ 02 represents the adjustment coefficient of the quadratic term of the k-th moment speed per unit value in the preset relationship function, x 30 It represents the adjustment coefficient of the cubic term of the per-unit value of the current at the kth moment in the preset relationship function.

[0112] In this embodiment, for small motors with power below 15Hp, copper loss and iron loss account for the largest proportion of power loss, and the temperature peak occurs in the overload state. Therefore, considering the actual computing power of the single-chip microcomputer, the part above the quadratic term in formula (20) is ignored to obtain the expression of the preset relationship function, as shown in formula (4).

[0113] In one embodiment of the present application, the process of executing the motor protection action according to the initial delay execution time includes:

[0114] The sampled current value and the sampled speed value of the motor within the initial delay execution time are obtained. In this embodiment, the sampled current value is obtained by collecting through a current sensor, and the collection period of the current sensor is consistent with the detection period of the historical current data of the motor. The sampled speed value is obtained by collecting through a speed sensor, and the sampling period of the speed sensor is consistent with the detection period of the historical speed data of the motor.

[0115] According to the comparison results of the sampled current value and the current current value, and the comparison results of the sampled speed value and the current speed value, the updated delayed execution time of the motor protection action is determined. In this embodiment, after determining the initial delayed execution time, if the sampled current value within the initial delayed execution time changes relative to the current current value or the sampled speed value changes relative to the current current value, the initial delayed execution time is updated, and the motor protection action is executed according to the updated delayed execution time, so that the delayed execution time of the motor protection action can be determined according to the real-time operating conditions of the motor, thereby improving the accuracy and flexibility of determining the delayed execution time of the motor protection action.

[0116] The motor protection action is executed according to the update delay execution time. In this embodiment, after the update delay execution time is obtained, the sampled current value and the sampled speed value of the motor within the update delay execution time are obtained; according to the comparison result of the sampled current value within the update delay execution time and the current current value, and the comparison result of the sampled speed value within the update delay execution time and the current speed value, the update delay execution time of the motor protection action is determined again, thereby adjusting the delay execution time of the motor protection action according to the real-time operation of the motor, and improving the accuracy and flexibility of determining the delay execution time of the motor protection action.

[0117] In one embodiment of the present application, according to the comparison result of the sampled current value and the current current value, and the comparison result of the sampled speed value and the current speed value, the process of determining the update delay execution time of the motor protection action includes:

[0118] If the sampled current value is consistent with the current current value, and the sampled speed value is consistent with the current speed value, the initial delayed execution time is used as the updated delayed execution time. In this embodiment, if the sampled current value has not changed relative to the current current value during the initial delayed execution time, and the sampled speed value has not changed relative to the current speed value during the initial delayed execution time, the initial delayed execution time has not changed, and the initial delayed execution time is used as the updated delayed execution time.

[0119] If the sampled current value is inconsistent with the current current value, and the sampled speed value is consistent with the current speed value, the update delay execution time is calculated according to the sampled current value, the current speed value and the motor thermal time coefficient. In this embodiment, if the sampled current value at a certain moment during the initial delay execution time changes relative to the current current value and the sampled speed value during the initial delay execution time does not change relative to the current speed value, the update delay execution time is calculated according to the sampled current value at that moment, the current speed value and the motor thermal time coefficient.

[0120] If the sampled current value is consistent with the current current value, and the sampled speed value is inconsistent with the current speed value, the update delay execution time is calculated according to the current current value, the sampled speed value and the motor thermal time coefficient. In this embodiment, the sampled current value is consistent with the current current value, and the sampled speed value at a certain moment is inconsistent with the current speed value, the update delay execution time is calculated according to the current current value, the sampled speed value at that moment and the motor thermal time coefficient.

[0121] If the sampled current value is inconsistent with the current current value, and the sampled speed value is inconsistent with the current speed value, the update delay execution time is calculated according to the sampled current value, the sampled speed value and the motor thermal time coefficient. In this embodiment, if the sampled current value at a certain moment is inconsistent with the current current value, and the sampled speed value at that moment is inconsistent with the current speed value, the update delay execution time is calculated according to the sampled current value at that moment, the sampled speed value at that moment and the motor thermal time coefficient.

[0122] In one embodiment of the present application, based on the second-order heat conduction model, a second-order heat conduction equation is established. The construction of the second-order heat conduction model fully considers the heating factors such as the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor, so as to correctly simulate the heat capacity of the synchronous motor and realize all operating areas of the synchronous motor (synchronous motor accelerating from a stop state to a high-speed state, synchronous motor The motor is in a deceleration state, etc.); and the second-order heat conduction equation is solved to obtain the preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed. The calculated temperature rise value of the motor stator winding at different unit times is made more accurate by adjusting the adjustment coefficient, the motor historical current data and the motor historical speed data in the preset relationship function, thereby improving the accuracy of the polynomial coefficient calculation in the regression equation, achieving the improvement of the accuracy of the delayed execution time of the motor protection action, and improving the matching degree between the delayed execution time characteristic curve of the motor protection action and the motor operation curve. It has been verified that the delayed execution time of the motor protection action calculated in an embodiment of the present application is greater than the delayed execution time of the motor protection action calculated in the related art, thereby increasing the maximum operating time of the motor under different working conditions, and giving full play to the ability of the motor to withstand various working conditions while ensuring the safe operation of the click.

[0123] In this embodiment, the delayed execution time of the motor protection action in the related art is as follows:

[0124] t y1 =[K / (I e / I r ) 2 -1] Formula (21)

[0125] Among them, t y1 represents the delayed execution time of the motor protection action in the related art, K ​​represents the motor thermal time constant in the related art, and I e Represents the motor equivalent current, I r Indicates the rated current of the motor.

[0126] In this embodiment, it can be known from formula (21) that in the related art, the delayed execution time is negatively correlated with the motor equivalent current, that is, the larger the motor equivalent current, the smaller the delayed execution time, the smaller the motor equivalent current, the larger the delayed execution time; on the other hand, the motor start time is negatively correlated with the motor equivalent current, that is, the larger the motor equivalent current, the smaller the motor start time, the smaller the motor equivalent current, the longer the motor start time. In the related art, in order to avoid the early arrival of the delayed execution time, the effective current of the motor will be reduced during the actual start-up process of the motor, which will inevitably lead to an increase in the start-up time of the motor. However, the present application does not need to reduce the effective current of the motor during the actual start-up process of the motor, and therefore, compared with the prior art, the start-up time of the motor is shortened.

[0127] The following describes an embodiment of the device of the present application, which can be used to implement the motor overload protection method in the above embodiment of the present application. For details not disclosed in the embodiment of the device of the present application, please refer to the embodiment of the motor overload protection method in the above embodiment of the present application.

[0128] Figure 4 is a block diagram of a motor overload protection device shown in an exemplary embodiment of the present application. The device can be applied to Figure 1 The implementation environment shown in the figure is specifically configured in the computer device 102. The device can also be applied to other exemplary implementation environments and specifically configured in other devices. This embodiment does not limit the implementation environment to which the device is applied.

[0129] like Figure 4 As shown, the exemplary motor overload protection device includes:

[0130] The current acquisition module 401 is used to acquire the current current value and the current speed value of the motor.

[0131] The time calculation module 402 is used to calculate the initial delay execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient.

[0132] The overload protection module 403 is used to execute the motor protection action according to the initial delay execution time.

[0133] In one embodiment of the present application, the current current value of the motor can be detected by a current sensor, or calculated by parameters such as the motor's power, voltage, and power factor. The current speed value of the motor can be detected by a speed sensor, or calculated by the motor's power supply frequency and the number of pole pairs of the motor's rotating magnetic field.

[0134] In one embodiment of the present application, the motor protection action is used to protect the motor from overload, and the motor protection action includes controlling the motor to stop running, controlling the motor power supply to trip, and other actions. The motor thermal time coefficient is determined by the motor historical temperature data, the motor historical current data, and the motor historical speed data, which improves the accuracy of the motor thermal time coefficient calculation and avoids using a fixed motor thermal time constant to calculate the delayed execution time of the motor protection action. Based on the current current value, the current speed value, and the motor thermal time coefficient, the process of calculating the initial delayed execution time of the motor protection action includes: converting the current current value into a current per unit value, and converting the current speed value into a speed per unit value; using the motor thermal time coefficient as the adjustment coefficient in the preset time fitting curve, using the current per unit value as the input current value in the preset time fitting curve, and using the speed per unit value as the input speed value in the preset time fitting curve, calculating the initial delayed execution time of the motor protection action, on the basis of improving the accuracy of the motor thermal time coefficient, improving the accuracy of the initial delayed execution time, thereby improving the protection effect on the motor.

[0135] In one embodiment of the present application, the process of executing a motor protection action according to an initial delayed execution time includes: obtaining a sampled current value and a sampled speed value of the motor within the initial delayed execution time; determining an updated delayed execution time of the motor protection action according to a comparison result between the sampled current value and the current current value, and a comparison result between the sampled speed value and the current speed value; executing the motor protection action according to the updated delayed execution time, and after determining the initial delayed execution time, if the sampled current value within the initial delayed execution time changes relative to the current current value or the sampled speed value changes relative to the current current value, the initial delayed execution time is updated, and the motor protection action is executed according to the updated delayed execution time, so that the delayed execution time of the motor protection action can be determined according to the real-time operating conditions of the motor, thereby improving the accuracy and flexibility of determining the delayed execution time of the motor protection action.

[0136] It should be noted that the motor overload protection device provided in the above embodiment and the motor overload protection method provided in the above embodiment belong to the same concept, wherein the specific manner in which each module and unit performs the operation has been described in detail in the method embodiment, and will not be repeated here. In practical applications, the motor overload protection device provided in the above embodiment can distribute the above functions to different functional modules as needed, that is, divide the internal structure of the device into different functional modules to complete all or part of the functions described above, and this is not limited here.

[0137] An embodiment of the present application also provides an electronic device, comprising: one or more processors; a storage device for storing one or more programs, when the one or more programs are executed by one or more processors, the electronic device implements the motor overload protection method provided in the above-mentioned embodiments.

[0138] Figure 5 The structure diagram of the computer system suitable for implementing the electronic device of the embodiment of the present application is shown. It should be noted that: Figure 5 The computer system 500 of the electronic device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0139] like Figure 5 As shown, the computer system 500 includes a central processing unit (CPU) 501, which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM) 502 or the program loaded from the storage part 508 to the random access memory (RAM) 503, such as executing the method in the above embodiment. In the RAM 503, various programs and data required for system operation are also stored. The CPU 501, the ROM 502 and the RAM 503 are connected to each other through the bus 504. The input / output (I / O) interface 505 is also connected to the bus 504.

[0140] The following components are connected to the I / O interface 505: an input section 506 including a keyboard, a mouse, etc.; an output section 507 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker; a storage section 508 including a hard disk, etc.; and a communication section 509 including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication section 509 performs communication processing via a network such as the Internet. A drive 510 is also connected to the I / O interface 505 as needed. A removable medium 511, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 510 as needed so that a computer program read therefrom is installed into the storage section 508 as needed.

[0141] In particular, according to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a computer program for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication section 509, and / or installed from a removable medium 511. When the computer program is executed by a central processing unit (CPU) 501, various functions defined in the system of the present application are executed.

[0142] It should be noted that the computer-readable medium shown in the embodiment of the present application can be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium can be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media can include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, wherein a computer-readable computer program is carried. This propagated data signal can take a variety of forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate or transmit a program for use by or in conjunction with an instruction execution system, apparatus or device. A computer program contained on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0143] The flowchart and block diagram in the accompanying drawings illustrate the possible architecture, functions and operations of the system, method and computer program product according to various embodiments of the present application. Wherein, each box in the flowchart or block diagram can represent a module, a program segment, or a part of the code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0144] The units involved in the embodiments described in this application may be implemented by software or hardware, and the units described may also be set in a processor. The names of these units do not, in some cases, constitute limitations on the units themselves.

[0145] Another aspect of the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor of a computer, causes the computer to execute the motor overload protection method as described above. The computer-readable storage medium may be included in the electronic device described in the above embodiment, or may exist independently without being assembled into the electronic device.

[0146] Another aspect of the present application also provides a computer program product or a computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the motor overload protection method provided in each of the above embodiments.

[0147] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A motor overload protection method, characterized in that: The method comprises: Get the current current value and current speed value of the motor; Based on the current current value, the current speed value and the motor thermal time coefficient, the initial delayed execution time of the motor protection action is calculated; the motor thermal time coefficient is determined by the motor historical temperature data, the motor historical current data and the motor historical speed data; the motor protection action is used to protect the motor from overload; The motor protection action is executed according to the initial delay execution time.

2. The motor overload protection method according to claim 1, characterized in that: The process of calculating the initial delayed execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient includes: Converting the current current value into a current per unit value, and converting the current speed value into a speed per unit value; The initial delayed execution time of the motor protection action is calculated by using the motor thermal time coefficient as the adjustment coefficient in the preset time fitting curve, using the current per unit value as the input current value in the preset time fitting curve, and using the speed per unit value as the input speed value in the preset time fitting curve.

3. The motor overload protection method according to claim 1, characterized in that: The process of determining the thermal time coefficient of the motor by using the historical temperature data, the historical current data and the historical speed data of the motor comprises: Obtaining a preset relationship function between the temperature rise of the motor stator winding and the motor current and the motor speed; the motor historical temperature data includes the detected temperature values ​​of the motor stator winding at different historical moments; the motor historical current data includes the detected current values ​​of the motor at different historical moments; the motor historical speed data includes the detected speed values ​​of the motor at different historical moments; Inputting the motor historical current data and the motor historical speed data into the preset relationship function to obtain the calculated temperature rise values ​​of the motor stator winding at different unit times; The preset relationship function is converted into a regression equation, and based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value, the polynomial coefficients in the regression equation are solved, and the solved polynomial coefficients are used as the motor thermal time coefficients.

4. The motor overload protection method according to claim 3, characterized in that: The process of solving the polynomial coefficients in the regression equation based on the detected temperature value, the calculated temperature rise value, the detected current value and the detected speed value includes: Calculating the difference between the detected temperature values ​​at adjacent moments as the actual temperature rise value of the stator winding of the motor at different unit times; The polynomial coefficients are calculated based on the actual temperature rise value, the calculated temperature rise value, the detected current value and the detected rotational speed value.

5. The motor overload protection method according to claim 3, characterized in that: Before obtaining a preset relationship function between the temperature rise of the motor stator winding and the motor current and motor speed, the method includes: Establishing a heat conduction equation of the motor; the variables in the heat conduction equation include the motor stator winding temperature, the motor stator winding heat capacity, the thermal resistance between the motor stator winding and the motor stator core, the motor stator winding copper loss, the motor stator core temperature, the motor stator core heat capacity, the thermal resistance between the motor stator core and the environment, the motor stator core iron loss and the overall temperature of the motor; The heat conduction equation is solved to obtain a preset relationship function between the temperature rise of the motor stator winding and the motor current and motor speed.

6. The motor overload protection method according to any one of claims 1 to 5, characterized in that: According to the initial delay execution time, the process of executing the motor protection action includes: Obtaining a sampled current value and a sampled speed value of the motor within the initial delay execution time; Determining the update delay execution time of the motor protection action according to the comparison result of the sampled current value and the current current value, and the comparison result of the sampled speed value and the current speed value; The motor protection action is executed according to the updated delayed execution time.

7. The motor overload protection method according to claim 6, characterized in that: The process of determining the update delay execution time of the motor protection action according to the comparison result of the sampled current value and the current current value, and the comparison result of the sampled speed value and the current speed value comprises: If the sampled current value is consistent with the current current value, and the sampled rotation speed value is consistent with the current rotation speed value, then the initial delayed execution time is used as the updated delayed execution time; If the sampled current value is inconsistent with the current current value, and the sampled speed value is consistent with the current speed value, then the update delay execution time is calculated according to the sampled current value, the current speed value and the motor thermal time coefficient; If the sampled current value is consistent with the current current value, and the sampled speed value is inconsistent with the current speed value, then the update delay execution time is calculated according to the current current value, the sampled speed value and the motor thermal time coefficient; If the sampled current value is inconsistent with the current current value, and the sampled speed value is inconsistent with the current speed value, the update delay execution time is calculated according to the sampled current value, the sampled speed value and the motor thermal time coefficient.

8. A motor overload protection device, characterized in that: The device comprises: A current acquisition module is used to obtain the current current value and current speed value of the motor; A time calculation module, used to calculate the initial delayed execution time of the motor protection action based on the current current value, the current speed value and the motor thermal time coefficient; the motor thermal time coefficient is determined by the motor historical temperature data, the motor historical current data and the motor historical speed data; the motor protection action is used to protect the motor from overload; The overload protection module is used to execute the motor protection action according to the initial delay execution time.

9. An electronic device, characterized in that: include: one or more processors; A storage device for storing one or more programs, when the one or more programs are executed by the one or more processors, enables the electronic device to implement the motor overload protection method as described in any one of claims 1 to 7.

10. A computer storage medium, characterized in that: include: Computer-readable instructions are stored thereon, and when the computer-readable instructions are executed by a processor of a computer, the computer is enabled to execute the motor overload protection method according to any one of claims 1 to 7.

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