1.Fault Problem: The UPS output is normal when there is mains, and the buzzer sounds when there is no mains, no output.
(1)Fault analysis: Judging from the phenomenon that the battery and the inverter are partially faulty, the following procedures can be checked:
①Check the battery voltage to see if the battery is not fully charged. If the battery is not fully charged, check whether the battery itself is faulty or the charging circuit is faulty;
②If the battery operating voltage is normal, check whether the inverter drive circuit works normally. If the drive circuit output is normal, the inverter is damaged;
③If the inverter drive circuit is not working properly, check the waveform generation circuit for the presence of the PWM control signal output. If there is a control signal output, the fault is in the inverter drive circuit;
④If the waveform generation circuit has no PWM control signal output, check whether the output is blocked due to the protection circuit operation, and if so, find the protection reason;
⑤If the protection circuit is not working and the working voltage is normal, and the waveform generation circuit has no PWM waveform output, the waveform generation circuit is damaged.
2.Fault problem: After the UPS is turned on, there is no display on the panel, and the UPS does not work:
(2)Fault analysis: Judging from the fault phenomenon, its fault is in the mains input, battery and mains detection part and battery voltage detection loop:
①If the mains input fuse is intact, check if the battery insurance is burnt, because some UPS will turn off all output and display of the UPS when the self-test does not have the battery voltage;
②If the battery is in good condition, check whether the mains detection circuit works normally. If the mains detection circuit is not working properly and the UPS does not have the no-mains start function, the UPS will also turn off all output and display.
③If the city detection circuit is working properly, check if the battery voltage detection circuit is normal.
3.Fault problem: UPS can only be powered by mains and cannot be converted to inverter.
(3)Fault analysis: The power supply to the inverter cannot be converted, indicating that the mains fails to the inverter power supply conversion:
①Whether the battery voltage is too low and the battery fuse is intact;
②If the battery is partially normal, check if the battery voltage detection circuit is normal.
③If the battery voltage detection circuit is normal, check whether the utility power supply to the inverter power supply conversion control output is normal.
4.Fault Problem:When a backup UPS has utility power, it works normally. When there is no mains, the inverter has output, but the output voltage is low, and the transformer emits loud noise:
(4)Fault analysis:The output of the inverter indicates that the final stage drive circuit is basically normal. The noise of the transformer indicates that the two arms of the push-pull circuit are asymmetrical. The detection steps are as follows:
①Check if the power is normal;
②If the power is normal, check whether the output signal of the pulse width output circuit is normal;
③If the output of the pulse width output circuit is normal, check if the output of the drive circuit is normal.