Frequently Asked Questions about Data Center UPS

What is a UPS System?

An uninterruptible power supply (UPS), also known as a backup battery, can provide backup power if your regular power supply fails or the voltage drops to an unacceptable level.

You may have a facility that is already equipped with a UPS (uninterruptible power supply) or even a generator. Even if you have a generator, you need a UPS device to ensure that there will be no power interruption. It can protect your valuable equipment and data from power problems, such as power surges and abnormal voltages.

In the event of a power failure, the UPS system will provide backup power from its internal battery. This allows your device to remain on during a power outage, which is especially useful for devices such as computers that may lose data when they are turned off unexpectedly.

A stand-alone UPS device can only keep the device powered for a limited time, usually less than 30 minutes, but it can be used in conjunction with facility generators to ensure that your infrastructure can continue to operate even in the event of a prolonged power outage

The Three Basic Functions of UPS: Voltage Stabilization, Filtering, Uninterrupted.

When the mains power is supplied, it is the function of the voltage stabilizer and the filter to ensure the normal operation of the equipment; when the mains is interrupted, it can pass the DC power provided by its DC power supply part (battery pack, diesel generator, etc.) It is converted into perfect AC power for the load, and the switch from mains power to battery power is generally 0 time switch, so that the load equipment can keep running without feeling any change, and truly ensure the uninterrupted operation of the equipment.

In the construction of weak current projects, UPS is set up to solve the uninterrupted power supply. UPS power installation is a more important link. Before installing the UPS, you need to consider the UPS input and output power distribution.

UPS Installation 7 Items

Generally, UPS manufacturers will provide users with complete and detailed UPS installation requirements and precautions. Only by meeting this requirement can the normal operation of the UPS power supply system be guaranteed.　

In actual application, the engineer can send the relevant parameters to the customer according to the actual situation of the UPS to be installed, so that the customer can construct according to this requirement. The following is an explanation one by one:

The fluctuation value of the input mains power provided by the user for the UPS is generally less than the nominal allowable mains fluctuation value of the UPS. For example, the nominal allowable mains input voltage fluctuation of a certain type of UPS is 220V+20%, then the user can be required for this item The fluctuation is +15%, which is conducive to the normal operation of UPS; the zero-to-ground voltage is generally required to be less than 1.5V without load and less than 2V with full load. Engineers can also propose this value according to site conditions and load requirements.

In order to eliminate common mode interference, UPS has added filter capacitors between zero and live wires to ground. There are currents between zero and fire and ground, which may cause unequal currents on the zero and live wires, which will trip the circuit breaker with leakage current. Therefore, the UPS front stage and load circuit cannot be equipped with a circuit breaker with leakage protection to avoid accidental power failure of the UPS and its load. It should be pointed out here that the main purpose for users to configure UPS is for the safe operation of important equipment such as computers, not for the safety of personnel. Therefore, the live parts of the line such as sockets, circuit breakers, etc. should not be frequently plugged in or opened. Together.

In order to eliminate interference, the input neutral line of most UPSs is isolated from the output neutral line or passed through a choke, so the neutral line of the UPS output (ie load) cannot be connected to the input power distribution when doing UPS power distribution. On the neutral bus. The user can connect the UPS output (load) neutral line to a single neutral line bar. Some brands of UPS have a direct connection between the input neutral line and the output neutral line inside the UPS, so the input neutral line and the output (load) neutral line can be connected to the same busbar.

The UPS input circuit breaker is designed to individually control the on and off of the UPS input power, so do not connect other electrical equipment to the lower port of the UPS input circuit breaker, so as not to affect the normal on and off of the UPS input power.

Here is a point. Some users require UPS to work on battery backup for a long time after the mains power failure. In this way, the capacity of the external long-delay battery provided by the UPS will be large. To ensure that this part of the external battery can be With sufficient charging current (usually 10% of the total AH of the external battery), the manufacturer will equip the UPS with an external long-delay battery charger. The AC input power of this charger must be turned on and off at the same time as the UPS input power. , To ensure that the external charger will charge the external battery when there is city power, and when the city power is off, the battery will immediately discharge to the UPS inverter through the charger. Therefore, the AC input power of this charger must be connected to the lower port of the same circuit breaker as the input power of the UPS.

When selecting input and output circuit breakers for UPS, firstly, the nominal rated voltage of the circuit breaker is required to meet the rated input and output voltage of the UPS. For example, single-in single-out UPS can choose single-pole (or N+1, or two-pole) rated voltage as AC220V or 250V circuit breaker, three-in, three-out UPS can choose a three-pole (or N+3, or four-pole) circuit breaker with a rated voltage of AC380V or 415V. It should be noted that the rated breaking capacity of the circuit breaker ICU must meet the requirements of the UPS manufacturer. Generally, the small UPS is 10KA or 6KA, and the large and medium-sized UPS are required to be above 30KA.

The connection between the UPS and the external long-delay battery should not be too long, otherwise the voltage drop on the battery connection will be too large. In addition, users often pay great attention to the ambient temperature and humidity of the UPS host. Placing the battery with the host can also provide a good working environment for the battery.

It is recommended that the user set up a separate power distribution panel (cabinet) for the UPS and its load to facilitate centralized and reliable control of the UPS and the load it protects. This switchboard (cabinet) must comply with relevant national standards.

The reliability of the data center power supply system is of paramount importance. It is conceivable that no matter how sophisticated the IT equipment is, how superior the function of the system, and how high its reliability is, once the power goes out, no matter how good the system is, it will not work. Therefore, the importance of equipment maintenance during operation cannot be ignored. It can be seen that the burden on the shoulders of maintenance personnel is very heavy.

• The Purpose Of Operation And Maintenance    

The reliability of the data center power supply system is of paramount importance. It is conceivable that no matter how sophisticated the IT equipment is, how superior the function of the system, and how high its reliability is, once the power goes out, no matter how good the system is, it will not work. Therefore, the importance of equipment maintenance in operation cannot be ignored. It can be seen that the burden on the shoulders of maintenance personnel is very heavy. 　

• Operation And Maintenance Tasks And Problems

In order to ensure the reliable operation of the power supply system, many good measures have been formulated in many places. But even so, there are many loopholes. The reliability of the equipment has been determined after leaving the factory. For example, some are born with deficiencies. For example, some power output isolation transformer windings use aluminum enameled wires instead of copper enameled wires. In all cases, accidents will happen when running at full load...but because of the equipment Statistics of failures caused by quality problems show that less than 30%, and 70% of failures come from the day after tomorrow. That is, man-made failure, which manifests as follows:

   1. Failure Caused By Improper Selection   

(1) The basic concept is unclear and easy to be misled by manufacturers.

For example, a highway bidding for UPS requires the UPS to have the ability to continue to supply power without discharging the battery after one or two phases are interrupted in the input. Because some manufacturers advertise that the battery of his UPS does not discharge after one phase of the input is interrupted, the UPS still has 50% of the power supply capacity; the battery still does not discharge after the input of two phases is interrupted, and the UPS still has 25% of the power supply capacity, which extends the battery's power. Service life. Users think this performance is good, and it is not difficult to find its shortcomings with a little brainstorming: if you want to enjoy its advantages, you must purchase a UPS with 4 times the load capacity, otherwise the current load will not be driven after one phase is broken. Then again, what if the UPS disconnects the two wires behind the input switch? Repair it or not? When will it be repaired? Can it be repaired after the power is completely cut off? Wait for how to solve this series of problems. If the user really buys such a UPS according to the actual capacity of the load, this is a huge hidden danger, which is a problem that cannot be solved by operation and maintenance. 

(2) Reasons for inconvenience. 

For example, some users have been using a certain brand of machine since the last century. At that time, due to objective reasons, despite the low input power factor, low efficiency, large size, high power consumption and high price, it was impossible and inconvenient to solve it. New models that are much superior to the original ones have already come out. For example, the new high-frequency machine structure UPS saves 50,000 kilowatts of electricity per 100 kilowatts per year compared with the original industrial frequency machine structure UPS, and this capacity is a few megawatts. The computer room can save millions of kilowatt-hours of electricity every year. However, for some reason, the energy-consuming machine was still included in the bid book without choosing the energy-saving equipment. I was afraid that it would not be safe to do so, and the structural characteristics of the machine were written into the bid book. This not only increases the investment and floor space of air-conditioning equipment, but also undoubtedly lays down hidden dangers for future operations. This is another problem that cannot be solved in operation and maintenance. 

(3) Pursue low prices. 

Some users think that UPS is the same, so they pursue low prices, which leads to failures. For example, a highway headquarters was greedy for cheap, and installed the machine on the first day and caught fire on the second day; a life insurance company purchased a machine at a low price and burned almost all the input circuits of IT equipment due to UPS failure in less than half a year, causing the system to be paralyzed ; Another example is a megawatt data center with multiple UPSs connected in parallel. Within a few months of installation, one of the inverter power tubes in one of the UPSs broke down and all UPSs were tripped...

   2. Failure Caused By Improper Use Environment    

Do not place the machine in accordance with the requirements of the environment in the manual, and some even put the UPS in the corridors and dripping basements that you can walk through. For example, several 200kVA UPSs are placed in a bungalow with only one layer of prefabricated panels on the roof, and the air conditioners are just two 5P comfortable air conditioners. Another example is a glass factory that puts the UPS in a powdered factory, and so on. Caused frequent failures.

   3. Malfunctions Caused By Imperfect Systems    

For example, some personnel on duty randomly connect electric stoves, rice cookers and vacuum cleaners to the UPS, causing overload and tripping; some personnel’s food causes rats to get into the machine and cause fire...

   4. Handover Failure

This type of failure is mainly caused by the lack of a group of management personnel or poor cooperation. For example, in a train station ticketing system, the front check-in staff disconnected the external battery pack of the UPS due to the moving machine location, and did not explain to the latecomer afterwards. As a result, the mains and UPS were out of power at the same time...

   5. Experience Failure

Experience is indispensable, it is a rare treasure. But experience has its relativity, that is, the experience gained on a certain kind of UPS may not be completely suitable for another kind of UPS, otherwise it will lead to failure. A telecommunications bureau used the same method to start another brand machine without reading the manual, which caused the inverter to burn out.

   6. Oversight Failure

Some devices will experience aging or early failure during operation, and failure will result if they are not checked in time. These cannot be found in automatic monitoring. For example, fuses that start to bend due to aging, loosening of battery structural screws, and minute cracks in the battery case after long-term battery discharge, etc., can cause failures if they are not discovered in time or are not handled in time after discovery.

   7. Failures Caused by Rushing into Battle

Do not have the slightest impatience when doing maintenance, you have to think about it before doing it. An engineer of a company wants to overhaul a user's running UPS. According to the regulations, the UPS must be removed from the maintenance bypass switch and then overhauled. However, according to the procedure, the automatic bypass must be activated first, and then the maintenance bypass switch should be closed. Perhaps the project has other urgent matters to be done. After entering the computer room, the bypass switch was closed without consideration, which caused the inverter power tube to explode.

   8. Secondary Failures Caused By Improper Maintenance    

Regular maintenance of UPS is necessary, but there should be a set of strict management procedures. Those who are irresponsible and do not perform regular or irregular maintenance according to regulations are important reasons for machine failure. In addition, it can also cause malfunctions during maintenance. For example, when measuring the potential of a circuit board with a multimeter probe, the probe will short-circuit two points and cause a malfunction. When a user discharges the battery, he removes the battery from the UPS. After the battery is discharged, the model is released when the battery is connected back, causing the current to explode. Another example is when an engineer accidentally slipped the adjustable wrench and hit the control panel when replacing the centrifugal fan. He didn't care at the time. After the fan was replaced, he couldn't turn on the machine. The inspection found that a device leg was broken...

   9. The Failure Caused By Static Electricity    

A computer room was shut down for maintenance as usual, but it could not be turned on after maintenance. After inspection, it was found that a component had a voltage breakdown. Recalling the maintenance process, it was found that the control board was swept through dust with a plastic toothbrush. Plastics can generate several thousand volts of friction electrostatic voltage on the surface of the drying device. Because the small signal circuit in the machine uses some MOS devices, these devices have low withstand voltage and are most afraid of static electricity. After measuring an ordinary plastic bag, it can generate an electrostatic voltage of 3000V by rubbing it with a circuit board. Therefore, it is best to put a grounding ring on your wrist when inspecting these circuit boards.

   10. Failure Caused by Overconfidence

Self-confidence in doing things is the foundation of success, but overconfidence can sometimes make mistakes. For example, an international bank should update its equipment after UPS has been in operation for 8 years, and the manufacturer has repeatedly reminded it. Since the UPS has rarely experienced problems in the past eight years, the user in charge repeatedly answered "No update". As a result, the UPS stopped powering for two hours due to aging failures a few months later, causing global business to be interrupted for two hours, resulting in great losses.　　According to international statistics, the nominal battery service life of 5 years is no more than 3 years. Usually, it should be replaced within 2 years if it is not maintained. The battery in an airport terminal was originally equipped for 4 hours, and it was still not replaced after 3 years. A power outage on the external grid, UPS backup time was only 4 hours, due to power outages caused losses...There are many similar man-made failures, not one by one. Exemplified.

In the final analysis, the selection of the power supply system is the first hurdle, and the inability to control this hurdle first planted the seeds of hidden dangers. The connection of the power system is the second level. With good equipment, if there is no good connection scheme, hidden dangers will be buried. A TV station was misled by the manufacturer due to the connection scheme. The power supply UPS failures of more than a dozen programs continue to occur, and most of them are unpredictable. This has been the case for several years, which has made maintenance personnel nervous and brain-wrenching. The connection scheme is a project, and it is not controlled by the maintenance personnel. Reluctantly, the factory engineers were on duty at major events and festivals. What's the use of this? The manufacturer's engineers can only give users psychological comfort at this point.