Inverter consists of main circuit, power circuit, IPM drive and protection circuit, cooling fan and other parts. Its structure mostly unit or modular form. Due to improper use or improper setting of the environment, the inverter may easily malfunction or malfunction, or can not meet the expected operating results. In order to take preventive measures, careful analysis of the causes of failure is particularly important. 1.1 main circuit common fault analysis The main loop mainly consists of three-phase or single-phase rectifier bridge, smoothing capacitors, filter capacitors, IPM inverter bridge, current limiting resistors, contactors and other components. Many of these common faults are caused by electrolytic capacitors. Electrolytic capacitor life is mainly imposed by the DC voltage at both ends and the internal temperature of the decision in the circuit design has been selected capacitor model, so the internal temperature of the electrolytic capacitor plays a decisive role in the life. Electrolytic capacitor will directly affect the life of the inverter, the general temperature rise of 10 ℃, life expectancy by half. Therefore, on the one hand, the installation should take into account the appropriate ambient temperature, on the other hand can take measures to reduce ripple current. Using AC or DC reactors with improved power factor reduces ripple current and extends the life of electrolytic capacitors. In capacitor maintenance, the deterioration of electrolytic capacitors is usually judged by the comparatively easy measurement of capacitance. When the capacitance is less than 80% of the rated value and the insulation resistance is less than 5 MΩ, the replacement of the electrolytic capacitors should be considered. 1.2 The main circuit typical fault analysis Symptom: When the inverter accelerates, decelerates or normal operation, an overcurrent trip occurs. First of all should be distinguished because of the load, or the cause of the inverter. In case of inverter fault, the current at trip can be queried through history, exceeding the rated current of the inverter or the set value of the electronic thermal relay , and the three-phase voltage and current are balanced, it should be considered whether there is overload Or mutation, such as motor stalling. In the larger load inertia, may be appropriate to extend the acceleration time, the process of the inverter itself is not damaged. If the current at the time of tripping can be judged as a fault of the IPM module or related part in the rated current of the inverter or within the setting range of the electronic thermal relay. First, you can determine whether the IPM module is damaged by measuring the positive and negative resistances of the main circuit output terminals U, V, W of the inverter and the P and N terminals on the DC side respectively. If the module is not damaged, then the drive circuit has failed. If the IPM module is over-current during deceleration or the inverter short-circuit trips to the ground, the inverter or the drive circuit of the upper half of the inverter is usually faulty. When the IPM module is over-current during acceleration, the module of the lower half-bridge or its driver Circuit part of the failure, the occurrence of these failures are mostly due to external dust into the inverter or the environment caused by humidity. 1.3 control loop failure analysis Control circuit Affect the life of the inverter is the power supply section, is a smoothing capacitor and IPM circuit board buffer capacitor, the principle of the same as above, but here the capacitor through the ripple current is basically not affected by the main loop load fixed value , So its life is mainly determined by the temperature and power on time. As the capacitors are soldered on the circuit board, it is difficult to judge the deterioration by measuring the capacitance, and it is generally estimated according to the ambient temperature of the capacitor and the usage time to approach its service life. Power circuit board to the control circuit, IPM drive circuit and the surface operation of the display panel and fan power supply, the power supply are generally from the main circuit DC voltage, through the switching power supply were rectified and then get. Therefore, a power supply short circuit, in addition to the damage of the rectifier circuit, but also may affect other parts of the power supply, such as due to misuse and control power and public ground short circuit, resulting in the power supply circuit board switching power supply part of the damage, the fan A short circuit in the power supply can cause other power supplies to go down. Generally observed by the power circuit board is relatively easy to find. Logic control circuit board is the core of the inverter, which integrates CPU, MPU, RAM, EEPROM and other large-scale integrated circuits, with high reliability, the probability of failure itself is small, but sometimes due to boot and make full control Terminals closed at the same time, resulting in frequency converter EEPROM failure, as long as the reset EEPROM on it. The IPM board contains drive and snubber circuits, as well as overvoltage, phase loss protection circuits. The PWM signal from the logic control board inputs the voltage drive signal to the IPM module through optical coupling. Therefore, the optical coupler on the IPM module should be measured while the detection module is fast. 1.4 cooling system The cooling system mainly includes heat sink and cooling fan. Cooling fan life is shorter, near the end of life, the fan vibration, noise increases the last stall, the inverter IPM overheating trip. The life of a cooling fan is limited by the bearing, which is approximately 10,000 to 35,000 h. When the inverter is running continuously, it takes 2 to 3 years to replace the fan or bearing. In order to extend the life of the fan, some products run only when the drive is running, not when the power is on. 1.5 external electromagnetic induction interference If interference sources exist around the inverter, they will intrude into the inverter through radiation or power cables, causing malfunction of the control circuit, resulting in abnormal operation or shutdown, or even damaging the inverter in serious cases. The specific methods to reduce noise interference are: all relays around the inverter, contactor control coil, the installation of surge voltage to prevent absorption devices, such as RC surge absorber, the connection can not exceed 20 cm; try to shorten the control loop with Line distance, and make it separate from the main circuit. The distance between the inverter control circuit wiring stubs should be more than 15 mm and keep a distance of more than 10 cm from the main circuit. When the inverter is far away from the motor (more than 100 m) At this time, on the one hand, the cross-sectional area of ​​the conductor can be enlarged to ensure that the voltage drop of the line is within 2%. At the same time, the output reactor of the inverter should be installed to compensate the charging current of the distributed capacitor caused by the long-distance conductor. The grounding terminal of inverter should be grounded according to the regulations. It must be reliably grounded at the special grounding point and can not be mixed with the welding and power grounding. The input of the inverter is equipped with a radio noise filter to reduce the input harmonic so as to reduce the noise from the power cord Electronic equipment noise; at the same time in the inverter output is also installed radio noise filter to reduce its output line noise. 1.6 installation environment The inverter belongs to the electronic device