How to check and repair the inverter failure of no response when powered on?

In the maintenance of frequency converters, we often encounter the situation that the frequency converter does not respond after being powered on. Under normal circumstances, the frequency converter will have corresponding fault prompts after being powered on even if there is a fault. So when the frequency converter does not respond after being powered on, how should we check and repair it?

How to check if the inverter does not respond after power-on

1. First, check if there is a problem with the power switch. If you are not sure, you can perform a professional power test. If it is a power problem, just change the power switch wiring!

2. If the power supply test is normal, we will conduct a static test. Set the multimeter to the resistance X10 position, connect the red test rod to the P terminal of the inverter, and the black test rod to R, S, and T in turn. At this time, there will be a resistance of about tens of ohms and it will be basically balanced. When the black test rod is connected to the P terminal and the red test rod is connected to R, S, and T in turn, there will be a resistance close to infinity. Then connect the red test rod to the N terminal and repeat the above process. If the results are the same, the static test is normal.

3. If the static test of the inverter is normal, we will conduct a dynamic test, that is, an on-board test. Start the inverter under no-load (without connecting the motor) and test the output voltage values ​​of the three phases U, V, and W. If there is a phase loss or three-phase imbalance, the module or driver board is faulty. When the output voltage is normal (no phase loss, three-phase balance), test with load. It is best to test at full load.

After completing the above operations, we can basically determine the specific reason why the inverter does not respond after power is turned on. At this time, we can solve the problem specifically. It is recommended that all friends should have professional inverter maintenance personnel to handle the above steps to avoid damage to the inverter.

Causes and solutions for the inverter not displaying fault when powered on

The reason why the inverter has no display when powered on usually occurs in three modules: one is the contactor; the second is the control panel of the inverter; the third is the power module that supplies power to the control panel.

Fault detection 1: When the inverter is powered on, there is normally a sound of the contactor closing. If there is no such sound, the contactor may be broken.

Solution: Replace the contactor with a new one.

Fault detection 2: If there is no problem with the contactor, check whether there is a problem with the power module. If the inverter high-voltage power supply LED is on, it means that the high-voltage DC power supply is normal. If there is no DC voltage in the low-voltage DC power supply, this is a phenomenon that the switching power supply is not working. The non-operation of the switching power supply is equivalent to the non-operation of the switch tube. If the DC voltage is not sent, the voltage-dropping resistor between the high-voltage DC terminal and the primary terminal of the pulse transformer is damaged and open-circuited, which results in the high-voltage DC power not being added to the primary winding of the pulse transformer. The switching power supply cannot work, and the entire inverter has no low-voltage DC power supply, resulting in a no display fault.

Solution: Replace the voltage-dropping resistor.

Fault detection three: The inverter high-voltage LED indicator is on, and the LED indicator on the main control board is also on, indicating that the inverter switch power supply is normal, and the DC voltage display on the main board and the main control board is normal. Then use an oscilloscope to check the main control board to see if there is any output signal. If there is no output signal, one of the chips HC245 is damaged.

Solution: Replace the HC245 chip

Disconnect the power cord and check whether the power supply is missing phase or open circuit. If the power supply is normal, power on again and check whether there is voltage at the DC side terminals P and N of the inverter intermediate circuit. If the above checks are normal, it is determined that the internal switching power supply of the inverter is damaged.

The inverter trips when powered on or sparks appear on the main power terminals:

Disconnect the power cord, check whether the inverter input terminal is short-circuited, and check whether the inverter intermediate circuit DC side terminals P and N are short-circuited. The possible cause is that the rectifier is damaged or the intermediate circuit is short-circuited.

No output during startup (motor does not start):

Disconnect the output motor line, restart the machine and observe the input frequency displayed on the inverter panel, and measure the AC output terminal at the same time. The possible reasons are that the inverter startup parameter settings or the running terminal wiring are wrong, or the inverter part is damaged or the motor is not correctly connected to the inverter.