Like other control devices, frequency converters are prone to malfunctions during application. To minimize losses and quickly identify the cause of the malfunction. Shengtang's engineers have compiled common problems that occur during the daily operation of frequency converters, as well as corresponding inspection methods. Today, the editor has listed them for everyone, hoping to be helpful.

1. Overcurrent fault

Overcurrent faults can generally be divided into acceleration, deceleration, and constant speed overcurrent. The main causes include short starting acceleration time, sudden increase in load, short circuit of frequency converter output, uneven load distribution, mismatch between frequency converter and motor capacity, damage to internal rectifier or inverter components, power phase loss, output disconnection, internal motor faults, and grounding faults.

For overcurrent faults, the maintenance method is as follows: during fault inspection, the load should be disconnected first to check the frequency converter. If the overcurrent fault still exists after disconnecting the load, it indicates that the internal components of the frequency converter are faulty and require further inspection and maintenance.

Corresponding measures can be taken to address these faults: extending acceleration time, designing load distribution, inspecting the circuit, preventing interference and mechanical vibration, and reducing sudden load changes.

2 Overvoltage fault

Inverter overvoltage fault refers to the overvoltage tripping of the inverter when the unit DC bus voltage exceeds. The main reasons for unit overvoltage faults are: firstly, the input side high-voltage power supply exceeds the allowable * * value; The second is causing overvoltage tripping of the frequency converter during deceleration. Inverter overvoltage faults include overvoltage when compensating capacitors are activated, lightning overvoltage, overvoltage due to short braking or deceleration time, power overvoltage, etc.

After the fault occurs, first check whether the input power voltage is stable, whether the motor starts in idle, and whether there is external force dragging. On the premise of confirming the stability of the input power supply voltage, an absorption device can be added to the input side of the power supply to reduce overvoltage factors. In cases where there may be surge overvoltage, lightning induced overvoltage, or overvoltage caused by compensating capacitors when closing or disconnecting, methods such as parallel surge absorption devices or series reactors can be used to solve the problem.

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

3. Undervoltage fault

Inverter undervoltage fault refers to the low voltage of the main circuit, such as 220V series below 180V, 380V series below 300V, etc. It is generally caused by power phase loss, too many inverters working or starting at the same time, damage to the thyristor of the DC limiting resistor or short-circuit limiting resistor in the internal DC circuit of the inverter, and interference between external or inverters. The solution is to inspect the input part of the frequency converter, check whether the air switch or contactor contacts of the frequency converter power supply are in good contact, whether the contact resistance is too high, whether the output voltage of the transformer is normal, and minimize the number of frequency converters that start or work at the same time to enhance the anti-interference ability of the frequency converter.

4. Overload fault

Inverter overload refers to the situation where the motor is able to rotate, but the operating current exceeds the rated value. The main reason is that the mechanical load is too heavy, and it may also be due to misoperation.

For overload faults, the first thing to check is whether the motor is heating up. If the temperature rise of the motor is not high, the first thing to check is whether the thermal protection function of the frequency converter is pre-set reasonably. If there is still margin in the frequency converter, the pre-set value should be relaxed; If the allowable current of the frequency converter is no longer sufficient, it indicates that the selection of the frequency converter is improper. The capacity of the frequency converter should be increased and replaced; Secondly, it is necessary to check whether the power supply voltage and the three-phase voltage on the motor side are balanced. If the voltage balance at the output end of the frequency converter, the problem lies in the circuit between the frequency converter and the motor; **Check for any misoperation. Measure the output current of the frequency converter with an ammeter under light or no-load conditions, compare it with the operating current value displayed on the screen, and check whether there is a significant error between the displayed and actual values. If there is, it indicates that the trip is a misoperation.

5 Overheating Fault

The causes of overheating faults in frequency converters include: high ambient temperature, poor ventilation of the frequency converter, blocked or damaged fans, and heavy loads. The solution is to check the heat dissipation of the inverter's bottom plate, as well as whether the inverter's own air duct or control cabinet air duct is blocked. Regular maintenance of the inverter should be carried out to remove air duct debris and maintain smooth ventilation.

6 Ground short circuit fault

The main reasons for the grounding short circuit tripping of the frequency converter are: damage to the motor insulation; Damage to cable insulation; Internal short circuit of frequency converter; Several motors are connected in parallel, and the output of the frequency converter has a large ground leakage current. In addition, cables have a certain distributed capacitance to the ground, and the magnitude of capacitive current is related to factors such as cable length and insulation material. The longer the cable length, the greater the capacitive current; The cable length is too long and the capacitance current to ground is high, which can cause the frequency converter to short-circuit and trip. To address this issue, a method of connecting a reactor in series between the output side of the frequency converter and the motor can be adopted.