I. Overview of UPS equipment

With the continuous development of computer information processing technology, today's communications systems, information processing systems, automatic control systems, traffic management systems, medical control systems and aerospace, weather and financial. Many departments have universally applied computers. In order to ensure the correct and safe operation of the computer, we have made increasingly stringent requirements on the power supply, and the UPS is designed to meet this requirement. An uninterruptible power system (Uninterruptible Power System) is known as the "uninterrupted power supply." "System" or "uninterruptible power supply system" is referred to as UPS. Now uninterruptible power supply, has quickly evolved from a less-respected role in the peripherals of computers to become the key device of the Internet and the defender of e-commerce. As the cornerstone of the information society, UPS has begun its new historical mission. With the advent of the Internet age, higher and higher requirements are placed on the quality of power supply, whether it is the entire network of equipment or data transmission channels. Complete protection to the end requires high-quality uninterrupted power supplies.

When the mains power supply has the following power quality problems:

(1) Surge.

(2) High pressure spikes.

(3) Transient overvoltage.

(4) voltage sags.

(5) Line noise.

(6) Frequency offset.

(7) Continuous low pressure.

(8) Mains interruption.

The UPS will ensure that the output will be stable, pure and uninterrupted sine wave AC voltage, so that the microcomputer system can work normally.

Second, the basic principle of application

From the basic application principle, UPS is a kind of power protection device with energy storage device, with inverter as the main component, and constant voltage and frequency stabilization output. Mainly consists of rectifiers, batteries, inverters and static switches.

1) Rectifier: A rectifier is a rectifying device, which is simply a device that converts alternating current (AC) to direct current (DC). It has two main functions: First, it changes the alternating current (AC) to direct current (DC), which is filtered to supply the load, or to the inverter. Second, it provides the battery with the charging voltage. Therefore, it also functions as a charger.

2) Battery: A battery is a device used by a UPS to store electrical energy. It is made up of several batteries connected in series. The capacity of the battery determines the time it takes to maintain discharge (power supply). Its main functions are: 1 When the utility power is normal, the electrical energy is converted into chemical energy stored in the battery. 2 When the mains fails, chemical energy is converted into electrical energy for the inverter or load;

3) Inverter: In general, an inverter is a device that converts direct current (DC) into alternating current (AC). It consists of inverter bridge, control logic and filter circuit.

4) Static switch: Static switch, also known as static switch, is a kind of non-contact switch, which is an AC switch composed of two thyristor (SCR) anti-parallel connection, which is closed and disconnected by the logic controller. control. Divided into two kinds of conversion type and parallel type. Switching switch is mainly used for two-way power supply system, its role is to achieve automatic switching from one way to another; parallel switch type is mainly used for parallel inverter and mains or multi-inverter.

At present, the mainstream UPS manufacturers include APC, SANTAK, etc. They all provide various levels of UPS to meet the needs of different user groups.

In principle, the UPS is a power electronic device that integrates digital and analog circuits and automatically controls the inverter and the maintenance-free energy storage device.

Functionally speaking, UPS can effectively purify the city power when the utility power is abnormal, and it can also supply power to computers and other equipment for a certain period of time when the utility power is suddenly interrupted, so that you can have plenty of time to deal with it;

In terms of usage, with the advent of information-based society, UPS is widely used in all aspects of information collection, transmission, processing, storage and application, and its importance is increasing with the increasing importance of information applications.

Third, common fault reference

Therefore, we (Sorrid UPS power supply solution experts) introduce the analysis and treatment of the common fault phenomena of UPS power supply. Through the following references, we can help some of our friends.

Problem 1: The UPS power output is normal when there is a commercial power supply, but the buzzer sounds when there is no commercial power, and there is no output.

Fault Analysis: From the phenomenon to battery and inverter faults, the following procedures can be checked:

1. Check the battery voltage to see if the battery is undercharged. If the battery is not fully charged, check whether the battery itself is faulty or the charging circuit is faulty.

2. 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.

3. If the inverter driver circuit is not working properly, check whether the waveform generation circuit has a PWM control signal output. If there is a control signal output, the fault is in the inverter drive circuit.

4. If the waveform generation circuit has no PWM control signal output, check whether the output is blocked due to the protection circuit work, and if so, find out the reason for protection;

5. If the protection circuit is not working and the working voltage is normal, and the waveform generation circuit does not output the PWM waveform, the waveform generation circuit is damaged.

The above order of troubleshooting can also be reversed, and sometimes the fault can be found faster.

Question 2: The power amplifier transistor of the inverter power stage is damaged. After replacing the transistor of the same type, the reason that the operation is burned out for a period of time is that the current is too large, and the cause of the excessive current is:

1, over-current protection failure. When the inverter output over-current, over-current protection circuit does not work;

2. The pulse width modulation (PWM) component is faulty, and the two complementary waveforms output are asymmetric, one conduction time is long, and the other conduction time is short, so that the two arms work unbalanced, and even two arms simultaneously conduct, resulting in two Damaged tube

3. The power tube parameters are quite different. At this time, even if you input symmetrical waveforms, the output will be asymmetric. The waveform will be biased by the output transformer, which will result in magnetic flux imbalance. Accumulation will cause the transformer to saturate and the current will suddenly increase. Power pipe, and one burns out, the other burns.

Question 3: The battery voltage is low, but more than ten hours after starting the charge, the battery voltage is still not enough.

Fault analysis: From the phenomenon to battery or charging circuit failure, check the following steps:

1, check the charging circuit input and output voltage is normal;

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

3. If the input and output of the charging circuit are normal after the battery is disconnected, it indicates that the battery has been damaged due to long-term uncharged, overdischarged, or already in service life.

Question 4: After the UPS is turned on, nothing is displayed on the panel. The UPS power supply does not work.

Fault analysis: Judging from the fault phenomenon, the fault is at the input of mains, battery and mains detection part and battery voltage

Detection circuit:

1. Check if the mains input fuse is burned out;

2. If the mains input fuse is intact, check whether the battery insurance is burned, because some UPS will shut down all the outputs and display of the UPS when the battery voltage is not detected by itself.

3. If the battery is in good condition, check if the mains detection circuit is working properly. If the mains detection circuit is not working properly and the UPS does not have no mains start function, the UPS will also turn off all outputs and displays.

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

Question 5: When the mains power supply is normal, the UPS is turned on, the inverter work indicator blinks, and the buzzer sounds intermittently. The UPS power supply can only work in the inverter state and cannot be switched to the mains work state.

Fault analysis: The inverter power supply cannot be converted to the mains power supply, indicating that the inverter power supply to the mains power supply conversion part has failed. It is necessary to focus on detection:

1. Whether the mains input fuse is damaged;

2. If the mains input fuse is in good condition, check if the output of the mains rectifying filter circuit is normal;

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

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

Question 6: A back-up UPS works normally when there is commercial power, and the inverter has output when there is no mains, but the output voltage is low, and the transformer emits loud noise.

Failure Analysis: The inverter has an output to indicate that the final stage 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 the power is normal;

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

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

Question 7: In the case of access to utility power, each time you turn on the UPS uninterruptible power supply, you hear the repeated action sound of the relay. The UPS power supply panel battery voltage is too low and the indicator lights up and the buzzer sounds.

According to the above fault phenomenon, it can be judged that the fault is caused by the battery voltage being too low, which results in unsuccessful startup of the UPS. Remove the battery and perform a balanced charge first (all batteries are charged in parallel). If it is still unsuccessful, only replace the battery.

Question 8: The UPS power supply can only be powered by the mains and cannot be converted to inverter power supply.

Failure Analysis: Can not be converted from utility power to inverter power supply, indicating that the utility power to the inverter power supply conversion part of the failure, we must focus on testing:

1, whether the battery voltage is too low, the battery fuse is intact;

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

If the battery voltage detection circuit is normal, check whether the output of the utility power to the inverter power supply conversion control is normal.

Question 9: Standby UPS power supply When the load is near full load, the mains power supply is normal, and the battery fuse blows when the battery is powered.

Failure analysis: The battery fuse is blown, indicating that the battery supply current is too large. The detection procedure is as follows:

1. Does the inverter breakdown?

2. Is the battery voltage too low?

3, if the battery voltage is too low, then detect the battery charging circuit is normal;

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