Motor restart protection method and system
By monitoring the motor stator current and heat dissipation times, the motor is prohibited from restarting within the set period, which solves the problem of heat accumulation caused by frequent start of the motor in a short period of time, ensuring the normal operation of the motor and the safety of the power grid.
Patent Information
- Application Number
- CN202411286931.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2024-12-27
AI Technical Summary
Frequent start of the motor in a short period of time leads to excessive heat accumulation, which may cause a fever or grid failure. Existing protective measures cannot effectively prevent such situations.
By monitoring the change in the motor stator current, the number of start-up and heat dissipation times is calculated. If the motor is prohibited from restarting when the set upper limit is reached, the processor executes a computer program to output a prohibit signal to control the motor to restart.
It effectively limits the number of starts of the motor, prevents excessive heat accumulation, ensures the normal operation of the motor, and avoids burning and grid failure.
Smart Images
Figure CN119209412A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of motor protection, and in particular relates to a motor restart protection method and system. Background Art
[0002] When the motor starts, the rotor current and stator current will increase greatly. The greater the current, the more heat will be generated. If the motor is started multiple times in a row, it will cause the motor to overheat or even burn out. The motor insulation material limits its maximum allowable temperature. If the operating temperature exceeds the allowable temperature, the insulation life will be shortened by half for every 8°C increase. Therefore, the motor must be equipped with protection to prevent the motor from being started frequently to avoid overheating.
[0003] Traditional motor protection usually has overheat protection. When the motor heats up to a certain limit, the overheat protection will be activated, the motor switch will be tripped, and the motor will stop running. Or the motor start timeout protection will be configured. When the motor start time is too long and reaches the start time limit, the motor switch will be tripped and the motor will stop running.
[0004] However, both overheat protection and motor start timeout protection stop the motor after it has started. In the power supply grid of industrial enterprises, short-term voltage drops (commonly known as "electrical fluctuations") caused by lightning strikes, short circuits, reclosing, starting of the same section of equipment, or fault removal often occur, and even occur frequently in a short period of time. When the "electrical fluctuation" ends and the voltage returns to normal, the motor will start directly, causing the motor to start too many times in a short period of time, accumulating too much heat, which may cause the motor to burn out or even cause grid failure. Summary of the invention
[0005] The object of the present invention is to provide a motor restart protection method and system to solve the problem that the motor is started too many times in a short time, which causes excessive heat accumulation and may cause the motor to burn out.
[0006] To solve the above technical problems, the present invention provides a motor restart protection method, the method comprising: if the cumulative number of motor startup heating times within a set period is greater than a set upper limit threshold, the motor restart is controlled to prohibit the motor from restarting within the period; the method for determining the cumulative number of motor startup heating times includes: Each time the motor stator current rises from no current to greater than the current starting setting value, the cumulative number of motor startup heating times increases by 1; each time the motor completes heat dissipation, the cumulative number of motor startup heating times decreases by 1.
[0007] Furthermore, the method for judging whether the motor has completed one heat dissipation includes: if the running heat dissipation time of the motor reaches the running heat dissipation time setting value, it is judged that the motor has completed one heat dissipation; if the stopping heat dissipation time of the motor reaches the stopping heat dissipation time setting value, it is judged that the motor has completed one heat dissipation.
[0008] Furthermore, the motor running heat dissipation duration is the motor running duration corresponding to the moment when the motor current decreases to below the current starting setting value and ends when the motor current increases to above the current starting setting value.
[0009] Furthermore, if the motor has stopped before the motor running and heat dissipation time reaches the running and heat dissipation time setting value, the timing of the corresponding motor running time from the moment the motor current drops below the current starting setting value until the moment the motor current rises above the current starting setting value is stopped, and when the timing starts from the moment the motor current drops below the current starting setting value again until the moment the motor current rises above the current starting setting value again, the timing continues.
[0010] Furthermore, the motor shutdown heat dissipation time length is the motor shutdown time length corresponding to the moment when the motor current decreases to below the current stop setting value and ends when the motor current increases to above the current stop setting value.
[0011] Furthermore, if the motor has been started before the motor shutdown and heat dissipation time reaches the shutdown and heat dissipation time setting value, the timing of the corresponding motor shutdown time from the moment the motor current drops below the current stop setting value until the moment the motor current rises above the current stop setting value is stopped, and when the timing starts from the moment the motor current drops below the current stop setting value again until the moment the motor current rises above the current stop setting value again, the timing continues.
[0012] Furthermore, the method of controlling the restart of the motor to prohibit the motor from restarting within the cycle includes: outputting a motor restart prohibiting signal to the control end of the motor within the cycle, and the motor restart prohibiting signal is used for the control end of the motor to prohibit the motor from restarting after receiving the signal.
[0013] In order to solve the above technical problems, the present invention also provides a motor restart protection system, including a processor, and the processor is used to execute a computer program to implement the steps of the motor restart protection method.
[0014] The beneficial effects of the above technical solution are as follows: the present invention provides a new motor restart protection method, which determines the starting behavior of the motor that generates heat through the change of the motor stator current, and determines the heat dissipation behavior that can offset the heat generated by the motor through the number of times the motor heat dissipation is completed, so as to determine the number of motor starts that can actually generate accumulated heat and affect the operation of the motor, thereby limiting the behavior of the motor accumulating heat that ultimately affects the operation of the motor, ensuring the normal operation of the motor, and solving the problem that the motor is started too many times in a short period of time, resulting in excessive accumulation of heat, which may cause the motor to burn out. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is an example diagram of a motor restart prohibition method of the motor restart protection method of the present invention; Figure 2 It is an example diagram of the motor starting current variation characteristic of the motor restart protection method of the motor restart protection method of the present invention; Figure 3 It is an example diagram of increasing the number of motor starts of the motor restart protection method of the motor restart protection method of the present invention; Figure 4 It is an example diagram of reducing the number of motor operation starts of the motor restart protection method of the motor restart protection method of the present invention; Figure 5 It is an example diagram of reducing the number of motor shutdown and starting times of the motor restart protection method of the motor restart protection method of the present invention; Figure 6 It is an example diagram of the heat dissipation process of the motor of the motor restart protection method of the present invention; Figure 7 It is an example diagram of the motor reset input of the motor restart protection method of the motor restart protection method of the present invention; Figure 8 It is a schematic diagram of the relationship between the number of motor starts and the heat dissipation characteristics of the motor restart protection method of the motor restart protection method of the present invention. DETAILED DESCRIPTION
[0016] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.
[0017] Motor restart protection method embodiment: The present embodiment provides a technical solution for a motor restart protection method, which determines the number of times the motor stator current exceeds the current start setting value as the cumulative number of motor startup heat generation according to the operation conditions of the motor heating and cooling, and takes the motor running time that meets the running heat dissipation time setting value after the motor current is reduced from above the current start setting value to below the current start setting value as the motor completing one heat dissipation, and takes the motor stop time that meets the stop heat dissipation time setting value after the motor current is reduced from above the current stop setting value to below the current stop setting value as the motor completing one heat dissipation, and subtracts the number of times the motor completes one heat dissipation from the number of times the motor starts to generate heat, to obtain the number of motor starts that can actually generate cumulative heat and affect the operation of the motor, and limits it to ensure the normal operation of the motor.
[0018] The motor restart protection method specifically includes: If the cumulative number of times the motor starts heating up within a set period is greater than the set upper limit threshold, the motor restart is controlled to prohibit the motor from restarting within the period; the method for determining the cumulative number of times the motor starts heating up includes: Each time the motor stator current rises from zero to greater than the current start setting value, the cumulative number of motor start heating increases by 1; each time the motor completes heat dissipation, the cumulative number of motor start heating decreases by 1. Figure 1 shown.
[0019] The present invention determines the starting behavior of the motor that will generate heat through the change of the motor stator current, and determines the heat dissipation behavior that can offset the heat generated by the motor through the number of times the motor heat dissipation is completed, so as to determine the number of motor starts that can actually generate accumulated heat and affect the operation of the motor, thereby limiting the behavior of the motor accumulating heat that ultimately really affects the operation of the motor, ensuring the normal operation of the motor, and solving the problem that the motor is started too many times in a short period of time, resulting in excessive accumulation of heat, which may cause the motor to burn out.
[0020] Specifically, the main factor limiting the restart of the motor is the motor temperature. The present invention adopts a method combining the motor temperature with the number of starts to determine whether to issue a prohibition on the motor restart; a fixed value "the maximum number of motor starts" (i.e., the cumulative number of motor start heating) is set. When the number of motor starts in a day is greater than the fixed value, the output prohibits the motor restart. The fixed values used in the present invention are shown in Table 1.
[0021] Table 1 Setting table Serial number name scope Step Length Default value 1 Maximum number of motor starts 1～10 1 10 2 Motor running cooling time setting 1s~6000s 0.01s 100s 3 Motor stop cooling time setting 0.01s~50000s 0.01s 100s Due to the characteristics of the stator current when the motor starts, the stator current rises from no current (the current is judged to be no current when it is less than 0.05 times the rated value) to more than 1.2 times the rated value, and then drops to near the rated value. Figure 2 As shown. Therefore, the increase in the number of motor starts is determined by the motor stator current. When the motor stator current rises from no current to more than 1.2 times the rated value, the number of motor starts increases by 1. Figure 3 shown.
[0022] In this embodiment, the judgment method for whether the motor has completed one heat dissipation includes: if the motor running heat dissipation time reaches the running heat dissipation time setting value, it is judged that the motor has completed one heat dissipation; if the motor shutdown heat dissipation time reaches the shutdown heat dissipation time setting value, it is judged that the motor has completed one heat dissipation.
[0023] Specifically, for naturally ventilated motors, it is considered that the running motor has completed one heat dissipation temperature to reach the ideal value after the "motor running heat dissipation time constant" (i.e. the motor running heat dissipation time); it is considered that the stopped motor has completed one heat dissipation temperature to reach the ideal value after the "motor stop heat dissipation time constant" (i.e. the motor stop heat dissipation time), and the number of motor starts is reduced by 1 each time the motor completes one heat dissipation. Figure 4 and Figure 5 shown.
[0024] In this embodiment, the motor operation heat dissipation time is the motor operation time corresponding to the time when the motor current decreases to below the current start setting value until the motor current increases to above the current start setting value again. If the motor has stopped before the motor operation heat dissipation time reaches the operation heat dissipation time setting value, the timing of the motor operation time corresponding to the time when the motor current decreases to below the current start setting value until the motor current increases to above the current start setting value again is stopped, and when the timing starts from the time when the motor current decreases to below the current start setting value again until the motor current increases to above the current start setting value again, the timing is continued.
[0025] The running and cooling time of the motor is accumulated to avoid missing the cooling time of the motor, which leads to too many accumulated heating times at the motor startup, so that the motor is prohibited from starting in advance.
[0026] Specifically, since the specific situation of motor heating is relatively complicated, for the convenience of research and analysis, it is assumed that the motor runs for a long time, the load remains unchanged, the total loss remains unchanged, the temperature of each part of the motor itself is uniform, and the ambient temperature remains unchanged. The temperature change law of the motor running with load is as follows: after the temperature rise (the value of the motor temperature exceeding the ambient temperature) stabilizes, if the load is reduced or the motor is stopped, the total loss in the motor and the heat generated per unit time Q will decrease or no longer be generated. In this way, the heat generated is less than the heat dissipated, which destroys the thermal equilibrium state, the temperature of the motor drops, and the temperature rise decreases. During the cooling process, as the temperature rise decreases, the heat dissipation per unit time also decreases. When the heat generation is equal to the heat dissipation, the motor no longer continues to cool down, and its temperature rise stabilizes at a new value. Specifically, Figure 6 As shown. Therefore, after the motor starts, the current decreases and the heat generated is less than the heat dissipation, which belongs to the motor heat dissipation process. Therefore, the start time of the motor running heat dissipation time is the end time of the motor start, that is, the time when the motor current drops from the large current to less than 1.2 times the rated value.
[0027] The motor running heat dissipation time can be calculated cumulatively. For example, when the motor running heat dissipation time timing does not reach the set value, it has stopped and does not meet the motor running conditions. At this time, the time is memorized and the timing continues to be accumulated when the motor starting conditions are met again.
[0028] In this embodiment, the motor shutdown heat dissipation time is the motor shutdown time corresponding to the time from the moment when the motor current decreases to below the current stop setting value to the moment when the motor current increases to above the current stop setting value again. If the motor has been started before the motor shutdown heat dissipation time has not reached the shutdown heat dissipation time setting value, the timing of the motor shutdown time corresponding to the time from the moment when the motor current decreases to below the current stop setting value to the moment when the motor current increases to above the current stop setting value again is stopped, and when the timing starts from the moment when the motor current decreases to below the current stop setting value again to the moment when the motor current increases to above the current stop setting value again, the timing is continued.
[0029] The motor shutdown cooling time is accumulated to avoid missing the cooling time of the motor, which leads to too many accumulated heating times when the motor starts, so that the motor is prohibited from starting in advance.
[0030] Specifically, after the motor stops running, it is also a heat dissipation process. The start time of the motor stop heat dissipation time is the moment when the motor stops. It is considered that the motor current changes from current to no current. If the current is less than 0.05 times the rated value, it is judged as no current, and if the current is greater than 0.05 times the rated value, it is judged as current. The motor stop heat dissipation time can be accumulated and calculated. For example, when the motor stop heat dissipation time timing does not reach the set value, it has been started and the motor stop condition is not met. At this time, the time is memorized and the timing continues to be accumulated when the motor stop condition is met again.
[0031] In this embodiment, the method of controlling the restart of the motor to prohibit the motor from restarting within the cycle includes: outputting a motor restart prohibiting signal to the control end of the motor within the cycle, and the motor restart prohibiting signal is used to prohibit the motor from restarting after the control end of the motor receives it.
[0032] Specifically, when the number of motor starts in one day is greater than the set value, a signal for prohibiting the motor from restarting is output to prohibit the motor from restarting.
[0033] In this embodiment, a reset input can also be set to reset the number of motor starts and prohibit the motor from restarting. Figure 7 shown.
[0034] The motor restart protection method of this embodiment prohibits the motor from starting again through the above technical means, thereby preventing the motor from accumulating too much heat and causing the motor to burn out. Compared with the overheat protection and motor start timeout protection in the prior art, the motor restart protection method calculates the number of motor starts and the cooling time to obtain the cumulative number of motor start heating, and limits it, so that the motor is stopped before the motor starts, and the motor is protected. The relationship between the motor operation, cooling time and number of starts is as follows: Figure 8 shown.
[0035] Motor restart protection system embodiment: The present invention also provides a motor restart protection system, including a processor, the processor is used to execute a computer program to implement the steps of the motor restart protection method. The specific process, principle and effect have been described in detail in the motor restart protection method embodiment, and will not be repeated here.
[0036] Specific implementation methods are given above, but the present invention is not limited to the described implementation methods. The basic idea of the present invention lies in the above basic scheme. For ordinary technicians in this field, it does not take creative work to design various deformed models, formulas, and parameters according to the teachings of the present invention. Changes, modifications, substitutions, and variations of the implementation methods without departing from the principles and spirit of the present invention still fall within the scope of protection of the present invention.
Claims
1. A motor restart protection method, characterized in that: The method includes: if the cumulative number of times the motor starts heating up within a set period is greater than a set upper limit threshold, then controlling the restart of the motor to prohibit the motor from restarting within the period; the method for determining the cumulative number of times the motor starts heating up includes: Each time the motor stator current rises from no current to greater than the current starting setting value, the cumulative number of motor startup heating times increases by 1; each time the motor completes heat dissipation, the cumulative number of motor startup heating times decreases by 1.
2. The motor restart protection method according to claim 1, characterized in that: The judgment method of whether the motor has completed one heat dissipation includes: if the motor running heat dissipation time reaches the running heat dissipation time setting value, it is judged that the motor has completed one heat dissipation; if the motor shutdown heat dissipation time reaches the shutdown heat dissipation time setting value, it is judged that the motor has completed one heat dissipation.
3. The motor restart protection method according to claim 2, characterized in that: The motor running heat dissipation time is the motor running time corresponding to the moment when the motor current decreases to below the current starting setting value and ends when the motor current increases to above the current starting setting value.
4. The motor restart protection method according to claim 3, characterized in that: If the motor has stopped before the motor running and cooling time reaches the running and cooling time setting value, the timing of the corresponding motor running time from the moment the motor current drops below the current starting setting value until the moment the motor current rises above the current starting setting value is stopped, and when the timing starts from the moment the motor current drops below the current starting setting value until the moment the motor current rises above the current starting setting value again, the timing is continued.
5. The motor restart protection method according to claim 2, characterized in that: The motor shutdown heat dissipation time is the motor shutdown time corresponding to the time when the motor current decreases to below the current stop setting value and ends when the motor current increases to above the current stop setting value.
6. The motor restart protection method according to claim 5, characterized in that: If the motor has been started before the motor shutdown and heat dissipation time reaches the shutdown and heat dissipation time setting value, the timing of the corresponding motor shutdown time from the moment the motor current drops below the current stop setting value until the moment the motor current rises above the current stop setting value is stopped, and when the timing starts from the moment the motor current drops below the current stop setting value until the moment the motor current rises above the current stop setting value again, the timing is continued.
7. The motor restart protection method according to any one of claims 1 to 6, characterized in that: The method of controlling the restart of the motor to prohibit the motor from restarting within the cycle includes: outputting a prohibiting motor restart signal to the control end of the motor within the cycle, and the prohibiting motor restart signal is used to prohibit the motor from restarting after the control end of the motor receives it.
8. A motor restart protection system, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the motor restart protection method as described in any one of claims 1 to 7.