What is UPS power supply - what are its uses and characteristics

UPS power supply, also known as uninterruptible power supply, is a constant voltage and frequency uninterruptible power supply with a backup device and a rectifier as the main component. Mainly used to provide uninterrupted power supply to a single computer, network system, or power electronic equipment. When the mains power is input normally, the UPS stabilizes the mains power and supplies it to the load for use. At this time, the UPS is an AC mains power stabilizer, and it also charges the internal battery, etc; When there is a sudden power outage, the UPS stops immediately supplying 220V AC power to the load through the method of inverter conversion, using the power from the internal battery to maintain normal operation and protect the load's software and hardware from damage.

A. The function and function of UPS power supply:

UPS stands for Uninterruptible Power System, which emerged with the birth of computers and is one of the commonly used peripheral devices in computers. In fact, UPS is a sudden power supply with a backup device and an inverter as the main component for constant voltage and constant rating. In its early stages of development, UPS was only considered as a backup power source. Later, due to power grid quality issues such as voltage surges, voltage spikes, voltage transients, voltage drops, sustained or undervoltage, and even voltage interruptions, the electronic systems of computers and other equipment were disrupted, resulting in serious consequences such as damage to sensitive components, loss of information, and disk program crashes, causing huge economic losses. Therefore, UPS is urgently valued and gradually developed into a power protection system with functions such as voltage stabilization, frequency stabilization, resonance, anti electromagnetic interference, and anti voltage surge.

At present, there are various types of UPS power supply equipment on the market, with output power ranging from 500VA to 3000kVA. When there is a supply of mains power to supplement the UPS, the UPS stabilizes the mains power (220V ± 5%) and supplies power to the computer. At this time, the UPS is a mains voltage regulator, and it also charges the internal battery. Due to different UPS designs, the range of UPS adaptation is also different. A variation of ± 10-15% in UPS output voltage is generally considered normal computer operating voltage. When the mains power is abnormal or cut off, UPS will immediately restore the computer system by maintaining the conversion of the internal battery power, in order to maintain the normal operation of the computer system and protect the software and hardware of the computer from loss.

B. Classification and characteristics of UPS power supply:

UPS power supplies can be divided into four categories based on their working mode: backup and online. According to their output waveform, they can be further divided into two types: square wave output and sine wave output. When the backup UPS power supply is supplied by the mains power normally, the mains power directly provides power to the load through the AC bypass channel and the transfer switch, and the signal in the machine is in a stopped working state. This UPS power supply is connected to a poorly performing mains connector on the relay. In addition, it has its role in improving the repeater of the mains voltage, but there is basically no improvement in the adverse effects such as frequency instability, distortion, and interference from the grid on the mains voltage. Only when the mains power supply is interrupted or below 170V, the battery only supplies power to the rectifier with low requirements for UPS power quality, and the load provides a stable and frequency AC power supply. The advantages of backup UPS power supply are high operating efficiency, low noise, and relatively cheap price, mainly suitable for power grids with low requirements for power supply quality.

When the online UPS power supply is supplied with normal mains power, it first converts the mains AC power supply to DC power supply, then performs pulse width modulation and excitation, and then converts the DC power supply back to AC power supply. That is, normally, AC power is corrected and provided to the load in the form of a warning device. Once the mains power is interrupted, the battery will immediately provide AC power to the load in the form of a warning device. Under normal circumstances, when there is mains power, the load is always powered by the topology of the UPS power supply, which avoids all the effects caused by voltage fluctuations and interference from the mains power grid. At this point, online conversion will cause backup UPS power supply regardless of the power quality of the UPS power supply, as it can significantly achieve load frequency stabilization, transformer power supply, and time reset when it is supplied from the mains to the grid.

The UPS power supply with square wave output has poor load capacity (40-60% of the rated load) and cannot carry inductive loads. If the load carried is too large, the third harmonic contained in the square wave output voltage affects the capacity current flowing into the load, and in severe cases, it can damage the power filter capacitor of the load. The relationship between the distortion degree of the output voltage waveform of a sine wave output UPS power supply and the load capacity is not as obvious as that of a square wave output UPS power supply. The load capacity is relatively high compared to the load, and it can carry a small amount of load capacity. Regardless of the type of UPS power supply, when they are in the waveform generator power supply state, unless the voltage cannot be reduced, they should generally not operate at full load or overload, otherwise it will significantly increase the failure rate of the UPS power supply.

C. Matching of UPS power supply and load:

Some UPS systems use watts (W) or kilowatts (kW) to represent their output power, such as 500W, 1kW, etc; Some UPS systems use volt ampere (VA) or kilovolt ampere (kVA) to represent their output power, such as 3000VA, 5kVA, etc. The general conversion relationship between VA and W is: watt is 0 in volt ampere. 8 times, such as 3kVA=2.4kw. UPS is used for supplying power to line loads, and each type of UPS has specific output power capabilities. If the maximum output power of a 3kVA UPS is 3kVA or 2.4kw, it is required that the total power consumption of the devices on this UPS should not exceed 2.4kw. Usually, devices are labeled with power consumption (or rated power), and in this case, the total rated power of all devices connected to the UPS should not exceed the output power of the UPS. This method is usually used to match the UPS output power with the load power consumption. But the starting power of some devices is 3-5 times the rated power (for example, if the rated power of a printer is 200W, then when calculating load matching, it needs to be converted as 5 × 200W=1000W). Other computer external devices, except for printers, usually have a startup power slightly greater than the load power. Therefore, when considering matching, it is best to match the load at 80% of the UPS output power.

A standard UPS, without an external battery, can provide power for approximately 6-10 minutes from the time of a power outage, assuming that its output power matches the load's power consumption (i.e. full load) (specific values are recorded in the UPS manual for each model). If the load power consumption is only half of the UPS output power (called habitual half load or 5) at 0% load rate, such as a 1000W UPS connected to a 500W load, it can supply power for 12-25 minutes. The UPS power supply time at different load levels can be calculated by doubling the load halving time. Proper use of UPS power supply can not only reduce the chance of UPS failure, but also effectively extend its service life.

D. When using USP power supplies, the following points should be noted:

(1). When using UPS power supply, it is necessary to strictly follow the relevant provisions of the manufacturer's product manual to ensure that the sequence of the live and neutral wires connected to the UPS power supply meets the requirements.

(2). The main purpose of equipping UPS is to prevent computer information loss and hard disk damage caused by sudden power outages, but some devices (such as printers) do not experience sudden power outages during operation. In order to save UPS energy, printers can consider connecting directly to the mains power without going through UPS. If it is a network system, it can be considered that UPS only supplies power to the host (or server) and related parts. This can ensure that UPS can use the most important equipment and replace the investment.

(3). Do not overload the UPS. The maximum load capacity of a UPS power supply should be 80% of its nominal load capacity (for example, for a 1000W UPS, match the load at an 80% load rate of 800W; for a 1000VA UPS, convert 80% to 800W and match the load at an 80% load rate of 640W). If overloaded, it often causes breakdown of the inverter transistor in the inverter state. In addition, when using UPS, it is strictly prohibited to connect inductive loads such as fluorescent lamps, and only pure electrical or smaller capacitive loads can be connected.

(4). When turning on and off the machine, attention should be paid to the order of power on and off: turn on the UPS first, and then turn on the power switch of the load later (preferably with a delay of 1-2 minutes to allow the UPS to fully enter the working state), and the power switches of the load should be turned on one by one. When turning off the machine, the order is exactly the opposite, turn off the power switches of the load one by one, and then turn off the UPS. UPS needs to be in a long-term on state, while computers and other loads only turn on after each use. After use, simply turn off the power switch of the computer and other loads.

(5). Do not turn off and turn on the UPS power supply. It is generally required to wait for at least 6 minutes after turning off the UPS power supply before turning it back on. Otherwise, the UPS power supply may be in a "startup failure" state, that is, the UPS power supply is in an abnormal state of neither mains power output nor inverter output.

(6) The electrical energy inside the UPS battery may be in trouble or approaching trouble for some reason. In order to compensate for battery energy and improve battery life, UPS needs to perform timely and continuous charging for a long time (usually displayed within 48 hours, with or without load), so that the battery will not cause faults. Newly purchased or stored UPS should be charged to 12 before use. UPS that is not used for long-term storage should be charged for 12 hours every 3 months. If it encounters high temperature areas, it should be charged every 2 months. UPS will damage the battery if it is not used for charging.