Why can't the frequency of the external potentiometer of the inverter be adjusted?

发布时间： 2024-08-15 11:26

概述：A frequency converter, the operation panel can be controlled normally

A frequency converter, the operation panel can be controlled normally, and the adjustment frequency can also be changed from 0 to 50HZ. However, with an external potentiometer, the frequency cannot be adjusted to 20HZ. What is the reason?

analyze the reason

The panel can adjust the frequency, but the external one cannot, indicating that the frequency converter itself has no problem. It is necessary to check whether there is any problem with the peripheral components or circuits given to you by the external potentiometer of the frequency converter.

First, ensure that the potentiometer is good, then ensure that the wiring to the inverter terminal is correct, and the rest is the inverter frequency setting problem.

The selection of the resistance value of the 1. potentiometer should correspond to the requirements of the manual.

The selection of the resistance value of the external potentiometer of the frequency converter, the analog signal of the frequency converter is generally: 0~10V,4 ~ 20ma, so when selecting the given value of the potentiometer, the following two situations should be considered:

1. Voltage signal 0~10V

When the external power supply voltage is 10V, if a potentiometer with a resistance of 10K is selected, the working current is 1mA. According to the field experience, as long as the analog signal is less than 1mA, the anti-interference capability is sufficient. So as long as the resistance of the potentiometer is less than or equal to 10K, you can.

If the output voltage of the inverter is 0 -- 10V, 10K potentiometer should be selected. If the output voltage of the inverter is 0 -- 5V, 4.7K potentiometer should be selected. If the current is too large, it will cause endless power loss.

2. Current signal 4 ~ 20ma

When the external input signal is 4 ~ 20ma, a 500 ohm resistor is connected in series in the circuit. Under 10V power supply, the corresponding resistance value of 20ma is 500.

2. check the maximum frequency setting and the upper limit frequency setting of the frequency converter

3. wiring

To check whether the wiring of the potentiometer pin is correct, when debugging the potentiometer, measure whether the voltage of the potentiometer pin changes.

The fixed terminals on both sides of the potentiometer are directly connected to the 10V power supply and ground signal on the inverter terminals. The sliding adjustable terminal in the middle of the potentiometer is connected to the analog output signal of the inverter, and then the resistance value of the potentiometer is adjusted to see whether the output voltage changes.

4. the frequency signal source parameters of the frequency converter,

To change the panel control frequency to the external pin control frequency, whether the parameter is set by panel or potentiometer or voltage, current or upper computer, the set parameter values are different.

5. check the line between the potentiometer to the inverter, there may be damage to the power cord or shielding wire, resulting in line leakage or short circuit.

The use of potentiometer has its limitations, because the potentiometer input is 0~10V voltage signal, and the voltage signal with the extension of the transmission distance by the interference increases. If the installation site is far away from the frequency converter, the accuracy of the signal transmission cannot be guaranteed. In this case, the distance between them should be shortened as much as possible. If the distance is too long, the resistance of the potentiometer will be smaller.

Most of the time, external problems cause the inverter to work abnormally, but we are always easy to suspect that the inverter itself is the problem.