At present, the AC speed control system is mainly referred to as the frequency conversion speed control system of the electronic power converter to the AC motor. The frequency conversion speed control system is superior to the characteristics of DC drive, and is used as the preferred transmission scheme in many occasions. Modern frequency conversion speed regulation basically adopts 16-bit or 32-bit single-chip microcomputer as the control core, thus realizing full digital control and speed regulation. The performance is basically similar to the DC speed regulation. However, when the inverter is used, the maintenance work is more complicated than the DC. Once the fault occurs, the ordinary electricians of the enterprise are difficult to handle. Here, the common faults of the inverter are analyzed. Approach.
First, the parameter setting class faults commonly used inverters in use, can meet the requirements of the drive system, the parameter settings of the inverter is very important, if the parameter settings are not correct, the inverter will not work properly.
1. Parameter setting common frequency converter. Generally, the factory has a default value for each parameter when leaving the factory. These parameters are called factory values. In the case of these parameter values, the user can operate normally in panel operation, but the panel operation does not meet the requirements of most transmission systems. Therefore, before using the inverter correctly, the user should proceed to the inverter parameters from the following aspects:
(1) Confirm the motor parameters. The inverter sets the power, current, voltage, speed and maximum frequency of the motor in the parameters. These parameters can be directly obtained from the motor nameplate.
(2) The control mode adopted by the inverter, namely speed control, torque control, PID control or other means. After taking the control method, it is generally necessary to perform static or dynamic identification according to the control accuracy.
(3) Set the startup mode of the inverter. Generally, the inverter is set to start from the panel at the factory. The user can select the startup mode according to the actual situation. You can use the panel, external terminal, communication mode and so on.
(4) For the selection of the given signal, the frequency of the inverter can also be given in various ways. The panel is given, the external reference, the external voltage or current is given, the communication mode is given, and of course the frequency of the inverter is given. It can also be the sum of one or several of these ways. After the above parameters are correctly set, the inverter can basically work normally. If you want better control effect, you can only modify the relevant parameters according to the actual situation.
2. Processing of parameter setting class faults Once the parameter setting class fault occurs, the inverter can not operate normally. Generally, the parameters can be modified according to the manual. If the above is not possible, it is best to restore all the parameters to the factory values, and then reset according to the above steps. For each company's inverter, the parameter recovery method is different.
Second, the overvoltage fault The overvoltage of the inverter is concentrated on the tributary voltage of the DC bus. Under normal circumstances, the inverter DC power is the average value after three-phase full-wave rectification. If calculated with a line voltage of 380V, the average DC voltage Ud=1.35U line = 513V. When the overvoltage occurs, the storage capacitor of the DC bus will be charged. When the voltage is up to 760V, the inverter overvoltage protection action. Therefore, the inverter has a normal operating voltage range. When the voltage exceeds this range, the inverter may be damaged. There are two types of common overvoltages.
1. Input AC power overvoltage This situation refers to the input voltage exceeding the normal range. Generally, the load is lighter on holidays, the voltage is increased or decreased, and the line is faulty. At this time, it is better to disconnect the power supply, check and process.
2. The probability of occurrence of over-voltage in power generation is higher, mainly because the synchronous speed of the motor is higher than the actual speed, so that the motor is in the power generation state, and the inverter does not have a brake unit installed. There are two cases that can cause this. A breakdown.
(1) When the inverter drags the large inertia load, its deceleration time is set relatively small. During the deceleration process, the speed of the inverter output is relatively fast, while the load is slowed down by the resistance of the load, so that the speed of the load drag motor It is higher than the speed corresponding to the frequency of the inverter output, the motor is in the power generation state, and the inverter has no energy feedback unit, so the voltage of the DC circuit of the inverter tributary rises, exceeds the protection value, and the fault occurs, which often occurs in the paper machine. In the dry part, dealing with such a fault can increase the regenerative braking unit, or modify the inverter parameters to set the inverter deceleration time longer.
The functions of increasing the regenerative braking unit include energy consumption type, parallel DC bus absorption type, and energy feedback type. The energy consumption type connects a braking resistor in parallel with the DC link of the inverter, and controls the on/off of the power tube by detecting the DC bus voltage. The parallel DC bus absorption type is used in a multi-motor transmission system. Such a system often has one or several motors that are often operated in a power generation state to generate regenerative energy that is absorbed by the motor in an electric state through the parallel bus. The energy feedback type inverter-side converter is reversible, and the inverter can return the regenerative energy to the grid when regenerative energy is generated.
(2) This fault may also occur when multiple electric actuators are operating the same load, mainly due to no load distribution. Taking two motors to drag a load as an example, when the actual rotational speed of one motor is greater than the synchronous speed of the other motor, the motor with a high rotational speed is equivalent to the prime mover, and the low rotational speed is in a power generating state, causing a malfunction. In the paper machine often occurs in the press section and the net section, and load distribution control is required during processing. It is possible to adjust the characteristics of the inverter in the branch of the paper machine drive speed chain.
Third, overcurrent faults Overcurrent faults can be divided into acceleration, deceleration, constant speed overcurrent. It may be caused by the acceleration/deceleration time of the inverter being too short, the load is abrupt, the load is not evenly distributed, and the output is short-circuited. At this time, it is generally possible to extend the acceleration/deceleration time, reduce the sudden change of the load, apply the energy-consuming braking element, carry out the load distribution design, and inspect the line. If the load inverter is disconnected or the overcurrent fault occurs, the inverter inverter circuit has been looped and the inverter needs to be replaced.
4. Overload Faults Overload faults include variable frequency overload and motor overload. It may be caused by the acceleration time being too short, the DC braking amount is too large, the grid voltage is too low, and the load is too heavy. Generally, the acceleration time can be extended, the braking time can be extended, the grid voltage can be checked, and the like. If the load is too heavy, the selected motor and inverter cannot be dragged by the load, or it may be caused by poor mechanical lubrication. If the former, the high-power motor and inverter must be replaced; if the latter, the production machinery should be inspected.
V. Other faults 1. Undervoltage indicates that there is a problem with the input part of the inverter power supply, and it needs to be checked before it can run.
2. If the temperature is too high, such as the motor has a temperature detecting device, check the heat dissipation of the motor; if the temperature of the inverter is too high, check the ventilation of the inverter.
First, the parameter setting class faults commonly used inverters in use, can meet the requirements of the drive system, the parameter settings of the inverter is very important, if the parameter settings are not correct, the inverter will not work properly.
1. Parameter setting common frequency converter. Generally, the factory has a default value for each parameter when leaving the factory. These parameters are called factory values. In the case of these parameter values, the user can operate normally in panel operation, but the panel operation does not meet the requirements of most transmission systems. Therefore, before using the inverter correctly, the user should proceed to the inverter parameters from the following aspects:
(1) Confirm the motor parameters. The inverter sets the power, current, voltage, speed and maximum frequency of the motor in the parameters. These parameters can be directly obtained from the motor nameplate.
(2) The control mode adopted by the inverter, namely speed control, torque control, PID control or other means. After taking the control method, it is generally necessary to perform static or dynamic identification according to the control accuracy.
(3) Set the startup mode of the inverter. Generally, the inverter is set to start from the panel at the factory. The user can select the startup mode according to the actual situation. You can use the panel, external terminal, communication mode and so on.
(4) For the selection of the given signal, the frequency of the inverter can also be given in various ways. The panel is given, the external reference, the external voltage or current is given, the communication mode is given, and of course the frequency of the inverter is given. It can also be the sum of one or several of these ways. After the above parameters are correctly set, the inverter can basically work normally. If you want better control effect, you can only modify the relevant parameters according to the actual situation.
2. Processing of parameter setting class faults Once the parameter setting class fault occurs, the inverter can not operate normally. Generally, the parameters can be modified according to the manual. If the above is not possible, it is best to restore all the parameters to the factory values, and then reset according to the above steps. For each company's inverter, the parameter recovery method is different.
Second, the overvoltage fault The overvoltage of the inverter is concentrated on the tributary voltage of the DC bus. Under normal circumstances, the inverter DC power is the average value after three-phase full-wave rectification. If calculated with a line voltage of 380V, the average DC voltage Ud=1.35U line = 513V. When the overvoltage occurs, the storage capacitor of the DC bus will be charged. When the voltage is up to 760V, the inverter overvoltage protection action. Therefore, the inverter has a normal operating voltage range. When the voltage exceeds this range, the inverter may be damaged. There are two types of common overvoltages.
1. Input AC power overvoltage This situation refers to the input voltage exceeding the normal range. Generally, the load is lighter on holidays, the voltage is increased or decreased, and the line is faulty. At this time, it is better to disconnect the power supply, check and process.
2. The probability of occurrence of over-voltage in power generation is higher, mainly because the synchronous speed of the motor is higher than the actual speed, so that the motor is in the power generation state, and the inverter does not have a brake unit installed. There are two cases that can cause this. A breakdown.
(1) When the inverter drags the large inertia load, its deceleration time is set relatively small. During the deceleration process, the speed of the inverter output is relatively fast, while the load is slowed down by the resistance of the load, so that the speed of the load drag motor It is higher than the speed corresponding to the frequency of the inverter output, the motor is in the power generation state, and the inverter has no energy feedback unit, so the voltage of the DC circuit of the inverter tributary rises, exceeds the protection value, and the fault occurs, which often occurs in the paper machine. In the dry part, dealing with such a fault can increase the regenerative braking unit, or modify the inverter parameters to set the inverter deceleration time longer.
The functions of increasing the regenerative braking unit include energy consumption type, parallel DC bus absorption type, and energy feedback type. The energy consumption type connects a braking resistor in parallel with the DC link of the inverter, and controls the on/off of the power tube by detecting the DC bus voltage. The parallel DC bus absorption type is used in a multi-motor transmission system. Such a system often has one or several motors that are often operated in a power generation state to generate regenerative energy that is absorbed by the motor in an electric state through the parallel bus. The energy feedback type inverter-side converter is reversible, and the inverter can return the regenerative energy to the grid when regenerative energy is generated.
(2) This fault may also occur when multiple electric actuators are operating the same load, mainly due to no load distribution. Taking two motors to drag a load as an example, when the actual rotational speed of one motor is greater than the synchronous speed of the other motor, the motor with a high rotational speed is equivalent to the prime mover, and the low rotational speed is in a power generating state, causing a malfunction. In the paper machine often occurs in the press section and the net section, and load distribution control is required during processing. It is possible to adjust the characteristics of the inverter in the branch of the paper machine drive speed chain.
Third, overcurrent faults Overcurrent faults can be divided into acceleration, deceleration, constant speed overcurrent. It may be caused by the acceleration/deceleration time of the inverter being too short, the load is abrupt, the load is not evenly distributed, and the output is short-circuited. At this time, it is generally possible to extend the acceleration/deceleration time, reduce the sudden change of the load, apply the energy-consuming braking element, carry out the load distribution design, and inspect the line. If the load inverter is disconnected or the overcurrent fault occurs, the inverter inverter circuit has been looped and the inverter needs to be replaced.
4. Overload Faults Overload faults include variable frequency overload and motor overload. It may be caused by the acceleration time being too short, the DC braking amount is too large, the grid voltage is too low, and the load is too heavy. Generally, the acceleration time can be extended, the braking time can be extended, the grid voltage can be checked, and the like. If the load is too heavy, the selected motor and inverter cannot be dragged by the load, or it may be caused by poor mechanical lubrication. If the former, the high-power motor and inverter must be replaced; if the latter, the production machinery should be inspected.
V. Other faults 1. Undervoltage indicates that there is a problem with the input part of the inverter power supply, and it needs to be checked before it can run.
2. If the temperature is too high, such as the motor has a temperature detecting device, check the heat dissipation of the motor; if the temperature of the inverter is too high, check the ventilation of the inverter.
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Label: Analysis of the causes and treatment methods of common faults of inverters
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