UPS uninterruptible power supply common fault repair method

Foreword

At present, all weak current projects are equipped with UPS, then the UPS has failed, will you repair it? If the manufacturer cannot arrive at the scene in time to solve the problem, can you perform simple repairs? This article mainly introduces the simple problem-solving methods of UPS.

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UPS, that is, uninterruptible power supply , is a system equipment that connects storage batteries (mostly lead-acid maintenance-free storage batteries) to the host and converts DC power to mains power through module circuits such as host inverters. It is mainly used to supply a single computer, Computer network systems or other power electronic equipment such as solenoid valves, pressure transmitters, etc. provide a stable, uninterrupted power supply. Its role is to supply power to computers and other equipment in a timely manner in the event of external power interruption, so as to avoid interruption of communication, loss of important data and hardware damage.However, when the UPS power supply is used to protect other objects, the UPS power supply itself often has some failures. If the UPS power supply fails, it cannot provide protection for the load.

In this article, I will introduce the analysis and treatment of common failure phenomena of UPS power supply :

Common problem one:

The UPS power output is normal when there is mains power, but the buzzer sounds long and no output when there is no mains power.

Failure analysis: From the phenomenon, it is judged as part of the battery and inverter problems, which can be checked according to the following procedures:

① Check the battery power to see if the battery is insufficiently charged. If the battery is insufficiently charged, check whether the battery is a problem or the charging circuit is faulty.

② If the battery working voltage is normal, check whether the inverter drive circuit works normally. If the drive circuit output is normal, the inverter is damaged.

③ If the inverter drive circuit works normally, check whether there is signal output from the waveform generating circuit. If there is a 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 protection circuit operation, and if so, find out the protection reason;

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

The above troubleshooting sequence can also be reversed, and sometimes problems may be found faster.

Common problem two:

The pair of power amplifier transistors of the inverter power stage are damaged. After replacing the same type of transistor, the reason for running for a while and then burned is that the current is too large, and the reasons for the excessive current are:

① Overcurrent protection is damaged. When the inverter output overcurrent occurs, the overcurrent protection circuit does not work;

②Pulse width modulation (PWM) component is faulty, the two complementary waveforms of the output are asymmetric, one has a long conduction time, and the other has a short conduction time, which makes the two arms work unstable, and even the two arms are turned on at the same time, resulting in two tubes. Damage at the same time;

③ The parameters of the power tube are inconsistent. At this time, even if a symmetrical waveform is input, the output will be asymmetric. This waveform passes the output transformer and causes bias magnetism, that is, the magnetic flux is unbalanced. Accumulation will cause the transformer to saturate and the current to increase sharply. One burned out and the other burned out.

Frequently Asked Question Three:

The battery voltage is low, but after more than ten hours of charging, the battery voltage still cannot be charged.

Failure analysis: Judging from the phenomenon may be the failure of the battery or charging circuit, you can check according to the following steps:

① Check whether the input and output voltage of the charging circuit is normal;

② If the input voltage of the charging circuit is normal and the output is abnormal, disconnect the battery and test again. If it is still abnormal, the charging circuit is faulty;

③ If the input and output of the charging circuit are normal after disconnecting the battery, it means that the battery has been damaged due to long-term non-charging, transient discharge, or the end of its life.

Frequently asked questions:

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

Failure analysis: Judging from the failure phenomenon, the failure is in the mains input, battery and mains detection section and battery voltage detection circuit:

① Check whether the mains input fuse is burned out;

② If the mains input fuse is intact, check whether the battery fuse is burned out, because some UPS will turn off all the output and display of the UPS when the battery voltage is not self-tested;

③ If the battery fuse is intact, check whether the mains detection circuit is working normally. If the mains detection circuit is not working properly and the UPS does not have the start-up function without mains power, the UPS will also turn off all output displays.

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

The above are common UPS problems and maintenance tips introduced to you. I hope they can help you, but for the sake of insurance, when you encounter a UPS failure, you still have to find a professional maintenance person to test and repair to avoid accidents and serious losses ...