Uninterruptible Power Supply (UPS) Troubleshooting FAQ

An uninterruptible power supply, also known as UPS or battery backup, is an electrical device that provide power source to the load during the power outages. The UPS is mainly used to provide a stable and uninterrupted power supply to personal computers, peripherals, network system telecommunication equipmentor other power electronic equipment etc.
Below are ATO searched UPS troubleshooting for FAQ's. Can't find your question? Contact us for help.

♦ Uninterruptible power supply output is normal when there's power supply, but the buzzer calls for long time without power supply, there's no output at the same time?
Fault analysis: The battery and inverter may break down. Inspections can be made by following step:

1. Check the battery voltage to see if it is fully charged. If it is not, further check if it's the fault of battery or the charging circuit.
2. If the battery voltage is normal, check whether the inverter's drive circuit works normally. If the drive circuit outputs normally, meaning the inverter breaks down.
3. If the inverter's drive circuit doesn't work normally, please check if the waveform generation circuit has PWM control signal output. If it has, meaning the fault lies in the inverter's drive circuit.
4. If the waveform generation circuit doesn't have PWM control signal output, please check if the output is blocked for protection circuit. If it is, find out the cause for protection.

Above fault removal sequence can also be implemented reversely, and the fault may be found out more quickly.

♦ Voltage is low, but after charging for more than ten hours, the voltage doesn't rise?
Fault analysis: The battery or charging circuit may break down. Inspections can be made by following steps:

1. Check whether the input and output voltage of the charging circuit is normal.
2. If the input of charging circuit is normal but output is abnormal, disconnect the battery and check again. If it's still abnormal, the charging circuit breaks down.
3. If input and output voltage of the charging circuit are normal after disconnecting the battery, that means the battery has been damaged for various reasons, such as long-term uncharged, service life ends.

♦ There's no display on the panel after the UPS starts, UPS doesn't work?
Fault analysis: the fault may lie in power input, battery and power detection, battery voltage test circuit:

1. Check if the power input fuse is burned out.
2. If the fuse works normally, check whether the battery fuse is burned out, because some uninterruptible power supply may close all outputs and display when it can't detect a voltage.
3. If the battery fuse is complete, please check if the power detection circuit works normally. If it doesn't work normally while UPS can't start without power supply, UPS will also close all outputs and display.
4. If the power detection circuit works normally, please check if the battery voltage test circuit is normal.

♦ UPS works normally under power supply, but when there's no power supply, the inverter outputs with low voltage while the transformer makes a lot of noise at the same time?
Fault analysis: Inverter has the output, meaning that the last drive circuit is basically normal. The transformer makes noise, meaning two arms of the push-pull circuit work asymmetry. Inspections can be made by following steps:

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

♦ Starting UPS under normal power supply, the inverter's operation indicator flashes and the buzzer makes intermittent calls, UPS can only work in inverter state, but can't work under the power supply?
Fault analysis: UPS can't transfer from inverter power supply to commercial power supply, that means the transformation part of inverter power supply to commercial power supply breaks down, it shall be carefully detected:

1. If the commercial power supply fuse breaks down.
2. If the fuse works well, check if the output of rectifier and filter circuit is normal.
3. If the output of rectifier and filter circuit is normal, check if the power supply detection circuit is normal.
4. If the power supply detection circuit is normal, check whether the control output of inverter power supply to commercial power supply is normal.