1 Introduction In modern industry, motor systems controlled by frequency converters offer significant energy savings, convenient adjustment and control, simple maintenance, network-based centralized control, remote control, and the ability to form automatic control systems with PLCs. These characteristics of frequency converters have led to their increasingly widespread application in power electronics systems, industrial automatic control, and other fields. While the installation, wiring, and debugging of different models and specifications of frequency converters on the market vary, the main methods and precautions are basically the same. This article describes and analyzes common frequency converter faults. 2 Common Frequency Converter Fault Analysis 2.1 Maintenance Principles: Static Before Dynamic Static refers to the state without power, while dynamic refers to the working state after power is applied. At the start of maintenance, remain calm and avoid blindly taking action. Ask questions, such as whether operating procedures have been violated, the symptoms of the fault, and whether internal parameters have been changed. Based on the situation, conduct an objective and general analysis of the fault, and then determine the location of the fault based on the fault indications displayed on the frequency converter. During maintenance, carefully read the frequency converter instruction manual to understand its maintenance precautions. Do not turn on the power rashly. First, do necessary safety checks by sight, touch and smell to avoid causing new faults. (1) Check if the fast fuse FU is burned out; (2) Check if there is solder or wire contact or fine metal falling between the two wires between the component leads on the circuit board; (3) Check if there are obvious signs of burning on the capacitor, rectifier bridge, inverter bridge, integrated circuit and other components; (4) Check if there are water droplets on the circuit board (especially for inverters used in humid environments); (5) Check if there is dust on the circuit board. Through the above checks, it can be found whether there are short circuit faults in the inverter and carbonized black parts of the components. 2.2 Problems that are easy to encounter when the parameters are set incorrectly (1) The inverter works normally when the motor is unloaded, but cannot start with a load. This problem often occurs under constant torque load. When encountering such problems, the acceleration and deceleration time settings or the torque setting value should be checked. (2) The inverter starts running, but the motor overloads and stops before it starts. For example, a 725kW-6 motor in a metallurgical plant frequently stops when it is put into operation. Upon inspection, the original bias frequency setting was 3Hz. Before the inverter received the running command but did not give the frequency adjustment signal, the motor would receive a low-frequency running command of 3Hz and would not be able to start. It was measured that the stall current of the motor reached 50A, which is about 3 times the rated current of the motor; the overload protection of the inverter was normal. The bias frequency was changed to 0Hz and the motor started normally. (3) The frequency has reached a large value, but the motor speed is still not high. For example, a newly put into use inverter has a large frequency setting, but the motor speed is significantly lower than other motors at the same frequency. The frequency gain setting was checked and found to be 200%. Since the frequency setting signal gain is the ratio of the set analog frequency signal to the output frequency, that is, if the set frequency is 40Hz, the actual output frequency is only 20Hz. After changing the setting gain to 100%, the problem was solved. (4) When the frequency rises to a certain value and continues to be adjusted upwards, the frequency stays at a certain value and keeps jumping, and the speed cannot be increased. If you encounter the above problems, you should check whether the maximum torque setting value is too small and whether the capacity of the inverter is too small. 2.3 Problems that are easily caused by the external environment If the cooling and ventilation of the inverter control room is poor or the fan is damaged, overheating protection tripping is likely to occur. It is important to keep the environment around the inverter clean and dry. It is strictly forbidden to place debris near the inverter. It should be kept away from vibration sources and impact sources. After each maintenance of the inverter, carefully check whether there are any missing screws and wires, etc., to prevent small metal objects from causing short circuit accidents of the inverter and to minimize various electromagnetic interferences. When measuring the insulation of the inverter (including the motor), a 500V megohmmeter should be used. If only the inverter is tested, all external wiring connected to the inverter terminals should be removed [1]. If the concentration of corrosive gas in the working environment is high, it will not only corrode the lead wires and printed circuit boards of components, but also accelerate the aging of plastic components and reduce insulation performance. In this case, the control box should be made into a closed structure and ventilated. 2.4 Overcurrent and overload (1) Light load overcurrent If the load is very light, but the overcurrent trips, the first thing to check is whether the motor magnetic circuit is saturated. A significant increase in excitation current or magnetic flux often leads to magnetic circuit saturation, at which point the core and coil will overheat. If the magnetic circuit is saturated, the inverter can be started normally by repeatedly adjusting the U/f ratio. (2) Overload overcurrent Some production machinery suddenly increases the load during operation, or even "gets stuck", the motor speed drops significantly, the current increases sharply, and the overload protection cannot act in time, resulting in overcurrent tripping. Solution: First, understand whether the machinery itself has a fault. If there is a fault, repair the machine. If this overload is a phenomenon that often occurs in the production process, consider increasing the transmission ratio between the motor and the load. Appropriately increasing the transmission ratio can reduce the resistance torque on the motor shaft and avoid the situation where it cannot be driven. If the transmission ratio cannot be increased, consider increasing the capacity of the motor and the inverter. (3) Overcurrent during speed increase or decrease This is often caused by excessive speed increase or decrease. It can be solved by extending the speed increase (decrease) time or accurately presetting the speed increase (decrease) self-processing (anti-stall) function [2]. (4) Overload If an overload occurs, the following three aspects should be checked: Is the mechanical load too heavy? Is the three-phase voltage balanced? Is the malfunction caused by a fault in the current detection part inside the inverter? Then handle it according to the actual situation. 3 Conclusion This article describes the common faults of inverters. If we can understand and analyze inverters better, it will help extend the service life of inverters, facilitate the normal operation of production and improve product quality.