The quality of a thing is relatively speaking. As a power supply used to drive the motor, the frequency converter's function is to regulate the speed. If the speed of the motor can be controlled according to the requirements, and the fluctuation error is less than the equipment requirements, the frequency converter is a good frequency converter.

The frequency converter meeting the speed requirements is normal

Generally, the frequency of general-purpose inverter is often accurate to one decimal place, such as 0.01Hz. For the rated frequency of 50Hz, 0.01 + 50 = 0.01%, but this is only the resolution on the display, which is usually not achieved. Generally, V / F open-loop controlled inverter, The accuracy can be controlled within + 0.5%, while for many loads, generally the speed fluctuation range is within 1-5%, which can meet the process requirements, especially for fans and pumps, the accuracy requirements are relatively rough, because as long as the frequency converter controls the motor to operate with load, the speed fluctuation is less than 5%, which is a normal frequency converter.

If the speed fluctuation of the motor controlled by the frequency converter is more than 5%, it does not necessarily mean that the frequency converter is broken. It may be caused by some parameters that are not adjusted properly. For example, the V / F ratio setting is unreasonable, and the acceleration and deceleration time is too short, which may cause the acceleration and deceleration to fluctuate severely. At this time, the problem can be solved by readjusting the parameters.

For vector controlled frequency converter, because of encoder feedback, the highest accuracy can be 0.01%, which is consistent with the resolution of the display value of the frequency converter. Of course, this is the steady-state accuracy, in fact, there will be great fluctuations during acceleration and deceleration, and general equipment will not require such a high level, generally around 0.05% can meet the control requirements of most equipment.

Vector control depends on the accuracy of the parameters of the motor model. At the same time, it has a lot to do with the adjustment of some parameters in the converter, such as gain and integral. Many times, you think the converter can't work, because the motor acceleration is weak and the speed fluctuation is very severe, which is often also a parameter problem. Just adjust it.

The frequency converter is broken. Basically, it can't drive the motor

Because of hardware problems, there are very few frequency converters with speed fluctuation, because the frequency converter design has many protection functions, such as overcurrent, overvoltage, undervoltage, overheating, overload, lack of equal alarm, When these alarms occur and cannot be reset, it can be considered that there is a hardware problem with the frequency converter, provided that the peripheral circuit is normal and there is no problem with the motor and load.

If there is no display when the power is on, the switch power is often burnt, resulting in no power supply to the main board and no display.

There are also some cases where the no-load operation is normal, and the overcurrent and overload alarm occurs when the load is loaded. These are generally caused by the problem of the drive circuit or the insufficient withstand voltage of the module.

If it is acceleration and deceleration overcurrent, the bus capacitance is often aged. In this case, it is necessary to repair and replace the capacitance.

As for short-circuit trip, smoke or peculiar smell during operation, it can be considered that there is a burning element inside and it can not be used any more.

Some mainboards fail to display normally, but they cannot accept the control logic and start to operate. When the factory value is restored and the parameters are reset to eliminate the disorder, it can also be considered that the frequency converter is broken.