Inverter undervoltage problem general processing method

Inverter undervoltage problem: The commonly used low-voltage inverters are AC-DC-AC inverters. The three-phase power supply receives DC power through the rectifier and supplies power to the inverter through the DC bus. The bus voltage should be approximately equal to 1.35 times the line voltage under normal conditions.

In order to protect the inverter, if the bus voltage is too low, the inverter will report an undervoltage fault and block the pulse output of the inverter. This is an important and necessary way to protect the drive components from damage. This fault cannot be blocked either.

There is a bus voltage checking mechanism inside the inverter. When the measured value of the bus voltage is lower than a certain threshold, the inverter will report an undervoltage fault.

There are many reasons for the undervoltage of the DC bus, which should be analyzed based on actual conditions. If you look for the root cause, then you can solve the problem.

1 The first is the effect from incoming line voltage.

If the quality of the power grid is not good and there is an instantaneous voltage drop, it is bound to cause the bus voltage to be too low. In the process of starting large-scale equipment, it is inevitable that the grid voltage will be reduced. Occasional momentary voltage dips are difficult to catch, which makes it difficult to diagnose the fault. If it can be confirmed that there is a problem with the quality of the power network (such as a short-term voltage drop caused by starting a large motor) and it is difficult to change such a power environment, the “automatic restart” function of the inverter can be enabled when the voltage is dropped. , Inverter undervoltage shutdown; In the grid recovery, the inverter automatically restarts.

Adding a voltage regulator at the line terminal is also a good choice. However, use the inverter only.

When thundering, it may also have a temporary impact on the grid voltage, it may also cause the inverter's undervoltage fault. However, thunder is a very accidental event and will not always confuse the operation of the inverter. However, for safety reasons, factories should have lightning protection measures.

2 The second is the influence from the output, ie the inverter side.

As the motor accelerates, the motor receives power from the inverter and converts it into kinetic energy. If the acceleration time is short and the acceleration is high, the bus voltage will be pulled down quickly, causing an undervoltage fault. In response to this situation, the general processing methods are:

• Increase the acceleration time • If a PID controller is used, pay attention to reduce the system response, reduce the P plus I, extend the filter time 3 and finally hardware problems.

If the internal voltage detection mechanism of the frequency converter is not working properly, or if the CPU processing mechanism has a problem, these are not parameters that can be solved and need to be repaired. Use a multimeter to measure the bus voltage. Compared with the inverter parameters, if the measured value of the bus voltage differs greatly from the displayed value, it can be considered as a fault of the inverter.

In addition, the most basic electrical faults have to be ruled out:

·Phase of power supply and brake unit have through phenomenon