UPS (Uninterruptible Power Supply) Troubleshooting

When there is mains power, the UPS output is normal, but when there is no mains power, the buzzer beeps for a long time and there is no output. Fault analysis: It is judged from the phenomenon that the battery and inverter are partially faulty, and can be checked according to the following procedures:

Case 1: When there is mains power, the UPS output is normal, but when there is no mains power, the buzzer beeps for a long time and there is no output.

Fault analysis: It is judged from the phenomenon that the battery and inverter are partially faulty, and can be checked according to the following procedures:

1. Check the battery voltage to see if the battery is undercharged. If the battery is insufficiently charged, check whether it is the battery itself or the charging circuit.
   If the working voltage of the battery is normal, check whether the inverter drive circuit works normally. If the output of the drive circuit is normal, the inverter is damaged.
2. If the inverter drive circuit does not work properly, check whether the waveform generation circuit has PWM control signal output. If there is a control signal output, it means that the fault is in the inverter drive circuit.
3. If there is no PWM control signal output from the waveform generation circuit, check whether its output is blocked due to the operation of the protection circuit and if so, find out the reason for the protection.
4. If the protection circuit does not work and the working voltage is normal, but the waveform generating circuit has no PWM waveform output, it means that the waveform generating circuit is damaged.
5. The above sequence can also be reversed, sometimes finding faults faster.

Case 2: The battery voltage is low, but the battery voltage still cannot be charged for more than ten hours after starting the charging.

Fault analysis: Judging from the phenomenon that the battery or charging circuit is faulty, you can check the following steps:

1. Check whether the input and output voltages of the charging circuit are normal.
2. If the input of the charging circuit is normal and the output is abnormal, disconnect the battery.
3. Re-test, if it is still abnormal, the charging circuit is faulty.
4. 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 uncharged, over-discharged or expired life.

Case 3: After the UPS is turned on, there is no display on the panel, and the UPS does not work.

Fault analysis: The fault is in the mains input, battery and mains. Please check the voltage of the part and the battery, and the detection circuit:

1. Check if the mains input fuse is blown.
2. If the mains input fuse is in good condition, check whether the battery fuse is burnt, because some UPS will turn off all the output and display of the UPS when the battery voltage cannot be checked by itself.
3. If the battery insurance is in good condition, check whether the main detection circuit works normally. If the mains detection circuit does not work properly and the UPS does not have the function of starting without mains, 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 works normally.

Case 4: A backup UPS works normally when there is the main power. When there is no main power, the inverter has output, but the output voltage is low, and the transformer makes a lot of noise.

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

1. Check whether the power is accurate.
2. If the power is correct, then check whether the output signal of the pulse width output circuit works normally.
   
3. If the output of the pulse width output circuit is normal, then check whether the output of the drive circuit works normally.