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How to check and repair the inverter without responding after power-on?

Dec 03, 2020

How to check and repair the inverter without responding after power-on?

During inverter maintenance, it is often encountered that the inverter does not respond after powering on. In the normal situation, the inverter will have corresponding fault prompt even if it is energized when there is a fault. Then when the inverter has no response after power-on, how should we check and repair it?


Checking method for no response after the inverter is powered on


1. First, check whether there is a problem with the power switch. If you are unsure, 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 perform a static test again. Set the multimeter to resistance X10, connect the red meter rod to the P terminal of the inverter, and the black meter rod to R, S, and T respectively. At this time, there will be a resistance of about tens of ohms and basically balanced. When the black meter rod is connected to the P terminal, and the red meter rod is connected to R, S, T in turn, there will be a resistance close to infinity at this time. Then connect the red meter stick to the N terminal and repeat the above process. If the result is the same, the static test is normal.


3. If the static test of the frequency converter is normal, we will conduct another dynamic test, namely the machine test. Start the inverter under no-load (no motor connection), and test the U, V, and W three-phase output voltage values. If there is a lack of phase, three-phase unbalance, etc., the module or drive board is faulty and the output voltage is normal (no lack of phase, three-phase balance), and load test. It is best to test at full load.


After the above operations are completed, we can basically determine the specific reason why the inverter does not respond after powering on. At this time, we can solve the problem specifically. It is recommended that all the steps above should be handled by professional inverter maintenance personnel to avoid damage to the inverter.


Reasons and solutions for the failure of inverter without display


Faults with no display cause when the inverter is powered on usually occur on three modules: one is the contactor; the other is the control panel of the inverter; the third is the power module that supplies power to the control panel.


Fault detection 1: At the moment when the inverter is energized, there is a sound of the contactor closing under normal circumstances. If there is no such sound, the contactor may be broken.


Solution: Replace with a new contactor.


Fault detection 2: If there is no problem with the contactor, check whether there is a problem with the power module. If the high-voltage power supply LED of the inverter is on, it indicates that the high-voltage DC power supply is normal. It is detected that the low-voltage DC power supply has no DC voltage, which is a phenomenon that the switching power supply does not work. The switching power supply does not work as the switching tube does not work, and the detection of DC voltage is not sent, then the voltage reduction resistance between the high-voltage DC terminal and the primary terminal of the pulse transformer is damaged and open, and the high-voltage DC power is not added to the primary winding of the pulse transformer on. The switching power supply cannot work, the whole inverter has no low-voltage DC power supply, and there is no display fault.


Solution: Replace the step-down resistor.


Fault detection 3: The high-voltage LED indicator of the inverter is on, and the LED indicator on the main control board is also on, indicating that the inverter's switching power supply is normal, and the DC voltage on the main board and main control board is normal. Is there an 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 has phase loss or open circuit. If the power supply is normal, check whether there is voltage at the DC side terminals P and N of the inverter intermediate circuit after the power is turned on. If the above check is normal, judge the inverter internal switching power supply damage.


Power-on trip or sparks appear at the main power terminal of the inverter:


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


No output at startup (motor does not start):


Disconnect the output motor cable, observe the input frequency displayed on the inverter panel after restarting, and measure the AC output terminal at the same time. The possible cause is that the inverter's startup parameter setting or the wiring of the running terminal is wrong, or the inverter part is damaged or the motor is not correctly connected to the inverter.