Maintenance methods of UPS common faults

At present, many weak current projects are equipped with UPS, so how to repair the ups in case of failure? If the manufacturer can't arrive at the site in time to solve the problem, can you carry out simple maintenance? The following describes the simple troubleshooting method of ups.

UPS, or uninterruptible power supply, is a system equipment that connects the battery (mostly lead-acid maintenance free battery) with the host and converts the DC power into the mains power through the module circuit such as the host inverter. It is mainly used to provide a stable and uninterrupted power supply for a single computer, computer network system or other power electronic equipment such as solenoid valve, pressure transmitter, etc. Its function is to supply power to the computer and other equipment in time when the power supply is interrupted outside, so as to avoid the interruption of communication, the loss of important data and the damage of hardware. However, when using UPS power supply as protection object, its ups power supply itself often has some failures. If UPS power supply fails, it can not provide protection function for the load. In this article, I will introduce the analysis and treatment of the common faults of UPS power supply: 1

The UPS power output is normal when there is mains power supply, but the buzzer will beep for a long time when there is no mains power supply. 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 whether the battery is under charged; if the battery is under charged, check whether it is the fault of battery itself or the fault of charging circuit. 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 does not have PWM waveform output, it means that the troubleshooting sequence above the damage of waveform generation circuit can also be reversed, sometimes it can find the common problems of faults faster. 2

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 reasons for the current too large are: ① the over-current protection fails. When the inverter output over-current, the over-current 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 two arms work unbalanced, or even both 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 waveform is input, the output will also be asymmetric. This waveform will cause magnetic bias through the output transformer, that is, 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. Three problems often arise:

The battery voltage is low, but it can not be charged for more than ten hours after starting. Fault analysis: judging from the phenomenon as the battery or charging circuit fault, check according to the following steps: ① check whether the input and output voltage of charging circuit is normal; ② if the input of charging circuit is normal and the output is abnormal, disconnect the battery for 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. The fourth problem often occurs:

After UPS power is turned on, there is no display on the panel, and UPS power 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 intact, check whether the battery fuse is burnt, because some ups will turn off all the ups output and display when the battery voltage is not detected by self inspection; 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. The above are the ups common problems and maintenance skills introduced to you. I hope they can help you, but for the sake of insurance, you still need to find professional maintenance personnel to test and repair in case of UPS failure, so as to avoid accidents and serious losses.