1, test rectifier circuit Find the result, you can judge the circuit has an abnormality, A. to the P and N terminals of the internal DC power supply of the inverter, adjust the multimeter to the resistance X10 file, the red bar is connected to P, and the black bar is respectively connected to R, S. , T, there are tens of ohms of resistance in normal, and the basic balance. Instead, the black bar is connected to the P terminal, and the red bar is sequentially connected to R, S, and T, and has a resistance close to infinity. The red bar is connected to the N-end and the above steps are repeated. The same result should be obtained. If there is a three-phase unbalance in the resistance value, the rectifier bridge is faulty. When the red pole is connected to the P terminal, the resistance is infinite, and it can be concluded that the rectifier bridge is faulty or the starting resistor is faulty. 2, test the inverter circuit Connect the red bar to the P terminal, and the black bar is connected to U, V, and W respectively. There should be a resistance of several tens of ohms, and the resistance values ​​of the phases are basically the same, and the inversion should be infinite. The N-end of the black meter bar, repeat the above steps should get the same result, otherwise it can be determined that the inverter module is faulty. After the static test result is normal, the dynamic test can be performed, that is, the power test machine is powered on. The following points must be noted before and after power-on: 1. Before power-on, you must confirm whether the input voltage is wrong. If the 380V power supply is connected to the 220V inverter, there will be a bomber (explosive capacitor, varistor, module, etc.); 2. Check whether the sockets of the inverter are properly connected, and whether the connection is loose. If the connection is abnormal, the inverter may malfunction. In severe cases, the inverter will be discharged. 3. After the power is turned on, the fault display content is detected, and the fault and the cause are preliminarily determined; 4. If the fault is not displayed, first check whether the parameter is abnormal, and after resetting the parameter, start the inverter under no-load (no motor), and test the U, V, W three-phase output voltage value. If there is a lack of phase, three-phase unbalance, etc., the module or the drive board is faulty; 5. In the case of normal output voltage (no phase loss, three-phase balance), the load test is as full load test as possible. 1, the rectifier module is damaged Usually caused by grid voltage or internal short circuit. Replace the rectifier bridge with the internal short circuit removed. When dealing with faults on site, it is important to check the user's power grid conditions, such as grid voltage, and whether there are equipment such as welding machines that are polluting the power grid. 2, the inverter module is damaged Usually caused by motor or cable damage and drive circuit failure. After repairing the drive circuit, the drive waveform is replaced and the module is replaced. After replacing the engine board in the field service, pay attention to check the motor and connecting cables. The drive can only be operated without any faults. 3, no display after power-on This is usually caused by damage to the switching power supply or damage to the soft charging circuit, so that the DC circuit is not DC-powered. If the starting resistor is damaged, the operation panel is damaged. 4, display over voltage or under voltage Usually due to input phase loss, the circuit is aging and the board is wet. The solution is to find out its voltage detection circuit and detection point and replace the damaged device. 5, showing over current or ground short Usually due to damage to the current sensing circuit. Such as Hall elements, op amp circuits, and so on. 6, the power supply and the driver board start to show over current Usually caused by damage to the drive circuit or inverter module. 7. The no-load output voltage is normal, and the overload or over current is displayed after loading. Usually caused by improper parameter settings or aging of the drive circuit. In the maintenance of the inverter, the object of overcurrent protection mainly refers to the case where the peak value of the current exceeds the allowable value of the inverter with abrupt nature. Because the overload capability of the inverter is poor, the overcurrent protection of the inverter is A crucial part has been developed so far. First, the cause of overcurrent 1. Overcurrent in the work, that is, the drag system has an overcurrent during the working process. The reason is mainly from the following aspects: 1 The motor encounters an impact load, or the drive mechanism is "stuck", causing a sudden increase in motor current. 2 The output side of the inverter is short-circuited, such as the short-circuit between the output terminals and the motor, or a short circuit inside the motor. 3 The inverter itself is not working properly. For example, two inverter devices of the same bridge arm in the inverter bridge are abnormal during the alternate work. For example, due to the high ambient temperature or the aging of the inverter device itself, the parameters of the inverter device are changed, resulting in one device being turned on during the alternation process, and the other device is still turned off in the future, causing the same The "straight through" of the upper and lower devices of a bridge arm causes the short-circuit state between the positive and negative terminals of the DC voltage. 2. Over-current when the speed is increased When the inertia of the load is large, and the speed-up time is set too short, it means that during the speed-up process, the working efficiency of the inverter rises too fast, and the synchronous speed of the motor rises rapidly. However, the rotational speed of the motor rotor cannot be kept up due to the large inertia of the load, and as a result, the rising current is too large. 3. Overcurrent in the deceleration When the inertia of the load is large and the deceleration time is set too short, it will cause overcurrent. Because the speed reduction time is too short, the synchronous speed decreases rapidly, and the rotor of the motor maintains a high speed due to the inertia of the load. At this time, the speed at which the rotor winding cuts the magnetic line is too large to generate an overcurrent. Second, the processing method 1. At the start of the start, it will trip at a rising speed. This is a phenomenon in which the overcurrent is very serious. 1 Is the working machine stuck? 2 Is there a short circuit on the load side, check if there is a short circuit to the ground with a megger 3 Is the inverter power module damaged? 4 The starting torque of the motor is too small, the drag system can't turn 2. Do not trip immediately when starting, but trip during operation, main inspection 1 The speed setting time is too short and the acceleration time is lengthened. 2 Deceleration time setting is too short, lengthening deceleration time 3 Torque compensation (U/F ratio) setting is too large, causing excessive no-load current at low frequencies 4 The electronic thermal relay is improperly set, and the operating current is set too small, causing the inverter to malfunction. 1, over voltage protection Causes and treatment methods for generating overvoltage: 1 The power supply voltage is too high 2 The speed reduction time is too short 3 During the speed reduction process, the discharge unit of the regenerative braking is not ideal, and it is too late to discharge. Please increase the external braking resistor and braking unit. 4 Please check if the discharge circuit has a fault and it does not discharge. For the low-power inverter, there is a strong discharge resistance damage. 2, under voltage protection Causes and treatment methods for undervoltage: 1 power supply voltage is too low 2 power supply phase loss; 3 Rectifier bridge fault: If some of the six rectifier diodes are short-circuited due to damage, the rectified voltage will drop. For the damage of the rectifier device and the thyristor, it should be checked and replaced in time. (1) Fan operation protection The built-in fan of the inverter is the main means of heat dissipation inside the cabinet, which will ensure the normal operation of the control circuit. Therefore, if the fan is not working properly, it should be protected immediately; (2) Overheat protection of inverter module heat sink The inverter module is the main component of heat generation in the inverter and the most important and most vulnerable component of the inverter. Therefore, each inverter is equipped with an overheat protection device on the heat dissipation plate; (3) Braking resistor overheat protection The nominal power of the braking resistor is selected for short-term operation. Therefore, once the power-on time is too long, it will overheat. At this time, it should be suspended and used after cooling. Or use a larger power resistor; (4) The inlet and outlet of the cooling air duct must not be blocked, and the ambient temperature may be higher than the allowable value of the inverter. (1) Noise problems and countermeasures. When the inverter is used to drive the motor, since the output voltage and current contain high-order harmonic components, the higher-order harmonic flux of the air gap increases, so the noise increases. Electromagnetic noise is characterized by an increase in noise near the natural frequency of the rotor because the low-order harmonic component in the output of the inverter resonates with the inherent mechanical frequency of the rotor. The higher harmonic components in the inverter output resonate with the core housing and the like, and the noise near the respective natural frequencies of these components increases. The noise generated by the drive motor of the inverter, especially the harsh noise, is related to the switching frequency of the PWM control, especially in the low frequency region. The following measures are generally used to stabilize and reduce noise: an AC reactor is connected to the output side of the inverter. If the electromagnetic torque has a margin, U / f can be made smaller. Use a special motor to check the resonance with the natural frequency of the shaft system (including the load) when the noise level of the lower frequency is severe. (2) Vibration problems and countermeasures. When the inverter is working, the magnetic field caused by the higher harmonics in the output waveform generates electromagnetic force for many mechanical components. The frequency of the power can always be close to or coincide with the natural frequency of these mechanical components, causing vibration caused by electromagnetic causes. The higher harmonics that have a large influence on vibration are mainly lower harmonic components, and have a greater influence in the PAM mode and the square wave PWM mode. However, when the sinusoidal PWM method is used, the low-order harmonic components are small and the influence is small. To reduce or eliminate vibration, an AC reactor can be connected to the output side of the inverter to absorb the higher harmonic current components in the inverter output current. When using the PAM mode or square wave PWM mode inverter, the sine wave PWM mode inverter can be used to reduce the ripple torque. In order to prevent vibration, the mechanical system connected from the motor to the load must make the entire system not harmonic with the electromagnetic force generated by the motor. Load matching and countermeasures There are many types of production machinery, different performance and process requirements, and different torque characteristics. Therefore, before applying the inverter, first understand the nature of the load on the motor, that is, the load characteristics, and then select the inverter and motor. . There are three types of loads: constant torque load, fan pump type load and constant power load. Different types of inverters should be selected for different load types. (3) Constant torque load The constant torque load is further divided into a friction type load and a potential energy type load. The starting torque of the friction type load generally requires about 150% of the rated torque, and the braking torque generally requires about 100% of the rated torque, so the frequency converter should choose to have constant torque characteristics, and both the starting and braking torques Larger inverters with large overload times and overload capacities, such as the FR-A540 series. The position energy can generally achieve a large starting torque and energy feedback function, which can realize the forward and reverse rotation quickly. The inverter should select a frequency converter with four quadrant operation capability, such as FR-A241 series. (4) Fan pump load The fan pump type load is a typical square torque load. The load at very low speed is very small and proportional to the square of the speed. The combination of a general-purpose inverter and a standard motor is most suitable. This kind of load does not require high performance of the inverter, only economical and reliable, so choose a frequency converter with U/f=const control mode, such as FR-A540(L). If the inverter output frequency is increased above the power frequency, the power increases sharply, sometimes exceeding the capacity of the motor inverter, causing the motor to overheat or fail to operate. Therefore, for this type of load torque, do not easily increase the frequency above the power frequency. (5) Constant power load Constant power load refers to the load whose torque is inversely proportional to the speed, but the power remains constant, such as coilers and machine tools. When using the inverter with constant power characteristics, pay attention to the problem: the output voltage of the inverter is fixed value control within the frequency range above the power frequency, so the torque generated by the motor is constant power, using standard motor and universal There is no problem with the combination of the inverter. In the frequency range below the power frequency, U/f constant value control, the torque generated by the motor and the load torque are opposite, and the combination of the standard motor and the general frequency converter is difficult to adapt, so it is specially designed. (6) fever problems and countermeasures The heating of the inverter is caused by the internal loss. The main circuit is mainly used, accounting for 98%, and the control circuit accounts for 2%. In order to ensure the normal and reliable operation of the inverter, the inverter must be dissipated. The main methods are: (1) Heat dissipation by fan: The built-in fan of the inverter can remove the heat dissipation inside the inverter cabinet. (2) Ambient temperature: The frequency converter is an electronic device, which contains electrolytic capacitors of electronic components, so the temperature has a great influence on its life. The ambient operating temperature of the general-purpose inverter generally requires -10 °C ~ +50 °C. If the operating temperature of the inverter can be reduced, the service life of the inverter is extended and the performance is stable. We have been busy with the maintenance of the inverter. (1) can extend the life of the inverter (2) Electrical appliances, we can say that the maintenance rate is reduced. (3) can also reflect the company's management, the company's image! The specific plan for our maintenance is as follows: 1. The inverter must be disassembled to see if there is any abnormality inside (such as looseness of the wire, loss of solder, looseness of the device, burnt of the device, burning phenomenon). 2. Check the internal aging components of the inverter, such as fans, power devices, power capacitors, and aging of the printed board. 3. Clean the internal dust, oil, corrosive and conductor impurities of the inverter. For the main printing plates such as: main control board, drive board, switching power supply board. Sprayed with a new imported electronic cleaner to remove the aging layer and conductive materials. 4. Advanced filming treatment is applied to the main control part of the inverter. It is dust-proof, anti-aging, anti-conductive, waterproof, and corrosive. 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