Inverter fault check method

With the development of power and electronic technology, as well as the transformation of a large number of industrial infrastructure equipment, more and more users in the field of control put forward higher requirements for electrical equipment. The appearance and application of the inverter makes the complicated control simple, making the production process more convenient, faster and more precise. However, the inverter is the same as other control devices, and it is inevitable that the fault will occur in the application. In order to reduce the loss, the fault type and the cause of the fault must be ascertained as soon as possible.

I have sorted out the common problems that occur in the daily operation of the inverter, and the corresponding inspection methods, I hope I can help you.

Overcurrent fault

Overcurrent faults can be generally divided into acceleration, deceleration, and constant speed overcurrent. The main reasons are that the starting acceleration time is too short, the load suddenly increases, the inverter output short circuit, the load distribution is uneven, the inverter and motor capacity do not match, and the internal Rectifier side or inverter side component damage, power supply phase loss, output disconnection, motor internal fault and ground fault.

For overcurrent faults, the overhaul method is as follows: When the fault is checked, the load should be disconnected first to check the inverter. If the overload fault still exists after the load is disconnected, the internal components of the inverter are faulty and further inspection and maintenance are required.

For these faults, corresponding measures can be taken: prolong the acceleration time, design the load distribution, check the line, prevent interference and mechanical vibration, and reduce sudden load changes.

Overvoltage fault

The overvoltage fault of the inverter refers to the overvoltage trip of the inverter when the DC link voltage of the unit exceeds. The main causes of overvoltage faults in the unit are: First, the input side high voltage power supply exceeds the allowable maximum value; second, the inverter overvoltage trip occurs during the deceleration process. Inverter overvoltage faults include overvoltage, lightning overvoltage, braking or deceleration time, excessive overvoltage, and power supply overvoltage when the compensation capacitor is input.

After the fault occurs, first check whether the input power supply voltage is stable, check whether the motor is started in idling, and whether there is any external force drag. Under the premise of confirming the stability of the input power supply voltage, increase the absorption device on the power input side to reduce the overvoltage factor. The overvoltage of the power supply input side, the overvoltage caused by lightning, and the overvoltage generated when the compensation capacitor is turned on or off. In the case of possible occurrence, it can be solved by means of a parallel surge absorber or a series reactor on the input side.

Overvoltage faults generally occur during shutdown, and are related to the intermediate circuit and the brake link. The main reason is that the brake resistor is damaged or the deceleration time is too short. Therefore, the treatment measures are to increase the deceleration time parameter or increase the braking resistor ( Braking unit).

Undervoltage fault

Inverter undervoltage fault refers to the voltage of the main circuit is too low, such as 220V series is lower than 180V, 380V series is lower than 300V, etc., generally due to lack of phase of the power supply, simultaneous operation or too many inverters starting at the same time, internal DC of the inverter The current-limiting resistor of the loop or the thyristor of the short-circuit current limiting resistor is damaged, and the interference between the outside or the inverter is caused.

The treatment measures are to check the input part of the inverter, check whether the inverter power supply is open or the contactor contact is good, the contact resistance is too large, the transformer output voltage is normal, and the inverter that starts or works at the same time is minimized. The number of units enhances the anti-jamming capability of the inverter.

Overload fault

Inverter overload means that the motor can rotate, but the running current exceeds the rated value. The main reason is that the mechanical load is too heavy, and it may be malfunction.

For overload faults, first check if the motor is hot. If the temperature rise of the motor is not high, first check whether the thermal protection function of the inverter is preset properly. If the inverter still has a margin, the preset value should be relaxed; if the allowable current of the inverter has no margin, It means that the inverter is not properly selected, the capacity of the inverter should be increased, and the inverter should be replaced. Secondly, check whether the supply voltage and the three-phase voltage on the motor side are balanced. If the voltage at the output of the inverter is balanced, the problem is on the line from the inverter to the motor; finally check if it is malfunctioning. In the case of light load or no load, use an ammeter to measure the output current of the inverter and compare it with the running current value displayed on the display to see if there is a large error between the display and the actual value. If there is, the trip is Malfunction.

Overheat fault

The causes of overheating faults of the inverter are: high ambient temperature, poor ventilation of the inverter, stuck or damaged fan, excessive load, etc.

The treatment measures are to check the heat dissipation of the bottom plate of the inverter, and whether the air duct of the inverter itself or the air duct of the control cabinet is blocked, and the frequency converter should be regularly inspected, the airway garbage should be removed, and the ventilation should be kept smooth.

Ground short circuit fault

The main causes of the inverter grounding short circuit trip are: motor insulation is damaged; cable insulation is damaged; the inverter is internally short-circuited; several motors are connected in parallel, and the inverter output has a large ground leakage current. In addition, the cable has a certain distributed capacitance to the ground. The magnitude of the capacitor current is related to the length of the cable and the insulation material. The longer the cable length, the larger the capacitor current; the cable length is too long, and the capacitance current to the ground is large, which will cause The inverter is shorted to ground short circuit.