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UPS common faults and how to eliminate

2020-06-22

                                                             

                                                         

                                                               UPS common faults and how to eliminate


  1. The ups output is normal when the power supply is available, but the buzzer will beep for a long time when the power supply is not available.


    Fault analysis: judging from the phenomenon as partial fault of battery and inverter, check according to the following procedures:

  1. Check the battery voltage to see if the battery is under charged. If the battery is under charged, check whether it is the battery itself or the charging circuit fault.

  2. If the working voltage of the battery is normal, check whether the driving circuit of the inverter works normally. If the output of the driving circuit is normal, it means that the inverter is damaged.

  3. If the inverter drive circuit does not work normally, check whether the waveform generation circuit has PWM control signal output. If there is control signal output, it means that the fault is in the inverter drive circuit.

  4. If the waveform generating circuit has no PWM control signal output, check whether its output is blocked due to the operation of the protection circuit, if so, find out the protection reason.

  5. If the protection circuit does not work and the working voltage is normal, and the waveform generation circuit has no PWM waveform output, it means that the waveform generation circuit is damaged.


 2. The battery voltage is low, but it can not be charged after more than ten hours of starting


  Fault analysis: judging from the phenomenon as battery or charging circuit fault, check as follows :

  1. Check whether the input and output voltage of charging circuit is normal or not.

  2. If the input of the charging circuit is normal and the output is abnormal, disconnect the battery and retest. If it is still abnormal, it is the charging circuit fault.

  3. If the input and output of the charging circuit are normal after the battery is disconnected, it means that the battery has been damaged due to long-term non charging, over discharging or reaching the service life.


3.A pair of power amplifier transistors of inverter power stage are damaged. After replacing the same type of transistors, the reason why they burn out after a period of operation is that the current is too large, and the reason why the current is too large as below :

  1. Overcurrent protection failure. When the inverter output overcurrent, the overcurrent protection circuit does not work.

  2. When the pulse width modulation (PWM) module fails, the output two complementary waveforms are asymmetric, one of them has a long conduction time, while the other has a short conduction time, which makes the work of the two arms unbalanced, or even the two arms are connected at the same time, causing damage to the two tubes.

  3. The parameters of the power tube are quite different. Even if the symmetrical wave is input, the output will be asymmetric. This wave will cause magnetic bias through the output transformer, i.e. the magnetic flux is unbalanced, which will lead to the saturation of the transformer and the sudden increase of the current. The power tube will be burnt out, and one will be burnt out, and the other will be burnt out with it.


 4. After turn on ups , there is no display on the panel and UPS does not work.


Fault analysis: judging from the fault phenomenon, the fault is in the mains input, battery, mains detection part and battery voltage detection circuit:

  1. Check whether the mains input fuse is burnt.

  2. If the mains input fuse is in good condition, check whether the battery fuse is burnt, because when some ups self check fails to reach the battery voltage, it will turn off all the ups output and display.

  3. If the battery is in good condition, check whether the power supply detection circuit works normally. If the power supply detection circuit does not work normally and the ups does not have the function of starting without power supply, the ups will also turn off all outputs and displays.

  4. If the city detection circuit works normally, then check whether the battery voltage detection circuit is normal.


5.One backup UPS works normally when the power supply is available, and the inverter has output when the power supply is not available, but the output voltage is low, and the transformer makes great noise.


Fault analysis: the output of the inverter indicates that the final drive circuit is basically normal, and the noise of the transformer indicates that the two arms of the push-pull circuit work asymmetrically. The detection steps are as follows :

  1. Check whether the power is normal.

  2. If the power is normal, check whether the output signal of pulse width output circuit is normal.

  3. If the output of the pulse width output circuit is normal, then check whether the output of the drive circuit is normal.


6.When the mains power supply is normal, turn on the ups, the working indicator light of the inverter flashes, and the buzzer makes an intermittent call. The ups can only work in the inverter state, and cannot be switched to the mains working state.


Fault analysis: it is unable to convert the inverter power supply to the mains power supply, which indicates that the inverter power supply to the mains power supply has some faults.

  1. Check the mains input fuse damaged or not.

  2. If the mains input fuse is in good condition, check whether the mains rectification and filter circuit output is normal.

  3. If the output of the mains rectifier filter circuit is normal, check whether the mains detection circuit is normal.

  4. If the power supply detection circuit is normal, then check whether the inverter power supply to the power supply conversion control output is normal.


7.When the load of backup UPS is close to full load, the mains power supply is normal, while the battery fuse is blown when the battery is powered.


Fault analysis: the fuse of the battery is broken, which means that the power supply of the battery flows through a large amount. The detection steps are as follows :

  1. Whether the inverter breaks down.

  2. Whether the battery voltage too low.

  3. If the battery voltage is too low, check whether the battery charging circuit is normal.

  4. If the battery charging circuit is normal, then check whether the battery voltage detection circuit works normally.


8.UPS can only be supplied by the municipal power supply instead of the inverter power supply.


Fault analysis: it is unable to convert the mains power supply to the inverter power supply, which indicates that the part of the mains power supply to the inverter power supply has faults, and it is necessary to focus on detection :

  1. Whether the battery voltage is too low and whether the battery fuse is intact.

  2. If the battery is partially normal, check whether the battery voltage detection circuit is normal.

  3. If the battery voltage detection circuit is normal, then check whether the conversion control output of mains supply to inverter supply is normal.